When power factor supersedes zT to determine power in a thermocouple

Abstract

The primary material parameter determining power in a thermoelectric is the figure of merit zT. This figure of merit comes from the requirement for thermal impedance matching between the thermoelectric legs and heat exchangers in an optimally designed thermoelectric module. However, in a thermocouple temperature sensor, the geometry is constrained for temperature sensing. If the geometry is constrained so that the length of the thermoelectric elements is greater than a characteristic length, then the material thermal conductivity becomes less relevant. This makes the power factor the determining material metric for power output in such a device designed for temperature sensing.