U-type unileg thermoelectric module: A novel structure for high-temperature application with long lifespan

Strong thermal stress caused by high temperature and difference of thermal expansion coefficient (CTE) will negatively influence the lifespan of the thermoelectric module. In this work, a new high temperature CaMnO3-based U-type unileg thermoelectric module, combining a unileg structure with pn-junction, is proposed and investigated. The novel design avoids the device failure due to different CTEs and high temperature gradients. As a result, the maximal thermal stress (sigma(max,TEM)) of 3.31 GPa and fatigue life of 41686 cycles are 46 % and 132 % of those of traditional modules at 6 W and 300 K, respectively. To further relieve stress concentration, the effect of rounded corners (r(u), r(l)), Ag layer thickness (HAg) and length of right legs (L-R), have been studied. It has been found that larger ru, and rl are suitable to relieve the local stress concentration, and the lowest sigma(max),TEM and highest power (P-max) are achieved at (r(u),r(l))=(0.1,0) and (0,0.5). Moreover, larger L-R and H-A are beneficial for mechanical properties by decreasing the peak stress and dispersing the high thermal stress regions, while module performance is improved at lower L-R and H-Ag. Results obtained from this U-type unileg thermoelectric module should influence and guide the design and optimization of high-temperature thermoelectric generators. (C) 2021 Elsevier Ltd. All rights reserved.