Stove fan
a thermoelectric generator, where a large-enough difference in temperature between the base of the fan (which sits on the stove) and the top of fan (which is cooled by a heat sink) causes a thermoelectric generator (which has a set of doped semiconductor elements, one being a P-type element and the other being an N-type element) to make a small electric current. This small current drives a small, low-torque motor.