Selection of Materials for Cascaded Thermoelectric Generators under Transient Thermal Loading

Materials for thermoelectric devices should have a large Seebeck coefficient, high electrical conductivity and low thermal conductivity as indicated by the thermoelectric figure of merit (ZT).  The figure of merit is temperature dependent, so multiple materials can be used in cascaded thermoelectric devices, in which each material is located according to its properties at the temperature expected at its location during operation.  Numerical modeling has shown that the energy conversion efficiencies of materials with the same figures of merit but different electrical/thermal conductivities depend on the position of the materials in the device (i.e. hot or cold region).  The differences in performance are larger under transient heating and cooling, but there are differences even under steady-state conditions.  In this paper, results of numerical modeling of thermoelectric generators will be presented to demonstrate how strategic materials placement can be used to improve device performance.