Characteristics and single/multi-objective optimization of thermoelectric generator by comprehensively considering inner-connection-and-contact effects and side-surface heat loss

Abstract

Thermoelectric generator (TEG) is a promising technology for waste heat recovery. Typical TEG module has a multi-material-layers sandwiched structure, in which the inherent inner-connection-and-contact (ICC) effects and side-surface heat loss may significantly degrade TEG performance. Therefore, quantitative assessment and analysis of the ICC effects and side-surface heat loss simultaneously are crucial for the optimization design of a TEG module. However, existing researches usually emphasize on the two factors separately and qualitatively. In this work, the whole ICC effects of interconnectors, solders and contact surfaces are equivalent to extra assumed ICC layers at both ends of thermoelement for the first time, and based on that a three-dimensional numerical model is established in COMSOL Multiphysics software with simultaneously considering the side-surface heat transfer coefficient ha of thermoelement. The ICC effects of a TEG module are identified by using BOBYQA optimization algorithm in COMSOL to match experimental data. It shows that, as ha increases, the recognized ICC thermal and electric resistances present linear opposite change; when ha > 12 Wm−2K−1, non-physical negative ICC electric resistance emerges. Then, based on the identified ICC effects and reasonable ha (≈5 Wm−2K−1), the results between present model and analytical theory are compared and discussed under the condition of fixed fill factor. Furthermore, multi-parameters optimization of the TEG is carried out for maximum output power, efficiency, power/cost ratio and their equally weighted multi-objective, respectively. The results show that (1) the optimal parameters such as thermoelement length Lopt and fill factor Fopt vary significantly depending on different optimization objectives; (2) the ICC effects can approximately double the Lopt and Fopt corresponding to maximum efficiency or power/cost ratio, while the ICC effects show negligible influence on the Fopt corresponding to maximum output power or equally weighted multi-objective.