Finite Element Thermomechanical Modeling of Large Area Thermoelectric Generators based on Bismuth Telluride Alloys

A recent investigation was carried out to evaluate the level of mechanical stress generated in a thermoelectric (TE) module subjected to a temperature gradient. The study was based on the numerical simulation of the thermomechanical behavior of realistic TE generator modules under various operating conditions and leg lengths. By the use of finite element analysis the behavior of large modules (30 x 30 mm(2) and 40 x 40 mm(2)) was examined under realistic boundary conditions at the heat exchange interfaces. For example, the module was constrained between two rigid plates under a given compressive load, and different sliding conditions were assessed. The plastic deformation of the soldering alloys was shown to reduce the amount of stress in the legs. One of the main results indicated that an increase in the maximum stress values appeared in the legs as they were closer to the edges. For such large modules, the simulation predicted a measurable displacement of the ceramic plates between the center and the edges of the module under steady state operation with a temperature difference of 100A degrees C. We provide a satisfactory experimental validation by optical profiler measurements.