The Carnot limit applies specifically to heat engines but later proofs on the 2nd law of thermodynamics still cap the conversion of heat to useful energy. As lo

The Carnot limit applies specifically to heat engines but later proofs on the 2nd law of thermodynamics still cap the conversion of heat to useful energy. As long as you keep that in mind, 19% Carnot efficiency is really impressive for a system like this with a small temp difference and no moving parts. I find their watts per cubic region an odd way to measure it given that you need heat flow across a surface to generate juice.