Sun Tracking Systems: A Review
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paper_title: Method of quick determination of the angle of slope and the orientation of solar collectors without a sun tracking system

paper_content:

Abstract The present work consists of an original and quick method allowing the determination of the optimal angle slope and the optimal orientation of solar collectors at any position in the Algerian National Territory, for different periods of possible utilization (15 days, 1–12 months) combined in a year (289 combinations for each position).
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paper_title: Optimum tilt angle and orientation for solar collector in Brunei Darussalam

paper_content:

One of the important parameters that affects the performance of a solar collector is its tilt angle with the horizontal. This is due to the fact that the variation of tilt angle changes the amount of solar radiation reaching the collector surface. A mathematical model was used for estimating the total (global) solar radiation on a tilted surface, and to determine the optimum tilt angle and orientation (surface azimuth angle) for the solar collector in Brunei Darussalam on a daily basis, as well as for a specific period. The optimum angle was computed by searching for the values for which the total radiation on the collector surface is a maximum for a particular day or a specific period. The results reveal that changing the tilt angle 12 times in a year (i.e. using the monthly-averaged optimum tilt angle) maintains approximately the total amount of solar radiation near the maximum value that is found by changing the tilt angle daily to its optimum value. This achieves a yearly gain in solar radiation of 5% more than the case of a solar collector fixed on a horizontal surface.
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paper_title: Optimum slope angle and orientation of solar collectors for different periods of possible utilization

paper_content:

Abstract A method to determine the optimum slope angle and orientation of solar collectors for different periods of operation (1–365 days) at any position in the Malaysian territory is described. The method utilizes both the direct and diffuse components of solar radiation. The ASHRAE standard atmosphere is used to calculate the direct component, whereas the isotropic diffuse model is used to calculate the diffuse component. For intermittent applications of solar energy such as crop drying, the optimum slope angle as well as the orientation can be found conveniently and accurately by this method.
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paper_title: Different strategies for maximum solar radiation collection on Mars surface

paper_content:

Abstract This paper deals with the optimum slope and orientation of a surface receiving solar radiation on the Mars surface (Northern hemisphere). A model to evaluate direct, diffuse and global irradiance on arbitrary tilted surfaces is developed. Also, the model estimates direct, diffuse and global irradiations on different time intervals, such as a day, a season or a year. Any of these irradiances/irradiations is a maximum for a certain optimum tilt angle. Most part of the primary data is based on Viking Landers measurements. The recommended strategies to collect the maximum amount of solar radiation depend on the dust content in the atmosphere. During the “clear” days the best strategy is to keep the receiving surface perpendicular on Sun’s rays. This strategy allows to collect the maximum direct solar radiation and it is recommended in the case of solar concentrators. A simpler procedure is to use a South oriented surface whose tilt angle is continuously adjusted in order to collect the maximum global irradiance. During the dust storms the dependence of the incident irradiance upon surface’s tilt and orientation becomes less important and simpler strategies are more convenient (e.g. a horizontal receiving surface or a once-per-day adjustment of the tilt angle).
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paper_title: Efficient orientation impacts of box-type solar cooker on the cooker performance

paper_content:

The addition of a plane reflector to a box-type solar cooker increases the obtained cooker temperature and this depends upon the efficient orientation of the cooker. In order to find out the effect of the cooker orientation on its performance, the present analysis is carried out. A method is outlined to find out a reflector performance factor and an orientation factor that depend upon the elevation angle of the sun, the solar surface azimuth angle and the reflector tilt angle. The analysis is applied to a cooker placed at Aden (Yemen). The results indicate that with proper cooker orientation the improvement in the performance of the cooker due to the reflector reached during winter is more than 100% at lower elevation angles and is more than 60% at higher elevation angles. It is concluded that with the help of the analysis the optimum position for any place, for any day of the year and for any specific time of the day can be found.
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paper_title: Absorption of solar energy in a room

paper_content:

The purpose of this study is to develop an analysis that allows an examination of the spatial distribution of the absorbed solar energy for a room. The room is composed of several areas that consist of an exterior window where solar beam and diffuse energies originate, an interior window, a door, and six opaque areas. Each area is subdivided into a number of discrete surfaces and an analysis based on the radiosity-irradiation method is used to determine the absorbed solar energy for each surface. A geometrically-based method is used to describe the location and magnitude of the directly incident solar beam energy for each surface. The influence of the number of discrete surfaces on the findings is examined. The results show that a grid pattern that produces discrete surfaces having dimensions of less than 0.3 m yields accurate results. Results are reported for different orientations of the room. As expected, the absorbed solar energy is high in regions where the solar beam energy irradiates a surface. The spatial distribution of the absorbed solar energy does vary significantly over the areas of the room. Measured solar energy values are used to compute the absorbed solar energy as a function of time of day. The movement of the energy across the surfaces of the room creates a time-varying value for the absorbed solar energy. Numerical values for the ratio of the absorbed solar energy for each area to the available solar energy from the exterior window are supplied.
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paper_title: Steering a field of mirrors using a shared computer-based controller☆

paper_content:

Abstract A system is described for steering a multiplicity of two-axis mirrors by means of a shared computerbased controller. No local feed-back is employed at the mirrors. The system is applicable to power towers as well as to multi-focus paraboloidal mirror systems. The operation and economic advantages of this system over alternatives is discussed and the results achieved so far with an actual system are given.
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paper_title: Power collection reduction by mirror surface nonflatness and tracking error for a central receiver solar power system

paper_content:

The effects of random waviness, curvature, and tracking error of plane-mirror heliostats in a rectangular array around a central-receiver solar power system are determined by subdividing each mirror into 484 elements, assuming the slope of each element to be representative of the surface slope average at its location, and summing the contributions of all elements and then of all mirrors in the array. Total received power and flux density distribution are computed for a given sun location and set of array parameter values. Effects of shading and blocking by adjacent mirrors are included in the calculation. Alt-azimuth mounting of the heliostats is assumed. Representative curves for two receiver diameters and two sun locations indicate a power loss of 20% for random waviness, curvature, and tracking error of 0.1° rms, 0.002 m−1, and 0.5°, 3σ, respectively, for an 18.2-m diam receiver and 0.3° rms, 0.005 m−1, and greater than 1°, respectively, for a 30.4-m diam receiver.
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paper_title: Theoretical derivation of heliostat tracking errors distribution

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The tracking error probability distribution is derived on a pure theoretical basis. Methods of integral geometry and geometrical probabilities are used to this purpose. The distribution performs reasonably well when compared with measurements from a small database. The performance of the theoretical distribution is compared with that of other (empirical) probability distributions. The practical relevance of using the present approach is also explained.
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paper_title: Sun tracking controller for multi-kW photovoltaic concentrator system

paper_content:

This paper describes a two-axis sun tracking controller designed to achieve low cost, high performance reliability, and operational flexibility for multi-kW to multihundred kW photovoltaic concentrator applications. The controller is based on an active sun sensing approach and allows an array assembly to track the sun within five arc-minutes. It has the capability to stow the array at night or during inclement weather conditions, communicate with an external computer, and provide autonomous operation and diagnostic monitoring. These functions along with the basic design goals were achieved by using a dedicated microprocessor. The prototype of the third generation sun tracker design has been designed, fabricated, and is now in the verification stage. It represents a significant improvement over the two earlier generations which were based on hard-wired logic. The sun tracking unit can be readily adapted for use on any application that requires sun pointing such as for monitoring direct beam solar irradiance with normal incidence pyrheliometer.
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paper_title: A subdegree precision sun tracker for 1000X microconcentrator modules

paper_content:

In this paper we present a subdegree precision pedestal sun tracker developed for 1000X microconcentrator modules. Setting a cost target of 100 /spl euro//m/sup 2/, a lightweight structure has been designed that, fully made out of commercially available parts, stays operative for wind speeds which account for at least 95% of the available direct solar radiation. The electronic tracking control unit relies on a strategy which resorts to high accuracy solar ephemeris, parameter fitting for a model of installation and manufacturing errors, an adaptive algorithm for absorbing unforeseen or time varying errors, and automatic calibration of cheap sun pointing sensors against array power output.
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paper_title: Design and implementation of a fuzzy logic computer-controlled sun tracking system

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This paper considers design and implementation of a computer-controlled sun tracking system to enhance the power output of photovoltaic (PV) solar panels. The tracking system is driven by two permanent magnet DC motors to provide motion of the PV panels in two axes. The control of the dual axis tracking system is not an easy task due to nonlinear dynamics and unavailability of the model parameters. Therefore, a PC-based fuzzy logic control algorithm utilizing the knowledge of the system behavior is designed in order to achieve the control objectives. The implementation of such a controller is realized by building an interfacing card consisting of sensor data acquisition, motor driving circuits, signal conditioning circuits and serial communication with the PC. A set of laboratory demonstrations shows the capability of the system to track the sun effectively.
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paper_title: Comparative study of peak power tracking techniques for solar storage system

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As the power supplied by solar arrays depends upon the insolation, temperature and array voltage, it is necessary to control the operating points to draw the maximum power of the solar array. The object of this paper is to investigate the maximum power tracking algorithms which were often used to compare the tracking efficiencies for the system operating under different controls. A simple method which combines a discrete time control and a PI compensator is used to track the maximum power points (MPPs) of the solar array. The implementation of the proposed converter system was based on a digital signal processor (DSP). The experimental tests were carried out, the tracking efficiencies are confirmed by simulations and experimental results.
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paper_title: 5 Wp PV module-based stand-alone solar tracking system

paper_content:

5 Watt-PV module is utilized for tracking solar oven concentrator system with 2.6 kW/sub th/ capacity and 200 Kg weight. The tracking system follows the sun autonomously in altitude and azimuth using only 5 Watt-peak PV solar module as a tracking energy source. The tracking system is driven by means of two 12 DCV motors of 36 W each, and fed by electrolytic condenser with 78000 /spl mu/Fd capacity charged properly by PV module. The PV based tracking system has two circuits in bridge, configuration using N- and P-channel power MOSFET transistors. This electronic circuit commands DC motor rotation way, as a function of the optical sensors for altitude and azimuth position.
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paper_title: Sun oriented and powered, 3 axis and spin stabilized CubeSats

paper_content:

CubeSat, a 1 kg 10 /spl times/ 10 /spl times/ 10 cm/sup 3/ picosatellite, has been developed by Stanford University and the California Polytechnic State University for use in student space experiments. These satellites are free flyers, and are ejected from "piggy back" canisters mounted on various launch vehicles. CubeSats currently under development have very limited stabilization capabilities. Most of the CubeSats are actually tumbling satellites. This lack of stabilization significantly limits their performance by reducing their ability to accurately point solar panels and instruments. This paper describes a 3-axis stabilized system and a spin stabilized system for CubeSat. It is used in conjunction with a sun-oriented attitude control system combined with a concentrating solar panel, all of which is achieved with a total mass of under 250 grams, thus allowing adequate mass for CubeSat satellite structure, batteries, and payloads within the 1.0 kg maximum.
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paper_title: Two axis tracking system for solar concentrators

paper_content:

A two axis tracking system is described for the focussing of sunlight in paraboloid-type solar reflectors used in solar thermal devices like solar cookers. This system consists of wormgear drives and four bar type kinematic linkages for effortless and accurate focussing of reflectors at low cost.
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paper_title: A novel maximum power point tracking control for photovoltaic power system under rapidly changing solar radiation

paper_content:

This paper proposes a novel MPPT control algorithm for a digitally implemented photovoltaic power system under rapidly changing solar radiation. The method of the MPPT control algorithm can be classified into two categories: perturb and observe (P&O) and incremental conductance (IncCond). In comparing the P&O and IncCond algorithms, the dynamic and tracking characteristic of the IncCond algorithm is better than P&O algorithm under rapidly changing solar radiation. But in the case of digital implementation, the InCond algorithm has an error on the decision of maximum power operation point (MPOP). To solve this problem, this paper proposes a improved IncCond algorithm, which can determine the MPOP under rapidly changing solar radiation by inserting a test signal in the control input. By simulation and experimentation, the validity of the proposed control algorithm is proved.
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paper_title: Design and construction of a one-axis sun-tracking system

paper_content:

Abstract This paper describes a tracking system which can be used with single-axis solar concentrating systems. The position and “status” of the Sun are detected by three light-dependent resistors (LDRs), one of which detects whether the collector is focused, whilst a second resistor determines if there is cloud cover, and the third senses whether it is day or night. The resultant signals are fed to an electronic control system which operates a low-speed 12-V d.c. motor which rotates the collector via a speed-reduction gearbox. The tracking system accuracy depends on the magnitude of the solar irradiance. The deviation from zero is 0.2 and 0.05° with solar radiation of 100 and 600 W m −2 , respectively. Both values suggest that the mechanism can be used satisfactorily for parabolic trough collectors of medium to high concentration ratios.
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paper_title: An artificial vision-based control system for automatic heliostat positioning offset correction in a central receiver solar power plant

paper_content:

This paper presents the development of a simplified and automatic heliostat positioning offset correction control system using artificial vision techniques and common CCD devices. The heliostats of a solar power plant reflect solar radiation onto a receiver (in this case, a volumetric receiver) placed at the top of a tower in order to provide a desired energy flux distribution correlated with the coolant flow (in this case air mass flow) through the receiver, usually in an open loop control configuration. There exist error sources that increase the complexity of the control system, some of which are systematic ones, mainly due to tolerances, wrong mirror facets alignment (optical errors), errors due to the approximations made when calculating the solar position, etc., that produce errors (offsets) in the heliostat orientation (aiming point). The approximation adopted in this paper is based on the use of a B/W CCD camera to correct these deviations in an automatic way imitating the same procedure followed by the operators. The obtained images are used to estimate the distance between the sunbeam centroid projected by the heliostats and a target placed on the tower, this distance thus is used for low accuracy offset correction purposes. Basic threshold-based image processing techniques are used for automatic correction.
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paper_title: The effect of using sun tracking systems on the voltage–current characteristics and power generation of flat plate photovoltaics

paper_content:

Abstract An experimental study was performed to investigate the effect of using different types of sun tracking systems on the voltage–current characteristics and electrical power generation at the output of flat plate photovoltaics (FPPV). Four electromechanical sun tracking systems, two axes, one axis vertical, one axis east–west and one axis north–south, were designed and constructed for the purpose of investigating the effect of tracking on the electrical values, current, voltage and power, according to the different loads (variable resistance). The above mentioned variables were measured at the output of the FPPV and compared with those on a fixed surface. The results indicated that the volt–ampere characteristics on the tracking surfaces were significantly greater than that on a fixed surface. There were increases of electrical power gain up to 43.87%, 37.53%, 34.43% and 15.69% for the two axes, east–west, vertical and north–south tracking, respectively, as compared with the fixed surface inclined 32° to the south in Amman, Jordan.
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paper_title: Performance of a self-aligning solar array tracking controller

paper_content:

Sandia's advanced SolarTrak control system provides Sun tracking, night and emergency stow, communication, and manual drive control functions, for one and two-axis solar trackers in a low-cost, user-friendly package. The author describes the hardware design features and sophisticated control algorithms, such as a six-degree self-alignment routine and a self-adjusting motor actuation time, that enhance SolarTrak's pointing accuracy and system reliability while at the same time reducing operation and maintenance requirements. Performance measurements taken on operating systems over the past year show that full-day pointing accuracies of better than +or-0.1 have been achieved. >
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paper_title: Sun Tracking Photo-Sensor for Solar Thermal Concentrating System

paper_content:

This paper presents the structure and application of a sun tracking photo-sensor, which controls the direction of a reflected solar radiation to be constant. The sensor has a very simple structure, in which two photo-cells are placed side by side in the bottom of a box with an aperture. When the reflected solar radiation passes through the aperture, the photo-cells are fractionally illuminated, and a electric current, which is proportional to the illuminated area, is generated on each photo-cell. The direction of the reflected solar radiation is kept to be constant by controlling the angle of the reflection mirror to make the two currents equal. The performance of the photo-sensor was tested with a mirror-telescope system and the sun tracking error was estimated to be less than 0.6 mrad on sunny day. To ascertain the applicability of the photo-sensor, a sensor-controlled heliostat, in which no computer-control system and rotary encoders were installed, was manufactured. The performance of the heliostat was evaluated by observing the radiation on the target screen which was placed 70 m south side of the heliostat, and the angular error within 2 mrad was achieved on sunny days, while the tracking error increased in various ways in cloudy weather. This photo-sensor is applicable for small solar furnace, sun lighting system, and sun tracking photovoltaic system.Copyright © 2004 by ASME
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paper_title: Robust maximum power point tracker using sliding mode controller for the three-phase grid-connected photovoltaic system

paper_content:

A robust maximum power point tracker (MPPT) using sliding mode controller for the three-phase grid-connected photovoltaic system has been proposed in this paper. Contrary to the previous controller, the proposed system consists of MPPT controller and current controller for tight regulation of the current. The proposed MPPT controller generates current reference directly from the solar array power information and the current controller uses the integral sliding mode for the tight control of current. The proposed system can prevent the current overshoot and provide optimal design for the system components. The structure of the proposed system is simple, and it shows robust tracking property against modeling uncertainties and parameter variations. Mathematical modeling is developed and the experimental results verify the validity of the proposed controller.
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paper_title: Effect of two-axis sun tracking on the performance of compound parabolic concentrators

paper_content:

An experimental study was performed to investigate the effect of using a two-axis sun tracking system on the thermal performance of compound parabolic concentrators (CPC). An electromechanical two-axis tracking system and two identical CPC collectors were designed and constructed for the purpose of the investigation. Two cases were examined: in the first, a batch feeding was used where no flow through the collector was allowed; in the second, different steady water flow rates were used. In both cases, the variations of water temperature in the systems were monitored. The tracking CPC collector showed a better performance with an increase in the collected energy of up to 75% compared with an identical fixed collector.
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paper_title: Efficiency improvements of photo-voltaic panels using a Sun-tracking system

paper_content:

This paper presents a Sun-tracking design, whereby the movement of a photo-voltaic module was controlled to follow the Sun's radiation using a programmable logic-controller (PLC) unit. All electronic circuits and the necessary software have been designed and developed to perform the technical tasks. A PLC unit was employed to control and monitor the mechanical movement of the PV module and to collect and store data related to the Sun's radiation. It is found that the daily output power of the PV was increased by more than 20% in comparison with that of a fixed module. The PV-tracking system can be employed as a stand-alone device and it could be connected to a personal computer through the RS232 serial port to monitor the whole process on a computer screen.
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paper_title: Developing a multipurpose sun tracking system using fuzzy control

paper_content:

The present work demonstrates the design and simulation of time controlled step sun tracking systems that include: one axis sun tracking with the tilted aperture equal to the latitude angle, equatorial two axis sun tracking and azimuth/elevation sun tracking. The first order Sugeno fuzzy inference system is utilized for modeling and controller design. In addition, an estimation of the insolation incident on a two axis sun tracking system is determined by fuzzy IF-THEN rules. The approach starts by generating the input/output data. Then, the subtractive clustering algorithm, along with least square estimation (LSE), generates the fuzzy rules that describe the relationship between the input/output data of solar angles that change with time. The fuzzy rules are tuned by an adaptive neuro-fuzzy inference system (ANFIS). Finally, an open loop control system is designed for each of the previous types of sun tracking systems. The results are shown using simulation and virtual reality. The site of application is chosen at Amman, Jordan (32° North, 36° East), and the period of controlling and simulating each type of tracking system is the year 2003.
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paper_title: Two axes sun tracking system with PLC control

paper_content:

Abstract In this paper, an electromechanical, two axes sun tracking system is designed and constructed. The programming method of control with an open loop system is employed where the programmable logic controller is used to control the motion of the sun tracking surface. An experimental study was performed to investigate the effect of using two axes tracking on the solar energy collected. The collected energy was measured and compared with that on a fixed surface tilted at 32° towards the south. The results indicate that the measured collected solar energy on the moving surface was significantly larger than that on a fixed surface. The two axes tracking surface showed a better performance with an increase in the collected energy of up to 41.34% compared with the fixed surface.
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paper_title: Analogue sun sensor based on the optical nonlinear compensation measuring principle

paper_content:

A novel angle measuring principle, the optical nonlinear compensation measuring principle, is presented in this paper based on which a novel analogue sun sensor technology has been developed. The design, the performance and the test of the analogue sun sensor are described. Test results show that the accuracy of the analogue sun sensor is better than 0.2° (3σ) in the entire FOV (field of view) of ±62°, both axes. Compared with other analogue sun sensors, the major advantage of this sun sensor is that its mass and size are relatively low, and that high accuracy and large FOV can be realized simultaneously.
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paper_title: General Sun Tracking Formula for Heliostats With Arbitrarily Oriented Axes

paper_content:

The most general form of solar tracking formulae of an arbitrarily oriented heliostat toward an arbitrarily located target on the Earth is presented. With this complete solution, the used azimuth-elevation, spinning-elevation tracking formula, etc., are the special cases of it. Therefore, more application may be sought out for many individual cases in solar engineering. The new form of tracking solution could bring changes in the geometry and structure of the design of heliostat to meet various requirements.
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paper_title: Solar position algorithm for solar radiation applications

paper_content:

Abstract There have been many published articles describing solar position algorithms for solar radiation applications. The best uncertainty achieved in most of these articles is greater than ±0.01° in calculating the solar zenith and azimuth angles. For some, the algorithm is valid for a limited number of years varying from 15 years to a hundred years. This report is a step by step procedure for implementing an algorithm to calculate the solar zenith and azimuth angles in the period from the year −2000 to 6000, with uncertainties of ±0.0003°. The algorithm is described in a book written by Jean Meeus in 1998. This report is written in a step by step format to simplify the complicated steps described in the book, with a focus on the sun instead of the planets and stars in general. It also introduces some changes to accommodate for solar radiation applications. The changes include changing the direction of measuring azimuth angles to be measured from north and eastward instead of being measured from south and eastward, and the direction of measuring the observer’s geographical longitude to be measured as positive eastward from Greenwich meridian instead of negative. This report also includes the calculation of incidence angle for a surface that is tilted to any horizontal and vertical angle, as described by Iqbals in 1983.
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paper_title: Design guidelines for a glazing with a seasonally dependent solar transmittance

paper_content:

The basic design guidelines for a window and facade glass which rejects direct solar radiation during the summer period and which transmits direct solar radiation during the remainder of the year are derived. The design employs purely passive control means and is based on the seasonal change of the incident angle of solar rays and on the capability of glass prisms to refract and totally reflect or transmit solar rays dependent on the relevant incident angle. Two new design elements essentially extend the applicability of the glass in accordance with window orientation and season of direct solar light rejection.
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paper_title: Report of the first prototype of non-imaging focusing heliostat and its application in high temperature solar furnace

paper_content:

Abstract Following the publication on the principle and theory of a newly proposed non-imaging focusing heliostat, this paper presents a report on the design, optical alignment and application of the first prototype heliostat. In the architecture of the first prototype, 25 mirrors, each with a dimension of 40×40 cm, are arranged into five rows and five columns to form a total reflective area of 4 m2. The design of the essential part of the first prototype heliostat will be discussed in this paper, which consists of two primary elements; a rotation–elevation system for tracking a mirror support frame which carries 25 mirror facets, and a separate two-axis tracking system for compensating (each second) off-axis aberrations of 24 slave facets relative to the central mirror, which is fixed in the mirror frame. The rotation–elevation system consists of a pedestal supporting a rotational tracking mechanism carrying a U-shaped arm and a second tracking system for tracking a moving frame in elevation. The moving frame carries a central stationary (relative to the frame) mirror, called a master mirror. Slave mirrors are arrayed in five rows and five columns, and eight stepper motors drive the outer four rows and columns relative to the master mirror via a computer programme implementing newly proposed formulas to eliminate the first-order aberration. With a second stage concentrator comprising a small aperture size parabolic mirror (diameter of 60 cm), a cost-effective high temperature solar furnace was constructed. In our experiment, the highest furnace temperature of 3400°C has been recorded through the melting of pure tungsten wires.
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paper_title: An algorithm for the computation of the solar position

paper_content:

A new algorithm for the determination of the solar position is proposed. The importance of tracking accurately the position of the sun is evident when considering high concentration thermal systems. In the literature are found many fast algorithms for the determination of the sun position within 0.01°, and complex astronomical algorithms that allow a precision of 0.0003° but at the price of a large amount of calculation. The algorithm proposed in this work has a precision that is half-way between the two cases (maximal error 0.0027°), that should be sufficient for all the applications in solar engineering, with a computational cost comparable to the cost of the fast algorithms.
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paper_title: Design and construction of non-imaging planar concentrator for concentrator photovoltaic system

paper_content:

A novel configuration of solar concentrator, which is the non-imaging planar concentrator, capable of producing much more uniform sunlight and reasonably high concentration ratio, is designed and constructed. This design is envisioned to be incorporated in concentrator photovoltaic (CPV) systems. The work presented here reports on the design, optical alignment and application of the prototype, which is installed at Universiti Tunku Abdul Rahman (UTAR), Malaysia. In the architecture of the prototype, 360 flat mirrors, each with a dimension of 4.0cm×4.0cm, are arranged into 24 rows and 15 columns with a total reflection area of about 5760cm2. In addition to that, illumination distribution for the prototype is simulated and its results are then compared with the experiment result.
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paper_title: Design and construction of a solar tracking system

paper_content:

An ideal tracker which follows the sun both north-south and east-west is designed and constructed. It is suitable for mounting a linear concentrator, focusing parabolic concentrator or photovoltaic array of aperture area 2 m2. The apparatus is built with two axes equational mount and controlled by a microprocessor system. The tracking is carried out by utilizing the astronomical coordinates of the sun. As such the present system gives improved tracking capability over the conventional sensor controlled tracker systems. The performance of the tracking system was studied with photovoltaic array mounted on it and tracking error of less than one degree was achieved. This tracking error can be reduced further by proper software.
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paper_title: Digital sun sensor based on the optical vernier measuring principle

paper_content:

A novel angle measuring principle, the optical vernier measuring principle, is presented in this paper based on which a high-accuracy digital sun sensor technology is developed. The design, the performance and the test of the digital sun sensor are described. Test results show that the accuracy of the digital sun sensor is better than 0.02° (about 1 min of arc) in the entire FOV (field of view) of ±64°. Compared with other sun sensors, the major advantage of this sun sensor is that high accuracy and large FOV can be realized with a photoelectric detector with fewer pixels.
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paper_title: General formula for on-axis sun-tracking system and its application in improving tracking accuracy of solar collector

paper_content:

Azimuth-elevation and tilt-roll tracking mechanism are among the most commonly used sun-tracking methods for aiming the solar collector towards the sun at all times. It has been many decades that each of these two sun-tracking methods has its own specific sun-tracking formula and they are not interrelated. In this paper, the most general form of sun-tracking formula that embraces all the possible on-axis tracking methods is presented. The general sun-tracking formula not only can provide a general mathematical solution, but more significantly it can improve the sun-tracking accuracy by tackling the installation error of the solar collector.
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paper_title: Passive optical solar tracking system.

paper_content:

An optical system consisting of a convex reflective sphere or cylinder and a collimating lens is proposed to produce a collimated beam of solar radiation whose direction of propagation varies only slightly over the course of a day. Called a passive optical solar tracking (POST) system, a spherical version of the proposed device has limited usefulness for daylighting applications due to the inverse relationship which is shown to exist between collimated beam directional stability and contained flux. A cylindrical version of the system exhibits greater promise for solar illumination of building interiors. Other applications for the device are proposed for the fields of solar research, education, and artistic design.
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paper_title: Tracking Systems Evaluation for the “Hybrid Lighting System”

paper_content:

As part of the design and development effort for the “Hybrid Lighting System,” Oak Ridge National Laboratory (ORNL) scientists have evaluated two potential candidate-tracking systems for the solar collector. The first system, the WattSun Solar Tracker, built by Array Technologies, utilizes a patented, closed loop, optical sun sensor to sense the sun’s position and track it. The second tracking system, SolarTrak Controller, built by Enhancement Electronics, Inc., is a micro controller-based tracking system. The SolarTrak micro controller-based Tracker’s sun position is determined by computing the celestial bearing of the sun with respect to the earth using the local time, date, latitude, longitude and time zone rather than sensing the relative bearing of the sun with optical receptors. This system connects directly to the mechanical system hardware supplied by Array Technologies. Both the WattSun Solar Tracker and the SolarTrak Controller were mounted on the prototype “Hybrid Lighting” mechanical system (array) hardware. A simple switch allowed independent testing of each system. Upon completion of the evaluation of the two systems we found the WattSun Solar Tracker controller to be unacceptable for use with our prototype hybrid lighting system. The SolarTrak Controller has performed well to date and provides suitable tracking accuracy for use with our prototype “Hybrid Lighting System”. After a six-month evaluation period at ORNL, the first prototype “Hybrid Lighting System” was installed at Ohio University as part of an “Enhanced Practical Photosynthetic CO2 Mitigation.” This document will highlight the results of the tracker investigation and outline the remaining issues to be addressed, to provide a suitable tracking system for our “Hybrid Lighting” collector.© 2003 ASME
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paper_title: Computing the solar vector

paper_content:

Abstract High-concentration solar thermal systems require the Sun to be tracked with great accuracy. The higher the system concentration, the greater this accuracy must be. The current trend in solar concentrator tracking systems is to use open-loop controllers that compute the direction of the solar vector based on location and time. To keep down the price of the tracking system, the controller is based on a low-cost microprocessor. These two facts impose important restrictions on the Sun position algorithm to be used in the controller, as it must be highly accurate and efficiently computable at the same time. In this paper, various algorithms currently available in the solar literature are reviewed and a new algorithm, developed at the Plataforma Solar de Almeria, which combines these two characteristics of accuracy and simplicity, is presented. The algorithm allows of the true solar vector to be determined with an accuracy of 0.5 minutes of arc for the period 1999–2015.
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Title: Sun Tracking Systems: A Review

Section 1: Introduction
Description 1: This section discusses the emergence of solar energy systems as a renewable energy source, the importance of sun tracking systems in capturing solar energy, and a brief overview of the paper's content.

Section 2: Gain in Energy Production
Description 2: This section outlines the historical and modern advancements in automatic solar tracking systems and their impact on energy gain through optimization techniques.

Section 3: Closed-loop Types of Sun Tracking Systems
Description 3: This section provides an in-depth review of closed-loop sun tracking systems that utilize feedback control principles, highlighting various implementations and their performance improvements.

Section 4: Open-loop Types of Sun Tracking Systems
Description 4: This section explores open-loop sun tracking systems that rely on pre-determined algorithms without feedback considerations and discusses their simplicity and cost-effectiveness.

Section 5: Conclusions
Description 5: This section summarizes the key advancements in sun tracking system algorithms, comparing closed-loop and open-loop types, and emphasizes their importance in enhancing solar energy collection and system performance.