Sunday, February 23, 2014

Is ammonia the holy grail for renewable energy storage?
























This piece was updated on 2/26/14 to reflect additional information and corrections discussed in my comment below.



Anonymous said...

I'm pretty sceptical. The energy losses through entropy would be huge, there are 4 changes of energy type, 6 if you include heat and kinetic. So the laws of thermodynamics are against if for a start. If society was to stop using nat gas for heating and cooking, the current hydro surplus would disappear or at least be greatly diminished. Maybe a niche storage system in unique circumstances, but not a 'holy grail.' The search continues then. Far more realistic to work on bringing societies energy consumption down. Though that is equally unlikely to be done voluntarily.

Anonymous said...

Thanks for the post.

Joe said...

A more important use would be to substitute the ammonia derived from 'green' electrolysis for the ammonia created from natural gas. If the green ammonia were used for agriculture (the most common use), it would reduce the huge carbon footprint of that industry.

ronald peddie said...

Ammonia produced form natural gas uses approx 2 tonnes of natural gas per tonne of Ammonia so the carbon footprint simply moves to the ammonia plant.
As the other correspondent states if you can make ammonia without carbon just use it as ammonia don't waste it as a very expensive fuel

Anonymous said...

Kurt - thanks for this interesting perspective.

To get a measure of its actual utility, how about a numerical comparison with the major contender for a liquid-fuel-energy-store, namely Methanol [CH3OH]?

The latter is proposed in "The Methanol Economy" by George Olaf (nobel laureate chemist) and focusses on its production from airborne carbon (CO2) plus hydrogen from electrolysis at Hydro plants. His thesis is very carefully built and addresses the integration issue with extant infrastructure, with the fuel's potential use in SI & EI engines, gas turbines, Direct Methanol Fuel Cells and others.

Notably like ammonia corrosion-proof tanks are needed, by it offers a beter energy density at 55% of petrol compared with 40%.

One aspect Olaf doesn't cover is that we face huge volumes of forestry being killed by pine beetles, droughts, etc - Last I heard the US had over 70,000sq mls dead, while British Columbia had over a billion tonnes standing dead awaiting rot or wildfire. I'd suggest that the best and necessary use for that timber is in the production of Biochar for soil fertility and carbon sequestration, but the wood's pyrolization in moderately efficient retorts yields about 28% of the feedstock's energy potential as waste hydrocarbon gasses, which are readily converted to methanol.

From this perspective the methanol option offers a far greater range of benefits in not only providing a carbon neutral liquid fuel, but also in potentially assisting the economics of what appears to be the only scaleable option for avoiding the massive AGW feedback of forest combustion or rot, while also achieving the requisite global scale of Carbon Recovery to begin the cleansing of the atmosphere.

I should be very interested to read your comparison of the two options for a liquid fuel energy store, as this is clearly an area of chronic and rising concern.


Lewis Cleverdon

Greg Vezina said...

A better way to use coal and other petroleum resources has been know for over fifty years. According to the Nov. 2102 "IEEE Dual Fuel Strategy" we can convert hydrocarbons into NH3, urea and char, thereby eliminating the carbon and other toxic chemicals instead of burning, flaring or venting them and it is much cheaper than dealing with emissions after combustion.

We can convert carbon fuelled power generators to use NH3 and oxygen, increasing the efficiency by as much as 50% and eliminating 100% of the emissions.

We can deep inject urea and char instead of other ammonia or phosphorous based fertilizer, increasing yield, reducing input costs and eliminating the phosphorous and nitrogen pollution.

We can utilize the existing NH3 industrial capacity by integrating or substituting alternative or off peak energy at the manufacturing stage. KRES- 5 makes more ammonia by energy substitution.

We can utilize the distribution infrastructure for fuel instead thereby supplying up to 10% of our fuel demand and use existing pipelines to move more energy stored in NH3 than can be moved as hydrocarbons, safely, with little or no long term or catastrophic consequences from any accidental spills.

Finally we can easily convert existing engines to use it as a fuel. AND

St. Roy said...

1217Kurt: This post coming from you surprises me. The H-B process is very energy intensive as is cleaving H from NH3. Seems like a crackpot scheme to me.

Kurt Cobb said...

Thanks for all the thoughtful comments. Let me respond, but not in order.

First, I mentioned that ammonia can be used directly in high compression engines which is correct. But, it turns out that it's not that difficult to adapt gasoline and standard diesel engines to run directly on ammonia which opens up a much wider range of applications without having to split hydrogen from ammonia. Ammonia also works in fuel cells.

There may still be some applications where hydrogen is needed and here it turns out that steam reforming (which is highly energy intensive) is not needed. An electrolytic cell of NH3 in water at room temperature will apparently do the trick.

This addresses concerns about how energy intensive ammonia might be as a fuel since it can be burned directly for most applications.

Second, I agree that if ammonia made from renewable energy can be produced in large enough quantities it might displace ammonia made from fossil fuels simply because it is cheaper. We are, of course, nowhere near that. But, it seems like a possibility.

Third, I was not aware of the IEEE Dual Fuel Strategy and will look into it.

Fourth, I am aware of ideas for using methanol and haven't taken them that seriously. Lewis Cleverdon has piqued my interest.

Fifth, St. Roy is correct that the Haber Bosch process is energy intensive. But if it is done with renewable energy, at least we are not putting more carbon in the air to create ammonia. There is, of course, some concern about the energy return on investment in this case. But for energy carriers we should be less concerned about that than about the efficacy of the liquid fuel within the current infrastructure. Making the current infrastructure carbon-free would be the fastest way to bring down our carbon emissions. Building a brand new infrastructure based on other fuels would take considerably longer.

Since I was in error about having to split hydrogen off from ammonia for all but high-compression engines, the concern that this splitting would be energy intensive has actually been addressed.

It's true that ammonia based on renewables might be expensive compared to fossil fuel-based methods for creating ammonia. We simply don't know whether this will be the case until there is some effort to bring ammonia production from renewables to scale. But even if this is the case, the cost of paying for more expensive ammonia that is relatively carbon-free is a small price to pay to mitigate climate change.