[curtis]

> What's the advantage over direct thermoelectric conversion?

Stirling engines can approach 50% efficiency [1], whereas thermocouples are usually less than 10% [2].

[1] https://en.wikipedia.org/wiki/Stirling_engine

[2] https://en.wikipedia.org/wiki/Thermoelectric_generator#Effic...

[jessriedel]

Cool, thanks! It's really surprising to me that inserting a mechanical intermediary has such a large efficiency advantage.

[brians]

Why does mechanical stuff suck? Because of friction of moving parts. Too much energy is lost to heat. For a thermal engine, if you can arrange to put the moving parts mostly on the hot side, that’s no longer loss.