Comprehensive study and optimization of concentrated photovoltaic-thermoelectric considering all contact resistances

A consequence of the integration of photovoltaic module and thermoelectric generator is the presence of thermal contact, which affects the heat transfer in the hybrid system. Thermal and electrical contact are inevitable in a thermoelectric generator and their effects on the performance of the thermoelectric generator can be significant if not properly managed. Therefore, this study presents a comprehensive three-dimensional numerical investigation on the effect of contact resistances on the performance of concentrated photovoltaic-thermoelectric using COMSOL 5.4 Multiphysics software. Four contact resistances are studied including thermoelectric thermal contact resistance, thermoelectric electrical contact resistance, photovoltaic-thermoelectric interface thermal contact resistance and thermoelectric generator-heat sink interface thermal contact resistance. Twelve contact resistance cases are considered, and a comparison study is presented to investigate the most important contact resistance. In addition, a parametric optimization study is performed to investigate the optimum values for thermoelectric leg height, load resistance, concentration ratio and convective heat transfer coefficient. Results show that ignoring all contact resistances in the hybrid system causes an overestimation of overall power output and efficiency by 7.6% and 7.4% respectively using the base values considered in this study. In addition, the thermal contact resistance between the thermoelectric generator and heat sink, and that between the photovoltaic-thermoelectric interface are found to be the most important contact resistances, which should be reduced. Furthermore, results show that the optimum thermoelectric external load resistance in a hybrid system is lower than that of the thermoelectric generator only system. This study will provide valuable guidance on photovoltaic-thermoelectric accurate modelling.