Progress Towards Maximizing the Performance of a Thermoelectric Power Generator

Abstract

This paper describes the design, modeling, initial build and testing of a novel thermoelectric power generator (TPG), incorporating state of the art material technology with optimized thermal management. A numerical model simulates the operation of the device and facilitates its design. Advanced multi-parameter, gradient-based optimization techniques are used to better understand the interactions between various design variables and parameters in order to progress towards an optimal TPG design. The device, made up of a series of segmented elements each comprised of up to three different materials, combines thermal isolation in the direction of flow with high power density thermoelectric (TE) material integrated directly into the heat exchanger device. Electrical current runs parallel to the heat source and sink surfaces in the device, allowing the integration of the TE material with multiple geometric degrees of freedom. This design attribute coupled with the thermal isolation thermodynamic cycle, allows each element of the TE device to be optimized semi-independently. Each p- and n-type element can have different aspect ratios (cross-sectional area divided by thickness) so that each material layer of each element has the highest possible ZT for each temperature range. The increased design flexibility helps address TE material compatibility issues associated with segmented elements and fluid flow that ordinarily degrade performance. Eliminating the impact of thermal expansion mismatch while still maintaining excellent thermal and electrical contacts is also a design goal. Additional design considerations are also discussed, including electrical and thermal connector design and minimizing interfacial resistances. The device described is suitable for both waste heat recovery and primary power applications. Initial test results from prototype builds are discussed