im thinking something small.
there are some 12v output units on AliBaba. Though a 5v 3amp unit would be cool.
i use a woodstove fan every day that works on the same principle.
a base to transfer heat to one side of the plate, and a heat sink on the other to create the temperature difference needed to create current.
its not going to charge a battery bank, but capturing heat as charging electricity for devices sounds cool to me. especially since im burning a fire every day in the winter…
interesting winter tinkering project…