I was reading about peltier coolers (thermoelectric coolers) and found interesting the peltier effect, where two different metalic materials under some electric current generates a temperature differential in each side of the peltier plate.
Sadly the efficience it's low (10% to 15% only), much lower than good vapor compression refrigeratos (like usual ice box in homes), making it a bad alternative to compressors, despite youtubers have many DIY project using peltier plates for small cooling devices.
But it's also interesting how the reverse, apply different temperatures to each side of the peltier plate, also works as a generator of electricity.
Again it have poor efficience (5% to 8%), otherwise it could replace turbines.
Thermoeletric generator uses peltier effect in reverse, and it's called
seebeck effect
I'm wondering if the claimed self charging battery, reported as using room temperature to recharge, could use some similar effect. But the seebeck effect, like Peltier effect, require a temperature differential on each side.
https://en.wikipedia.org/wiki/Thermoelectric_cooling
https://en.wikipedia.org/wiki/Thermoelectric_generator
https://en.wikipedia.org/wiki/Thermoelectric_effect