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by darksaints
2395 days ago
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Looks like you've been going down a similar path as me. Unfortunately, liquid fuels from pure electricity is extremely energy inefficient. For example, the fischer tropsch process will consume the hydrogen that you've split with precious electricity, and only half of that will make its way into the fuel, the other half of ends up converting back into water. And that is before you figure out how to get CO2 in concentrations high enough to be cost effective. You might want to check out plasma reforming. It's the path I'm currently on, although targeted for a different end product. https://drexel.edu/nyheiminstitute/researchlabs/plasma-energ... |
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I mostly think I have to be doing some chemistry/math wrong, based on how not terrible the energy efficiency is. I'd love corrections or reading material, as this is not a knowledgeable area for me. - 2 CO2 + 9 H20 + 12e- -> C2H5OH + 12 OH- = 0.084 V - over voltage of 1.2 V is best - 1kWh @ 1.2V yields 30 moles electrons - 30 moles electrons has theoretical yield 2.5 moles ethanol = 0.146 L ethanol - reduced to appx 116ml ethanol due to selectivity - 116ml ethanol has raw energy of 778 Wh, probably 550 Wh recoverable with Combined Heat and Power
I think 55% round trip efficiency for energy-dense long term storage would be big. Of course, this isn't that (math is partially based on theoretical bests, ethanol isn't long term, CO2 capture and material movement not accounted for).
Thanks for the plasma reforming tip!