Theoretical analysis of performance of variable cross-section thermoelectric generators: Effects of shape factor and thermal boundary conditions
2020
Liu, Hai-Bo | Wang, Shuo-Lin | Yang, Yan-Ru | Chen, Wei-Hsin | Wang, Xiaodong
Variable cross-section legs have been recently used to replace conventional legs for improving the thermoelectric generator (TEG) performance. However, some contradictory results have been reported and not fully understood. In this study, a comprehensive theoretical analysis is conducted to investigate the performance of variable cross-section TEGs via the one-dimensional energy equilibrium approach. The emphasis is placed on the influence of boundary conditions applied to the hot and cold ends of TEGs. A shape factor, m, is proposed to characterize various complex leg shapes, which connects the thermal and electric resistances of variable cross-section legs to those of conventional legs. Analytical expressions of the maximum output power, conversion efficiency, and working current of the conventional and variable cross-section TEGs under eight possible combinations of boundary conditions are respectively derived. On the basis of these expressions, it is concluded that, as compared with conventional legs, variable cross-section legs always enhance the maximum conversion efficiency, and maintain or reduce the maximum working current; however, they may improve or deteriorate the maximum output power, depending on the type of boundary conditions. The shape factor is found to determine the degree of performance enhancement or deterioration.
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