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A comment on CO2 battery could make wind and solar dispatchable at a lower price. Parent comment

Re:CO2 battery could make wind and solar dispatchable at a l... by amelius on Sunday August 01, 2021 @08:21AM (#28025757)
> Interesting: CO2 gets pressurized, cooled to liquid temperatures via refrigeration, then uncompressed to spin a turbine when energy is needed.

Can someone explain the maximum theoretical efficiency of this process from basic thermodynamic principles?

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Re:CO2 battery could make wind and solar dispatchable at a l... by pjc50 on Sunday August 01, 2021 @01:21PM (#28028060)
Carnot cycle, isn't it? Not great for efficiency, probably less than 50% round trip.
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Re:CO2 battery could make wind and solar dispatchable at a l... by ghkbrew on Sunday August 01, 2021 @04:37PM (#28029691)
Carnot is for heat engines. So the maximum efficiency of converting a heat differential into kinetic energy.

This is converting electricity into kinetic energy and vice versa. So it'd be the product of those two maximum efficiencies, whatever they are.

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Re:CO2 battery could make wind and solar dispatchable at a l... by ben_w on Monday August 02, 2021 @03:57AM (#28034018)
> This is converting electricity into kinetic energy and vice versa.

Where do you get that from? The article definitely seems to me to be describing a heat engine.

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Re:CO2 battery could make wind and solar dispatchable at a l... by contravariant on Sunday August 01, 2021 @05:41PM (#28030302)
Basic thermodynamics doesn't prevent you from cooling something reversibly.

That said plenty of the steps involved here are likely not 100% efficient, and I'm somewhat unsure where they're recovering the energy involved in the gas-liquid phase-transition, if at all.

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