Solid-State Cooling, Part I

An overview of solid-state cooling vs. conventional vapor cycle and an update of the status of Peltier devices is presented. The key challenge to implementing solid-state cooling is to find materials and configurations that minimize their inherent losses. The Peltier effect causes heat to flow from the cold side to the hot side, in the same direction of current flow through the P-type pellets and in the opposite direction of current flow through the N-type pellets. Much research has focused on creating quantum wells or quantum dots that provide greater electron mobility for the electrons that are actually transporting heat, while decreasing the thermal conductivity at the same time. In conventional, commercially available devices, the electric resistance and thermal conduction losses are significant enough to limit ZT at room temperature to 1.0, with the maximum COP being well below the COP of vapor cycle systems.