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A comment on World’s largest battery maker announces major breakthrough in energy density. Parent comment

Re:World’s largest battery maker announces major breakthroug... by masklinn on Friday April 21, 2023 @05:41AM (#35651574)
> the absolute best theoretical efficiency of this might be 70%

While ICE are heat engines with a theoretical limit of 70%, they’re more specialised subsets described by the Otto (gas) and Diesel (… diesel) cycles, which have a much lower theoretical maximum.

Just plugging the temperature ranges into Carnot will give you a Carnot limit of 50%, and using Otto will yield 46% (https://physics.stackexchange.com/a/98992).

Add in that gas engines are not spherical and into a vacuum (losses and delays) and you’re in the 30s.

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Re:World’s largest battery maker announces major breakthroug... by qikInNdOutReply on Friday April 21, 2023 @06:41AM (#35651923)
Wrap the combustion engine with a heatpump to a small steam engine?
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Re:World’s largest battery maker announces major breakthroug... by osigurdson on Friday April 21, 2023 @07:34AM (#35652280)
It isn't precisely "wrapped", but this is essentially how all natural gas fired generation facilities work.

https://en.wikipedia.org/wiki/Combined_cycle_power_plant

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Re:World’s largest battery maker announces major breakthroug... by greesil on Friday April 21, 2023 @10:41AM (#35654479)
I think the parent is referring to harvesting some of the waste heat
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Re:World’s largest battery maker announces major breakthroug... by Sohcahtoa82 on Friday April 21, 2023 @04:29PM (#35659632)
The added weight and complexity would probably negate any benefit gained.
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