Experimental study of the influences of surface roughness and thermal interface material on the performance of a thermoelectric generator

Reducing surface roughness and using thermal interface materials (TIMs) at the interfaces between a thermoelectric generator (TEG), heat source, and heat sink are effective strategies for decreasing the thermal contact resistance (TCR) and enhancing the TEG performance. To evaluate the influences of parameters such as the surface roughness, the thermal conductivity of TIM and loading pressure, we conducted experiments to measure the open-circuit voltage and output power of the TEG under various installation conditions. We also analysed the changes in TCR and temperature difference across the TEG module. The experimental findings were validated with numerical simulations using COMSOL Multiphysics under specific conditions. Our results revealed that reducing surface roughness and using TIM could substantially reduce the TCR, increase the temperature difference across the TEG, and increase the output power from the TEG. In our experiments, we used a temperature controller, cartridge heaters and thermocouples to regulate and record the temperatures of the heat source and heat sink. When maintaining a temperature difference of 53 K between the heat source and heat sink, and loading pressure set at 0.2 MPa, without using TIM, as the surface roughness decreased from 2.2 mu m to 0.37 mu m and to 0.03 mu m, leading to a reduction in the TCR from 0.22 K W-1 to 0.17 K W-1 and to 0.13 K/W. Simultaneously, the open-circuit voltage increased from 1.32 V to 1.65 V and to 1.86 V, and the maximum output power increased from 0.26 W to 0.44 W and to 0.58 W. Additionally, when the surface roughness was 0.37 mu m, after using TIM with thermal conductivity of 1 W/m-K, 2 W m-1-K-1, and 5 W m-1-K-1, the open-circuit voltage reached 1.44 V, 1.74 V and 1.94 V, respectively, and the maximum power reached 0.31 W, 0.51 W and 0.65 W, respectively.