The Sodium Heat Engine is an ingenious device: https://en.wikipedia.org/wiki/Alkali-metal_thermal_to_electric_converter https://en.wikipedia.org/wiki/Alkali-met

The Sodium Heat Engine is an ingenious device: https://en.wikipedia.org/wiki/Alkali-metal_thermal_to_electric_converter https://en.wikipedia.org/wiki/Alkali-metal_thermal_to_electr... Best thing: no moving parts required!