Influence of Thomson Effect on Nonlinear Thermo-Electric-Mechanical Coupling Behavior of Hybrid Thermoelectric-Piezoelectric Energy Harvester

Hybrid energy harvester with thermoelectric (TE) and piezoelectric (PE) generators can convert heat and mechanical energy into electricity simultaneously. Thermo-electric-mechanical coupling model is quite necessary to predict its performance. Under large temperature difference, Thomson heat cannot be neglected in TE device analyses. In addition, to harvesting higher energy, the PE beam is usually designed for large deformation. This study investigates the effect of Thomson effect and nonlinear vibration on the coupled thermoelectric-mechanical behavior of hybrid TE-PE system. Based on the simplification of heat sink and the thermoelectric model with Thomson heat, the thermoelectric field of TE part is obtained. The heat sink beam of TE part is also the substrate layer of PE part, the governing equation of nonlinear vibration is obtained based on Hamilton's principle. The output power of hybrid system with and without Thomson heat is analyzed. Numerical results show that material parameters and structure dimensions of hybrid energy harvester can influence performance of TE part and PE part simultaneously. When the temperature difference is small, the influence of Thomson effect on the performance of hybrid TE- PE system is weak. Output power of PE part can either be depressed or promoted by the Thomson effect of TE part, depending on the temperature-dependent Seebeck coefficient. As length of PE layer increasing, the heat dissipation effect of heat sink is reduced. This leads to that the temperature difference between the cold-end and hot-end of TE part is decreased, and performance of TE part is reduced. The paper analyzes the interaction among TE part and PE part in hybrid energy harvester. This study could be useful for guiding the searching for hybrid TE- PE energy harvester which is potentially high performance.