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Comment by mikewarot | Hacker News Reader

There must be an error in the math somewhere...

This could greatly improve the efficiency of burning coal.

Let's say you burn a ton of coal, (assume pure carbon for this example) getting 2460 kWh of power, per ref: [1]

You then put the resultant 3 2/3 ton of CO2 through this process, at a cost of 843 kWh, recovering 920 kg of carbon.

You've now consumed net 80 kg of carbon, generated 2460-843 --> 1617 kWh of electricity, for a net of 20,212 kWh/ton of Carbon burned.

This page [1] says a ton of coal gives 2460 kWh of electricity

1 - https://www.mcginley.co.uk/news/how-much-of-each-energy-sour....

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I'm a little skeptical of the results as well. A tonne of CO2 releases 2489 kW*hr of free energy when formed from C and O2.

However, reading the original paper, it seems like the end product is "highly oxidized carbon", "akin to that of slightly crystalline graphene oxide". So they're not claiming to undo the carbon oxidization, more to vitrify the carbon oxide in a solid phase. This, presumably, takes significantly less energy than reducing the carbon.

Any chance you have a link to the preprint, or know of a non paywall source?

One thing missing is the energy cost of removing/drying the carbon flakes from the system, then moving themfor combustion. In a closed loop, you could create a cycle that consumed co2 and reconstituted it by burning and reproducing co2, but it would taper off. Yes, you could burn the carbon flakes to produce more energy than the system consumes, but you'll need more oxygen from the environment to maintain the reaction. At 92% efficiency, you'd run out of oxygen to maintain combustion after a dozen cycles or so, in a closed system. With an endless amount of atmospheric co2, the picture changes.

2460 kwh, at 12 cents per kwh, translates to $295 of electricity per ton. It optimally produces twice as much as it consumes.

Maybe a Stirling engine that uses a belt feeder, with the flakes skimmed from the catalytic reaction chamber onto the belt, drying in the heat of combustion, then dropped into the burner, and the exhaust bubbled back into the solvent. Then it could deposit the excess flakes while producing power by directly consuming co2?

This is pretty phenomenal, edging into the "too good to be true" domain.

Anyway, pointing out that pure carbon can be burned is good thinking.

... it can be buried though (just not in oceans because it will just be turned back into CO2) or even reused in carbon-composite materials.

That sounds like a perpetual motion machine. What am I missing?

It sounds like this violates conservation of energy then?

Couldn’t you then burn the carbon and oxygen you created to get out more lower than you put in?

No, more oxygen is required to sustain the process of combustion. Just like extracting energy from wind, it's only limitless because the environment is massive. In a closed system, this reaction would taper out quickly, it relies on endless amounts of fuel from the atmosphere. A perpetual motion system produces energy from a closed system. Real world systems can tap into ambient energy, even if it's stored chemically. The only thing novel about using this process to produce fuel is the lack of lengthy intermediate steps between fuel and extracting energy from chemical reactions.

It looks like it's not pure carbon that is produced but a variation of graphene oxide, though, which can't be a easily burned to maintain the reaction. It can be reduced, and then burned, though, so there's still potential for a co2 power cycle.

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