Modeling and Simulation of Energy Systems: A Review
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paper_title: Opportunities and challenges for a sustainable energy future

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Access to clean, affordable and reliable energy has been a cornerstone of the world's increasing prosperity and economic growth since the beginning of the industrial revolution. Our use of energy in the twenty–first century must also be sustainable. Solar and water–based energy generation, and engineering of microbes to produce biofuels are a few examples of the alternatives. This Perspective puts these opportunities into a larger context by relating them to a number of aspects in the transportation and electricity generation sectors. It also provides a snapshot of the current energy landscape and discusses several research and development opportunities and pathways that could lead to a prosperous, sustainable and secure energy future for the world.
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paper_title: Bio-fuels from thermochemical conversion of renewable resources: A review

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Demand for energy and its resources, is increasing every day due to the rapid outgrowth of population and urbanization. As the major conventional energy resources like coal, petroleum and natural gas are at the verge of getting extinct, biomass can be considered as one of the promising environment friendly renewable energy options. Different thermo-chemical conversion processes that include combustion, gasification, liquefaction, hydrogenation and pyrolysis, have been used to convert the biomass into various energy products. Although pyrolysis is still under developing stage but during current energy scenario, pyrolysis has received special attention as it can convert biomass directly into solid, liquid and gaseous products by thermal decomposition of biomass in absence of oxygen. In this review article, the focus has been made on pyrolysis while other conventional processes have been discussed in brief. For having better insight, various types of pyrolysis processes have been discussed in detail including slow, fast, flash and catalytic pyrolysis processes. Besides biomass resources and constituents, the composition and uses of pyrolysis products have been discussed in detail. This review article aim to focus on various operational parameters, viz. temperature and particle size of biomass and product yields using various types of biomasses.
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paper_title: A review of energy models

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Energy is a vital input for social and economic development of any nation. With increasing agricultural and industrial activities in the country, the demand for energy is also increasing. Formulation of an energy model will help in the proper allocation of widely available renewable energy sources such as solar, wind, bioenergy and small hydropower in meeting the future energy demand in India. During the last decade several new concepts of energy planning and management such as decentralized planning, energy conservation through improved technologies, waste recycling, integrated energy planning, introduction of renewable energy sources and energy forecasting have emerged. In this paper an attempt has been made to understand and review the various emerging issues related to the energy modeling. The different types of models such as energy planning models, energy supply-demand models, forecasting models, renewable energy models, emission reduction models, optimization models have been reviewed and presented. Also, models based on neural network and fuzzy theory have been reviewed and discussed. The review paper on energy modeling will help the energy planners, researchers and policy makers widely.
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paper_title: A review of computer tools for analysing the integration of renewable energy into various energy systems

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This paper includes a review of the different computer tools that can be used to analyse the integration of renewable energy. Initially 68 tools were considered, but 37 were included in the final analysis which was carried out in collaboration with the tool developers or recommended points of contact. The results in this paper provide the information necessary to identify a suitable energy tool for analysing the integration of renewable energy into various energy-systems under different objectives. It is evident from this paper that there is no energy tool that addresses all issues related to integrating renewable energy, but instead the [`]ideal' energy tool is highly dependent on the specific objectives that must be fulfilled. The typical applications for the 37 tools reviewed (from analysing single-building systems to national energy-systems), combined with numerous other factors such as the energy-sectors considered, technologies accounted for, time parameters used, tool availability, and previous studies, will alter the perception of the [`]ideal' energy tool. In conclusion, this paper provides the information necessary to direct the decision-maker towards a suitable energy tool for an analysis that must be completed.
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paper_title: A review of current challenges and trends in energy systems modeling

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The requirements made on energy system models have changed during the last few decades. New challenges have arisen with the implementation of high shares of Renewable Energies. Along with the climate goals of the Paris Agreement, the national greenhouse gas strategies of industrialized countries involve the total restructuring of their energy systems. In order to archive these climate goals, fitted and customized models are required. For that reason, this paper focuses on national energy system models that incorporate all energy sectors and can support governmental decision making processes. The reviewed models are evaluated in terms of their characteristics, like their underlying methodology, analytical approach, time horizon and transformation path analysis, spatial and temporal resolution, licensing and modeling language. These attributes are set in the context of the region and time in which they were developed in order to identify trends in modeling. Furthermore, the revealed trends are set in the context of current challenges in energy systems modeling. Combining specified research questions and specific greenhouse gas reduction strategies, this paper will help researchers and decision makers find appropriate energy system models.
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paper_title: Modeling of hybrid renewable energy systems

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Hybrid renewable energy systems (HRES) are becoming popular for remote area power generation applications due to advances in renewable energy technologies and subsequent rise in prices of petroleum products. Economic aspects of these technologies are sufficiently promising to include them in developing power generation capacity for developing countries. Research and development efforts in solar, wind, and other renewable energy technologies are required to continue for, improving their performance, establishing techniques for accurately predicting their output and reliably integrating them with other conventional generating sources. The paper describes methodologies to model HRES components, HRES designs and their evaluation. The trends in HRES design show that the hybrid PV/wind energy systems are becoming gaining popular. The issues related to penetration of these energy systems in the present distribution network are highlighted.
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paper_title: Introduction to Energy Systems Modelling

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The energy demand and supply projections of the Swiss government funded by the Swiss Federal Office of Energy and carried out by a consortium of institutes and consulting companies are based on two types of energy models: macroeconomic general equilibrium models and bottom-up models for each sector. While the macroeconomic models are used to deliver the economic, demographic and policy framework conditions as well as the macroeconomic impacts of particular scenarios, the bottom-up models simulate the technical developments in the final energy sectors and try to optimise electricity generation under the given boundary conditions of a particular scenario. This introductory article gives an overview of some of the energy models used in Switzerland and — more importantly — some insights into current advanced energy system modelling practice pointing to the characteristics of the two modelling types and their advantages and limitations.
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paper_title: Energy overview for globalized world economy: Source, supply chain and sink

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Energy use of the globalized world economy is comprehensively overviewed by means of a systems input-output analysis based on statistics of 2010. Emphases are put on the sources of primary energy exploitation, inter-regional trade imbalance of energy use via global supply chains, and sinks of energy use in final demand. The largest final user turns out to be the United States, compared with China as the leading energy exploiter. The global trade volume of energy use is shown in magnitude up to about 90% of the global primary energy exploited. The United States is recognized as the world’s biggest energy use importer, in contrast to Russia as the biggest exporter. Approximately one third of global primary energy exploited is shown to be embodied in inter-regional net trade. Japan and Russia are respectively illustrated to be the world’s leading net importer and leading net exporter of energy use. For China as the leading energy exploiter, about 30% of its exploited energy is for foreign regions’ final use, and 70% for its own final use. For the European Union as the largest sink region, nearly 80% of the energy required in its final use is from foreign regions, led by Russia. As reflected in the results, the conventional perspective based only on the direct energy consumption by region inevitably leads to inter-regional “energy grabbing” and “carbon leakage”, which raises a serious concern of “regional decrease at the expense of global increase”. In current context of energy shortage and climate change, this global energy overview can provide essential strategic implications at the international, national and regional scales for sustainable energy policy making.
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paper_title: A Review on Optimization Modeling of Energy Systems Planning and GHG Emission Mitigation under Uncertainty

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Energy is crucial in supporting people’s daily lives and the continual quest for human development. Due to the associated complexities and uncertainties, decision makers and planners are facing increased pressure to respond more effectively to a number of energy-related issues and conflicts, as well as GHG emission mitigation within the multiple scales of energy management systems (EMSs). This quandary requires a focused effort to resolve a wide range of issues related to EMSs, as well as the associated economic and environmental implications. Effective systems analysis approaches under uncertainty to successfully address interactions, complexities, uncertainties, and changing conditions associated with EMSs is desired, which require a systematic investigation of the current studies on energy systems. Systems analysis and optimization modeling for low-carbon energy systems planning with the consideration of GHG emission reduction under uncertainty is thus comprehensively reviewed in this paper. A number of related methodologies and applications related to: (a) optimization modeling of GHG emission mitigation; (b) optimization modeling of energy systems planning under uncertainty; and (c) model-based decision support tools are examined. Perspectives of effective management schemes are investigated, demonstrating many demanding areas for enhanced research efforts, which include issues of data availability and reliability, concerns in uncertainty, necessity of post-modeling analysis, and usefulness of development of simulation techniques.
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paper_title: Review of models and actors in energy mix optimization – can leader visions and decisions align with optimum model strategies for our future energy systems?

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Organizational behavior and stakeholder processes continually influence energy strategy choices and decisions. Although theoretical optimizations can provide guidance for energy mix decisions from a pure physical systems engineering point of view, these solutions might not be optimal from a political or social perspective. Improving the transparency of our vision sharing and strategy making processes in a systematic way is therefore as important as the actual systems engineering solutions proposed by the modeling tools. Energy trend forecasting and back-casting, scenarios and system analysis have matured into powerful modeling tools for providing advice on optimizing our future energy solutions. The integrated use and iterative improvement of all these approaches can result in energy systems that become better optimized. Such an integrated approach is particularly important to those who have decision-making power over our future energy direction. Some of the challenges and opportunities for energy strategists that strive to promote optimal decisions on our future energy solutions are highlighted in this state-of-the-art review.
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paper_title: Application of energy system models for designing a low-carbon society

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Abstract Rising concern about the effect of greenhouse gas (GHG) emissions on climate change is pushing national governments and the international community to achieve sustainable development in an economy that is less dependent on carbon emitting activities – a vision that is usually termed a “low-carbon society” (LCS). Since the utilization of energy resources is the main source of GHG emissions, restructuring current energy systems in order to incorporate low-carbon energy technologies is essential for the realization of the LCS vision. Energy policies promoting the penetration of these technologies must view the role of energy in society as a system, composed of several energy resources, conversion technologies and energy demand sectors. The feasibility of the LCS in the future can be better understood by means of energy models. Energy models are valuable mathematical tools based on the systems approach. They have been applied to aid decision-making in energy planning, to analyze energy policies and to analyze the implications arising from the introduction of technologies. The design of the LCS requires innovative energy systems considering a trans-disciplinary approach that integrates multi-dimensional elements, related to social, economic, and environmental aspects. This paper reviews the application of energy models considering scenarios towards an LCS under the energy systems approach. The models reviewed consider the utilization of waste for energy, the penetration of clean coal technologies, transportation sector models as a sample of sectoral approaches, and models related to energy-for-development issues in rural areas of developing countries.
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paper_title: Design of Sustainable Biofuel Processes and Supply Chains: Challenges and Opportunities

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The current methodological approach for developing sustainable biofuel processes and supply chains is flawed. Life cycle principles are often retrospectively incorporated in the design phase resulting in incremental environmental improvement rather than selection of fuel pathways that minimize environmental impacts across the life cycle. Further, designing sustainable biofuel supply chains requires joint consideration of economic, environmental, and social factors that span multiple spatial and temporal scales. However, traditional life cycle assessment (LCA) ignores economic aspects and the role of ecological goods and services in supply chains, and hence is limited in its ability for guiding decision-making among alternatives—often resulting in sub-optimal solutions. Simultaneously incorporating economic and environment objectives in the design and optimization of emerging biofuel supply chains requires a radical new paradigm. This work discusses key research opportunities and challenges in the design of emerging biofuel supply chains and provides a high-level overview of the current “state of the art” in environmental sustainability assessment of biofuel production. Additionally, a bibliometric analysis of over 20,000 biofuel research articles from 2000-to-present is performed to identify active topical areas of research in the biofuel literature, quantify the relative strength of connections between various biofuels research domains, and determine any potential research gaps.
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paper_title: Optimization of IGCC processes with reduced order CFD models

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Abstract Integrated gasification combined cycle (IGCC) plants have significant advantages for efficient power generation with carbon capture. Moreover, with the development of accurate CFD models for gasification and combined cycle combustion, key units of these processes can now be modeled more accurately. However, the integration of CFD models within steady-state process simulators, and subsequent optimization of the integrated system, still presents significant challenges. This study describes the development and demonstration of a reduced order modeling (ROM) framework for these tasks. The approach builds on the concepts of co-simulation and ROM development for process units described in earlier studies. Here we show how the ROMs derived from both gasification and combustion units can be integrated within an equation-oriented simulation environment for the overall optimization of an IGCC process. In addition to a systematic approach to ROM development, the approach includes validation tasks for the CFD model as well as closed-loop tests for the integrated flowsheet. This approach allows the application of equation-based nonlinear programming algorithms and leads to fast optimization of CFD-based process flowsheets. The approach is illustrated on two flowsheets based on IGCC technology.
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paper_title: Future directions in process and product synthesis and design

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Abstract The incorporation of renewable energy sources to the market has brought a new golden era for process synthesis along with new challenges and opportunities. In this work, we give a brief review of the state of the art and then present challenges and future directions in this exciting area. The biggest driver is the rapid improvement in computer technology which greatly increases the number of factors that can be considered during the design process. Thus, some of the key future directions lie in integrating the design process with other aspects of process systems engineering, such as scheduling, planning, control, and supply chain management. In addition, sustainability is now a major consideration in which the design process must consider not only economic sustainability, but social sustainability and environmental sustainability when making design decisions. The tools available to address these challenges are limited but we are in a position to develop them based on strong chemical engineering principles following a multidisciplinary approach with contributions from other disciplines such as biology and biochemistry, computer science, materials, and chemistry.
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paper_title: A review of modelling approaches and tools for the simulation of district-scale energy systems

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We present a comprehensive review of modelling approaches and associated software tools that address district-level energy systems. Buildings play an important role in urban energy systems regarding both the demand and supply of energy. It is no longer sufficient to simulate building energy use assuming isolation from the microclimate and energy system in which they operate, or to model an urban energy system without consideration of the buildings that it serves. This review complements previous studies by focussing on models that address district-level interactions in energy systems, and by assessing the capabilities of the software tools available alongside the theory of the modelling approaches used.
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paper_title: Hybrid and single feedstock energy processes for liquid transportation fuels: A critical review

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Abstract This review provides a detailed account of the key contributions within the energy communities with specific emphasis on thermochemically based hybrid energy systems for liquid transportation fuels. Specifically, the advances in the indirect liquefaction of coal to liquid (CTL), natural gas to liquid (GTL), biomass to liquid (BTL), coal and natural gas to liquid (CGTL), coal and biomass to liquid (CBTL), natural gas and biomass to liquid (BGTL), and coal, biomass, and natural gas to liquid (CBGTL) are presented. This review is the first work that provides a comprehensive description of the contributions for the single-feedstock energy systems and the hybrid feedstock energy systems, for single stand-alone processes and energy supply chain networks. The focus is on contributions in (a) conceptual design, (b) process simulation, (c) economic analysis, (d) heat integration, (e) power integration, (f) water integration, (g) process synthesis, (h) life cycle analysis, (i) sensitivity analysis, (j) uncertainty issues, and (k) supply chain. A classification of the contributions based on the products, as well as different research groups is also provided.
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paper_title: Future opportunities and challenges in the design of new energy conversion systems

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Abstract In this perspective, an overview of the key challenges and opportunities in the design of new energy systems is presented. Recent shifts in the prices of natural energy resources combined with growing environmental concerns are creating a new set of challenges for process design engineers. Due to the massive scale and impact of energy conversion processes, some of the best solutions to the energy crisis lie in the design of new process systems which address these new problems. In particular, many of the most promising solutions take a big-picture approach by integrating many different processes together to take advantage of synergies between seemingly unrelated processes. This paper is an extended version of a paper published as part of the proceedings of the 8th International Conference on the Foundations of Computer-Aided Process Design (FOCAPD 2014) Adams (2014) .
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paper_title: A review of modelling tools for energy and electricity systems with large shares of variable renewables

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Abstract This paper presents a thorough review of 75 modelling tools currently used for analysing energy and electricity systems. Increased activity within model development in recent years has led to several new models and modelling capabilities, partly motivated by the need to better represent the integration of variable renewables. The purpose of this paper is to give an updated overview of currently available modelling tools, their capabilities and to serve as an aid for modellers in their process of identifying and choosing an appropriate model. A broad spectrum of modelling tools, ranging from small-scale power system analysis tools to global long-term energy models, has been assessed. Key information regarding the general logic, spatiotemporal resolution as well as the technological and economic features of the models is presented in three comprehensive tables. This information has been validated and updated by model developers or affiliated contact persons, and is state-of-the-art as of the submission date. With the available suite of modelling tools, most challenges of today's electricity system can be assessed. For a future with an increasing share of variable renewables and increasing electrification of the energy system, there are some challenges such as how to represent short-term variability in long-term studies, incorporate the effect of climate change and ensure openness and transparency in modelling studies.
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paper_title: Energy systems modeling for twenty-first century energy challenges

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Energy systems models are important methods used to generate a range of insight and analysis on the supply and demand of energy. Developed over the second half of the twentieth century, they are now seeing increased relevance in the face of stringent climate policy, energy security and economic development concerns, and increasing challenges due to the changing nature of the twenty-first century energy system. In this paper, we look particularly at models relevant to national and international energy policy, grouping them into four categories: energy systems optimization models, energy systems simulation models, power systems and electricity market models, and qualitative and mixed-methods scenarios. We examine four challenges they face and the efforts being taken to address them: (1) resolving time and space, (2) balancing uncertainty and transparency, (3) addressing the growing complexity of the energy system, and (4) integrating human behavior and social risks and opportunities. In discussing these challenges, we present possible avenues for future research and make recommendations to ensure the continued relevance for energy systems models as important sources of information for policy-making.
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paper_title: A review of urban energy system models: Approaches, challenges and opportunities

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Energy use in cities has attracted significant research in recent years. However such a broad topic inevitably results in number of alternative interpretations of the problem domain and the modelling tools used in its study. This paper seeks to pull together these strands by proposing a theoretical definition of an urban energy system model and then evaluating the state of current practice. Drawing on a review of 219 papers, five key areas of practice were identified – technology design, building design, urban climate, systems design, and policy assessment – each with distinct and incomplete interpretations of the problem domain. We also highlight a sixth field, land use and transportation modelling, which has direct relevance to the use of energy in cities but has been somewhat overlooked by the literature to date. Despite their diversity, these approaches to urban energy system modelling share four common challenges in understanding model complexity, data quality and uncertainty, model integration, and policy relevance. We then examine the opportunities for improving current practice in urban energy systems modelling, focusing on the potential of sensitivity analysis and cloud computing, data collection and integration techniques, and the use of activity-based modelling as an integrating framework. The results indicate that there is significant potential for urban energy systems modelling to move beyond single disciplinary approaches towards a sophisticated integrated perspective that more fully captures the theoretical intricacy of urban energy systems.
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paper_title: A review of energy systems models in the UK: Prevalent usage and categorisation

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In this paper, a systematic review of academic literature and policy papers since 2008 is undertaken with an aim of identifying the prevalent energy systems models and tools in the UK. A list of all referenced models is presented and the literature is analysed with regards sectoral coverage and technological inclusion, as well as mathematical structure of models.
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paper_title: Energy-economic models and the environment

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Abstract The current century—an era of environmental awareness—requires energy resources to satisfy the world's future energy demands. We can use current energy use scenarios to help us to understand how energy systems could change. Such scenarios are not an exercise in prophecy; rather they are designed to challenge our thinking in order to make better decisions today. The conventional modeling approach tends to extrapolate changes in energy consumption from historical trends; however, technology innovation sometimes causes drastic reforms in energy systems in the industrial, commercial, residential and transportation sectors. The economic aspects are another key issue to be considered in order to understand future changes in energy systems. The quantity of the energy supply is set to meet the price of the energy demand of end users. This occurs on the condition that the price of the energy supply equates with the price on the demand side under the market mechanism. This paper reviews the various issues associated with the energy-economic model and its application to national energy policies, renewable energy systems, and the global environment.
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paper_title: A review of energy system models.

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Purpose – The purpose of this paper is to provide a comparative overview of existing energy system models to see whether they are suitable for analysing energy, environment and climate change policies of developing countries.Design/methodology/approach – The paper reviews the available literature and follows a systematic comparative approach to achieve its purpose.Findings – The paper finds that the existing energy system models inadequately capture the developing country features and the problem is more pronounced with econometric and optimisation models than with accounting models.Originality/value – Inaccurate representation of energy systems in the models can lead to inaccurate decisions and poor policy prescriptions. Thus, the paper helps policy makers and users to be aware of the possible pitfalls of various energy system models.
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paper_title: Optimization of single mixed-refrigerant natural gas liquefaction processes described by nondifferentiable models

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Abstract A new strategy for the optimization of natural gas liquefaction processes is presented, in which flowsheets formulated using nondifferentiable process models are efficiently and robustly optimized using an interior-point algorithm. The constraints in the optimization formulation lead to solutions that ensure optimal usage of the area of multistream heat exchangers in the processes in order to minimize irreversibilities. The process optimization problems are solved reliably without the need for a complex initialization procedure even when highly accurate descriptions of the process stream cooling curves are required. In addition to the well-studied PRICO liquefaction process, two significantly more complex single mixed-refrigerant processes are successfully optimized and results are reported for each process subject to constraints imposed by several different operating scenarios.
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paper_title: Agent-based modeling on technological innovation as an evolutionary process

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Abstract This paper describes a multi-agent model built to simulate the process of technological innovation, based on the widely accepted theory that technological innovation can be seen as an evolutionary process. The actors in the simulation include producers and a large number of consumers. Every producer will produce several types of products at each step. Each product is composed of several design parameters and several performance parameters (fitness components). Kauffman’s famous NK model is used to deal with the mapping from a design parameter space (DPS) to a performance parameter space (PPS). In addition to the constructional selection, which can be illustrated by the NK model, we added environmental selection into the simulation and explored technological innovation as the result of the interaction between these two kinds of selection.
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paper_title: Modeling technology adoptions for sustainable development under increasing returns, uncertainty, and heterogeneous agents

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This paper presents a stylized model of technology adoptions for sustainable development under the three potentially most important "stylized facts": increasing returns to adoption, uncertainty, and heterogeneous agents following diverse technology development and adoption strategies. The stylized model deals with three technologies and two heterogeneous agents: a risk-taking one and a risk-averse one. Interactions between the two agents include trade in resources and goods, and technological spillover (free riding and technology trade). With the two heterogeneous agents, we run optimizations to minimize their aggregated costs in order to find out what rational behaviors are under different assumptions if the two agents are somehow cooperative. By considering uncertain carbon taxes, the model also addresses environmental issues as potential driving forces for technology adoptions.
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paper_title: The Use and Effects of Knowledge-Based System Explanations: Theoretical Foundations and a Framework for Empirical Evaluation

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Ever since MYCIN introduced the idea of computer-based explanations to the artificial intelligence community, it has come to be taken for granted that all knowledge-based systems KBS need to provide explanations. While this widely-held belief has led to much research on the generation and implementation of various kinds of explanations, there has been no theoretical basis to justify the use of explanations by KBS users. This paper discusses the role of KBS explanations to provide an understanding of both the specific factors that influence explanation use and the consequences of such use. ::: ::: The first part of the paper proposes a model based on cognitive learning theories to identify the reasons for the provision of KBS explanations from the perspective of facilitating user learning. Using the feedforward and feedback operators of cognitive learning the paper develops strategies for providing KBS explanations and classifies the various types of explanations found in current KBS applications. ::: ::: This second part of the paper presents a two-part framework to investigate empirically the use of KBS explanations. The first part of the framework focuses on the potential factors that influence the explanation seeking behavior of KBS users, including user expertise, the types of explanations provided and the level of user agreement with the KBS. The second part of the framework explores the potential effects of the use of KBS explanations and specifically considers four distinct categories of potential effects: explanation use behavior, learning, perceptions, and judgmental decision making.
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paper_title: Engineering Design via Surrogate Modelling: A Practical Guide

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Preface. About the Authors. Foreword. Prologue. Part I: Fundamentals. 1. Sampling Plans. 1.1 The 'Curse of Dimensionality' and How to Avoid It. 1.2 Physical versus Computational Experiments. 1.3 Designing Preliminary Experiments (Screening). 1.3.1 Estimating the Distribution of Elementary Effects. 1.4 Designing a Sampling Plan. 1.4.1 Stratification. 1.4.2 Latin Squares and Random Latin Hypercubes. 1.4.3 Space-filling Latin Hypercubes. 1.4.4 Space-filling Subsets. 1.5 A Note on Harmonic Responses. 1.6 Some Pointers for Further Reading. References. 2. Constructing a Surrogate. 2.1 The Modelling Process. 2.1.1 Stage One: Preparing the Data and Choosing a Modelling Approach. 2.1.2 Stage Two: Parameter Estimation and Training. 2.1.3 Stage Three: Model Testing. 2.2 Polynomial Models. 2.2.1 Example One: Aerofoil Drag. 2.2.2 Example Two: a Multimodal Testcase. 2.2.3 What About the k -variable Case? 2.3 Radial Basis Function Models. 2.3.1 Fitting Noise-Free Data. 2.3.2 Radial Basis Function Models of Noisy Data. 2.4 Kriging. 2.4.1 Building the Kriging Model. 2.4.2 Kriging Prediction. 2.5 Support Vector Regression. 2.5.1 The Support Vector Predictor. 2.5.2 The Kernel Trick. 2.5.3 Finding the Support Vectors. 2.5.4 Finding . 2.5.5 Choosing C and epsilon. 2.5.6 Computing epsilon : v -SVR 71. 2.6 The Big(ger) Picture. References. 3. Exploring and Exploiting a Surrogate. 3.1 Searching the Surrogate. 3.2 Infill Criteria. 3.2.1 Prediction Based Exploitation. 3.2.2 Error Based Exploration. 3.2.3 Balanced Exploitation and Exploration. 3.2.4 Conditional Likelihood Approaches. 3.2.5 Other Methods. 3.3 Managing a Surrogate Based Optimization Process. 3.3.1 Which Surrogate for What Use? 3.3.2 How Many Sample Plan and Infill Points? 3.3.3 Convergence Criteria. 3.3.4 Search of the Vibration Isolator Geometry Feasibility Using Kriging Goal Seeking. References. Part II: Advanced Concepts. 4. Visualization. 4.1 Matrices of Contour Plots. 4.2 Nested Dimensions. Reference. 5. Constraints. 5.1 Satisfaction of Constraints by Construction. 5.2 Penalty Functions. 5.3 Example Constrained Problem. 5.3.1 Using a Kriging Model of the Constraint Function. 5.3.2 Using a Kriging Model of the Objective Function. 5.4 Expected Improvement Based Approaches. 5.4.1 Expected Improvement With Simple Penalty Function. 5.4.2 Constrained Expected Improvement. 5.5 Missing Data. 5.5.1 Imputing Data for Infeasible Designs. 5.6 Design of a Helical Compression Spring Using Constrained Expected Improvement. 5.7 Summary. References. 6. Infill Criteria With Noisy Data. 6.1 Regressing Kriging. 6.2 Searching the Regression Model. 6.2.1 Re-Interpolation. 6.2.2 Re-Interpolation With Conditional Likelihood Approaches. 6.3 A Note on Matrix Ill-Conditioning. 6.4 Summary. References. 7. Exploiting Gradient Information. 7.1 Obtaining Gradients. 7.1.1 Finite Differencing. 7.1.2 Complex Step Approximation. 7.1.3 Adjoint Methods and Algorithmic Differentiation. 7.2 Gradient-enhanced Modelling. 7.3 Hessian-enhanced Modelling. 7.4 Summary. References. 8. Multi-fidelity Analysis. 8.1 Co-Kriging. 8.2 One-variable Demonstration. 8.3 Choosing X c and X e . 8.4 Summary. References. 9. Multiple Design Objectives. 9.1 Pareto Optimization. 9.2 Multi-objective Expected Improvement. 9.3 Design of the Nowacki Cantilever Beam Using Multi-objective, Constrained Expected Improvement. 9.4 Design of a Helical Compression Spring Using Multi-objective, Constrained Expected Improvement. 9.5 Summary. References. Appendix: Example Problems. A.1 One-Variable Test Function. A.2 Branin Test Function. A.3 Aerofoil Design. A.4 The Nowacki Beam. A.5 Multi-objective, Constrained Optimal Design of a Helical Compression Spring. A.6 Novel Passive Vibration Isolator Feasibility. References. Index.
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paper_title: Expert system methodologies and applications—a decade review from 1995 to 2004

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Abstract This paper surveys expert systems (ES) development using a literature review and classification of articles from 1995 to 2004 with a keyword index and article abstract in order to explore how ES methodologies and applications have developed during this period. Based on the scope of 166 articles from 78 academic journals (retrieved from five online database) of ES applications, this paper surveys and classifies ES methodologies using the following eleven categories: rule-based systems, knowledge-based systems, neural networks, fuzzy ESs, object-oriented methodology, case-based reasoning, system architecture, intelligent agent systems, database methodology, modeling, and ontology together with their applications for different research and problem domains. Discussion is presented, indicating the followings future development directions for ES methodologies and applications: (1) ES methodologies are tending to develop towards expertise orientation and ES applications development is a problem-oriented domain. (2) It is suggested that different social science methodologies, such as psychology, cognitive science, and human behavior could implement ES as another kind of methodology. (3) The ability to continually change and obtain new understanding is the driving power of ES methodologies, and should be the ES application of future works.
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paper_title: A hybrid neural network-first principles approach to process modeling

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A hybrid neural network-first principles modeling scheme is developed and used to model a fedbatch bioreactor. The hybrid model combines a partial first principles model, which incorporates the available prior knowledge about the process being modeled, with a neural network which serves as an estimator of unmeasuredprocess parameters that are difficult to model from first principles. This hybrid model has better properties than standard “black-box” neural network models in that it is able to interpolate and extrapolate much more accurately, is easier to analyze and interpret, and requires significantly fewer training examples. Two alternative state and parameter estimation strategies, extended Kalman filtering and NLP optimization, are also considered. When no a priori known model of the unobserved process parameters is available, the hybrid network model gives better estimates of the parameters, when compared to these methods. By providing a model of these unmeasured parameters, the hybrid network can also make predictions and hence can be used for process optimization. These results apply both when full and partial state measurements are available, but in the latter case a state reconstruction method must be used for the first principles component of the hybrid model.
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paper_title: A combined first-principles and data-driven approach to model building

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Abstract We address a central theme of empirical model building: the incorporation of first-principles information in a data-driven model-building process. By enabling modelers to leverage all available information, regression models can be constructed using measured data along with theory-driven knowledge of response variable bounds, thermodynamic limitations, boundary conditions, and other aspects of system knowledge. We expand the inclusion of regression constraints beyond intra-parameter relationships to relationships between combinations of predictors and response variables. Since the functional form of these constraints is more intuitive, they can be used to reveal hidden relationships between regression parameters that are not directly available to the modeler. First, we describe classes of a priori modeling constraints. Next, we propose a semi-infinite programming approach for the incorporation of these novel constraints. Finally, we detail several application areas and provide extensive computational results.
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paper_title: A Versatile Simulation Method for Complex Single Mixed Refrigerant Natural Gas Liquefaction Processes

paper_content:

Natural gas liquefaction is an energy intensive process with very small driving forces particularly in the low temperature region. Small temperature differences in the heat exchangers and high operating and capital costs require the use of an accurate and robust simulation tool for analysis. Unfortunately, state-of-the-art process simulators such as Aspen Plus and Aspen HYSYS have significant limitations in their ability to model multistream heat exchangers, which are critical unit operations in liquefaction processes. In particular, there exist no rigorous checks to prevent temperature crossovers from occurring in the heat exchangers, and the parameters must therefore be determined through a manual iterative approach to establish feasible operating conditions for the process. A multistream heat exchanger model that performs these checks, as well as area calculations for economic analysis, has previously been developed using a nonsmooth modeling approach. In addition, the model was used to successfully si...
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paper_title: The Role of Solid Oxide Fuel Cells in Advanced Hybrid Power Systems of the Future

paper_content:

In pursuing the implementation of highly efficient, emission-free power, the U.S. Department of Energy (DOE) is looking to the development of hybrid power systems that make use of the coupling of an electrochemical device with a heat engine, or more specifically, a solid oxide fuel cell (SOFC) and a gas turbine.1-4 The synergies of coupling these systems in a hybrid configuration provide the potential for reaching the highest possible electric conversion efficiency ever realized.5 As such, advanced hybrid power systems that incorporate a fuel cell and a gas turbine represent fossil or renewable energy production technology that provide the opportunity for a significant improvement in generation efficiency.6 An example of a simplified process diagram of the power cycle in a hybrid fuel cell gas turbine is shown in Fig. 1. While much of the DOE-sponsored research focuses on improving the performance of solid oxide fuel cells, a hardware simulation facility has been built by the Office of Research and Development at the National Energy Technology Laboratory (NETL) to explore both synergies and technical issues associated with integrated hybrid systems. The facility is part of the Hybrid Performance (Hyper) project, and is made available for public research collaboration with universities, industry, and other research institutions. The Hyper facility is capable of simulating high temperature fuel cell systems from 300 kW to 700 kW coupled with a 120 kW turbine. The purpose of the Hyper project is to specifically address this higher risk research by combining the flexibility of numerical simulation with the accuracy of experimental hardware.7 An illustration of the Hyper facility is shown in Fig. 2. The Hyper facility makes use of pressure vessels and piping to simulate the volume and flow impedance of the cathode and a burner controlled by a real-time fuel cell model running on a dSpace hardware-in-the-loop simulation platform to simulate the fuel cell thermal effluent. The hardware used to simulate the fuel cell is integrated with a 120 kW Garrett Series 85 auxiliary power unit (APU) for turbine and compressor system. The APU consists of single shaft, direct coupled turbine operating at a nominal 40,500 rpm, a two-stage radial compressor, and gear driven synchronous generator. The electrical generator is loaded by an isolated, continuously variable 120 kW resistor Fig. 2. Illustration of the Hybrid Performance (Hyper) simulation facility at NETL. Fig. 1. Simplified flow diagram of a representative direct fired, recuperated fuel cell gas turbine hybrid system.
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paper_title: Modeling chemical processes using prior knowledge and neural networks

paper_content:

We present a method for synthesizing chemical process models that combines prior knowledge and artificial neural networks. The inclusion of prior knowledge is investigated as a means of improving the neural network predictions when trained on sparse and noisy process data. Prior knowledge enters the hybrid model as a simple process model and first principle equations. The simple model controls the extrapolation of the hybrid in the regions of input space that lack training data. The first principle equations, such as mass and component balances, enforce equality constraints. The neural network compensates for inaccuracy in the prior model. In addition, inequality constraints are imposed during parameter estimation. For illustration, the approach is applied in predicting cell biomass and secondary metabolite in a fed-batch fermentation. The results show that prior knowledge enhances the generalization capabilities of a pure neural network model. The approach is shown to require less data for parameter estimation, produce more accurate and consistent predictions, and provide more reliable extrapolation
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paper_title: Surrogate model generation using self-optimizing variables

paper_content:

Abstract This paper presents the application of self-optimizing concepts for more efficient generation of steady-state surrogate models. Surrogate model generation generally has problems with a large number of independent variables resulting in a large sampling space. If the surrogate model is to be used for optimization, utilizing self-optimizing variables allows to map a close-to-optimal response surface, which reduces the model complexity. In particular, the mapped surface becomes much “flatter”, allowing for a simpler representation, for example, a linear map or neglecting the dependency of certain variables completely. The proposed method is studied using an ammonia reactor which for some disturbances shows limit-cycle behaviour and/or reactor extinction. Using self-optimizing variables, it is possible to reduce the number of manipulated variables by three and map a response surface close to the optimal response surface. With the original variables, the response surface would include also regions in which the reactor is extinct.
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paper_title: Intelligent systems in process engineering: a review

paper_content:

Abstract The purpose of this review is three-fold. First, sketch the directions that research and industrial applications of “intelligent systems” have taken in several areas of process engineering. Second, identify the emerging trends in each area, as well as the common threads that cut across several domains of inquiry. Third, stipulate research and development themes of significant importance for the future evolution of “intelligent systems” in process engineering. The paper covers the following seven areas: diagnosis of process operations; monitoring and analysis of process trends; intelligent control; heuristics and logic in planning and scheduling of process operations; modeling languages, simulation, and reasoning; intelligence in scientific computing; knowledge-based engineering design. Certain trends seem to be common and will (in all likelihood) characterize the nature of the future deployment of “intelligent systems”. These trends are: (1) Specialization to narrowly defined classes of problems. (2) Integration of multiple knowledge representations , so that all of relevant knowledge is captured and utilized. (3) Integration of processing methodologies , which tends to blur the past sharp distinctions between AI-based techniques and those from operations research, systems and control theory, probability and statistics. (4) Rapidly expanding range of industrial applications with significant increase in the scope of engineering tasks and size of problems.
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paper_title: Fuel Cell Gas Turbine Hybrid Simulation Facility Design

paper_content:

Fuel cell hybrid power systems have potential for the highest electrical power generation efficiency. Fuel cell gas turbine hybrid systems are currently under development as the first step in commercializing this technology. The dynamic interdependencies resulting from the integration of these two power generation technologies is not well understood. Unexpected complications can arise in the operation of an integrated system, especially during startup and transient events. Fuel cell gas turbine systems designed to operate under steady state conditions have limitations in studying the dynamics of a transient event without risk to the more fragile components of the system. A 250kW experimental fuel cell gas turbine system test facility has been designed at the National Energy Technology Laboratory (NETL), U.S. Department of Energy to examine the effects of transient events on the dynamics of these systems. The test facility will be used to evaluate control strategies for improving system response to transient events and load following. A fuel cell simulator, consisting of a natural gas burner controlled by a real time fuel cell model, will be integrated into the system in place of a real solid oxide fuel cell. The use of a fuel cell simulator in the initial phases allows for the exploration of transient events without risk of destroying an actual fuel cell. Fuel cell models and hybrid system models developed at NETL have played an important role in guiding the design of facility equipment and experimental research planning. Results of certain case studies using these models are discussed. Test scenarios were analyzed for potential thermal and mechanical impact on fuel cell, heat exchanger and gas turbine components. Temperature and pressure drop calculations were performed to determine the maximum impact on system components and design. Required turbine modifications were designed and tested for functionality. The resulting facility design will allow for examination of startup, shut down, loss of load to the fuel cell during steady state operations, loss of load to the turbine during steady state operations and load following.Copyright © 2002 by ASME
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paper_title: Simulation of Dual Mixed Refrigerant Natural Gas Liquefaction Processes Using a Nonsmooth Framework

paper_content:

Natural gas liquefaction is an energy intensive process where the feed is cooled from ambient temperature down to cryogenic temperatures. Different liquefaction cycles exist depending on the application, with dual mixed refrigerant processes normally considered for the large-scale production of Liquefied Natural Gas (LNG). Large temperature spans and small temperature differences in the heat exchangers make the liquefaction processes difficult to analyze. Exergetic losses from irreversible heat transfer increase exponentially with a decreasing temperature at subambient conditions. Consequently, an accurate and robust simulation tool is paramount to allow designers to make correct design decisions. However, conventional process simulators, such as Aspen Plus, suffer from significant drawbacks when modeling multistream heat exchangers. In particular, no rigorous checks exist to prevent temperature crossovers. Limited degrees of freedom and the inability to solve for stream variables other than outlet temperatures also makes such tools inflexible to use, often requiring the user to resort to a manual iterative procedure to obtain a feasible solution. In this article, a nonsmooth, multistream heat exchanger model is used to develop a simulation tool for two different dual mixed refrigerant processes. Case studies are presented for which Aspen Plus fails to obtain thermodynamically feasible solutions.
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paper_title: Artificial neural network models for biomass gasification in fluidized bed gasifiers

paper_content:

Abstract Artificial neural networks (ANNs) have been applied for modeling biomass gasification process in fluidized bed reactors. Two architectures of ANNs models are presented; one for circulating fluidized bed gasifiers (CFB) and the other for bubbling fluidized bed gasifiers (BFB). Both models determine the producer gas composition (CO, CO 2 , H 2 , CH 4 ) and gas yield. Published experimental data from other authors has been used to train the ANNs. The obtained results show that the percentage composition of the main four gas species in producer gas (CO, CO 2 , H 2 , CH 4 ) and producer gas yield for a biomass fluidized bed gasifier can be successfully predicted by applying neural networks. ANNs models use in the input layer the biomass composition and few operating parameters, two neurons in the hidden layer and the backpropagation algorithm. The results obtained by these ANNs show high agreement with published experimental data used R 2 > 0.98. Furthermore a sensitivity analysis has been applied in each ANN model showing that all studied input variables are important.
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paper_title: Agent-based supply chain management*/1: framework

paper_content:

Abstract In the face of highly competitive markets and constant pressure to reduce lead times, enterprises today consider supply chain management to be the key area where improvements can significantly impact the bottom line. More enterprises now consider the entire supply chain structure while taking business decisions. They try to identify and manage all critical relationships both upstream and downstream in their supply chains. Some impediments to this are that the necessary information usually resides across a multitude of resources, is ever changing, and is present in multiple formats. Most supply chain decision support systems (DSSs) are specific to an enterprise and its supply chain, and cannot be easily modified to assist other similar enterprises and industries. In this two-part paper, we propose a unified framework for modeling, monitoring and management of supply chains. The first part of the paper describes the framework while the second part illustrates its application to a refinery supply chain. The framework integrates the various elements of the supply chain such as enterprises, their production processes, the associated business data and knowledge and represents them in a unified, intelligent and object-oriented fashion. Supply chain elements are classified as entities, flows and relationships. Software agents are used to emulate the entities i.e. various enterprises and their internal departments. Flows—material and information—are modeled as objects. The framework helps to analyze the business policies with respect to different situations arising in the supply chain. We illustrate the framework by means of two case studies. A DSS for petrochemical cluster management is described together with a prototype DSS for crude procurement in a refinery.
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paper_title: Robust simulation and optimization methods for natural gas liquefaction processes

paper_content:

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2018.
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paper_title: Agent-based modeling: Methods and techniques for simulating human systems

paper_content:

Agent-based modeling is a powerful simulation modeling technique that has seen a number of applications in the last few years, including applications to real-world business problems. After the basic principles of agent-based simulation are briefly introduced, its four areas of application are discussed by using real-world applications: flow simulation, organizational simulation, market simulation, and diffusion simulation. For each category, one or several business applications are described and analyzed.
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paper_title: A Critical Survey of Agent-Based Wholesale Electricity Market Models

paper_content:

The complexity of electricity markets calls for rich and flexible modeling techniques that help to understand market dynamics and to derive advice for the design of appropriate regulatory frameworks. Agent-Based Computational Economics (ACE) is a fairly young research paradigm that offers methods for realistic electricity market modeling. A growing number of researchers have developed agent-based models for simulating electricity markets. The diversity of approaches makes it difficult to overview the field of ACE electricity research; this literature survey should guide the way through and describe the state-of-the-art of this research area. In a conclusive summary, shortcomings of existing approaches and open issues that should be addressed by ACE electricity researchers are critically discussed.
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paper_title: Reliable Flash Calculations: Part 2. Process Flowsheeting with Nonsmooth Models and Generalized Derivatives

paper_content:

This article presents new methods for robustly simulating process flowsheets containing nondifferentiable models, using recent advances in exact sensitivity analysis for nonsmooth functions. Among other benefits, this allows flowsheeting problems to be equipped with newly developed nonsmooth inside-out algorithms for nonideal vapor–liquid equilibrium calculations that converge reliability, even when the phase regime at the results of these calculations is unknown a priori. Furthermore, process models for inherently nonsmooth unit operations may be seamlessly integrated into process flowsheets, so long as computationally relevant generalized derivative information is computed correctly and communicated to the flowsheet convergence algorithm. These techniques may be used in either sequential-modular simulations or simulations in which the most challenging modules are solved using tailored external procedures, while the remaining flowsheet equations are solved simultaneously. This new nonsmooth flowsheeting ...
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paper_title: Modeling technological change in energy systems – From optimization to agent-based modeling

paper_content:

Operational optimization models are one of the main streams in modeling energy systems. Agent-based modeling and simulation seem to be another approach getting popular in this field. In either optimization or agent-based modeling practices, technological change in energy systems is a very important and inevitable factor that researchers need to deal with. By introducing three stylized models, namely, a traditional optimization model, an optimization model with endogenous technological change, and an agent-based model, all of which were developed based on the same deliberately simplified energy system, this paper compares how technological change is treated differently in different modeling practices for energy systems, the different philosophies underlying them, and the advantages/disadvantages of each modeling practice. Finally, this paper identifies the different contexts suitable for applying optimization models and agent-based models in decision support regarding energy systems.
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paper_title: Simulation of biomass gasification with a hybrid neural network model.

paper_content:

Gasification of several types of biomass has been conducted in a fluidized bed gasifier at atmospheric pressure with steam as the fluidizing medium. In order to obtain the gasification profiles for each type of biomass, an artificial neural network model has been developed to simulate this gasification processes. Model-predicted gas production rates in this biomass gasification processes were consistent with the experimental data. Therefore, the gasification profiles generated by neural networks are considered to have properly reflected the real gasification process of a biomass. Gasification profiles identified by neural network suggest that gasification behavior of arboreal types of biomass is significantly different from that of herbaceous ones.
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paper_title: Computationally relevant generalized derivatives: theory, evaluation and applications

paper_content:

A new method for evaluating generalized derivatives in nonsmooth problems is reviewed. Lexicographic directional (LD-)derivatives are a recently developed tool in nonsmooth analysis for evaluating generalized derivative elements in a tractable and robust way. Applicable to problems in both steady-state and dynamic settings, LD-derivatives exhibit a number of advantages over current theory and algorithms. As highlighted in this article, the LD-derivative approach now admits a suitable theory for inverse and implicit functions, nonsmooth dynamical systems and optimization problems, among others. Moreover, this technique includes an extension of the standard vector forward mode of automatic differentiation (AD) and acts as the natural extension of classical calculus results to the nonsmooth case in many ways. The theory of LD-derivatives is placed in the context of state-of-the-art methods in nonsmooth analysis, with an application in multistream heat exchanger modelling and design used to illustrate the use...
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paper_title: An agent-based approach for supply chain retrofitting under uncertainty

paper_content:

In this work, decisions that have a long lasting effect on the supply chain (SC) such as the design and retrofit of a production/distribution network are considered. The retrofitting tasks are accomplished by using a SC agent-oriented simulation system, which model each entity belonging to the SC as an independent agent. The starting point is a set of possible design options for the existing SC. For each design alternative a performance index is obtained through the agent-based framework by looking for the best value of the operational variables associated to the resulting network. The proposed methodology allows to address the design of complex SCs which are hard to be modelled otherwise, for example by means of standard mathematical programming tools. Specifically, the multi-agent system is suitable for SCs that are either driven by pull strategies or operate under uncertain environments, in which the mathematical programming approaches are likely to be inferior due to the high computational effort required. The advantages of our approach are highlighted through a case study comprising several plants, warehouses and retailers.
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paper_title: Neural networks for control systems: a survey

paper_content:

Abstract This paper focuses on the promise of artificial neural networks in the realm of modelling, identification and control of nonlinear systems. The basic ideas and techniques of artificial neural networks are presented in language and notation familiar to control engineers. Applications of a variety of neural network architectures in control are surveyed. We explore the links between the fields of control science and neural networks in a unified presentation and identify key areas for future research.
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paper_title: Executable cell biology

paper_content:

Computational modeling of biological systems is becoming increasingly important in efforts to better understand complex biological behaviors. In this review, we distinguish between two types of biological models—mathematical and computational—which differ in their representations of biological phenomena. We call the approach of constructing computational models of biological systems 'executable biology', as it focuses on the design of executable computer algorithms that mimic biological phenomena. We survey the main modeling efforts in this direction, emphasize the applicability and benefits of executable models in biological research and highlight some of the challenges that executable biology poses for biology and computer science. We claim that for executable biology to reach its full potential as a mainstream biological technique, formal and algorithmic approaches must be integrated into biological research. This will drive biology toward a more precise engineering discipline.
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paper_title: Modeling, simulation, sensitivity analysis, and optimization of hybrid systems

paper_content:

Hybrid (discrete/continuous) systems exhibit both discrete state and continuous state dynamics which interact to such a significant extent that they cannot be decoupled and must be analyzed simultaneously. We present an overview of the work that has been done in the modeling, simulation, sensitivity analysis, and optimization of hybrid systems, paying particular attention to the interaction between discrete and continuous dynamics. A concise intuitive framework for hybrid system modeling is presented, together with discussions on robust state event location, transfer functions of the continuous state at discontinuities, parametric sensitivity analysis of hybrid systems, and challenges in optimization.
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paper_title: Simulation of a Dual Mixed Refrigerant LNG Process using a Nonsmooth Framework

paper_content:

Abstract Natural gas liquefaction is an energy intensive process with very small driving forces at cryogenic temperatures. Small temperature differences arise from the excessive exergy destruction that occurs from irreversible heat transfer at low temperatures. As a result, even a small change in driving forces in the low temperature region can propagate into large exergy losses that must be compensated by additional compression power. Along with the significant investments and operating costs associated with these processes, this demands a robust and accurate simulation tool. Nonsmooth simulation models for single mixed refrigerant processes already exist in the literature. However, these processes are relatively simple, and are normally only considered for small-scale production or floating operations. Other processes, such as dual mixed refrigerant processes, are therefore normally considered for large-scale production of LNG. It is necessary to investigate whether the nonsmooth flowsheeting strategy is capable of also handling these more complex liquefaction processes. This article describes a simulation model for a dual mixed refrigerant process. The model is solved for two cases using the Peng-Robinson equation of state, each solving for a different set of unknown variables. Both cases converged within a few iterations, showing nearly identical results to simulations run in Aspen Plus.
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paper_title: Multistream heat exchanger modeling and design

paper_content:

A new model formulation and solution strategy for the design and simulation of processes involving multistream heat exchangers (MHEXs) is presented. The approach combines an extension of pinch analysis with an explicit dependence on the heat exchange area in a nonsmooth equation system to create a model which solves for up to three unknown variables in an MHEX. Recent advances in automatic generation of derivative-like information for nonsmooth equations make the method tractable, and the use of nonsmooth equation solving methods make the method very precise. Several illustrative examples and a case study featuring an offshore liquefied natural gas production concept are presented which highlight the flexibility and strengths of the formulation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3390–3403, 2015
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paper_title: Disjunctive modeling for optimal control of hybrid systems

paper_content:

Abstract In this contribution, a novel approach for the modeling and numerical optimal control of hybrid (discrete–continuous dynamic) systems based on a disjunctive problem formulation is proposed. It is shown that a disjunctive model representation, which constitutes an alternative to mixed-integer model formulations, provides a very flexible, intuitive and effective way to formulate hybrid (discrete–continuous dynamic) optimization problems. The structure and properties of the disjunctive process models can be exploited for an efficient and robust numerical solution by applying generalized disjunctive programming techniques. The proposed modeling and optimization approach will be illustrated by means of optimal control of hybrid systems embedding linear discrete–continuous dynamic models.
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paper_title: Modeling of combined discrete/continuous processes

paper_content:

The dynamic behavior of processing systems exhibits both continuous and significant discrete aspects. Process simulation is therefore a combined discrete/continuous simulation problem. In addition, there is a critical need for a declarative process modeling environment to encompass the entire range of processing system operation, from purely continuous to batch. These issues are addressed by this article. ::: ::: A new formal mathematical description of the combined discrete/continuous simulation problem is introduced to enhance the understanding of the fundamental discrete changes required to model processing systems. The modeling task is decomposed into two distinct activities: modeling fundamental physical behavior, and modeling the external actions imposed on this physical system. Both require significant discrete components. Important contributions include a powerful representation for discontinuities in physical behavior, and the first detailed consideration of how complex sequences of control actions may be modeled in a general manner.
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paper_title: On Hybrid Petri Nets

paper_content:

Petri nets (PNs) are widely used to model discrete event dynamic systems (computer systems, manufacturing systems, communication systems, etc). Continuous Petri nets (in which the markings are real numbers and the transition firings are continuous) were defined more recently; such a PN may model a continuous system or approximate a discrete system. A hybrid Petri net can be obtained if one part is discrete and another part is continuous. This paper is basically a survey of the work of the authors' team on hybrid PNs (definition, properties, modeling). In addition, it contains new material such as the definition of extended hybrid PNs and several applications, explanations and comments about the timings in Petri nets, more on the conflict resolution in hybrid PNs, and connection between hybrid PNs and hybrid automata. The paper is illustrated by many examples.
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paper_title: Use of Latent Variables to Reduce the Dimension of Surrogate Models

paper_content:

In this paper, we propose extensions for surrogate model fitting based on partial least square (PLS) regression. The method itself consists of a three step procedure, in which first, linear mass balances are established, then PLS regression is used to reduce the number of independent variables, and finally non-linear surrogate models are fitted to the latent variables defined via the PLS regression. As PLS regression looks for relationships between independent and dependent variables, preprocessing of the sampled data was investigated. Preprocessing improves the fit of the surrogate model by a factor of two in a case study given by the ammonia synthesis reactor section. The additional application of process knowledge allows a new grid definition with incorporated dependencies between independent variables resulting in a further improvement of the fit.
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paper_title: A Review of Multiscale Analysis: Examples from Systems Biology, Materials Engineering, and Other Fluid–Surface Interacting Systems

paper_content:

Abstract Multiscale simulation is an emerging scientific field that spans many disciplines, including physics, chemistry, mathematics, statistics, chemical engineering, mechanical engineering, and materials science. This review paper first defines this new scientific field and outlines its objectives. An overview of deterministic, continuum models and discrete, particle models is then given. Among discrete, particle models, emphasis is placed on Monte Carlo stochastic simulation methods in well-mixed and spatially distributed systems. Next, a classification of multiscale methods is carried out based on separation of length and time scales and the computational and mathematical approach taken. Broadly speaking, hybrid simulation and coarse graining or mesoscopic modeling are identified as two general and complementary approaches of multiscale modeling. The former is further classified into onion- and multigrid-type simulation depending on length scales and the presence or not of gradients. Several approaches, such as the net event, the probability weighted, the Poisson and binomial τ -leap, and the hybrid, are discussed for acceleration of stochastic simulation. In order to demonstrate the unifying principles of multiscale simulation, examples from different areas are discussed, including systems biology, materials growth and other reacting systems, fluids, and statistical mechanics. While the classification is general and examples from other scales and tools are touched upon, in this review emphasis is placed on stochastic models, their coarse graining, and their integration with continuum deterministic models, i.e., on the coupling of mesoscopic and macroscopic scales. The concept of hierarchical multiscale modeling is discussed in some length. Finally, the importance of systems-level tools such as sensitivity analysis, parameter estimation, optimization, control, model reduction, and bifurcation in multiscale analysis is underscored.
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paper_title: The nature and role of process systems engineering

paper_content:

Abstract In this article the author is going to attempt to establish Process Systems Engineering as an important core field in Chemical Engineering. Therefore, the definition of Process Systems Engineering, its necessity in the field of Chemical Engineering, its philosophical backbone and an opinion on the general structure of Process Systems Engineering are given first. later, the important roles which Process Systems Engineering have played in the past and will have to play in the future are mentioned with concrete examples of research done in the author's laboratory. The need for continuous research and development in this field is stressed in conclusion.
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paper_title: Towards a Process Modeling Methodolgy

paper_content:

Recent advances in nonlinear process control call for more detailed first principles based mathematical models to adequately represent the nonlinear process behavior. Despite the increasing demand for rigorous dynamic models, there has been little fundamental work in recent years to contribute to a better understanding of model development. This is because modeling has either been viewed as a solved problem or as an art rather than a science. Systematic methods of modeling are therefore lacking. In order to satify the needs of nonlinear model-based control, this contribution suggests a process modeling methodolgy based on systems theoretical concepts. The focus is on the derivation of the process model equations prior to their implementation by means of some of the available simulation tools.
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paper_title: Challenges in the new millennium: Product discovery and design, enterprise and supply chain optimization, global life cycle assessment

paper_content:

This paper first provides an overview of the financial state of the process industry, major issues it currently faces, and job placement of chemical engineers in the U.S. These facts combined with an expanded role of Process Systems Engineering, are used to argue that to support the “value preservation” and “value growth” industry three major future research challenges need to be addressed: Product Discovery and Design, Enterprise and Supply Chain Optimization, and Global Life Cycle Assessment. We provide a brief review of the progress that has been made in these areas, as well as the supporting methods and tools for tackling these problems. Finally, we provide some concluding remarks.
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paper_title: ENVIRONMENTALLY CONSCIOUS CHEMICAL PROCESS DESIGN

paper_content:

▪ Abstract The environment has emerged as an important determinant of the performance of the modern chemical industry. This paper reviews approaches for incorporating environmental issues into the design of new processes and manufacturing facilities. The organizational framework is the design process itself, which includes framing the problem and generating, analyzing, and evaluating alternatives. A historical perspective on the chemical process synthesis problem illustrates how both performance objectives and the context of the design have evolved to the point where environmental issues must be considered throughout the production chain. In particular, the review illustrates the need to view environmental issues as part of the design objectives rather than as constraints on operations. A concluding section identifies gaps in the literature and opportunities for additional research.
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paper_title: Multi-scale optimization for process systems engineering

paper_content:

Abstract Efficient nonlinear programming (NLP) algorithms and modeling platforms have led to powerful process optimization strategies. Nevertheless, these algorithms are challenged by recent evolution and deployment of multi-scale models (such as molecular dynamics and complex fluid flow) that apply over broad time and length scales. Integrated optimization of these models requires accurate and efficient reduced models (RMs). This study develops a rigorous multi-scale optimization framework that substitutes RMs for complex original detailed models (ODMs) and guarantees convergence to the original optimization problem. Based on trust region concepts this framework leads to three related NLP algorithms for RM-based optimization. The first follows the classical gradient-based trust-region method, the second avoids gradient calculations from the ODM, and the third avoids frequent recourse to ODM evaluations, using the concept of ϵ -exact RMs. We illustrate these algorithms with small examples and discuss RM-based optimization case studies that demonstrate their performance and effectiveness.
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paper_title: TRENDS IN COMPUTER-AIDED PROCESS MODELING

paper_content:

Process modeling is an important task during many process engineering activities such as steady-state and dynamic process simulation, process synthesis or control system design and implementation. The demand for models of varying detail is expected to steadily increase in the future due to advances in model-based process engineering methodologies. Computer assistance to support the development and implementation of adequate and transparent models is indispensable to minimize the engineering effort. The state of the art and current trends in computer-aided modeling are presented in this contribution which is intended to serve as a survey and a tutorial at the same time.
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paper_title: Optimization of single mixed-refrigerant natural gas liquefaction processes described by nondifferentiable models

paper_content:

Abstract A new strategy for the optimization of natural gas liquefaction processes is presented, in which flowsheets formulated using nondifferentiable process models are efficiently and robustly optimized using an interior-point algorithm. The constraints in the optimization formulation lead to solutions that ensure optimal usage of the area of multistream heat exchangers in the processes in order to minimize irreversibilities. The process optimization problems are solved reliably without the need for a complex initialization procedure even when highly accurate descriptions of the process stream cooling curves are required. In addition to the well-studied PRICO liquefaction process, two significantly more complex single mixed-refrigerant processes are successfully optimized and results are reported for each process subject to constraints imposed by several different operating scenarios.
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paper_title: A hybrid neural network-first principles approach to process modeling

paper_content:

A hybrid neural network-first principles modeling scheme is developed and used to model a fedbatch bioreactor. The hybrid model combines a partial first principles model, which incorporates the available prior knowledge about the process being modeled, with a neural network which serves as an estimator of unmeasuredprocess parameters that are difficult to model from first principles. This hybrid model has better properties than standard “black-box” neural network models in that it is able to interpolate and extrapolate much more accurately, is easier to analyze and interpret, and requires significantly fewer training examples. Two alternative state and parameter estimation strategies, extended Kalman filtering and NLP optimization, are also considered. When no a priori known model of the unobserved process parameters is available, the hybrid network model gives better estimates of the parameters, when compared to these methods. By providing a model of these unmeasured parameters, the hybrid network can also make predictions and hence can be used for process optimization. These results apply both when full and partial state measurements are available, but in the latter case a state reconstruction method must be used for the first principles component of the hybrid model.
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paper_title: A combined first-principles and data-driven approach to model building

paper_content:

Abstract We address a central theme of empirical model building: the incorporation of first-principles information in a data-driven model-building process. By enabling modelers to leverage all available information, regression models can be constructed using measured data along with theory-driven knowledge of response variable bounds, thermodynamic limitations, boundary conditions, and other aspects of system knowledge. We expand the inclusion of regression constraints beyond intra-parameter relationships to relationships between combinations of predictors and response variables. Since the functional form of these constraints is more intuitive, they can be used to reveal hidden relationships between regression parameters that are not directly available to the modeler. First, we describe classes of a priori modeling constraints. Next, we propose a semi-infinite programming approach for the incorporation of these novel constraints. Finally, we detail several application areas and provide extensive computational results.
---
paper_title: A Versatile Simulation Method for Complex Single Mixed Refrigerant Natural Gas Liquefaction Processes

paper_content:

Natural gas liquefaction is an energy intensive process with very small driving forces particularly in the low temperature region. Small temperature differences in the heat exchangers and high operating and capital costs require the use of an accurate and robust simulation tool for analysis. Unfortunately, state-of-the-art process simulators such as Aspen Plus and Aspen HYSYS have significant limitations in their ability to model multistream heat exchangers, which are critical unit operations in liquefaction processes. In particular, there exist no rigorous checks to prevent temperature crossovers from occurring in the heat exchangers, and the parameters must therefore be determined through a manual iterative approach to establish feasible operating conditions for the process. A multistream heat exchanger model that performs these checks, as well as area calculations for economic analysis, has previously been developed using a nonsmooth modeling approach. In addition, the model was used to successfully si...
---
paper_title: Modeling chemical processes using prior knowledge and neural networks

paper_content:

We present a method for synthesizing chemical process models that combines prior knowledge and artificial neural networks. The inclusion of prior knowledge is investigated as a means of improving the neural network predictions when trained on sparse and noisy process data. Prior knowledge enters the hybrid model as a simple process model and first principle equations. The simple model controls the extrapolation of the hybrid in the regions of input space that lack training data. The first principle equations, such as mass and component balances, enforce equality constraints. The neural network compensates for inaccuracy in the prior model. In addition, inequality constraints are imposed during parameter estimation. For illustration, the approach is applied in predicting cell biomass and secondary metabolite in a fed-batch fermentation. The results show that prior knowledge enhances the generalization capabilities of a pure neural network model. The approach is shown to require less data for parameter estimation, produce more accurate and consistent predictions, and provide more reliable extrapolation
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paper_title: Simulation of Dual Mixed Refrigerant Natural Gas Liquefaction Processes Using a Nonsmooth Framework

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Natural gas liquefaction is an energy intensive process where the feed is cooled from ambient temperature down to cryogenic temperatures. Different liquefaction cycles exist depending on the application, with dual mixed refrigerant processes normally considered for the large-scale production of Liquefied Natural Gas (LNG). Large temperature spans and small temperature differences in the heat exchangers make the liquefaction processes difficult to analyze. Exergetic losses from irreversible heat transfer increase exponentially with a decreasing temperature at subambient conditions. Consequently, an accurate and robust simulation tool is paramount to allow designers to make correct design decisions. However, conventional process simulators, such as Aspen Plus, suffer from significant drawbacks when modeling multistream heat exchangers. In particular, no rigorous checks exist to prevent temperature crossovers. Limited degrees of freedom and the inability to solve for stream variables other than outlet temperatures also makes such tools inflexible to use, often requiring the user to resort to a manual iterative procedure to obtain a feasible solution. In this article, a nonsmooth, multistream heat exchanger model is used to develop a simulation tool for two different dual mixed refrigerant processes. Case studies are presented for which Aspen Plus fails to obtain thermodynamically feasible solutions.
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paper_title: Reliable Flash Calculations: Part 2. Process Flowsheeting with Nonsmooth Models and Generalized Derivatives

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This article presents new methods for robustly simulating process flowsheets containing nondifferentiable models, using recent advances in exact sensitivity analysis for nonsmooth functions. Among other benefits, this allows flowsheeting problems to be equipped with newly developed nonsmooth inside-out algorithms for nonideal vapor–liquid equilibrium calculations that converge reliability, even when the phase regime at the results of these calculations is unknown a priori. Furthermore, process models for inherently nonsmooth unit operations may be seamlessly integrated into process flowsheets, so long as computationally relevant generalized derivative information is computed correctly and communicated to the flowsheet convergence algorithm. These techniques may be used in either sequential-modular simulations or simulations in which the most challenging modules are solved using tailored external procedures, while the remaining flowsheet equations are solved simultaneously. This new nonsmooth flowsheeting ...
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paper_title: Simulation of biomass gasification with a hybrid neural network model.

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Gasification of several types of biomass has been conducted in a fluidized bed gasifier at atmospheric pressure with steam as the fluidizing medium. In order to obtain the gasification profiles for each type of biomass, an artificial neural network model has been developed to simulate this gasification processes. Model-predicted gas production rates in this biomass gasification processes were consistent with the experimental data. Therefore, the gasification profiles generated by neural networks are considered to have properly reflected the real gasification process of a biomass. Gasification profiles identified by neural network suggest that gasification behavior of arboreal types of biomass is significantly different from that of herbaceous ones.
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paper_title: Computationally relevant generalized derivatives: theory, evaluation and applications

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A new method for evaluating generalized derivatives in nonsmooth problems is reviewed. Lexicographic directional (LD-)derivatives are a recently developed tool in nonsmooth analysis for evaluating generalized derivative elements in a tractable and robust way. Applicable to problems in both steady-state and dynamic settings, LD-derivatives exhibit a number of advantages over current theory and algorithms. As highlighted in this article, the LD-derivative approach now admits a suitable theory for inverse and implicit functions, nonsmooth dynamical systems and optimization problems, among others. Moreover, this technique includes an extension of the standard vector forward mode of automatic differentiation (AD) and acts as the natural extension of classical calculus results to the nonsmooth case in many ways. The theory of LD-derivatives is placed in the context of state-of-the-art methods in nonsmooth analysis, with an application in multistream heat exchanger modelling and design used to illustrate the use...
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paper_title: Simulation of a Dual Mixed Refrigerant LNG Process using a Nonsmooth Framework

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Abstract Natural gas liquefaction is an energy intensive process with very small driving forces at cryogenic temperatures. Small temperature differences arise from the excessive exergy destruction that occurs from irreversible heat transfer at low temperatures. As a result, even a small change in driving forces in the low temperature region can propagate into large exergy losses that must be compensated by additional compression power. Along with the significant investments and operating costs associated with these processes, this demands a robust and accurate simulation tool. Nonsmooth simulation models for single mixed refrigerant processes already exist in the literature. However, these processes are relatively simple, and are normally only considered for small-scale production or floating operations. Other processes, such as dual mixed refrigerant processes, are therefore normally considered for large-scale production of LNG. It is necessary to investigate whether the nonsmooth flowsheeting strategy is capable of also handling these more complex liquefaction processes. This article describes a simulation model for a dual mixed refrigerant process. The model is solved for two cases using the Peng-Robinson equation of state, each solving for a different set of unknown variables. Both cases converged within a few iterations, showing nearly identical results to simulations run in Aspen Plus.
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paper_title: Multistream heat exchanger modeling and design

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A new model formulation and solution strategy for the design and simulation of processes involving multistream heat exchangers (MHEXs) is presented. The approach combines an extension of pinch analysis with an explicit dependence on the heat exchange area in a nonsmooth equation system to create a model which solves for up to three unknown variables in an MHEX. Recent advances in automatic generation of derivative-like information for nonsmooth equations make the method tractable, and the use of nonsmooth equation solving methods make the method very precise. Several illustrative examples and a case study featuring an offshore liquefied natural gas production concept are presented which highlight the flexibility and strengths of the formulation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3390–3403, 2015
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paper_title: Use of Latent Variables to Reduce the Dimension of Surrogate Models

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In this paper, we propose extensions for surrogate model fitting based on partial least square (PLS) regression. The method itself consists of a three step procedure, in which first, linear mass balances are established, then PLS regression is used to reduce the number of independent variables, and finally non-linear surrogate models are fitted to the latent variables defined via the PLS regression. As PLS regression looks for relationships between independent and dependent variables, preprocessing of the sampled data was investigated. Preprocessing improves the fit of the surrogate model by a factor of two in a case study given by the ammonia synthesis reactor section. The additional application of process knowledge allows a new grid definition with incorporated dependencies between independent variables resulting in a further improvement of the fit.
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paper_title: A Review of Multiscale Analysis: Examples from Systems Biology, Materials Engineering, and Other Fluid–Surface Interacting Systems

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Abstract Multiscale simulation is an emerging scientific field that spans many disciplines, including physics, chemistry, mathematics, statistics, chemical engineering, mechanical engineering, and materials science. This review paper first defines this new scientific field and outlines its objectives. An overview of deterministic, continuum models and discrete, particle models is then given. Among discrete, particle models, emphasis is placed on Monte Carlo stochastic simulation methods in well-mixed and spatially distributed systems. Next, a classification of multiscale methods is carried out based on separation of length and time scales and the computational and mathematical approach taken. Broadly speaking, hybrid simulation and coarse graining or mesoscopic modeling are identified as two general and complementary approaches of multiscale modeling. The former is further classified into onion- and multigrid-type simulation depending on length scales and the presence or not of gradients. Several approaches, such as the net event, the probability weighted, the Poisson and binomial τ -leap, and the hybrid, are discussed for acceleration of stochastic simulation. In order to demonstrate the unifying principles of multiscale simulation, examples from different areas are discussed, including systems biology, materials growth and other reacting systems, fluids, and statistical mechanics. While the classification is general and examples from other scales and tools are touched upon, in this review emphasis is placed on stochastic models, their coarse graining, and their integration with continuum deterministic models, i.e., on the coupling of mesoscopic and macroscopic scales. The concept of hierarchical multiscale modeling is discussed in some length. Finally, the importance of systems-level tools such as sensitivity analysis, parameter estimation, optimization, control, model reduction, and bifurcation in multiscale analysis is underscored.
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paper_title: Bio-fuels from thermochemical conversion of renewable resources: A review

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Demand for energy and its resources, is increasing every day due to the rapid outgrowth of population and urbanization. As the major conventional energy resources like coal, petroleum and natural gas are at the verge of getting extinct, biomass can be considered as one of the promising environment friendly renewable energy options. Different thermo-chemical conversion processes that include combustion, gasification, liquefaction, hydrogenation and pyrolysis, have been used to convert the biomass into various energy products. Although pyrolysis is still under developing stage but during current energy scenario, pyrolysis has received special attention as it can convert biomass directly into solid, liquid and gaseous products by thermal decomposition of biomass in absence of oxygen. In this review article, the focus has been made on pyrolysis while other conventional processes have been discussed in brief. For having better insight, various types of pyrolysis processes have been discussed in detail including slow, fast, flash and catalytic pyrolysis processes. Besides biomass resources and constituents, the composition and uses of pyrolysis products have been discussed in detail. This review article aim to focus on various operational parameters, viz. temperature and particle size of biomass and product yields using various types of biomasses.
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paper_title: Modeling of biomass gasification: A review

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Biomass is being considered seriously as a source of energy generation worldwide. Among the various routes available for biomass based energy generation, biomass gasification is one of the most important routes that are being studied extensively. Biomass gasification is a thermo-chemical conversion process of biomass materials within a reactor. Number of inter-related parameters concerning the type of fuel, the reactor design and operating parameters effect the functioning of the gasifier. Understanding of this working principle is essential for the end user. The end user may be an individual who is interested in the output of the gasifier or the reactor manufacturer who is interested to develop the most optimum design or a planner who is in requirement of a gasifier which will give the best performance for a specific fuel type. Research and development both in the experimental and computational aspect of gasification has been numerous. Computational modeling tools are advantageous in many situations due to their capability of allowing the user to find the optimum conditions for a given reactor without going in for actual experimentation which is both time consuming and expensive. The modeling works of gasification process requires a systematic logical analysis in order to efficiently disseminate the embedded information. An attempt has been made in this study to categorise the recent modeling works based on certain specific criteria such as type of gasifier, feedstock, modeling considerations and evaluated parameters. Comparative assessments are made of the modeling techniques and output for each category of the models. The information is anticipated to be useful for researchers, end users as well as planners.
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paper_title: Combining coal gasification and natural gas reforming for efficient polygeneration

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Abstract A techno-economic analysis of several process systems to convert coal and natural gas to electricity, methanol, diesel, and gasoline is presented. For these polygeneration systems, a wide range of product portfolios and market conditions are considered, including the implementation of a CO 2 emissions tax policy and optional carbon capture and sequestration technology. A new strategy is proposed in which natural gas reforming is used to cool the gasifier, rather than steam generation. Simulations along with economic analyses show that this strategy provides increased energy efficiency and can be the optimal design choice in many market scenarios.
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paper_title: Top ten fundamental challenges of biomass pyrolysis for biofuels

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Pyrolytic biofuels have technical advantages over conventional biological conversion processes since the entire plant can be used as the feedstock (rather than only simple sugars) and the conversion process occurs in only a few seconds (rather than hours or days). Despite decades of study, the fundamental science of biomass pyrolysis is still lacking and detailed models capable of describing the chemistry and transport in real-world reactors is unavailable. Developing these descriptions is a challenge because of the complexity of feedstocks and the multiphase nature of the conversion process. Here, we identify ten fundamental research challenges that, if overcome, would facilitate commercialization of pyrolytic biofuels. In particular, developing fundamental descriptions for condensed-phase pyrolysis chemistry (i.e., elementary reaction mechanisms) are needed since they would allow for accurate process optimization as well as feedstock flexibility, both of which are critical to any modern high-throughput process. Despite the benefits to pyrolysis commercialization, detailed chemical mechanisms are not available today, even for major products such as levoglucosan and hydroxymethylfurfural (HMF). Additionally, accurate estimates for heat and mass transfer parameters (e.g., thermal conductivity, diffusivity) are lacking despite the fact that biomass conversion in commercial pyrolysis reactors is controlled by transport. Finally, we examine methods for improving pyrolysis particle models, which connect fundamental chemical and transport descriptions to real-world pyrolysis reactors. Each of the ten challenges is presented with a brief review of relevant literature followed by future directions which can ultimately lead to technological breakthroughs that would facilitate commercialization of pyrolytic biofuels.
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paper_title: Dynamic simulation and control of an integrated gasifier/reformer system. Part II: Discrete and model predictive control

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Abstract Part I of this series presented an analysis of a multi-loop proportional-integral (PI) control system for an integrated coal gasifier/steam methane reformer system, operating in both counter-current and co-current configurations, for syngas production in a flexible polygeneration plant. In this work, a discrete-PI control system and an offset-free linear model predictive controller (MPC) are presented for the co-current configuration to address process interactions and sampling delay. The MPC model was identified from ‘data’ derived from simulations of the rigorous plant model, with a Luenberger observer augmented to the MPC, to estimate and eliminate plant-model mismatch. MPC offered superior set point tracking relative to discrete-PI control, especially in cases where discrete-PI destabilized the system. The offset-free MPC was developed to solve in less than a second to facilitate online deployment.
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paper_title: Integrated Process Simulation and CFD for Improved Process Engineering

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Abstract This paper describes recent efforts to seamlessly integrate process simulation and computational fluid dynamics (CFD) using open standard interfaces for computer-aided process engineering. A reaction-separation-recycle flowsheet coupled with a CFD stirred tank reactor model is presented as an example to demonstrate the applicability of the integration approach and its potential to improve process engineering. The results show that the combined simulation offers new opportunities to analyze and optimize overall plant performance with respect to mixing and fluid flow behavior.
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paper_title: Simultaneous process synthesis, heat, power, and water integration of thermochemical hybrid biomass, coal, and natural gas facilities

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Abstract A comprehensive wastewater network is introduced into a thermochemical based process superstructure that will convert biomass, coal, and natural gas to liquid (CBGTL) transportation fuels. The mixed-integer nonlinear optimization (MINLP) model includes simultaneous heat, power, and water integration that utilizes heat engines to recover electricity from waste heat and several treatment units to process and recycle wastewater. A total of 108 case studies are analyzed which consist of combinations of six coal feedstocks, three biomass feedstocks, three plant capacities, and two process superstructures. This study discusses important process topological differences between the case studies and illustrates each component of the process synthesis framework using the two medium-sized capacity case studies that have low-volatile bituminous coal and biomass feedstocks.
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paper_title: Combining coal gasification, natural gas reforming, and solid oxide fuel cells for efficient polygeneration with CO2 capture and sequestration

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Several polygeneration process systems are presented which convert natural gas and coal to gasoline, diesel, methanol, and electricity. By using solid oxide fuel cells as the primary electricity generator, the presented systems improve upon a recently introduced concept by which natural gas is reformed inside the radiant cooler of a gasifier. Simulations and techno-economic analyses performed for a wide range of process configurations and market conditions show that this strategy results in significant efficiency and profitability improvements when CO2 capture and sequestration are employed. Market considerations for this analysis include variations in purchase prices of the coal and natural gas, sale prices of the products, and CO2 emission tax rates.
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paper_title: Toward Novel Hybrid Biomass, Coal, and Natural Gas Processes for Satisfying Current Transportation Fuel Demands, 1: Process Alternatives, Gasification Modeling, Process Simulation, and Economic Analysis

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This paper, which is the first part of a series of papers, introduces a hybrid coal, biomass, and natural gas to liquids (CBGTL) process that can produce transportation fuels in ratios consistent with current U.S. transportation fuel demands. Using the principles of the H2Car process, an almost-100% feedstock carbon conversion is attained using hydrogen produced from a carbon or noncarbon source and the reverse water-gas-shift reaction. Seven novel process alternatives that illustrate the effect of feedstock, hydrogen source, and light gas treatment on the process are considered. A complete process description is presented for each section of the CBGTL process including syngas generation, syngas treatment, hydrocarbon generation, hydrocarbon upgrading, and hydrogen generation. Novel mathematical models for biomass and coal gasification are developed to model the nonequilibrium effluent conditions using a stoichiometry-based method. Input−output relationships are derived for all vapor-phase components, cha...
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paper_title: Multi-scale Optimization for Advanced Energy Processes

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Abstract Advanced energy systems demand powerful and systematic optimization strategies for analysis, high performance design and efficient operation. Such processes are modeled through a heterogeneous collection of device-scale and process scale models, which contain distributed and lumped parameter models of varying complexity. This work addresses the integration and optimization of advanced energy models through multi-scale optimization strategies. In particular, we consider the optimal design of advanced energy processes by merging device-scale (e.g., CFD) models with flowsheet simulation models through sophisticated model reduction strategies. Recent developments in surrogate-based optimization have led to a general decomposition framework with multiple scales and convergence guarantees to the overall multi-scale optimum. Here, we sketch two trust region-based algorithms, one requiring gradients from the detailed model and one that is derivative-free; both demonstrate multi-scale optimization of advanced energy processes. Motivated by an advanced Integrated Gasification Combined Cycle (IGCC) process, we present two case studies that include PSA models for carbon capture and CFD models for gasification and combustion.
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paper_title: Metabolic engineering of microorganisms for biofuels production: from bugs to synthetic biology to fuels

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Metabolic engineering of microorganisms for biofuels production: from bugs to synthetic biology to fuels Sung Kuk Lee, Howard Chou, Timothy S Ham, Taek Soon Lee, and Jay D Keasling ABSTRACT The ability to generate microorganisms that can produce biofuels similar to petroleum-based transportation fuels would allow the use of existing engines and infrastructure and would save an enormous amount of capital required for replacing the current infrastructure to accommodate biofuels that have properties significantly different from petroleum-based fuels. Several groups have demonstrated the feasibility of manipulating microbes to produce molecules similar to petroleum-derived products, albeit at relatively low productivity (e.g. maximum butanol production is around 20 g/L). For cost-effective production of biofuels, the fuel-producing hosts and pathways must be engineered and optimized. Advances in metabolic engineering and synthetic biology will provide new tools for metabolic engineers to better understand how to rewire the cell in order to create the desired phenotypes for the production of economically viable biofuels. INTRODUCTION Alternative transportation fuels are in high demand owing to concerns about climate change, the global petroleum supply, and energy security [ 1,2]. Currently, the most widely used biofuels are ethanol generated from starch (corn) or sugar cane and biodiesel produced from vegetable oil or animal fats [3 ]. However, ethanol is not an ideal fuel molecule in that it is not compatible with the existing fuel infrastructure for distribution and storage owing to its corrosivity and high hygroscopicity [1,4 ]. Also, it contains only about 70% of the energy content of gasoline. Biodiesel has similar problems (URL: http:// www.bdpedia.com/biodiesel/alt/alt.html): it cannot be transported in pipelines because its cloud and pour points are higher than those for petroleum diesel (petrodiesel), and its energy content is approximately 11% lower than that of petrodiesel. Furthermore, both ethanol and bio-diesel are currently produced from limited agricultural resources, even though there is a large, untapped resource of plant biomass (lignocellulose) that could be utilized as a renewable source of carbon-neutral, liquid fuels [ 5]. Microbial production of transportation fuels from renew-able lignocellulose has several advantages. First, the production is not reliant on agricultural resources commonly used for food, such as corn, sugar cane, soybean, and palm oil. Second, lignocellulose is the most abundant biopolymer on earth. Third, new biosynthetic pathways can be engineered to produce fossil-fuel replacements, including short- chain, branched-chain, and cyclic alcohols, alkanes, alkenes, esters and aromatics. The development of cost-effective and energy-efficient processes to convert lignocellulose into fuels is hampered by significant roadblocks, including the lack of genetic engineering tools for native producer organisms (non-model organ-isms), and difficulties in optimizing metabolic pathways and balancing the redox state in the engineered microbes [ 6]. Furthermore, production potentials are limited by the low activity of pathway enzymes and the inhibitory effect of fuels and byproducts from the upstream biomass processing steps on microorganisms responsible for producing fuels. Recent advances in synthetic biology and metabolic engineering will make it possible to overcome these hurdles and engineer microorganisms for the cost- effective production of biofuels from cellulosic biomass. In this review, we examine the range of choices available as potential biofuel candidates and production hosts, review the recent methods used to produce biofuels, and discuss how tools from the fields of metabolic engineering and synthetic biology can be applied to produce transportation fuels using genetically engineered micro-organisms. Liquid fuels and alternative biofuel molecules An understanding of what makes a good fuel is important in order to retool microorganisms to produce more useful alternative biofuels. The best fuel targets for the near term will be molecules that are already found in or similar to components of fossil-based fuel in order to be compatible with existing engines (spark ignition engine for gasoline, compression ignition engine for diesel fuel, and gas turbine for jet fuel). There are several relevant factors to consider when designing biofuel candidates ( Table 1). Energy contents, the combustion quality described by octane or cetane number, volatility, freezing point,
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paper_title: Oxy-fuel combustion of pulverized coal: Characterization, fundamentals, stabilization and CFD modeling

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Oxy-fuel combustion has generated significant interest since it was proposed as a carbon capture technology for newly built and retrofitted coal-fired power plants. Research, development and demonstration of oxy-fuel combustion technologies has been advancing in recent years; however, there are still fundamental issues and technological challenges that must be addressed before this technology can reach its full potential, especially in the areas of combustion in oxygen-carbon dioxide environments and potentially at elevated pressures. This paper presents a technical review of oxy-coal combustion covering the most recent experimental and simulation studies, and numerical models for sub-processes are also used to examine the differences between combustion in an oxidizing stream diluted by nitrogen and carbon dioxide. The evolution of this technology from its original inception for high temperature processes to its current form for carbon capture is introduced, followed by a discussion of various oxy-fuel systems proposed for carbon capture. Of all these oxy-fuel systems, recent research has primarily focused on atmospheric air-like oxy-fuel combustion in a CO2-rich environment. Distinct heat and mass transfer, as well as reaction kinetics, have been reported in this environment because of the difference between the physical and chemical properties of CO2 and N2, which in turn changes the flame characteristics. By tracing the physical and chemical processes that coal particles experience during combustion, the characteristics of oxy-fuel combustion are reviewed in the context of heat and mass transfer, fuel delivery and injection, coal particle heating and moisture evaporation, devolatilization and ignition, char oxidation and gasification, as well as pollutants formation. Operation under elevated pressures has also been proposed for oxy-coal combustion systems in order to improve the overall energy efficiency. The potential impact of elevated pressures on oxy-fuel combustion is discussed when applicable. Narrower flammable regimes and lower laminar burning velocity under oxy-fuel combustion conditions may lead to new stability challenges in operating oxy-coal burners. Recent research on stabilization of oxy-fuel combustion is reviewed, and some guiding principles for retrofit are summarized. Distinct characteristics in oxy-coal combustion necessitate modifications of CFD sub-models because the approximations and assumptions for air-fuel combustion may no longer be valid. Advances in sub-models for turbulent flow, heat transfer and reactions in oxy-coal combustion simulations, and the results obtained using CFD are reviewed. Based on the review, research needs in this combustion technology are suggested.
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paper_title: Polygeneration of fuels and chemicals

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Research advances in the rapidly growing field of polygeneration are highlighted. Although ‘polygeneration’ has had many meanings, the chemical engineering community has overwhelmingly settled on a meaning which describes a process that co-produces at least two products: electricity, and at least one chemical or fuel via a thermochemical route that does not rely on petroleum. The production of syngas is almost always the primary intermediate for energy conversion, but the feeds, products, technologies, and pathways vary widely. However, the choice of the most optimal polygeneration system is highly dependent on circumstance, and often results in systems with only one fuel or chemical co-produced with electricity. Conversely, the synergistic use of multiple types of feedstocks can have important profitability benefits.
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paper_title: Synthetic biology and biomass conversion: a match made in heaven?

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To move our economy onto a sustainable basis, it is essential that we find a replacement for fossil carbon as a source of liquid fuels and chemical industry feedstocks. Lignocellulosic biomass, available in enormous quantities, is the only feasible replacement. Many micro-organisms are capable of rapid and efficient degradation of biomass, employing a battery of specialized enzymes, but do not produce useful products. Attempts to transfer biomass-degrading capability to industrially useful organisms by heterologous expression of one or a few biomass-degrading enzymes have met with limited success. It seems probable that an effective biomass-degradation system requires the synergistic action of a large number of enzymes, the individual and collective actions of which are poorly understood. By offering the ability to combine any number of transgenes in a modular, combinatorial way, synthetic biology offers a new approach to elucidating the synergistic action of combinations of biomass-degrading enzymes in vivo and may ultimately lead to a transferable biomass-degradation system. Also, synthetic biology offers the potential for assembly of novel product-formation pathways, as well as mechanisms for increased solvent tolerance. Thus, synthetic biology may finally lead to cheap and effective processes for conversion of biomass to useful products.
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paper_title: CFD modeling to study fluidized bed combustion and gasification

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Abstract The increase in application of fluidized bed combustion and gasification devices throughout world means that more consideration will be given to improve design and reduce emissions of these. Due to excellent thermal and mixing properties fluidized beds are generally preferred over the fixed bed combustors and gasifiers. Computational Fluid Dynamic (CFD) is a technique which helps to optimize the design and operation of fluidized bed combustor and gasifiers. Recent progression in numerical techniques and computing efficacy has advanced CFD as a widely used practice to provide efficient design solutions in fluidized bed industry. In this paper an extensive review of CFD modeling to study combustion and gasification in fluidized beds has been done. This paper introduces the fundamentals involved in developing a CFD solution for fluidized bed combustion and gasification. Mathematical equations governing the fluid flow, heat and mass transfer and chemical reactions in fluidized bed combustion and gasifiers systems are described and main CFD models are presented. The aim is to illustrate what can be done and also to identify trends and those areas where further work is needed.
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paper_title: Optimization of IGCC processes with reduced order CFD models

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Abstract Integrated gasification combined cycle (IGCC) plants have significant advantages for efficient power generation with carbon capture. Moreover, with the development of accurate CFD models for gasification and combined cycle combustion, key units of these processes can now be modeled more accurately. However, the integration of CFD models within steady-state process simulators, and subsequent optimization of the integrated system, still presents significant challenges. This study describes the development and demonstration of a reduced order modeling (ROM) framework for these tasks. The approach builds on the concepts of co-simulation and ROM development for process units described in earlier studies. Here we show how the ROMs derived from both gasification and combustion units can be integrated within an equation-oriented simulation environment for the overall optimization of an IGCC process. In addition to a systematic approach to ROM development, the approach includes validation tasks for the CFD model as well as closed-loop tests for the integrated flowsheet. This approach allows the application of equation-based nonlinear programming algorithms and leads to fast optimization of CFD-based process flowsheets. The approach is illustrated on two flowsheets based on IGCC technology.
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paper_title: Process/equipment co-simulation for design and analysis of advanced energy systems

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Abstract The grand challenge facing the power and energy industries is the development of efficient, environmentally friendly, and affordable technologies for next-generation energy systems. To provide solutions for energy and the environment, the U.S. Department of Energy's (DOE) National Energy Technology Laboratory (NETL) and its research partners in industry and academia are relying increasingly on the use of sophisticated computer-aided process design and optimization tools. In this paper, we describe recent progress toward developing an Advanced Process Engineering Co-Simulator (APECS) for the high-fidelity design, analysis, and optimization of energy plants. The APECS software system combines steady-state process simulation with multiphysics-based equipment simulations, such as those based on computational fluid dynamics (CFD). These co-simulation capabilities enable design engineers to optimize overall process performance with respect to complex thermal and fluid flow phenomena arising in key plant equipment items, such as combustors, gasifiers, turbines, and carbon capture devices. In this paper we review several applications of the APECS co-simulation technology to advanced energy systems, including coal-fired energy plants with carbon capture. This paper also discusses ongoing co-simulation R&D activities and challenges in areas such as CFD-based reduced-order modeling, knowledge management, advanced analysis and optimization, and virtual plant co-simulation. Continued progress in co-simulation technology – through improved integration, solution, and deployment – will have profound positive impacts on the design and optimization of high-efficiency, near-zero emission fossil energy systems.
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paper_title: Baseline Flowsheet Model for IGCC with Carbon Capture

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Integrated gasification combined cycle (IGCC) processes have the potential for high thermal efficiency with a low energy penalty for carbon capture. Many researchers have proposed various innovations to improve upon the efficiency of the IGCC process. However, the analysis methods of most publications are generally not transparent and these published results are exceedingly difficult to reproduce. The National Energy Technology Laboratory (NETL) report [Cost and Performance Baseline for Fossil Energy Plants: Bituminous Coal and Natural Gas to Electricity Final Report; U.S. Department of Energy, Office of Fossil Energy, NETL, DOE/NETL-2010/1397, 2010] is widely used as a reference by researchers and by industry. To enable researchers to have a consistent and transparent framework for analyzing IGCC flowsheets and potential innovations, a baseline model derived from the NETL report is described herein and the corresponding flowsheet model and its full documentation are available online from this journal for...
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paper_title: High-efficiency power production from coal with carbon capture

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A zero-emissions power plant with high efficiency is presented. Syngas, produced by the gasification of coal, is shifted to produce H2 which in turn fuels stacks of solid oxide fuel cells. Because the fuel cells maintain separate anode and cathode streams, air can be used as the oxygen source without diluting the fuel exhaust with nitrogen. This enables recovery of CO2 from the exhaust with a very small energy penalty. As a result, an absorption-based CO2 recovery process is avoided, as well as the production of large quantities of high-purity O2, allowing a high overall thermal efficiency and essentially eliminating the energy penalty for carbon capture. © 2010 American Institute of Chemical Engineers AIChE J, 2010
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paper_title: Municipal solid waste to liquid transportation fuels – Part I: Mathematical modeling of a municipal solid waste gasifier

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Abstract This paper presents a generic gasifier model towards the production of liquid fuels using municipal solid waste (MSW) as a feedstock. The MSW gasification has been divided into three zones: pyrolysis, oxidation, and reduction. The pyrolysis zone has been mathematically modeled with an optimization based monomer model. Then, the pyrolysis, oxidation, and reduction zones are defined with different chemical reactions and equations in which some extents of these reactions are not known a priori. Using a nonlinear parameter estimation approach, the unknown gasification parameters are obtained to match the experimental gasification results in the best possible way. The results suggest that a generic MSW gasifier mathematical model can be obtained in which the average error is 8.75%. The mathematical model of the MSW gasifier is of major importance since it can be a part of a process superstructure towards the production of liquid transportation fuels.
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paper_title: Bioconversion of lignocellulosic biomass: biochemical and molecular perspectives

paper_content:

In view of rising prices of crude oil due to increasing fuel demands, the need for alternative sources of bioenergy is expected to increase sharply in the coming years. Among potential alternative bioenergy resources, lignocellulosics have been identified as the prime source of biofuels and other value-added products. Lignocelluloses as agricultural, industrial and forest residuals account for the majority of the total biomass present in the world. To initiate the production of industrially important products from cellulosic biomass, bioconversion of the cellulosic components into fermentable sugars is necessary. A variety of microorganisms including bacteria and fungi may have the ability to degrade the cellulosic biomass to glucose monomers. Bacterial cellulases exist as discrete multi-enzyme complexes, called cellulosomes that consist of multiple subunits. Cellulolytic enzyme systems from the filamentous fungi, especially Trichoderma reesei, contain two exoglucanases or cellobiohydrolases (CBH1 and CBH2), at least four endoglucanases (EG1, EG2, EG3, EG5), and one β-glucosidase. These enzymes act synergistically to catalyse the hydrolysis of cellulose. Different physical parameters such as pH, temperature, adsorption, chemical factors like nitrogen, phosphorus, presence of phenolic compounds and other inhibitors can critically influence the bioconversion of lignocellulose. The production of cellulases by microbial cells is governed by genetic and biochemical controls including induction, catabolite repression, or end product inhibition. Several efforts have been made to increase the production of cellulases through strain improvement by mutagenesis. Various physical and chemical methods have been used to develop bacterial and fungal strains producing higher amounts of cellulase, all with limited success. Cellulosic bioconversion is a complex process and requires the synergistic action of the three enzymatic components consisting of endoglucanases, exoglucanases and β-glucosidases. The co-cultivation of microbes in fermentation can increase the quantity of the desirable components of the cellulase complex. An understanding of the molecular mechanism leading to biodegradation of lignocelluloses and the development of the bioprocessing potential of cellulolytic microorganisms might effectively be accomplished with recombinant DNA technology. For instance, cloning and sequencing of the various cellulolytic genes could economize the cellulase production process. Apart from that, metabolic engineering and genomics approaches have great potential for enhancing our understanding of the molecular mechanism of bioconversion of lignocelluloses to value added economically significant products in the future.
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paper_title: Municipal solid waste to liquid transportation fuels – Part II: Process synthesis and global optimization strategies

paper_content:

Abstract This paper investigates the production of liquid transportation fuels from municipal solid waste (MSW). A comprehensive process synthesis superstructure is utilized that incorporates a novel mathematical model for MSW gasification. The production of liquid products proceeds through a synthesis gas intermediate that can be converted into Fischer–Tropsch hydrocarbons or methanol. The methanol can be converted into either gasoline or olefins, and the olefins may subsequently be converted into gasoline and distillate. Simultaneous heat, power, and water integration is included within the process synthesis framework to minimize utilities costs. A rigorous deterministic global optimization branch-and-bound strategy is utilized to minimize the overall cost of the waste-to-liquids (WTL) refinery and determine the optimal process topology. Several case studies are presented to illustrate the process synthesis framework and the nonconvex mixed-integer nonlinear optimization model presented in this paper. This is the first study that explores the possibility of liquid fuels production from municipal solid waste utilizing a process synthesis approach within a global optimization framework. The results suggest that the production of liquid fuels from MSW is competitive with petroleum-based processes. The effect that the delivered cost of municipal solid waste has on the overall cost of liquids production is also investigated parametrically.
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paper_title: Optimization framework for the simultaneous process synthesis, heat and power integration of a thermochemical hybrid biomass, coal, and natural gas facility

paper_content:

Abstract A thermochemical based process superstructure and its mixed-integer nonlinear optimization (MINLP) model are introduced to convert biomass (switchgrass), coal (Illinois #6), and natural gas to liquid (CBGTL) transportation fuels. The MINLP model includes simultaneous heat and power integration utilizing heat engines to recover electricity from the process waste heat. Four case studies are presented to investigate the effect of CO 2 sequestration (CCS) and greenhouse gas (GHG) reduction targets on the process topology along with detailed parametric analysis on the role of biomass and electricity prices. Topological similarities for the case studies include selection of solid/vapor-fueled gasifiers and iron-catalyzed Fischer-Tropsch units that facilitate the reverse water–gas-shift reaction. The break-even oil price was found to be $57.16/bbl for CCS with a 50% GHG reduction, $62.65/bbl for CCS with a 100% GHG reduction, $82.68/bbl for no CCS with a 50% GHG reduction, and $91.71 for no CCS with a 100% GHG reduction.
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paper_title: Dynamic simulation and control of an integrated gasifier/reformer system. Part I: Agile case design and control

paper_content:

Abstract This two-part series investigates the feasibility of the operation and control of a novel gasifier cooling system which integrates steam methane reformer tubes into a gasifier radiant syngas cooler. This approach capitalizes on available exergy by producing valuable H 2 -rich synthesis gas (syngas) for liquid fuel production. In Part I (this work), an ‘agile’ device design was developed for both counter-current and co-current flow configurations, wherein a PI control structure was designed to achieve performance objectives. Key trade-offs were found between the configurations: the counter-current design was more robust and effective in rejecting moderate and severe gasifier disturbances, while providing greater cooling duty and natural gas throughput, but at the expense of higher tube wall temperatures, which can greatly reduce tube lifetime. The co-current design operates in a safer temperature range and satisfactorily rejects moderate disturbances, but requires feedforward control to handle extreme gasifier upsets. Using the co-current design, the flexibility of the device to adjust natural gas throughput based on variations in downstream syngas demand was demonstrated.
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paper_title: Modelling, Comparison and Operation Experiences of Entrained Flow Gasifier

paper_content:

Abstract In this paper a generic entrained flow gasifier is modelled in Aspen Plus using different designs e.g. wet/dry feed as well as wet and dry quench. The models are verified with the corresponding data from real existing plants or reference data from the literature. All of them are found to reproduce the raw gas composition as well as synthesis gas yield with acceptable deviation. The comparison of the selected designs revealed the poor performance of the wet feed compared to the dry design. The corresponding cold gas efficiency of 72.1% is much lower than the 83% for the dry feed cases. Furthermore the specific synthesis gas production is 12% lower at 12% higher oxygen demand. On the other hand, the power demand for the gasification island is found to be 60–70% lower than in the dry feed case. Therefore the wet feed design is recommended only in case of high pressure gasification. During, an exergy analysis of the different raw gas cooling concepts the disadvantage of the direct quench became obvious. Combinations of gas quench and heat recovery results in exergy losses of 52.4%. The heat recovery design showed much better exergy efficiency of 63.8%. Especially the wet quench design showed high looses and is therefore restricted to applications incorporating a down stream shift unit.
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paper_title: Polygeneration as a future sustainable energy solution – A comprehensive review

paper_content:

Integrating multiple utility outputs to obtain better efficient system has been a good option. After cogeneration and trigeneration, polygeneration emerges as a possible sustainable solution with optimum resource utilization, better efficiency and environment friendliness. Several possible polygeneration has been conceptualized, performance assessed theoretically as available in literature. Both inputs and outputs vary in these reported works. A few prototype development and experimental result analysis are also reported. Several optimization tools based on objective function are used to develop efficient polygeneration. Assessment criteria of polygeneration are also multi dimensional and may be defined on a case to case basis with definite objective. In this paper a comprehensive review of available literature is done to assess the status of polygeneration as a possible sustainable energy solution. Possible future research in this field is also logically predicted at the end of this review.
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paper_title: Modelling coal gasification with CFD and discrete phase method

paper_content:

In the present paper the authors describe a computational fluid dynamics model of a two-stage, oxygen blown, entrained flow, coal slurry gasifier for use in advanced power plant simulations. The discrete phase method is used to simulate the coal slurry flow. The physical and chemical processing of coal slurry gasification is implemented by calculating the discrete phase trajectory using a Lagrangian formulation. The particle tracking is coupled with specific physical processes, in which the coal particles sequentially undergo moisture release, vaporisation, devolatilisation, char oxidation and char gasification. Using specified plant boundary conditions, the gasification model predicts a synthesis gas composition that is very close to the values calculated by a restricted equilibrium reactor model tuned to represent typical experimental data. The char conversions are 100 and 86% for the first stage and second stage respectively.
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paper_title: Modelling, simulation and design of an integrated radiant syngas cooler and steam methane reformer for use with coal gasification

paper_content:

Abstract In this work, a novel process intensification design is proposed to integrate the Radiant Syngas Cooler (RSC) utilised to cool the coal-derived synthesis gas in entrained-bed gasifiers and a steam methane reformer (SMR). The feasibility of the proposed integrated system is analyzed by developing a rigorous, dynamic, multi-dimensional model and establishing design heuristics for the integrated system. Two different flow configurations are explored; co-current and counter-current. The simulation results show that the proposed concept is feasible that allows for methane conversions as high as 80% in co-current mode and 88% in counter-current mode. The results also demonstrate that the counter-current design, though with higher conversion and cooling duty provided when compared to co-current designs, is limited by the tube wall material limitations. Our analysis shows that the total avoided CO 2 emissions is 13.3 tonnes/h by using the proposed integrated configuration in place of an external reformer for the natural gas feed rates considered in this study. In addition, a sensitivity analysis is performed on key model assumptions and the resulting effect on the performance is assessed. The sensitivity results have helped identify key factors to consider prior to pilot-scale implementation and further improvement for agile designs; a one third reduction in tube length reduced pressure drop by as much as 50% but reduces methane conversion by 15% points, neglecting slag deposition on tubes over-predicts performance only by 3%, and a 10% change in gas emissivity calculations affects model prediction of performance by less than 1%.
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paper_title: INTEGRATION OF PRODUCTION PLANNING AND SCHEDULING: OVERVIEW CHALLENGES AND OPPORTUNITIES

paper_content:

We review the integration of medium-term production planning and short-term scheduling. We begin with an overview of supply chain management and the associated planning problems. Next, we formally define the production planning problem and explain why integration with scheduling leads to better solutions. We present the major modeling approaches for the integration of scheduling and planning decisions, and discuss the major solution strategies. We close with an account of the challenges and opportunities in this area.
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paper_title: Model-size reduction techniques for large-scale biomass production and supply networks

paper_content:

This paper is concerned with developing several model-size reduction techniques for the analysis of large-scale renewable production and supply networks. They are (i) Reducing the connectivity in a biomass supply chain network, (ii) Eliminating unnecessary variables and constraints, (iii) Merging the collection centres. The proposed model-size reduction techniques brought computational time improvements of several magnitudes compared, with the high performance linear system solution techniques and still with a little loss in accuracy. When the methods are combined the time reductions are more significant. A proposed procedure for combining the methods can be implemented for any supply chain model with a large number of components.
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paper_title: Prospective and perspective review in integrated supply chain modelling for the chemical process industry

paper_content:

There is a large body of work on modelling and optimisation of the supply chain in the chemical process industry. This review summarises the most recent concepts and structural components constituting the SC. It describes the enlarged scope presently attributed to supply chain management, which departs from classical approaches focused on operations to a more integrated conception that jointly considers necessary decisions from other business functional areas (e.g. corporate finances, new product development, environmental management), as well as captures the complex dynamics characterizing the supply chain management (SCM) problem. Moreover, new perspectives come into focus for enterprise-wide decision-making through the use of ontologies that provide a general model representation for different decision-support levels at different time and space scales.
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paper_title: Strategic planning, design, and development of the shale gas supply chain network

paper_content:

The long-term planning of the shale gas supply chain is a relevant problem that has not been addressed before in the literature. This article presents a mixed-integer nonlinear programming (MINLP) model to optimally determine the number of wells to drill at every location, the size of gas processing plants, the section and length of pipelines for gathering raw gas and delivering processed gas and by-products, the power of gas compressors, and the amount of freshwater required from reservoirs for drilling and hydraulic fracturing so as to maximize the net present value of the project. Because the proposed model is a large-scale nonconvex MINLP, we develop a decomposition approach based on successively refining a piecewise linear approximation of the objective function. Results on realistic instances show the importance of heavier hydrocarbons to the economics of the project, as well as the optimal usage of the infrastructure by properly planning the drilling strategy. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2122–2142, 2014
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paper_title: Waste biomass-to-energy supply chain management: a critical synthesis.

paper_content:

The development of renewable energy sources has clearly emerged as a promising policy towards enhancing the fragile global energy system with its limited fossil fuel resources, as well as for reducing the related environmental problems. In this context, waste biomass utilization has emerged as a viable alternative for energy production, encompassing a wide range of potential thermochemical, physicochemical and bio-chemical processes. Two significant bottlenecks that hinder the increased biomass utilization for energy production are the cost and complexity of its logistics operations. In this manuscript, we present a critical synthesis of the relative state-of-the-art literature as this applies to all stakeholders involved in the design and management of waste biomass supply chains (WBSCs). We begin by presenting the generic system components and then the unique characteristics of WBSCs that differentiate them from traditional supply chains. We proceed by discussing state-of-the-art energy conversion technologies along with the resulting classification of all relevant literature. We then recognize the natural hierarchy of the decision-making process for the design and planning of WBSCs and provide a taxonomy of all research efforts as these are mapped on the relevant strategic, tactical and operational levels of the hierarchy. Our critical synthesis demonstrates that biomass-to-energy production is a rapidly evolving research field focusing mainly on biomass-to-energy production technologies. However, very few studies address the critical supply chain management issues, and the ones that do that, focus mainly on (i) the assessment of the potential biomass and (ii) the allocation of biomass collection sites and energy production facilities. Our analysis further allows for the identification of gaps and overlaps in the existing literature, as well as of critical future research areas.
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paper_title: Process industry supply chains: Advances and challenges

paper_content:

Abstract A large body of work exists in process industry supply chain optimisation. We describe the state of the art of research in infrastructure design, modelling and analysis and planning and scheduling, together with some industrial examples. We draw some conclusions about the degree to which different classes of problem have been solved, and discuss challenges for the future.
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paper_title: Optimal design of sustainable chemical processes and supply chains: A review

paper_content:

Abstract The importance of balancing social, environmental and economic objectives in companies’ development has cultivated a growing awareness on the sustainable optimal design and planning of supply chains. In the past years, significant research effort has been devoted to extend current approaches to capture these objectives in order to guarantee long term sustainability. Among the various approaches developed, inventory management, product design, production planning and control for remanufacturing, product recovery, reverse logistics and closed-loop supply chains have gained more attention in the literature. In this paper, we review some of the relevant research on sustainable chemical processes and supply chain design focusing on three main areas: (i) sustainable supply chains with respect to energy efficiency and waste management, (ii) environmentally sustainable supply chains and (iii) sustainable water management. The emerging challenges in this area are summarized, and future opportunities are highlighted.
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paper_title: Biomass supply chain design and analysis: Basis, overview, modeling, challenges, and future

paper_content:

Biofuels are identified as the potential solution for depleting fossil fuel reserves, increasing oil prices, and providing a clean, renewable energy source. The major barrier preventing the commercialization of lignocellulosic biorefineries is the complex conversion process and their respective supply chain. Efficient supply chain management of a lignocellulosic biomass is crucial for success of second generation biofuels. This paper systematically describes energy needs, energy targets, biofuel feedstocks, conversion processes, and finally provides a comprehensive review of Biomass Supply Chain (BSC) design and modeling. Specifically, the paper presents a detailed review of mathematical programming models developed for BSC and identifies key challenges and potential future work. This review will provide readers with a starting point for understanding biomass feedstocks and biofuel production as well as detailed analysis of the BSC modeling and design.
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paper_title: Nationwide energy supply chain analysis for hybrid feedstock processes with significant CO2 emissions reduction

paper_content:

Integrating diverse energy sources to produce cost-competitive fuels requires efficient resource management. An optimization framework is proposed for a nationwide energy supply chain network using hybrid coal, biomass, and natural gas to liquids (CBGTL) facilities, which are individually optimized with simultaneous heat, power, and water integration using 162 distinct combinations of feedstock types, capacities, and carbon conversion levels. The model integrates the upstream and downstream operations of the facilities, incorporating the delivery of feedstocks, fuel products, electricity supply, water, and CO2 sequestration, with their geographical distributions. Quantitative economic trade-offs are established between supply chain configurations that (a) replace petroleum-based fuels by 100%, 75%, and 50% and (b) utilize the current energy infrastructures. Results suggest that cost-competitive fuels for the US transportation sector can be produced using domestically available coal, natural gas, and sustainably harvested biomass via an optimal network of CBGTL plants with significant GHG emissions reduction from petroleum-based processes. © 2012 American Institute of Chemical Engineers AIChE J, 2012
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paper_title: Supply chain design and optimization: Challenges and opportunities

paper_content:

Abstract Optimal supply chain design is vital to the success of industrial concerns now more than ever before. This paper reviews some principal research opportunities and challenges in the field of supply chain design. The growing area of enterprise-wide optimization and the increasing importance of energy and sustainability issues provide plentiful opportunities for supply chain design research. However, modeling, algorithmic, and computational challenges arise from these research opportunities. There are three major technical challenge areas where knowledge gaps can be addressed in supply chain design, namely multi-scale challenges, multi-objective and sustainability challenges, and multi-player challenges. This paper provides an overview of opportunity areas, a description of relevant technical challenges, and a perspective on how these challenges might be addressed in supply chain design. Illustrative examples are presented to illuminate avenues for future research.
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paper_title: District heating and cooling: Review of technology and potential enhancements

paper_content:

District energy systems are reviewed and possible future enhancements involving expanded thermal networks are considered. Various definitions, classifications and applications of district cooling and heating are discussed and elements of a district energy system are described. Also, the integration of combined heat and power (CHP) with district energy, permitting the cogeneration of electricity and heat, is examined from several points of view and for various locations and applications. One of the main advantages of district heating and cooling systems is their environmental benefits, which are explained in detail. The economics of a thermal network system, as a major factor in the justification for any project, is elaborated upon from industrial, governmental and societal perspectives. Furthermore, related regulations at government levels are suggested based on various investigations. The efficiency of district energy is discussed and exergy analysis, as an effective method for calculating the efficiency of a thermal network, is explained. Finally, other advantages of the district energy technology for communities are pointed out. This review of district heating and cooling considers technical, economic and environmental aspects and helps identify possibilities for future study on district energy systems.
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paper_title: Biomass-to-bioenergy and biofuel supply chain optimization: Overview, key issues and challenges

paper_content:

Abstract This article describes the key challenges and opportunities in modeling and optimization of biomass-to-bioenergy supply chains. It reviews the major energy pathways from terrestrial and aquatic biomass to bioenergy/biofuel products as well as power and heat with an emphasis on “drop-in” liquid hydrocarbon fuels. Key components of the bioenergy supply chains are then presented, along with a comprehensive overview and classification of the existing contributions on biofuel/bioenergy supply chain optimization. This paper identifies fertile avenues for future research that focuses on multi-scale modeling and optimization, which allows the integration across spatial scales from unit operations to biorefinery processes and to biofuel value chains, as well as across temporal scales from operational level to strategic level. Perspectives on future biofuel supply chains that integrate with petroleum refinery supply chains and/or carbon capture and sequestration systems are presented. Issues on modeling of sustainability and the treatment of uncertainties in bioenergy supply chain optimization are also discussed.
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paper_title: Multi-scale optimization for process systems engineering

paper_content:

Abstract Efficient nonlinear programming (NLP) algorithms and modeling platforms have led to powerful process optimization strategies. Nevertheless, these algorithms are challenged by recent evolution and deployment of multi-scale models (such as molecular dynamics and complex fluid flow) that apply over broad time and length scales. Integrated optimization of these models requires accurate and efficient reduced models (RMs). This study develops a rigorous multi-scale optimization framework that substitutes RMs for complex original detailed models (ODMs) and guarantees convergence to the original optimization problem. Based on trust region concepts this framework leads to three related NLP algorithms for RM-based optimization. The first follows the classical gradient-based trust-region method, the second avoids gradient calculations from the ODM, and the third avoids frequent recourse to ODM evaluations, using the concept of ϵ -exact RMs. We illustrate these algorithms with small examples and discuss RM-based optimization case studies that demonstrate their performance and effectiveness.
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paper_title: Advanced process engineering co-simulation using CFD-based reduced order models

paper_content:

The process and energy industries face the challenge of designing the next generation of plants to operate with unprecedented efficiency and near-zero emissions, while performing profitably amid fluctuations in costs for raw materials, finished products, and energy. To achieve these targets, the designers of future plants are increasingly relying upon modeling and simulation to create virtual plants that allow them to evaluate design concepts without the expense of pilot-scale and demonstration facilities. Two of the more commonly used simulation tools include process simulators for describing the entire plant as a network of simplified equipment models and computational fluid dynamic (CFD) packages for modeling an isolated equipment item in great detail by accounting for complex thermal and fluid flow phenomena. The Advanced Process Engineering Co-Simulator (APECS) sponsored by the U.S. Department of Energy’s (DOE) National Energy Technology Laboratory (NETL) has been developed to combine process simulation software with CFD-based equipment simulation software so that design engineers can analyze and optimize the coupled fluid flow, heat and mass transfer, and chemical reactions that drive overall plant performance (Zitney et al., 2006). The process/CFD software integration was accomplished using the process-industry standard CAPE-OPEN interfaces.
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paper_title: Supply chain optimisation for the process industries: Advances and opportunities

paper_content:

Supply chain management and optimisation is a critical aspect of modern enterprises and a flourishing research area. This paper presents a critical review of methodologies for enhancing the decision-making for process industry supply chains towards the development of optimal infrastructures (assets and network) and planning. The presence of uncertainty within supply chains is discussed as an important issue for efficient capacity utilisation and robust infrastructure decisions. The incorporation of business/financial and sustainability aspects is also considered and future challenges are identified.
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paper_title: Process/equipment co-simulation for design and analysis of advanced energy systems

paper_content:

Abstract The grand challenge facing the power and energy industries is the development of efficient, environmentally friendly, and affordable technologies for next-generation energy systems. To provide solutions for energy and the environment, the U.S. Department of Energy's (DOE) National Energy Technology Laboratory (NETL) and its research partners in industry and academia are relying increasingly on the use of sophisticated computer-aided process design and optimization tools. In this paper, we describe recent progress toward developing an Advanced Process Engineering Co-Simulator (APECS) for the high-fidelity design, analysis, and optimization of energy plants. The APECS software system combines steady-state process simulation with multiphysics-based equipment simulations, such as those based on computational fluid dynamics (CFD). These co-simulation capabilities enable design engineers to optimize overall process performance with respect to complex thermal and fluid flow phenomena arising in key plant equipment items, such as combustors, gasifiers, turbines, and carbon capture devices. In this paper we review several applications of the APECS co-simulation technology to advanced energy systems, including coal-fired energy plants with carbon capture. This paper also discusses ongoing co-simulation R&D activities and challenges in areas such as CFD-based reduced-order modeling, knowledge management, advanced analysis and optimization, and virtual plant co-simulation. Continued progress in co-simulation technology – through improved integration, solution, and deployment – will have profound positive impacts on the design and optimization of high-efficiency, near-zero emission fossil energy systems.
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paper_title: Supply chain modeling: past, present and future

paper_content:

Over the years, most of the firms have focused their attention to the effectiveness and efficiency of separate business functions. As a new way of doing business, however, a growing number of firms have begun to realize the strategic importance of planning, controlling, and designing a supply chain as a whole. In an effort to help firms capture the synergy of inter-functional and inter-organizational integration and coordination across the supply chain and to subsequently make better supply chain decisions, this paper synthesizes past supply chain modeling efforts and identifies key challenges and opportunities associated with supply chain modeling. We also provide various guidelines for the successful development and implementation of supply chain models.
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paper_title: Progresses and challenges in process industry supply chains optimization

paper_content:

Process industry supply chains (SCs) involve challenging and complex problems that have been addressed by the process systems engineering community in recent years. Shah in 2005 (Shah N: Process industry supply chains: advances and challenges. Comput Chem Eng 2005, 29 :1225–1235. The paper provides a comprehensive review on the process industry supply chains. Discusses major achievements and explores industrial examples. Challenges are identified where the evidence that supply chains of the future will be quite different from the past is recognized) stated in his review that process industry SCs were still striving to improve efficiency and responsiveness and were facing new challenges that needed further research. Optimization was pointed out as a possible path to follow aiming at building tools that can help the involved decision makers. From that time onwards several works have explored this pathway but there is still space for improvement, especially due to the outer shell of new emerging problems. The present paper provides a brief review of the progress that has been made on process industry SCs focusing in recent years (2008 onwards). Conclusions on the work done are strained, while the tendencies and future challenges in the area are identified.
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paper_title: Reduced Order Model Based on Principal Component Analysis for Process Simulation and Optimization

paper_content:

It is well-known that distributed parameter computational fluid dynamics (CFD) models provide more accurate results than conventional, lumped-parameter unit operation models used in process simulation. Consequently, the use of CFD models in process/equipment co-simulation offers the potential to optimize overall plant performance with respect to complex thermal and fluid flow phenomena. Because solving CFD models is time-consuming compared to the overall process simulation, we consider the development of fast reduced order models (ROMs) based on CFD results to closely approximate the high-fidelity equipment models in the co-simulation. By considering process equipment items with complicated geometries and detailed thermodynamic property models, this study proposes a strategy to develop ROMs based on principal component analysis (PCA). Taking advantage of commercial process simulation and CFD software (for example, Aspen Plus and FLUENT), we are able to develop systematic CFD-based ROMs for equipment model...
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paper_title: Enterprise-wide modeling & optimization—An overview of emerging research challenges and opportunities

paper_content:

The process systems engineering (PSE) as well as the operations research and management science (ORMS) literature has hitherto focused on disparate processes and functions within the enterprise. These themes have included upstream R&D pipeline management, planning and scheduling in batch and continuous manufacturing systems and more recently supply chain optimization under uncertainty. In reality, the modern process enterprise functions as a cohesive entity involving several degrees of cross-functional co-ordination across enterprise planning and process functions. The complex organizational structures underlying horizontally and vertically integrated process enterprises challenge our understanding of cross-functional co-ordination and its business impact. This article looks at the impact of enterprise-wide cross-functional coordination on enterprise performance, sustainability and growth prospects. Cross-functional coordination is defined as the integration of strategic and tactical decision-making processes involving the control of financial and inventory flows (both internal and external) as well as resource deployments. Initially, we demonstrate the existence of cross-functional decision-making dependencies using an enterprise network model. Subsequently, we discuss interactions between enterprise planning decisions involving project financing, debt-equity balancing, R&D portfolio selection, risk hedging with real derivative instruments, supply chain asset creation and marketing contracts which influence decision-making at the activity/process level. Several case studies are included to re-enforce the point that planning and process decisions need to be integrated.
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paper_title: Optimization framework for the simultaneous process synthesis, heat and power integration of a thermochemical hybrid biomass, coal, and natural gas facility

paper_content:

Abstract A thermochemical based process superstructure and its mixed-integer nonlinear optimization (MINLP) model are introduced to convert biomass (switchgrass), coal (Illinois #6), and natural gas to liquid (CBGTL) transportation fuels. The MINLP model includes simultaneous heat and power integration utilizing heat engines to recover electricity from the process waste heat. Four case studies are presented to investigate the effect of CO 2 sequestration (CCS) and greenhouse gas (GHG) reduction targets on the process topology along with detailed parametric analysis on the role of biomass and electricity prices. Topological similarities for the case studies include selection of solid/vapor-fueled gasifiers and iron-catalyzed Fischer-Tropsch units that facilitate the reverse water–gas-shift reaction. The break-even oil price was found to be $57.16/bbl for CCS with a 50% GHG reduction, $62.65/bbl for CCS with a 100% GHG reduction, $82.68/bbl for no CCS with a 50% GHG reduction, and $91.71 for no CCS with a 100% GHG reduction.
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paper_title: Enterprise-wide optimization for industrial demand side management: Fundamentals, advances, and perspectives

paper_content:

Abstract The active management of electricity demand, also referred to as demand side management (DSM), has been recognized as an effective approach to improving power grid performance and consumer benefits. Being large electricity consumers, the power-intensive process industries play a key role in DSM. In particular, enterprise-wide optimization (EWO) for industrial DSM has emerged as a major area of interest for both researchers and practitioners. In this work, we introduce the reader to the fundamentals of power system economics, provide a definition of DSM that reflects more strongly the consumer's perspective, and present a comprehensive review of existing works on EWO for industrial DSM. The review is organized into four parts, which correspond to the four main challenges that we identify as: (1) accurate modeling of operational flexibility, (2) integration of production and energy management, (3) decision-making across multiple time and space scales, and (4) optimization under uncertainty. Finally, we highlight research gaps and future opportunities in this area.
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paper_title: Municipal solid waste to liquid transportation fuels – Part III: An optimization-based nationwide supply chain management framework

paper_content:

An optimization-based supply chain management framework for municipal solid waste (MSW) to liquid transportation fuels (WTL) processes is presented. First, a thorough analysis of landfill operations and annual amounts of MSW that are deposited across the contiguous United States is conducted and compared with similar studies. A quantitative supply chain framework that simultaneously accounts for the upstream and downstream WTL value chain operations is then presented. A large-scale mixed-integer linear optimization model that captures the interactions among MSW feedstock availabilities and locations, WTL refinery locations, and product delivery locations and demand capacities is described. The model is solved for both the nationwide and statewide WTL supply chains across numerous case studies. The results of the framework yield insights into the strategic placement of WTL refineries in the United States as well as topological information on the feedstock and product flows. The results suggest that large-scale WTL supply chains can be competitive, with breakeven oil prices ranging between $64-$77 per barrel.
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paper_title: 5 Scope for the Application of Mathematical Programming Techniques in the Synthesis and Planning of Sustainable Processes

paper_content:

Sustainability has recently emerged as a key issue in process systems engineering (PSE). Mathematical programming techniques offer a general modeling framework for including environmental concerns in the synthesis and planning of chemical processes. In this paper, we review major contributions in process synthesis and supply chain management, highlighting the main optimization approaches that are available, including the handling of uncertainty and the multi-objective optimization of economic and environmental objectives. Finally, we discuss challenges and opportunities identified in the area.
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paper_title: Energy from gasification of solid wastes.

paper_content:

Gasification technology is by no means new: in the 1850s, most of the city of London was illuminated by "town gas" produced from the gasification of coal. Nowadays, gasification is the main technology for biomass conversion to energy and an attractive alternative for the thermal treatment of solid waste. The number of different uses of gas shows the flexibility of gasification and therefore allows it to be integrated with several industrial processes, as well as power generation systems. The use of a waste-biomass energy production system in a rural community is very interesting too. This paper describes the current state of gasification technology, energy recovery systems, pre-treatments and prospective in syngas use with particular attention to the different process cycles and environmental impacts of solid wastes gasification.
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paper_title: Using GREENSCOPE indicators for sustainable computer-aided process evaluation and design

paper_content:

Abstract Manufacturing sustainability can be increased by educating those who design, construct, and operate facilities, and by using appropriate tools for process evaluation and design. The U.S. Environmental Protection Agency's GREENSCOPE methodology and tool, for evaluation and design of chemical processes, suits these purposes. This work describes example calculations of GREENSCOPE indicators for the oxidation of toluene and puts them into context with best- and worst-case limits. Data available from the process is transformed by GREENSCOPE into understandable information which describes sustainability. An optimization is performed for various process conversions, with results indicating a maximum utility at intermediate conversions. Lower conversions release too much toluene through a purge stream; higher conversions lead to the formation of too many byproducts. Detailed results are elucidated through the context of best- and worst-case limits and graphs of total utility and GREENSCOPE indicator values, which are calculated within an optimization framework for the first time.
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paper_title: Waste-to-energy: A review of the status and benefits in USA.

paper_content:

The USA has significant experience in the field of municipal solid waste management. The hierarchy of methodologies for dealing with municipal solid wastes consists of recycling and composting, combustion with energy recovery (commonly called waste-to-energy) and landfilling. This paper focuses on waste-to-energy and especially its current status and benefits, with regard to GHG, dioxin and mercury emissions, energy production and land saving, on the basis of experience of operating facilities in USA.
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paper_title: Methods and tools for sustainable process design

paper_content:

After overcoming its earlier denial of negative environmental impacts, the chemical industry has been working toward enhancing its sustainability. Early efforts focused on reducing pollution from individual processes, while today, the focus is on reducing impacts throughout the life cycle. Current methods for sustainable process design solve large multiobjective optimization problems, and attempt to consider economic, environmental and social aspects. This paper provides an overview of recent developments in sustainable process design and its applications. These methods use the latest advances in process systems engineering, but are lagging in their use of advances in Sustainable Engineering. More work is needed for considering impacts over the full life cycle boundary, and to ensure that sustainable designs do not exceed nature's capacity to provide the needed ecosystem goods and services.
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paper_title: Combining petroleum coke and natural gas for efficient liquid fuels production

paper_content:

Abstract This work explores the technical feasibility and economic profitability of converting petroleum coke (petcoke) and natural gas to liquid fuels via Fischer-Tropsch synthesis. Different petcoke conversion strategies were examined to determine the conversion pathway which can be competitive with current market prices with little or no adverse environmental impacts. Three main design approaches were considered: petcoke gasification only, combined petcoke gasification and natural gas reforming through traditional processing steps, and combined petcoke gasification and natural gas reforming by directly integrating the gasifier's radiant cooler with the gas reformer. The designs investigated included scenarios with and without carbon capture and sequestration, and with and without CO2 emission tax penalties. The performance metrics considered included net present value, life cycle greenhouse gas emissions, and the cost of CO2 avoided. The design configuration that integrated natural gas reforming with the gasification step directly showed to be the more promising design for the wide range of analyses performed. The Aspen Plus simulation files have been made freely available to the public.
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paper_title: Work and Heat Integration: An emerging research area

paper_content:

Abstract The extension from Heat Integration (HI) and design of Heat Exchanger Networks (HENs) to including heating and cooling effects from pressure changing equipment has been referred to as Work and Heat Integration and design of Work and Heat Exchange Networks (WHENs). This is an emerging research area of Process Synthesis, however, WHENs is a considerably more complex design task than HENs. A key challenge is the fact that temperature changes (related to heat) and pressure changes (related to work) of process streams are interacting. Changes in inlet temperatures to compressors and expanders resulting from heat integration will influence work consumption and production. Likewise, pressure changes by compression and expansion will change the temperatures of process streams, thus affecting heat integration. As a result, Composite and Grand Composite Curves will change shape due to pressure changes in the process. The thermodynamic path of process streams from supply (pressure, temperature) to target state is not known and depends on the sequence of heating, cooling, compression and expansion. This paper introduces a definition and describes the development of WHENs. Future research challenges related to methodology development and industrial applications will be addressed. The potential of WHENs will be indicated through examples in literature.
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paper_title: Global optimization for the synthesis of integrated water systems in chemical processes

paper_content:

In this paper, we address the problem of optimal synthesis of an integrated water system, where water using processes and water treatment operations are combined into a single network such that the total cost of obtaining freshwater for use in the water using operations, and treating wastewater is globally minimized. A superstructure that incorporates all feasible design alternatives for water treatment, reuse and recycle, is proposed. We formulate the optimization of this structure as a non-convex Non-Linear Programming (NLP) problem, which is solved to global optimality. The problem takes the form of a non-convex Generalized Disjunctive Program (GDP) if there is a flexibility of choosing different treatment technologies for the removal of the various contaminants in the wastewater streams. A new deterministic spatial branch and contract algorithm is proposed for optimizing such systems, in which piecewise under- and over-estimators are used to approximate the non-convex terms in the original model to obtain a convex relaxation whose solution gives a lower bound on the global optimum. These lower bounds are made to converge to the solution within a branch and bound procedure. Several examples are presented to illustrate the optimization of the integrated networks using the proposed algorithm.
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paper_title: Indicators of Sustainable Development for Industry

paper_content:

Despite numerous actions worldwide which call for adoption of more sustainable strategies, relatively little has been done on a practical level so far on the pretext that the issue is too complex and not fully understood. This paper follows the argument that it is important that today's decision-makers address the issue of sustainability, however imperfectly, as ignoring it may only exacerbate the problem for future generations. In particular, the paper concentrates on measuring the level of sustainability of industry with he aim of further informing the debate in this area. It proposes a general framework with a relatively simple, yet comprehensive set of indicators for identification of more sustainable practices for industry. The indicators cover the three aspects of sustainability—environmental, economic and social—and among others, include environmental impacts, financial and ethical indicators. The framework is applicable across industry; however, more specific indicators for different sectors have to be defined separately, on a case-by-case basis. It allows a modular approach for gradual incorporation of the framework into the organizational structure. The life cycle approach ensures that the most important stages in the life cycle and their impacts are identified and targeted for improvements. The framework also provides a link between micro and macro-aspects of sustainable development through appropriate indicators. Thus, it serves as a tool which can assist companies in assessing their performance with regard to goals and objectives embedded in the idea of sustainable development.
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paper_title: A Modular Approach to Sustainability Assessment and Decision Support in Chemical Process Design

paper_content:

In chemical and allied industries, process design sustainability has gained public concern in academia, industry, government agencies, and social groups. Over the past decade, a variety of sustainability indicators have been introduced, but with various challenges in application. It becomes clear that the industries need urgently practical tools for conducting systematic sustainability assessment on existing processes and/or new designs and, further, for helping derive the most desirable design decisions. This paper presents a systematic, general approach for sustainability assessment and design selection through integrating hard (quantitative) economic and environmental indicators along with soft (qualitative) indicators for social criteria into design activities. The approach contains four modules: a process simulator module, an equipment and inventory acquisition module, a sustainability assessment module, and a decision support module. The modules fully utilize and extend the capabilities of the process simulator Aspen Plus, Aspen Simulation Workbook, and a spreadsheet, where case model development, data acquisition and analysis, team contribution assessment, and decision support are effectively integrated. The efficacy of the introduced approach is illustrated by the example of biodiesel process design, where insightful sustainability analysis and persuasive decision support show its superiority over commonly practiced technoeconomy evaluation approaches.
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paper_title: ENVIRONMENTALLY CONSCIOUS CHEMICAL PROCESS DESIGN

paper_content:

▪ Abstract The environment has emerged as an important determinant of the performance of the modern chemical industry. This paper reviews approaches for incorporating environmental issues into the design of new processes and manufacturing facilities. The organizational framework is the design process itself, which includes framing the problem and generating, analyzing, and evaluating alternatives. A historical perspective on the chemical process synthesis problem illustrates how both performance objectives and the context of the design have evolved to the point where environmental issues must be considered throughout the production chain. In particular, the review illustrates the need to view environmental issues as part of the design objectives rather than as constraints on operations. A concluding section identifies gaps in the literature and opportunities for additional research.
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paper_title: Multi-objective optimization of process cogeneration systems with economic, environmental, and social tradeoffs

paper_content:

Process cogeneration is an effective strategy for exploiting the positive aspects of combined heat and power in the process industry. Traditionally, decisions for process cogeneration have been based mostly on economic criteria. With the growing interest in sustainability issues, there is need to consider economic, environmental, and social aspects of cogeneration. The objective of this article is to develop an optimization framework for the design of process cogeneration systems with economic, environmental, and social aspects. Process integration is used as the coordinating framework for the optimization formulation. First, heat integration is carried out to identify the heating utility requirements. Then, a multi-header steam system is designed and optimized for inlet steam characteristics and their impact on power, fixed and operating costs, greenhouse gas emissions, and jobs. A genetic algorithm is developed to solve the optimization problem. Multi-objective tradeoffs between the economic, environmental, and social aspects are studied through Pareto tradeoffs. A case study is solved to illustrate the applicability of the proposed procedure.
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paper_title: Environmentally conscious long-range planning and design of supply chain networks

paper_content:

Abstract In this paper, a mathematical programming-based methodology is presented for the explicit inclusion of life cycle assessment (LCA) criteria as part of the strategic investment decisions related to the design and planning of supply chain networks. By considering the multiple environmental concerns together with the traditional economic criteria, the planning task is formulated as a multi-objective optimization problem. Over a long-range planning horizon, the methodology utilizes mixed integer modelling techniques to address strategic decisions involving the selection, allocation and capacity expansion of processing technologies and assignment of transportation links required to satisfy the demands at the markets. At the operational level, optimal production profiles and flows of material between various components within the supply chain are determined. As such, the formulation presented here combines the elements of the classical plant location and capacity expansion problems with the principles of LCA to develop a quantitative decision-support tool for environmentally conscious strategic investment planning.
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paper_title: Sustainable development of primary steelmaking under novel blast furnace operation and injection of different reducing agents

paper_content:

Abstract This paper presents a numerical study of economics and environmental impact of an integrated steelmaking plant, using surrogate, empirical and shortcut models based on mass and energy balance equations for the unit operations. In addition to the steelmaking processes, chemical processes such as pressure/temperature swing adsorption, membrane, chemical absorption technologies are included for gas treatment. A methanol plant integrated with a combined heat and power plant forms a polygeneration system that utilizes energy and gases of the site. The overall model has been applied using mathematical programming to find an optimal design and operation of the integrated plant for an economic objective under several development stages of the technology. New concepts studied are blast furnace operation with different degrees of top gas recycling and oxygen enrichment of the blast to full oxygen blast furnace. Coke in the process may be partially replaced with other carbon carriers. The system is optimized by maximizing the net present value, which includes investment costs for the new unit processes as well as costs of feed materials, CO 2 emission and sequestration, operation costs and credit for products produced. The effect of using different fuels such as oil, natural gas, pulverized coal, coke oven gas, charcoal and biomass is studied, particularly focusing on biomass torrefaction and the effect of integration on arising reductant in steelmaking to reduce emissions from the system. The effects of steel plant capacity on the optimal choice of carbon carriers are also studied. It is demonstrated that it is possible to decrease the specific CO 2 emissions of primary steelmaking from fossil fuels from 1.6 t of CO 2 to a level of 0.75–1.0 t and further by more than 50% through the integration of biofuels in considered scenarios.
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paper_title: Optimization of Coke Oven Gas Desulphurization and Combined Cycle Power Plant Electricity Generation

paper_content:

Many steel refineries generate significant quantities of coke oven gas (COG), which is in some cases used only to generate low pressure steam and small amounts of electric power. In order to improve energy efficiency and reduce net greenhouse gas emissions, a combined cycle power plant (CCPP) where COG is used as fuel is proposed. However, desulfurization is necessary before the COG can be used as a fuel input for a CCPP. Using a local steel refinery as a case study, a proposed desulfurization process is designed to limit the H2S content in COG to less than 1 ppmv, and simulated using ProMax. In addition, the proposed CCPP plant is simulated in Aspen Plus and is optimized using GAMS to global optimality with net present value as the objective function. Furthermore, the carbon tax is considered in this study. The optimized CCPP plant was observed to generate more than twice the electrical efficiency when compared to the status quo for the existing steel refinery. Thus, by generating more electricity within...
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paper_title: Cannibals with Forks: The Triple Bottom Line of 21st Century Business

paper_content:

Introduction - is capitalism sustainable? seven revolutions for sustainable capitalism revolution 1 - competition - going for the triple win revolution 2 - values - from me to we revolution 3 - information and transparency - no hiding place revolution 4 - lifecylces - from conception to resurrection revolution 5 - partnerships - after the honeymoon revolution 6 - time - three scenarios revolution 7 - corporate governance - stake in the future the sustainability transition - value shifts, value migrations the worlds of money and power the sustainability audit - how are you placed?
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paper_title: Selection of the Economic Objective Function for the Optimization of Process Flow Sheets

paper_content:

This paper highlights the problem of selecting the most suitable economic optimization criteria for mathematical programming approaches to the synthesis, design, and optimization of chemical process flow sheets or their subsystems. Minimization of costs and maximization of profit are the most frequently used economic criteria in technical papers. However, there are many other financial measures which can lead to different optimal solutions if applied in the objective function. This paper describes the characteristics of the optimal solutions obtained with various optimization criteria like the total annual cost, the profit, the payback time, the equivalent annual cost, the net present worth, and the internal rate of return. It was concluded that the maximization of the net present worth (NPW) with a discount rate equal to the minimum acceptable rate of return (MARR) is probably the most appropriate method for the optimization of process flow sheets or their subsystems. Similar or equal solutions can be ob...
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paper_title: Product and Process Design Principles: Synthesis, Analysis, and Evaluation

paper_content:

1. Introduction to Chemical Product Design 1S Supplement to Chapter 1 2. Product-Development Process PART 1 BASIC CHEMICALS PRODUCT DESIGN 3. Materials Technology for Basic Chemicals: Molecular-Structure Design 3S Supplement to Chapter 3 4. Process Creation for Basic Chemicals 5. Simulation to Assist in Process Creation 6. Heuristics for Process Synthesis 7. Reactor Design and Synthesis of Networks Containing Reactors 7S Supplement to Chapter 7 8. Synthesis of Separation Trains 9. Heat and Power Integration 9S Suppliment to Chapter 9 Second Law Analysis 10. Mass Integration 11. Optimal Design and Scheduling of Batch Processes 12. Plantwide Controllability Assessment 12S Supplement to Chapter 12 Flowsheet Controllability Analysis 13. Basic Chemicals Product Design Case Studies PART 2 INDUSTRIAL CHEMICALS PRODUCT DESIGN 14. Materials and Process/Manufacturing Technologies for Industrial Chemical Products 15. Industrial Chemicals Product Design Case Studies PART 3 CONFIGURED CONSUMER PRODUCT DESIGN 16. Materials, Process/Manufacturing, and Product Technologies for Con"?gured Consumer Products 16S Supplement to Chapter 16 17. Con"?gured Consumer Product Design Case Studies PART 4 DETAILED DESIGN, EQUIPMENT SIZING, OPTIMIZATION, AND PRODUCT-QUALITY ANALYSIS 18. Heat Exchanger Design 19. Separation Tower Design 20. Pumps, Compressors, and Expanders 21. Polymer Compounding 22. Cost Accounting and Capital Cost Estimation 22S Supplement to Chapter 22 23. Annual Costs, Earnings, and Pro"?tability Analysis 23S Supplement to Chapter 23 24. Design Optimization 25. Six-Sigma Design Strategies PART 5 DESIGN REPORT 26. Written Reports and Oral Presentations APPENDIXES INDICES
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paper_title: Introduction to Stochastic Programming

paper_content:

The aim of stochastic programming is to find optimal decisions in problems which involve uncertain data. This field is currently developing rapidly with contributions from many disciplines including operations research, mathematics, and probability. At the same time, it is now being applied in a wide variety of subjects ranging from agriculture to financial planning and from industrial engineering to computer networks. This textbook provides a first course in stochastic programming suitable for students with a basic knowledge of linear programming, elementary analysis, and probability. The authors aim to present a broad overview of the main themes and methods of the subject. Its prime goal is to help students develop an intuition on how to model uncertainty into mathematical problems, what uncertainty changes bring to the decision process, and what techniques help to manage uncertainty in solving the problems.In this extensively updated new edition there is more material on methods and examples including several new approaches for discrete variables, new results on risk measures in modeling and Monte Carlo sampling methods, a new chapter on relationships to other methods including approximate dynamic programming, robust optimization and online methods.The book is highly illustrated with chapter summaries and many examples and exercises. Students, researchers and practitioners in operations research and the optimization area will find it particularly of interest. Review of First Edition:"The discussion on modeling issues, the large number of examples used to illustrate the material, and the breadth of the coverage make'Introduction to Stochastic Programming' an ideal textbook for the area." (Interfaces, 1998)
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paper_title: Process synthesis optimization and flexibility evaluation of air separation cycles

paper_content:

The solution is discussed of the process synthesis problem for cryogenic air separation using techniques from process synthesis optimization. The mass and energy balances for the process are represented by a simplified algebraic model in which material stream flows and pressures appear as continuous variables and the various equipment choices for components of the air separation cycle are represented by binary variables. The resulting model corresponds to a mixed-integer nonlinear programming (MINLP) formulation and enables numerical optimization of the cycle. The two problems addressed are the selection of the optimal equipment set for a given product slate and the flexibility determination of the chosen cycle. The flexibility analysis is complemented with unique visual techniques that depict the feasible region and use of the recently proposed convex-hull approach. The calculations are illustrated for low-purity (95%) oxygen plants using the Lachmann cycle. © 2005 American Institute of Chemical Engineers AIChE J, 2005
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paper_title: Production of FT transportation fuels from biomass; technical options, process analysis and optimisation, and development potential

paper_content:

Fischer–Tropsch (FT) diesel derived from biomass via gasification is an attractive clean and carbon neutral transportation fuel, directly usable in the present transport sector. System components necessary for FT diesel production from biomass are analysed and combined to a limited set of promising conversion concepts. The main variations are in gasification pressure, the oxygen or air medium, and in optimisation towards liquid fuels only, or towards the product mix of liquid fuels and electricity. The technical and economic performance is analysed. For this purpose, a dynamic model was built in Aspen Plus®, allowing for direct evaluation of the influence of each parameter or device, on investment costs, FT and electricity efficiency and resulting FT diesel costs. FT diesel produced by conventional systems on the short term and at moderate scale would probably cost 16 €/GJ. In the longer term (large scale, technological learning, and selective catalyst), this could decrease to 9 €/GJ. Biomass integrated gasification FT plants can only become economically viable when crude oil price levels rise substantially, or when the environmental benefits of green FT diesel are valued. Green FT diesel also seems 40–50% more expensive than biomass derived methanol or hydrogen, but has clear advantages with respect to applicability to the existing infrastructure and car technology.
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paper_title: Recent Advances in Mathematical Programming Techniques for the Optimization of Process Systems under Uncertainty

paper_content:

Abstract Optimization under uncertainty has been an active area of research for many years. However, its application in Process Synthesis has faced a number of important barriers that have prevented its effective application. Barriers include availability of information on the uncertainty of the data (ad-hoc or historical), determination of the nature of the uncertainties (exogenous vs. endogenous), selection of an appropriate strategy for hedging against uncertainty (robust optimization vs. stochastic programming), large computational expense (often orders of magnitude larger than deterministic models), and difficulty in the interpretation of the results by non-expert users. In this paper, we describe recent advances that have addressed some of these barriers.
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paper_title: Analysis Synthesis And Design Of Chemical Processes

paper_content:

Thank you for downloading analysis synthesis and design of chemical processes. Maybe you have knowledge that, people have search numerous times for their chosen readings like this analysis synthesis and design of chemical processes, but end up in infectious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they juggled with some harmful virus inside their desktop computer.
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paper_title: Evolution of concepts and models for quantifying resiliency and flexibility of chemical processes

paper_content:

Abstract This paper provides a historical perspective and an overview of the pioneering work that Manfred Morari developed in the area of resiliency for chemical processes. Motivated by unique counter-intuitive examples, we present a review of the early mathematical formulations and solution methods developed by Grossmann and co-workers for quantifying Static Resiliency (Flexibility). We also give a brief overview of some of the seminal ideas by Manfred Morari and co-workers in the area of Dynamic Resiliency. Finally, we provide a review of some of the recent developments that have taken place since that early work.
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paper_title: Large-scale gasification-based coproduction of fuels and electricity from switchgrass

paper_content:

Large-scale gasification-based systems for producing Fischer-Tropsch (F-T) fuels (diesel and gasoline blendstocks), dimethyl ether (DME), or hydrogen from switchgrass – with electricity as a coproduct in each case are assessed using a self-consistent design, simulation, and cost analysis framework. We provide an overview of alternative process designs for coproducing these fuels and power assuming commercially mature technology performance and discuss the commercial status of key component technologies. Overall efficiencies (lower-heating-value basis) of producing fuels plus electricity in these designs ranges from 57% for F-T fuels, 55–61% for DME, and 58–64% for hydrogen. Detailed capital cost estimates for each design are developed, on the basis of which prospective commercial economics of future large-scale facilities that coproduce fuels and power are evaluated. © 2009 Society of Chemical Industry and John Wiley & Sons, Ltd
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paper_title: Flexibility analysis of process supply chain networks

paper_content:

Abstract One of the key fundamentals for organizations to remain competitive in the present economic climate is to effectively manage their supply chains under uncertainty. The notion of supply chain flexibility attempts to characterize the ability of a supply chain to perform satisfactorily in the face of uncertainty. However, limited quantitative analysis is available. In this work, we utilize a flexibility analysis framework developed within the context of process operations and design to characterize supply chain flexibility. This framework also provides a quantitative mapping to various types of flexibility discussed in the operations research and management science literature. Two case studies are included to illustrate the application of this framework for analyzing the flexibility of existing supply chain processes, as well as utilizing it in supply chain design.
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paper_title: Robust optimization -- methodology and applications

paper_content:

Robust Optimization (RO) is a modeling methodology, combined with computational tools, to process optimization problems in which the data are uncertain and is only known to belong to some uncertainty set. The paper surveys the main results of RO as applied to uncertain linear, conic quadratic and semidefinite programming. For these cases, computationally tractable robust counterparts of uncertain problems are explicitly obtained, or good approximations of these counterparts are proposed, making RO a useful tool for real-world applications. We discuss some of these applications, specifically: antenna design, truss topology design and stability analysis/synthesis in uncertain dynamic systems. We also describe a case study of 90 LPs from the NETLIB collection. The study reveals that the feasibility properties of the usual solutions of real world LPs can be severely affected by small perturbations of the data and that the RO methodology can be successfully used to overcome this phenomenon.
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paper_title: Comparative life cycle environmental assessment of CCS technologies

paper_content:

Abstract Hybrid life cycle assessment is used to assess and compare the life cycle environmental impacts of electricity generation from coal and natural gas with various carbon capture and storage (CCS) technologies consisting of post-combustion, pre-combustion or oxyfuel capture; pipeline CO 2 transport and geological storage. The systems with a capture efficiency of 85–96% decrease net greenhouse gas emission by 64–78% depending on the technology used. Calculation of other life cycle impacts shows significant trade-offs with fresh-water eutrophication and toxicity potentials. Human toxicity impact increases by 40–75%, terrestrial ecotoxicity by 60–120%, and freshwater eutrophication by 60–200% for the different technologies. There is a two- to four-fold increase in freshwater ecotoxicity potential in the post-combustion approach. The increase in toxicity for pre-combustion systems is 40–80% for the coal and 50–90% for the gas power plant. The increase in impacts for the oxyfuel approach mainly depends on energy demand for the air separation unit, giving an increase in various toxicity potentials of 35–70% for coal and 60–105% for natural gas system. Most of the increase in impacts with CCS systems is due to the energy penalty and the infrastructure development chain.
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paper_title: Life Cycle Assessment: Principles, Practice and Prospects

paper_content:

Life Cycle Assessment (LCA) has developed in Australia over the last 20 years into a technique for systematically identifying the resource flows and environmental impacts associated with the provision of products and services. Interest in LCA has accelerated alongside growing demand to assess and reduce greenhouse gas emissions across different manufacturing and service sectors. ::: ::: Life Cycle Assessment focuses on the reflective practice of LCA, and provides critical insight into the technique and how it can be used as a problem-solving tool. It describes the distinctive strengths and limitations of LCA, with an emphasis on practice in Australia, as well as the application of LCA in waste management, the built environment, water and agriculture. Supported by examples and case studies, each chapter investigates contemporary challenges for environmental assessment and performance improvement in these key sectors. ::: ::: LCA methodologies are compared to the emerging climate change mitigation policy and practice techniques, and the uptake of ‘quick’ LCA and management tools are considered in the light of current and changing environmental agendas. The authors also debate the future prospects for LCA technique and applications.
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paper_title: Recent developments in Life Cycle Assessment

paper_content:

Life Cycle Assessment is a tool to assess the environmental impacts and resources used throughout a product's life cycle, i.e., from raw material acquisition, via production and use phases, to waste management. The methodological development in LCA has been strong, and LCA is broadly applied in practice. The aim of this paper is to provide a review of recent developments of LCA methods. The focus is on some areas where there has been an intense methodological development during the last years. We also highlight some of the emerging issues. In relation to the Goal and Scope definition we especially discuss the distinction between attributional and consequential LCA. For the Inventory Analysis, this distinction is relevant when discussing system boundaries, data collection, and allocation. Also highlighted are developments concerning databases and Input-Output and hybrid LCA. In the sections on Life Cycle Impact Assessment we discuss the characteristics of the modelling as well as some recent developments for specific impact categories and weighting. In relation to the Interpretation the focus is on uncertainty analysis. Finally, we discuss recent developments in relation to some of the strengths and weaknesses of LCA.
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paper_title: System boundary selection in life-cycle inventories using hybrid approaches.

paper_content:

Life-cycle assessment (LCA) is a method for evaluating the environmental impacts of products holistically, including direct and supply chain impacts. The current LCA methodologies and the standards by the International Organization for Standardization (ISO) impose practical difficulties for drawing system boundaries; decisions on inclusion or exclusion of processes in an analysis (the cutoff criteria) are typically not made on a scientific basis. In particular, the requirement of deciding which processes could be excluded from the inventory can be rather difficult to meet because many excluded processes have often never been assessed by the practitioner, and therefore, their negligibility cannot be guaranteed. LCA studies utilizing economic input-output analysis have shown that, in practice, excluded processes can contribute as much to the product system under study as included processes; thus, the subjective determination of the system boundary may lead to invalid results. System boundaries in LCA are discussed herein with particular attention to outlining hybrid approaches as methods for resolving the boundary selection problem in LCA. An input-output model can be used to describe at least a part of a product system, and an ISO-compatible system boundary selection procedure can be designed by applying hybrid input-output-assisted approaches. There are several hybrid input-output analysis-based LCA methods that can be implemented in practice for broadening system boundary and also for ISO compliance.
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paper_title: Life cycle analyses of bulk-scale solid oxide fuel cell power plants and comparisons to the natural gas combined cycle

paper_content:

In this work, detailed cradle-to-grave life cycle analyses are performed for a current state-of-the art natural gas combined cycle and a bulk-scale solid fuel cell power plant fuelled by natural gas. Life cycle inventories are performed for multiple configurations of each plant, including designs with carbon capture capability. Consistent boundaries (including all supply chain and upstream processes) and unit bases for each process are defined for each process. The ReCiPe 2008 life cycle assessment method is used to quantify the impacts of each plant at both mid- and end-point levels. Three impact assessment perspectives (individualist, hierarchist, and egalitarian) are considered. The results of these life cycle analyses are compared in order to determine the environmental trade-offs between potential power generation pathways. Results indicate that power generation using solid oxide fuel cells has a smaller life cycle impact than the natural gas combined cycle when the entire life cycle of each option is considered.
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paper_title: Environmental Life-Cycle Assessment

paper_content:

Concept/Methodology History of Life Cycle inventory Systems Comparison of Methodologies Applications Industrial Application Data Bases/Data Quality Streamlining Eco-labeling Product Certification Policy Public Use Relationship to P2 Substainability Global Competitiveness Design for the Environment DFE in Europe Industrial DRE Applications Future Impacts Computer Tools European Perspective Total Cost Assessment Federal Activities Curriculum Development Future Trends.
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paper_title: Handbook on life cycle assessment operational guide to the ISO standards

paper_content:

Preface. Foreword. Part 1: LCA in Perspective. 1. Why a new Guide to LCA? 2. Main characteristics of LCA. 3. International developments. 4. Guiding principles for the present Guide. 5. Reading guide. Part 2a: Guide. Reading guidance. 1. Management of LCA projects: procedures. 2. Goal and scope definition. 3. Inventory analysis. 4. Impact assessment. 5. Interpretation. Appendix A: Terms, definitions and abbreviations. Part 2b: Operational annex. List of tables. Reading guidance. 1. Management of LCA projects: procedures. 2. Goal and scope definition. 3. Inventory analysis. 4. Impact assessment. 5. Interpretation. 6. References. Part 3: Scientific background. Reading guidance. 1. General introduction. 2. Goal and scope definition. 3. Inventory analysis. 4. Impact assessment. 5. Interpretation. 6. References. Annex A: Contributors. Appendix B: Areas of application of LCA. Appendix C: Partitioning economic inputs and outputs to product systems.
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paper_title: Methodologies for social life cycle assessment

paper_content:

Goal, Scope and Background. In recent years several different approaches towards Social Life Cycle Assessment (SLCA) have been developed. The purpose of this review is to compare these approaches in order to highlight methodological differences and general shortcomings. SLCA has several similarities with other social assessment tools, although, in order to limit the expanse of the review, only claims to address social impacts from an LCA-like framework are considered. Main Features. The review is to a large extent based on conference proceedings and reports, which are not all easily accessible, since very little has been published on SLCA in the open literature. The review follows the methodological steps of the environmental LCA (ELCA) known from the ISO 14044 standard. Results. The review reveals a broad variety in how the approaches address the steps of the ELCA methodology, particularly in the choice and formulation of indicators. The indicators address a wide variety of issues; some approaches focus on impacts created in the very close proximity of the processes included in the product system, whereas others focus on the more remote societal consequences. Only very little focus has been given to the use stage in the product life cycle. Another very important difference among the proposals is their position towards the use of generic data. Several of the proposals argue that social impacts are connected to the conduct of the company leading to the conclusion that each individual company in the product chain has to be assessed, whereas others claim that generic data can give a sufficiently accurate picture of the associated social impacts. Discussion. The SLCA approaches show that the perception of social impacts is very variable. An assessment focusing on social impacts created in the close proximity of the processes included in the product system will not necessarily point in the same direction as an assessment that focuses on the more societal consequences. This points toward the need to agree on the most relevant impacts to include in the SLCA in order to include the bulk of the situation. Regarding the use of generic data as a basis for the assessment, this obviously has an advantage over using site specific data in relation to practicality, although many authors behind the SLCA ESS-Submission Editor: Dr. David Hunkeler
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paper_title: A Modular Approach to Sustainability Assessment and Decision Support in Chemical Process Design

paper_content:

In chemical and allied industries, process design sustainability has gained public concern in academia, industry, government agencies, and social groups. Over the past decade, a variety of sustainability indicators have been introduced, but with various challenges in application. It becomes clear that the industries need urgently practical tools for conducting systematic sustainability assessment on existing processes and/or new designs and, further, for helping derive the most desirable design decisions. This paper presents a systematic, general approach for sustainability assessment and design selection through integrating hard (quantitative) economic and environmental indicators along with soft (qualitative) indicators for social criteria into design activities. The approach contains four modules: a process simulator module, an equipment and inventory acquisition module, a sustainability assessment module, and a decision support module. The modules fully utilize and extend the capabilities of the process simulator Aspen Plus, Aspen Simulation Workbook, and a spreadsheet, where case model development, data acquisition and analysis, team contribution assessment, and decision support are effectively integrated. The efficacy of the introduced approach is illustrated by the example of biodiesel process design, where insightful sustainability analysis and persuasive decision support show its superiority over commonly practiced technoeconomy evaluation approaches.
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paper_title: 2.1. Econometric techniques: Theory versus practice

paper_content:

This paper introduces the basic concepts used in econometric modeling, and describes five prescriptions to avoid common real-world pitfalls in that style of modeling. The paper begins by comparing econometric modeling with other forms of modeling used in energy modeling and engineering. It describes what an econometric model is, and how to build one. It then gives a detailed explanation of many facets of the five prescriptions: pay attention to uncertainty; don't expect a free lunch when devising specifications; pay attention to prior information; don't expect to draw conclusions without adequate data; and check the historical track record of your model. The issues of generalization and robustness over time receive special attention; they are important in practice, and subtle in theory. Finally, the paper discusses model development in practice, building upon experience with PURHAPS, a model I developed for the Energy Information Administration (EIA).
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paper_title: Energy models for demand forecasting—A review

paper_content:

Energy is vital for sustainable development of any nation – be it social, economic or environment. In the past decade energy consumption has increased exponentially globally. Energy management is crucial for the future economic prosperity and environmental security. Energy is linked to industrial production, agricultural output, health, access to water, population, education, quality of life, etc. Energy demand management is required for proper allocation of the available resources. During the last decade several new techniques are being used for energy demand management to accurately predict the future energy needs. In this paper an attempt is made to review the various energy demand forecasting models. Traditional methods such as time series, regression, econometric, ARIMA as well as soft computing techniques such as fuzzy logic, genetic algorithm, and neural networks are being extensively used for demand side management. Support vector regression, ant colony and particle swarm optimization are new techniques being adopted for energy demand forecasting. Bottom up models such as MARKAL and LEAP are also being used at the national and regional level for energy demand management.
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paper_title: OSeMOSYS: The Open Source Energy Modeling System: An introduction to its ethos, structure and development

paper_content:

This paper discusses the design and development of the Open Source Energy Modeling System (OSeMOSYS). It describes the model's formulation in terms of a 'plain English' description, algebraic formulation, implementation'in terms of its full source code, as well as a detailed description of the model inputs, parameters, and outputs. A key feature of the OSeMOSYS implementation is that it is contained in less than five pages of documented, easily accessible code. Other existing energy system models that do not have this emphasis on compactness and openness makes the barrier to entry by new users much higher, as well as making the addition of innovative new functionality very difficult. The paper begins by describing the rationale for the development of OSeMOSYS and its structure. The current preliminary implementation of the model is then demonstrated for a discrete example. Next, we explain how new development efforts will build on the existing OSeMOSYS codebase. The paper closes with thoughts regarding the organization of the OSeMOSYS community, associated capacity development efforts, and linkages to other open source efforts including adding functionality to the LEAP model.
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paper_title: Inside the integrated assessment models: Four issues in climate economics

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Good climate policy requires the best possible understanding of how climatic change will impact on human lives and livelihoods in both industrialized and developing counties. Our review of recent contributions to the climate-economics literature assesses 30 existing integrated assessment models in four key areas: the connection between model structure and the type of results produced; uncertainty in climate outcomes and projection of future damages; equity across time and space; and abatement costs and the endogeneity of technological change. Differences in treatment of these issues are substantial and directly affect model results and their implied policy prescriptions. Much can be learned about climate economics and modelling technique from the best practices in these areas; there is unfortunately no existing model that incorporates the best practices on all or most of the questions we examine.
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paper_title: Progress in integrated assessment and modelling

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Environmental processes have been modelled for decades. However. the need for integrated assessment and modeling (IAM) has,town as the extent and severity of environmental problems in the 21st Century worsens. The scale of IAM is not restricted to the global level as in climate change models, but includes local and regional models of environmental problems. This paper discusses various definitions of IAM and identifies five different types of integration that Lire needed for the effective solution of environmental problems. The future is then depicted in the form of two brief scenarios: one optimistic and one pessimistic. The current state of IAM is then briefly reviewed. The issues of complexity and validation in IAM are recognised as more complex than in traditional disciplinary approaches. Communication is identified as a central issue both internally among team members and externally with decision-makers. stakeholders and other scientists. Finally it is concluded that the process of integrated assessment and modelling is considered as important as the product for any particular project. By learning to work together and recognise the contribution of all team members and participants, it is believed that we will have a strong scientific and social basis to address the environmental problems of the 21st Century.
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paper_title: Designing a Model for the Glogbal Energy System—GENeSYS-MOD: An Application of the Open-Source Energy Modeling System (OSeMOSYS)

paper_content:

This paper develops a path for the global energy system up to 2050, presenting a new application of the open-source energy modeling system (OSeMOSYS) to the community. It allows quite disaggregate energy and emission analysis: Global Energy System Model (GENeSYS-MOD) uses a system of linear equations of the energy system to search for lowest-cost solutions for a secure energy supply, given externally defined constraints, mainly in terms of CO2-emissions. The general algebraic modeling system (GAMS) version of OSeMOSYS is updated to the newest version and, in addition, extended and enhanced to include e.g., a modal split for transport, an improved trading system, and changes to storages. The model can be scaled from small-scale applications, e.g., a company, to cover the global energy system. The paper also includes an application of GENeSYS-MOD to analyze decarbonization scenarios at the global level, broken down into 10 regions. Its main focus is on interdependencies between traditionally segregated sectors: electricity, transportation, and heating; which are all included in the model. Model calculations suggests that in order to achieve the 1.5–2 °C target, a combination of renewable energy sources provides the lowest-cost solution, solar photovoltaic being the dominant source. Average costs of electricity generation in 2050 are about 4 €cents/kWh (excluding infrastructure and transportation costs).
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paper_title: Opening the black box of energy modelling: strategies and lessons learned

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The global energy system is undergoing a major transition, and in energy planning and decision-making across governments, industry and academia, models play a crucial role. Because of their policy relevance and contested nature, the transparency and open availability of energy models and data are of particular importance. Here we provide a practical how-to guide based on the collective experience of members of the Open Energy Modelling Initiative (Openmod). We discuss key steps to consider when opening code and data, including determining intellectual property ownership, choosing a licence and appropriate modelling languages, distributing code and data, and providing support and building communities. After illustrating these decisions with examples and lessons learned from the community, we conclude that even though individual researchers' choices are important, institutional changes are still also necessary for more openness and transparency in energy research.
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paper_title: Methods for IA: The challenges and opportunities ahead

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There is increasing recognition and credibility for the rapidly evolving field of Integrated Assessment (IA). Within the setting of the political arena it is accepted that IA can be supportive in the long-term policy planning process, while in the scientific arena more and more scientists do realise the complementary value of IA research. One of the best indicators for this increased recognition is the establishment of the European Forum on Integrated Environmental Assessment (EFIEA) by the European Commission DGXII. In spite of this growing appreciation for IA, the methodological basis of IA is still narrow, and lags behind the high expectations from the outside world. Broadening the basis of the methodologies underlying IA should therefore be one of the top priorities of the IA community. This paper deals with some ideas which could form a basis for an IA research agenda for the next 5–10 years. One of the problems of IA is still the many definitions and interpretations that circulate (Weyant et al. [118], Rotmans and Dowlatabadi [100], Parson [85–87], Ravetz [91], Jaeger et al. [49]). Notwithstanding this diversity, these definitions have two elements in common, i.e., interdisciplinarity and decision support. These two common elements make Integrated Assessment difficult to plan and even harder to conduct. Instead of coming up with another definition of IA, we simply focus on the above commonalities as points of departure for exploring challenges for the future. Thus irrespective of whatever definition is taken, IA can be described as
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paper_title: MESAP/TIMES- Advanced Decision Support for Energy and Environmental Planning

paper_content:

In view of the requirements for climate and environmental protection and the increased international competition within a deregulated energy market, authorities and energy providers want to improve their competence of strategic planning in order to identify robust decisions for the upcoming threats and opportunities. This paper presents the planning tool MESAP/TIMES which integrates the TIMES optimization model and the MESAP software environment for energy and environmental planning. Questions that may be studied with MESAP/TIMES range e.g. from the planning of a local energy system, over the evaluation of energy technologies on a national scale up to the analysis of carbon permit trading strategies in the international Kyoto protocol discussion.
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paper_title: Energy scientists must show their workings

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Public trust demands greater openness from those whose research is used to set policy, argues Stefan Pfenninger.
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paper_title: A review of energy systems models in the UK: Prevalent usage and categorisation

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In this paper, a systematic review of academic literature and policy papers since 2008 is undertaken with an aim of identifying the prevalent energy systems models and tools in the UK. A list of all referenced models is presented and the literature is analysed with regards sectoral coverage and technological inclusion, as well as mathematical structure of models.
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paper_title: What Does Europe Pay for Clean Energy? – Review of Macroeconomic Simulation Studies

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This paper analyses the macroeconomic costs of environmental regulation in European energy markets on the basis of existing macroeconomic simulation studies. The analysis comprises the European emssion trading scheme, energy taxes, measures in the transport sector, and the promotion of renewable energy sources. We find that these instruments affect the European economy, in particular the energy intensive industries and the industries that produce internationally tradeable goods. From a macroeconomic point of view, however, the costs of environmental regulation appear to be modest. The underlying environmental targets and the efficient design of regulation are key determinants for the cost burden.
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paper_title: Impacts of new energy technology using generalized input-output analysis

paper_content:

Abstract The economic and environmental impacts of several new energy technologies (high and low BTU coal gasification and the gas turbine topping cycle) were examined for the 1980–1985 time period. A projected 1980–1985 U.S. input-output matrix was augmented to include environmental and resource usage variables. Engineering studies were used to modify the input-output matrix to represent the introduction of new energy technologies. The results illustrate the high sensitivity of capital investment to the rate of growth of energy consumption. The results also illustrate several economic mechanisms that will help to hold total capital investment within its historical bounds as a percentage of GNP. The methodology and many possible applications and extensions of generalized input-output model are included. A short critique of the methodology is also presented.
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paper_title: Energy impact of consumption decisions

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The energy cost of goods and services is computed, and applications are discussed. The method utilizes the data base of input-output economics, but entails additional analysis. Applications range over consumption options for individuals, business, industry, and government; from the total energy cost of bus versus auto travel to the national import-export balance.
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paper_title: USEEIO: A new and transparent United States environmentally-extended input-output model

paper_content:

National-scope environmental life cycle models of goods and services may be used for many purposes, not limited to quantifying impacts of production and consumption of nations, assessing organization-wide impacts, identifying purchasing hotspots, analyzing environmental impacts of policies, and performing streamlined life cycle assessment. USEEIO is a new environmentally-extended input-output model of the United States fit for such purposes and other sustainable materials management applications. USEEIO melds data on economic transactions between 389 industry sectors with environmental data for these sectors covering land, water, energy and mineral usage and emissions of greenhouse gases, criteria air pollutants, nutrients and toxics, to build a life cycle model of 385 US goods and services. In comparison with existing US models, USEEIO is more current with most data representing year 2013, more extensive in its coverage of resources and emissions, more deliberate and detailed in its interpretation and combination of data sources, and includes formal data quality evaluation and description. USEEIO is assembled with a new Python module called the IO Model Builder capable of assembling and calculating results of user-defined input-output models and exporting the models into LCA software. The model and data quality evaluation capabilities are demonstrated with an analysis of the environmental performance of an average hospital in the US. All USEEIO files are publicly available bringing a new level of transparency for environmentally-extended input-output models.
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paper_title: Process to planet: A multiscale modeling framework toward sustainable engineering

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To prevent the chance of unintended environmental harm, engineering decisions need to consider an expanded boundary that captures all relevant connected systems. Comprehensive models for sustainable engineering may be developed by combining models at multiple scales. Models at the finest “equipment” scale are engineering models based on fundamental knowledge. At the intermediate “value chain” scale, empirical models represent average production technologies, and at the coarsest “economy” scale, models represent monetary and environmental exchanges for industrial sectors in a national or global economy. However, existing methods for sustainable engineering design ignore the economy scale, while existing methods for life cycle assessment do not consider the equipment scale. This work proposes an integrated, multiscale modeling framework for connecting models from process to planet and using them for sustainable engineering applications. The proposed framework is demonstrated with a toy problem, and potential applications of the framework including current and future work are discussed. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3332–3352, 2015
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paper_title: The National Energy Modeling System: A Large-Scale Energy-Economic Equilibrium Model

paper_content:

The National Energy Modeling System (NEMS) is a large-scale mathematical model that computes equilibrium fuel prices and quantities in the U.S. energy sector and is currently in use at the U.S. Department of Energy (DOE). At present, to generate these equilibrium values, NEMS iteratively solves a sequence of linear programs and nonlinear equations. This is a nonlinear Gauss-Seidel approach to arrive at estimates of market equilibrium fuel prices and quantities. In this paper, we present existence and uniqueness results for NEMS-type models based on a nonlinear complementarity/variational inequality problem format. Also, we document mathematically, for the first time, how the inputs and the outputs for each NEMS module link together.
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paper_title: Application of rolling horizon optimization to an integrated solid-oxide fuel cell and compressed air energy storage plant for zero-emissions peaking power under uncertainty

paper_content:

Abstract In this study, the application of a rolling horizon optimization strategy to an integrated solid-oxide fuel cell/compressed air energy storage plant for load-following is investigated. A reduced-order model of the integrated plant is used to simulate and optimize each optimization interval as a mixed integer non-linear program. Forecasting uncertainties are considered through the addition of measurement noise and use of stochastic Monte Carlo simulations. The addition of rolling horizon optimization gives significant reductions to the sum-of-squared-errors between the demand and supply profiles. A sensitivity analysis is used to show that increasing the forecasting and optimization horizon improves load tracking with diminishing returns. Incorporating white Gaussian noise to demand forecasts has a marginal impact on error, even when a relatively high noise power of is used. Consistently over- or under-predicting demand has a greater impact on the plant's load-tracking error. However, even under worst-case forecasting scenarios, using a rolling horizon optimization scheme provides a more than 50% reduction in error when compared to the original system. An economic objective function is formulated to improve gross revenue using electricity spot-prices, but results in a trade-off with load-following performance. The results indicate that the rolling horizon optimization approach could potentially be applied to future municipal-scale fuel cell/compressed air storage systems to achieve power levels which closely follow real grid power cycles using existing prediction models.
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paper_title: Combined heat-and-power plants and district heating in a deregulated electricity market

paper_content:

In this paper, a municipality with district heating supplied via boilers and combined heat-and-power (CHP) plants is studied. The electricity load in the municipality is provided for by the CHP plant and electricity bought from the Nordic electricity market. It is therefore desirable to produce as much electricity as possible during periods when the price of electricity is high. The variations in the price of electricity over a 24-h period are significant. The idea presented in this paper is that heat storage can be used to maximise the amount of electricity produced in the CHP plants during peak-price periods. It can also be used to minimise the use of plants with higher operational costs. For storing heat, both a hot-water accumulator at the CHP plant and storage in the building stock are suggested. The situation is analysed using a mixed integer linear-programming model and a case study is presented for the city of Linkoping, a City of approximately 130,000 inhabitants, situated 200 km south of Stockholm in Sweden. A simple model for forecasting the electricity price on the Nordic electricity market is also presented.
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paper_title: Optimal Multi-scale Capacity Planning for Power-Intensive Continuous Processes under Time-sensitive Electricity Prices and Demand Uncertainty, Part I: Modeling

paper_content:

Abstract Time-sensitive electricity prices (as part of so-called demand-side management in the smart grid) offer economical incentives for large industrial customers. In part I of this paper, we propose an MILP formulation that integrates the operational and strategic decision-making for continuous power-intensive processes under time-sensitive electricity prices. We demonstrate the trade-off between capital and operating expenditures with an industrial case study for an air separation plant. Furthermore, we compare the insights obtained from a model that assumes deterministic demand with those obtained from a stochastic demand model. The value of the stochastic solution (VSS) is discussed, which can be significant in cases with an unclear setup, such as medium baseline product demand and growth rate, large variance or skewed demand distributions. While the resulting optimization models are large-scale, they can be solved within three days of computational time. A decomposition algorithm for speeding-up the solution time is described in part II.
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paper_title: Product Environmental Life‐Cycle Assessment Using Input‐Output Techniques

paper_content:

Summary ::: Life-cycle assessment (LCA) facilitates a systems view in environmental evaluation of products, materials, and processes. Life-cycle assessment attempts to quantify environmental burdens over the entire life-cycle of a product from raw material extraction, manufacturing, and use to ultimate disposal. However, current methods for LCA suffer from problems of subjective boundary definition, inflexibility, high cost, data confidentiality, and aggregation. ::: ::: This paper proposes alternative models to conduct quick, cost effective, and yet comprehensive life-cycle assessments. The core of the analytical model consists of the 498 sector economic input-output tables for the U.S. economy augmented with various sector-level environmental impact vectors. The environmental impacts covered include global warming, acidification, energy use, non-renewable ores consumption, eutrophication, conventional pollutant emissions and toxic releases to the environment. Alternative models are proposed for environmental assessment of individual products, processes, and life-cycle stages by selective disaggregation of aggregate input-output data or by creation of hypothetical new commodity sectors. To demonstrate the method, a case study comparing the life-cycle environmental performance of steel and plastic automobile fuel tank systems is presented.
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paper_title: Comparing two life cycle assessment approaches: a process model vs. economic input-output-based assessment

paper_content:

We compare two tools for Life Cycle Assessment (LCA). The software GaBi (Ganzheitliche Bilanzierung Integrated Assessment) from Germany is based on a process model approach, as recommended by the Society of Environmental Toxicology and Chemistry (SETAC). These results are contrasted to those from the method developed by Carnegie Mellon University's Green Design Initiative, Economic Input-Output Life Cycle Analysis (EIO-LCA). The EIO-LCA model uses economic input-output matrices, and industry sector level environmental and nonrenewable resource consumption data to assesses the economy-wide environmental impacts of products and processes. The results from the alternative approaches are compared in terms of toxic chemical releases, conventional pollutant emissions, energy use by fuel type, and use of ores. We find that most of the values from the two tools are within the same order of magnitude, despite the fundamental differences in the models. We contrast the two approaches to identify their relative strengths and weaknesses.
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paper_title: Expanding exergy analysis to account for ecosystem products and services

paper_content:

Exergy analysis is a thermodynamic approach used for analyzing and improving the efficiency of chemical and thermal processes. It has also been extended for life cycle assessment and sustainability evaluation of industrial products and processes. Although these extensions recognize the importance of capital and labor inputs and environmental impact, most of them ignore the crucial role that ecosystems play in sustaining all industrial activity. Decisions based on approaches that take nature for granted continue to cause significant deterioration in the ability of ecosystems to provide goods and services that are essential for every human activity. Accounting for nature's contribution is also important for determining the impact and sustainablility of industrial activity. In contrast, emergy analysis, a thermodynamic method from systems ecology, does account for ecosystems, but has encountered a lot of resistance and criticism, particularly from economists, physicists, and engineers. This paper expands the...
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paper_title: Errors in Conventional and Input-Output—based Life—Cycle Inventories

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Conventional process‐analysis‐type techniques for compiling life‐cycle inventories suffer from a truncation error, which is caused by the omission of resource requirements or pollutant releases of higher‐order upstream stages of the production process. The magnitude of this truncation error varies with the type of product or process considered, but can be on the order of 50%. One way to avoid such significant errors is to incorporate input‐output analysis into the assessment framework, resulting in a hybrid life‐cycle inventory method. Using Monte‐Carlo simulations, it can be shown that uncertainties of input‐output– based life‐cycle assessments are often lower than truncation errors in even extensive, third‐order process analyses.
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paper_title: Sustainable process design by the process to planet framework

paper_content:

Sustainable process design (SPD) problems combine a process design problem with life cycle assessment (LCA) to optimize process economics and life cycle environmental impacts. While SPD makes use of recent advances in process systems engineering and optimization, its use of LCA has stagnated. Currently, only process LCA is utilized in SPD, resulting in designs based on incomplete and potentially inaccurate life cycle information. To address these shortcomings, the multiscale process to planet (P2P) modeling framework is applied to formulate and solve the SPD problem. The P2P framework offers a more comprehensive analysis boundary than conventional SPD and greater modeling detail than advanced LCA methodologies. Benefits of applying this framework to SPD are demonstrated with an ethanol process design case study. Results show that current methods shift emissions outside the analysis boundary, while applying the P2P modeling framework results in environmentally superior process designs. Future extensions of the P2P framework are discussed. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3320–3331, 2015
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paper_title: High-efficiency power production from natural gas with carbon capture

paper_content:

Abstract A unique electricity generation process uses natural gas and solid oxide fuel cells at high electrical efficiency (74%HHV) and zero atmospheric emissions. The process contains a steam reformer heat-integrated with the fuel cells to provide the heat necessary for reforming. The fuel cells are powered with H2 and avoid carbon deposition issues. 100% CO2 capture is achieved downstream of the fuel cells with very little energy penalty using a multi-stage flash cascade process, where high-purity water is produced as a side product. Alternative reforming techniques such as CO2 reforming, autothermal reforming, and partial oxidation are considered. The capital and energy costs of the proposed process are considered to determine the levelized cost of electricity, which is low when compared to other similar carbon capture-enabled processes.
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paper_title: The Exergy Method of Thermal Plant Analysis

paper_content:

The subject of this book, the Exergy Method also known as the Availability Analysis, is a method of ::: thermodynamic analysis in which the basis of evaluation of thermodynamic losses follows from ::: the Second Law rather than the First Law of Thermodynamics. As a result of the recent developments in this technique combined with the increasing need to conserve fuel, the Exergy Method has gained in the last few years many new followers, both among practising engineers and academics. Its advantages, in relation to the traditional techniques which rely mainly on the First Law are now generally recognised. Although the Exergy Method has featured as the subject of many published papers in scientific and engineering journals and at conferences, very few comprehensive English language books on this subject have been published so far. This book is particularly intended for engineers ::: and students specialising in thermal and chemical plant design and operation as well as for applied scientists concerned with various aspects of conservation of energy. It introduces the subject in a manner that can be understood by anyone who is familiar with the fundamentals of Applied hermodynamics.Numerous examples are used in the book to aid the reader in assimilating the basic concepts and in mastering the techniques. The book contains a number of tables and charts which will be found of great assistance in calculations concerning topics such as thermoeconomics, refrigeration, ::: cryogenic processes, combustion, power generation and various aspects of chemical and process engineering.
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paper_title: Thermodynamic Input-Output Analysis of Economic and Ecological Systems

paper_content:

Ecological resources constitute the basic support system for all activity on earth. These resources include products such as air, water, minerals and crude oil and services such as carbon sequestration and pollution dissipation (Tilman et al. 2002; Daily 1997; Costanza et al. 1997; Odum 1996). However, traditional methods in engineering and economics often fail to account for the contribution of ecosystems despite their obvious importance. The focus of these methods tends to be on short-term economic objectives, while long-term sustainability issues get shortchanged. Such ignorance of ecosystems is widely believed to be one of the primary causes behind a significant and alarming deterioration of global ecological resources (WRI 2000; WWF 2000; UNEP 2002). To overcome the shortcomings of existing methods, and to make them ecologically more conscious, various techniques have been developed in recent years (Holliday et al. 2002). These techniques can be broadly divided into two categories, namely preference-based and biophysical methods. The preference-based methods use human valuation to account for ecosystem resources (AIChE 2004; Balmford et al. 2002; Bockstael et al. 2000; Costanza et al. 1997). These methods either use a single monetary unit to readily compare economic and ecological contributions, or use multi-criteria decision making to address trade-offs between indicators in completely different units. However, preference-based methods do not necessitate
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paper_title: Process to planet: A multiscale modeling framework toward sustainable engineering

paper_content:

To prevent the chance of unintended environmental harm, engineering decisions need to consider an expanded boundary that captures all relevant connected systems. Comprehensive models for sustainable engineering may be developed by combining models at multiple scales. Models at the finest “equipment” scale are engineering models based on fundamental knowledge. At the intermediate “value chain” scale, empirical models represent average production technologies, and at the coarsest “economy” scale, models represent monetary and environmental exchanges for industrial sectors in a national or global economy. However, existing methods for sustainable engineering design ignore the economy scale, while existing methods for life cycle assessment do not consider the equipment scale. This work proposes an integrated, multiscale modeling framework for connecting models from process to planet and using them for sustainable engineering applications. The proposed framework is demonstrated with a toy problem, and potential applications of the framework including current and future work are discussed. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3332–3352, 2015
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paper_title: Integrating Hybrid Life Cycle Assessment with Multiobjective Optimization: A Modeling Framework

paper_content:

By combining life cycle assessment (LCA) with multiobjective optimization (MOO), the life cycle optimization (LCO) framework holds the promise not only to evaluate the environmental impacts for a given product but also to compare different alternatives and identify both ecologically and economically better decisions. Despite the recent methodological developments in LCA, most LCO applications are developed upon process-based LCA, which results in system boundary truncation and underestimation of the true impact. In this study, we propose a comprehensive LCO framework that seamlessly integrates MOO with integrated hybrid LCA. It quantifies both direct and indirect environmental impacts and incorporates them into the decision making process in addition to the more traditional economic criteria. The proposed LCO framework is demonstrated through an application on sustainable design of a potential bioethanol supply chain in the UK. Results indicate that the proposed hybrid LCO framework identifies a considera...
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paper_title: Application of the exergetic cost theory to the CGAM problem

paper_content:

An optimization strategy for complex thermal systems is presented. The strategy is based on conventional techniques and incorporates assumptions and consequences of the exergetic cost theory (ECT) and of symbolic exergoeconomics. In addition to the results obtained by consventional techniques, this method provides valuable information about the interaction of components.
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paper_title: Exergy, waste accounting, and life-cycle analysis

paper_content:

The authors argue that thermodynamics offers a means of accounting for both resource inputs and waste outputs in a systematic and uniform way. The new feature of the present work is to extend the applications of exergy analysis to resource and waste accounting and to present the results in an integrated analytical framework, namely, life-cycle analysis (LCA). We conclude that exergy is appropriate for general statistical use, both as a measure of resource stocks and flows and as a measure of waste emissions and potential for causing environmental harm.
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paper_title: System boundary selection in life-cycle inventories using hybrid approaches.

paper_content:

Life-cycle assessment (LCA) is a method for evaluating the environmental impacts of products holistically, including direct and supply chain impacts. The current LCA methodologies and the standards by the International Organization for Standardization (ISO) impose practical difficulties for drawing system boundaries; decisions on inclusion or exclusion of processes in an analysis (the cutoff criteria) are typically not made on a scientific basis. In particular, the requirement of deciding which processes could be excluded from the inventory can be rather difficult to meet because many excluded processes have often never been assessed by the practitioner, and therefore, their negligibility cannot be guaranteed. LCA studies utilizing economic input-output analysis have shown that, in practice, excluded processes can contribute as much to the product system under study as included processes; thus, the subjective determination of the system boundary may lead to invalid results. System boundaries in LCA are discussed herein with particular attention to outlining hybrid approaches as methods for resolving the boundary selection problem in LCA. An input-output model can be used to describe at least a part of a product system, and an ISO-compatible system boundary selection procedure can be designed by applying hybrid input-output-assisted approaches. There are several hybrid input-output analysis-based LCA methods that can be implemented in practice for broadening system boundary and also for ISO compliance.
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paper_title: A brief Commented History of Exergy From the Beginnings to 2004

paper_content:

This paper presents a brief critical and analytical account of the development of the concept of exergy and of its applications. It is based on a careful and extended (in time) consultation of a very large body of published references taken from archival journals, textbooks and other monographic works, conference proceedings, technical reports and lecture series. We have tried to identify the common thread that runs through all of the references, to put different issues into perspective, to clarify dubious points, to suggest logical and scientific connections and priorities. It was impossible to eliminate our respective biases that still affect the “style” of the present paper: luckily, some of our individual biases “cancelled out” at the time of writing, and some were corrected by our Reviewers (to whom we owe sincere thanks for the numerous and very relevant corrections and suggestions). The article is organized chronologically and epistemologically: it turns out that the two criteria allow for a quite clear systematization of the subject matter, because the development of the exergy concept was rather “linear”. This work is addressed to our Colleagues who are involved in theoretical research, industrial development, and societal applications of exergy concepts: if they extract from this article the idea of an extraordinary epistemological uniformity in the development of the concept of exergy, our goal will be achieved. The other addressees of this paper are Graduate Students taking their first steps in this field: in their case, we hope that consultation of our paper will prompt them to adopt and maintain throughout their career a scholarly valid method of research, which implies studying and respecting our scientific roots (the sources) but venturing freely and creatively into unknown territory. In the Conclusions we try to forecast future developments: this is the only part of the paper that is an intentional expression of our own views: the previous historical-scientific exposition is instead based on verifiable facts and accepted opinions.
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paper_title: Cumulative exergy consumption and cumulative degree of perfection of chemical processes

paper_content:

The paper presents methods of calculating the cumulative exergy consumption and introduces the notion of the cumulative degree of perfection of the entire chain of production processes leading to the material under consideration. Tables of values calculated on the basis of cumulative energy consumption indices have been included.
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paper_title: Net Energy Analysis and the Energy Requirements of Energy Systems

paper_content:

Foreword by Alvin M. Weinberg Part I: Energy Systems Introduction Man's Use of Energy Locations and Concentrations of Energy Energy--When and at What Rate? The Energy Services Part II: Valuations of Energy National and International Energy Statistics The Physicist's Approach Valuation of Energy in Engineering The Role of Energy in Economics The View of the Conservationist Part III: Methods of Cumulative Energy Accounting A Short History of Energy Accounting Useful Questions in Energy Accounting Problems in Applying Net-Energy Analysis Process Analysis and the Input-Output Method Schools of Net-Energy Analysis Indexes of Systems' Performance and Sankey Diagrams Part IV: Energy Accounting of Energy Carriers Electricity-Producing Systems Fuel-Producing Systems Part V: Energy Accounting of Energy Services Direct and Indirect Energy Requirements of Transport Systems Process Heat and Mechanical Drive Warm Water and Space Heat Part VI: Concluding Remarks Purpose and Method Answers and Partial Answers to Some Policy Questions
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paper_title: Exergy Analysis of Thermal, Chemical, and Metallurgical Processes

paper_content:

In addition to the exergy analysis of thermal processes, e.g. heat engines and commercial power stations, for which the methods described have been long established, the book considers the chemical and metallurgical process industries. Charts and tables are provided for the determination of the exergy of many typical substances. Examples are drawn from the fields of thermal, chemical and metallurgical engineering and the exergetic efficiency of typical processes is calculated. The book also discusses the application of the exergy concept to the problem of the economical optimization of complex plants and the implications to the environment of pollution due to external exergy losses. An Instructor's Manual is available which contains outline solutions to the problems listed at the end of each chapter.
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paper_title: Practical approaches for applying thermoeconomic analysis to energy conversion systems : Benchmarking and comparative application

paper_content:

Abstract In the last decades, thermoeconomic analysis emerged as a combination of exergy analysis and cost accounting principles, widely used for multiple purposes: to account for the exergy and economic costs of energy systems products, to derive the structures of such costs for the design optimization purpose, and to perform system diagnosis quantifying the source and the impact of malfunctions and dysfunctions within the analyzed process. Traditionally, thermoeconomic analysis is referred to as Exergy Cost Analysis or Exergoeconomic Cost Analysis. The former is based on the so-called Exergy Cost Theory, focused on the evaluation of exergy cost of the system products, while the latter is focused on the evaluation of monetary cost following the same theory. Currently, many practical approaches are available in the literature for the application of thermoeconomic analysis and Exergy Cost Theory to energy conversion systems, while a comprehensive classification, benchmarking and comparison of such approaches is missing. This paper aims to fill this gap through the following activities: first of all, a brief but comprehensive literature review related to the theoretical developments and applications of thermoeconomic analysis method is performed. Secondly and for the purpose of benchmarking, the main practical approaches identified for the application of Exergy Cost Theory are presented and formalized, including the fundamental aspects related to the definition of auxiliary relations and the reallocation of the exergy cost of the residues. Finally, the identified approaches are comparatively applied to the standard CGAM problem, and the advantages and drawbacks of each approach are discussed. It is found that the definition of the functional diagram and the numerical solution of the system through input-output analysis seem to be more straightforward with respect to the other approaches, leading also to the formalization of an unambiguous method to reallocate the exergy cost of the residual flows.
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paper_title: Off-Design Modeling of Natural Gas Combined Cycle Power Plants: An Order Reduction by Means of Thermoeconomic Input–Output Analysis

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In a European context characterized by growing need for operational flexibility across the electricity sector, the combined cycle power plants are increasingly subjected to cyclic operation. These new operation profiles cause an increase of production costs and decrease of revenues, which undermines the competitiveness of the combined cycles. Power plant operators need tools to predict the effect of off-design operation and control mechanisms on the performance of the power plant. Traditional Thermodynamic or Thermoeconomic models may be unpractical for the operators, due to their complexity and the computational effort they require. This study proposes a Thermoeconomic Input–Output Analysis model for the on- and off-design performance prediction of energy systems, and applies it to La Casella Natural Gas Combined Cycle (NGCC) power plant, in Italy. It represents a stand-alone, reduced order model, where the cost structure of the plant products and the Thermoeconomic performance indicators are derived for on- and off-design conditions as functions of the load and of different control mechanisms, independently from the Thermodynamic model. The results of the application show that the Thermoeconomic Input–Output Analysis model is a suitable tool for power plant operators, able to derive the same information coming from traditional Thermoeconomic Analysis with reduced complexity and computational effort.
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paper_title: The underestimated potential of solar energy to mitigate climate change

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Despite being currently under-represented in IPCC reports, PV generation represents a growing share of power generation. This Perspective argues that underestimating PV potential led to suboptimal integration measures and that specific deployment strategies for emerging economies should be developed.
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paper_title: Technological learning in energy–environment–economy modelling: A survey

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Abstract This paper aims at providing an overview and a critical analysis of the technological learning concept and its incorporation in energy–environment–economy models. A special emphasis is put on surveying and discussing, through the so-called learning curve, both studies estimating learning rates in the energy field and studies incorporating endogenous technological learning in bottom-up and top-down models. The survey of learning rate estimations gives special attention to interpreting and explaining the sources of variability of estimated rates, which is shown to be mainly inherent in R&D expenditures, the problem of omitted variable bias, the endogeneity relationship and the role of spillovers. Large-scale models survey show that, despite some methodological and computational complexity related to the non-linearity and the non-convexity associated with the learning curve incorporation, results of the numerous modelling experiments give several new insights with regard to the analysis of the prospects of specific technological options and their cost decrease potential (bottom-up models), and with regard to the analysis of strategic considerations, especially inherent in the innovation and energy diffusion process, in particular the energy sector's endogenous responses to environment policy instruments (top-down models).
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paper_title: The role of technology diffusion in a decarbonizing world to limit global warming to well below 2 °C: An assessment with application of Global TIMES model

paper_content:

Abstract Low-carbon power generation technologies such as wind, solar and carbon capture and storage are expected to play major roles in a decarbonized world. However, currently high cost may weaken the competitiveness of these technologies. One important cost reduction mechanism is the “learning by doing”, through which cumulative deployment results in technology costs decline. In this paper, a 14-region global energy system model (Global TIMES model) is applied to assess the impacts of technology diffusion on power generation portfolio and CO2 emission paths out to the year 2050. This analysis introduces three different technology learning approaches, namely standard endogenous learning, multiregional learning and multi-cluster learning. Four types of low-carbon power generation technologies (wind, solar, coal-fired and gas-fired CCS) undergo endogenous technology learning. The modelling results show that: (1) technology diffusion can effectively reduce the long-term abatement costs and the welfare losses caused by carbon emission mitigation; (2) from the perspective of global optimization, developed countries should take the lead in low-carbon technologies’ deployment; and (3) the establishment of an effective mechanism for technology diffusion across boundaries can enhance the capability and willingness of developing countries to cut down their CO2 emission.
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paper_title: High-efficiency power production from natural gas with carbon capture

paper_content:

Abstract A unique electricity generation process uses natural gas and solid oxide fuel cells at high electrical efficiency (74%HHV) and zero atmospheric emissions. The process contains a steam reformer heat-integrated with the fuel cells to provide the heat necessary for reforming. The fuel cells are powered with H2 and avoid carbon deposition issues. 100% CO2 capture is achieved downstream of the fuel cells with very little energy penalty using a multi-stage flash cascade process, where high-purity water is produced as a side product. Alternative reforming techniques such as CO2 reforming, autothermal reforming, and partial oxidation are considered. The capital and energy costs of the proposed process are considered to determine the levelized cost of electricity, which is low when compared to other similar carbon capture-enabled processes.
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paper_title: Alternative energy technologies

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Fossil fuels currently supply most of the world's energy needs, and however unacceptable their long-term consequences, the supplies are likely to remain adequate for the next few generations. Scientists and policy makers must make use of this period of grace to assess alternative sources of energy and determine what is scientifically possible, environmentally acceptable and technologically promising.
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paper_title: Hydrogen supply chain architecture for bottom-up energy systems models. Part 2: Techno-economic inputs for hydrogen production pathways

paper_content:

Abstract This article is the second paper of a serial study on hydrogen energy system modelling. In the first study, we proposed a stylized hydrogen supply chain architecture and its pathways for the representation of hydrogen systems in bottom-up energy system models. In this current paper, we aim to present and assess techno-economic inputs and bandwidths for a hydrogen production module in bottom-up energy system models. After briefly summarizing the current technological status for each production method, we introduce the parameters and associated input data that are required for the representation of hydrogen production technologies in energy system modelling activities. This input data is described both as numeric values and trend line modes that can be employed in large or small energy system models. Hydrogen production technologies should be complemented with hydrogen storage and delivery pathways to fully understand the system integration. In this context, we will propose techno-economic inputs and technological background information for hydrogen delivery pathways in later work, as the final paper of this serial study.
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paper_title: Integration of market dynamics into the design of biofuel processes

paper_content:

Abstract Wood is considered one of the main future feedstocks in the production of second generation biofuels in Europe. While feedstock cost has a major impact on production cost, wood prices are expected to change significantly once biorefineries enter the raw material market as new high volume consumers. Therefore, wood market dynamics and approximate price forecasting should be integrated into decision-making during the design phase. In this contribution we show how such an integration could be realized by combining a preliminary process model to determine the raw material demand and a spatial partial equilibrium model of the wood market to predict the price development. This approach is illustrated on a case study examining the production of 2-methyltetrahydrofuran (MTHF) as a novel biofuel component, which is converted from deciduous wood grown in Germany.
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paper_title: How far away is hydrogen? Its role in the medium and long-term decarbonisation of the European energy system ☆

paper_content:

Hydrogen is a promising avenue for decarbonising energy systems and providing flexibility. In this paper, the JRC-EU-TIMES model – a bottom-up, technology-rich model of the EU28 energy system – is used to assess the role of hydrogen in a future decarbonised Europe under two climate scenarios, current policy initiative (CPI) and long-term decarbonisation (CAP). Our results indicate that hydrogen could become a viable option already in 2030 – however, a long-term CO2 cap is needed to sustain the transition. In the CAP scenario, the share of hydrogen in the final energy consumption of the transport and industry sectors reaches 5% and 6% by 2050. Low-carbon hydrogen production technologies dominate, and electrolysers provide flexibility by absorbing electricity at times of high availability of intermittent sources. Hydrogen could also play a significant role in the industrial and transport sectors, while the emergence of stationary hydrogen fuel cells for hydrogen-to-power would require significant cost improvements, over and above those projected by the experts.
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paper_title: Hydrogen supply chain architecture for bottom-up energy systems models. Part 1: Developing pathways

paper_content:

Abstract The integration of hydrogen energy systems in the overall energy system is an important and complex subject for hydrogen supply chain management. The efficiency of the integration depends on finding optimum pathways for hydrogen supply. Accordingly, energy systems modelling methods and tools have been implemented to obtain the best configuration of hydrogen processes for a defined system. The appropriate representation of hydrogen technologies becomes an important stage for energy system modelling activities. This study, split in consecutive parts, has been conducted to analyse how representative hydrogen supply pathways can be integrated in energy systems modelling. The current paper, the first part of a larger study, presents stylised pathways of hydrogen supply chain options, derived on the basis of a detailed literature review. It aims at establishing a reference hydrogen energy system architecture for energy modelling tools. The subsequent papers of the study will discuss the techno-economic assumptions of the hydrogen supply chain components for energy modelling purposes.
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paper_title: Comparison of CO2 Capture Approaches for Fossil-Based Power Generation: Review and Meta-Study

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This work is a meta-study of CO2 capture processes for coal and natural gas power generation, including technologies such as post-combustion solvent-based carbon capture, the integrated gasification combined cycle process, oxyfuel combustion, membrane-based carbon capture processes, and solid oxide fuel cells. A literature survey of recent techno-economic studies was conducted, compiling relevant data on costs, efficiencies, and other performance metrics. The data were then converted in a consistent fashion to a common standard (such as a consistent net power output, country of construction, currency, base year of operation, and captured CO2 pressure) such that a meaningful and direct comparison of technologies can be made. The processes were compared against a standard status quo power plant without carbon capture to compute metrics such as cost of CO2 emissions avoided to identify the most promising designs and technologies to use for CO2 emissions abatement.
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paper_title: A review of learning rates for electricity supply technologies

paper_content:

A variety of mathematical models have been proposed to characterize and quantify the dependency of electricity supply technology costs on various drivers of technological change. The most prevalent model form, called a learning curve, or experience curve, is a log-linear equation relating the unit cost of a technology to its cumulative installed capacity or electricity generated. This one-factor model is also the most common method used to represent endogenous technical change in large-scale energy-economic models that inform energy planning and policy analysis. A characteristic parameter is the “learning rate,” defined as the fractional reduction in cost for each doubling of cumulative production or capacity. In this paper, a literature review of the learning rates reported for 11 power generation technologies employing an array of fossil fuels, nuclear, and renewable energy sources is presented. The review also includes multi-factor models proposed for some energy technologies, especially two-factor models relating cost to cumulative expenditures for research and development (R&D) as well as the cumulative installed capacity or electricity production of a technology. For all technologies studied, we found substantial variability (as much as an order of magnitude) in reported learning rates across different studies. Such variability is not readily explained by systematic differences in the time intervals, geographic regions, choice of independent variable, or other parameters of each study. This uncertainty in learning rates, together with other limitations of current learning curve formulations, suggests the need for much more careful and systematic examination of the influence of how different factors and assumptions affect policy-relevant outcomes related to the future choice and cost of electricity supply and other energy technologies.
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paper_title: Effects of technological learning on future cost and performance of power plants with CO2 capture

paper_content:

This paper demonstrates the concept of applying learning curves in a consistent manner to performance as well as cost variables in order to assess the future development of power plants with CO2 capture. An existing model developed at Carnegie Mellon University, which had provided insight into the potential learning of cost variables in power plants with CO2 capture, is extended with learning curves for several key performance variables, including the overall energy loss in power plants, the energy required for CO2 capture, the CO2 capture ratio (removal efficiency), and the power plant availability. Next, learning rates for both performance and cost parameters were combined with global capacity projections for fossil-fired power plants to estimate future cost and performance of these power plants with and without CO2 capture. The results of global learning are explicitly reported, so that they can be used for other purposes such as in regional bottom-up models. Results of this study show that IGCC with CO2 capture has the largest learning potential, with significant improvements in efficiency and reductions in cost between 2001 and 2050 under the condition that around 3100 GW of combined cycle capacity is installed worldwide. Furthermore, in a scenario with a strict climate policy, mitigation costs in 2030 are 26, 11, 19 €/t (excluding CO2 transport and storage costs) for NGCC, IGCC, and PC power plants with CO2 capture, respectively, compared to 42, 13, and 32 €/t in a scenario with a limited climate policy. Additional results are presented for IGCC, PC, and NGCC plants with and without CO2 capture, and a sensitivity analysis is employed to show the impacts of alternative assumptions on projected learning rates of different systems.
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paper_title: Learning through a portfolio of carbon capture and storage demonstration projects

paper_content:

Carbon capture and storage is considered an important element to meet our climate mitigation targets. This Perspective explores the history of the first wave of projects and what challenges must be faced if widespread deployment is to be successful.
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Title: Modeling and Simulation of Energy Systems: A Review
Section 1: Introduction
Description 1: Write about the importance of energy in the modern economy, the expected increase in energy consumption, and the necessity of transitioning to a sustainable energy future through the engagement of various stakeholders.

Section 2: Categorization According to Modeling Approach
Description 2: Present an overview of the different classes of energy system models, categorized into computational, mathematical, and physical models.

Section 3: The PSE Approach to Energy System Modeling and Simulation
Description 3: Discuss the Process Systems Engineering (PSE) approach, focusing on multi-scale systems engineering, sustainable process engineering, and emerging trends within the PSE community.

Section 4: The EE Approach to Energy System Modeling and Simulation
Description 4: Explain the Energy Economics (EE) approach, including demand and supply forecasting models, bottom-up models, and top-down models.

Section 5: Combining PSE and EE Approaches
Description 5: Make the case for combining PSE and EE approaches, highlighting opportunities such as optimal design and operation processes using demand and price forecasts, sustainability analysis using hybrid methods, and accounting for feedback effects of breakthrough technologies.

Section 6: Concluding Remarks
Description 6: Summarize the key points of the paper, emphasizing the importance of bridging the PSE and EE fields to get a holistic picture of the long-term performance of energy systems in a wider economic and policy context.