The Importance of Considering Parasitic Heat Losses When Modeling TEG Performance for High-Temperature Applications
For a thermoelectric generator (TEG) with nonideal heat exchangers, the electrical power output can be maximized by matching the thermal resistances of the TEG Rteg and heat exchangers Rhx. Due to the fact that TEG elements are not thermally isolated from the surroundings, this study shows that inner heat losses are significant for proper thermal resistance matching—particularly for TEG systems for high-temperature applications. The inner heat losses are here defined as parasitic heat transfer mechanisms within the space between the thermoelectric (TE) couple legs. Analytical modeling is carried out using a thermal resistance network and applied to determine the performance of a TE system comprising a finned heat sink as well as a TEG with base area of A = 6 × 6 × 10−4 m2 and leg width of a = 3 × 10−3 m. The performance of different TEG designs is evaluated, and the optimum thermal resistance ratio, i.e., Rhx/Rteg, obtained for different values of leg length and built-in TE couple leg number. Finally, the developed analytical model is employed in a multiobjective TEG design optimization scheme, based on the theory of Pareto efficiency, to maximize the power output while minimizing the amount of TE material required. The results obtained from the multiobjective optimization reveal that the amount of TE material required in a module can be reduced by 6.63% without any power output loss in comparison with the results of one-parameter optimization.
KeywordsThermoelectric generator heat exchanger heat loss high temperature design optimization Pareto frontier
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The authors are grateful for financial support from Sächsische AufbauBank (Grant No. 100234924). Furthermore, the authors would like to thank Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) and the Chair of Hydrogen and Nuclear Energy (WKET) for providing material data as well as productive discussions.
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