Structural optimization of solar thermoelectric generators considering thermal stress conditions

Abstract

The optimization of the thermoelectric leg (TEL) structure is an effective means which can improve the thermoelectric performance of solar thermoelectric generator (STEG), however, the optimized dimensions may not satisfy the allowed stress and thus prevent the STEG from normal operation properly. To address this issue, we constructed a coupled thermal-electrical-stress multi-physical field model of STEG, and optimized the STEG structure under the condition of allowed stress. The results show that when the allowed stress is not considered, the optimal ratio of cross-sectional ratio (f) to height (h) is 0.03 mm−1 to maximize the thermoelectric conversion efficiency, but then the maximum thermal stress of the STEG far exceeds the allowed stress of the material. When the allowed stress conditions are considered, the critical cross-sectional ratio of the module is much higher than the optimal cross-sectional ratio. The critical output power that can be obtained from the module is 38.5% less than the maximum output power without considering the allowed stress, and the influence of thermal stress on the optimal structural parameters is significant at a high concentration ratio. The critical output power gradually increases with the increase in the concentration ratio, and a greater output performance can be obtained at larger heights, while a greater output power density can be obtained at smaller heights. The outcomes presented by this study have certain guide to the construction of high-efficiency STEG.