Thermoelectric Modules for Low-grade Waste Heat Recovery*

Annually, over 60% of global energy consumption is rejected as waste heat. Recovering a fraction of the wasted heat provides a transformative impact on overall energy saving. Thermoelectric generators (TEGs) are environmentally friendly devices that can directly convert heat to electricity. TEGs are reliable for waste heat recovery and power generation applications. Recent studies have reported the conversion efficiency of TEGs up to 14% under laboratory conditions. However, the practical efficiency of TEGs used in an actual environment is less than a few percent. The performance of the TEGs is influenced by materials figure of merit (zT), temperature gradient, internal electrical and thermal contact resistances, external thermal resistance, and boundary conditions. Commercial modules are not typically designed for specific applications when the thermal resistance of the heat source or sink is high. Therefore, depending on the application, materials and module designs are required to maximize energy recovery.

In this study, we use experimental and numerical methods to investigate the effect of thermoelectric materials properties (i.e., electrical conductivity, Seebeck coefficient, and thermal conductivity), device parameters, boundary conditions, and thermal resistances on TEG performance in a realistic environment. We optimize the module parameters to achieve the highest power and efficiency in such an environment. For this goal, we designed and fabricated different thermoelectric modules and tested them under practical application conditions. The application of such TEGs is in self-powered building sensors and electronic vehicles.