what is the efficiency of a peltier junction? how many watts of power does it to take to move a watt of heat?

Question

previously I calculated that an 11 EER air conditioner (moves 11btus per watt) would move 5 watts of heat for each watt used by the AC. how effecient is a peltier juncton (AKA TEC)?
thanks

what is ohmic? do you mean electric resistive heat? I would think peltier would be better because even if 3 watts of power gives you 4 watts of heat by moving it, in resistive 3=3.

using a peltier on a heat source you are running anywaysis great! I have seen peltier fans that sit on a wood stove and run themselves

Answer 1

The most efficient peltier junctions use semiconductors, not metals, and even they're not very efficient. A mechanical heat pump using evaporation and condensation of a fluid can shift three watts of heat for every watt of power consumed, so they're an economical form of heating in the winter as well as air conditioning in summer. But even the best thermocouples require several watts of electricity for every watt of heat moved. So the only purposes for which they're suitable are for small-scale cooling without moving parts and for generating small amounts of power from a heat supply. In Siberia they're used to power a radio with the waste heat from a fire. But ordinary ohmic heating will always be a more efficient way to turn electric power into heat.