If you look up Stirling engines on the internet, you’ll immediately find a load of toys and hobby kits for a device that runs seemingly by magic.

Don’t write it off because of that, the Romans invented the Steam engine like 1800 years before trains, they just wrote it off as a child’s toy.

A lot of shit generates an insane amount of heat, if we can harvest the temp differential a couple times during cooling process, it’s literally free energy. Even if it just runs the fans/pumps in the cooling. It would be somewhat self regulating even, although we couldn’t rely solely on this or we’d run into the same issue as nuke reactors with positive power coefficients.