Stirling radioisotope generator. Besides the cryocooler, the Stirling engine is in use in some other niche applications. The free piston Stirling engine (FPSE), uses an alternating magnetic field ...
The model Stirling engine is a staple of novelty catalogues, and we daresay that were it not for their high price there might be more than one Hackaday reader or writer who might own one.