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> Peltier junction, a thermo-electric device that translates electric power into heat, and perversely, into cool.
Apply current @ 3-12 VDC to the gizmo and it extracts thermal energy from one face, thereby cooling it.
The heat is dumped onto the other face, thereby heating it.

Please note: you must use a heat sink on the hot side or the junction will fry itself, since it can quickly create a 65° C temperature differential in a no load situation.

Stack two, or build a cascade to increase the thermal differential created.

Or run it backwards.
[Seebeck effect]
Apply heat or cold to the relevant face and produce a current.<

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