Numerical and Experimental Investigations of Thermoelectric Generators for Wasted Heat Recovery.
Résumé
Thermoelectricity appears to be one of the promising solutions to produce carbon-neutral electricity from waste heat energy. Thermoelectric (TE) modules are robust, maintenance free, noiseless and have been tested in space since more than fifty years. However the use of thermoelectric generators (TEG) to recover waste heat energy is still limited due to their low efficiency. There are mainly two ways to increase this efficiency: researches on new materials and researches on a better use of existing modules. Our study focuses on the second way: optimization of TEG. Hot combustion gases rejected in the air (automotives, boats, airplanes, incinerators, biomass stoves) are a great source of wasted heat and were chosen as heat source in this study. A numerical model using the Matlab\textregistered software, based on multi-physics equations such as heat transfer, fluid mechanics and thermoelectricity was developed to predict the different thermal and electrical powers. In parallel, an experimental set-up was built to compare and validate this model. This set-up is composed of a thermal loop with a hot gas source, a cold fluid, a hot fin exchanger, a cold tubular exchanger and thermoelectric modules. The number and the place of these modules can be changed to study different configurations. A specific maximum power point tracker DC/DC converter charging a battery is added in order to study the electrical power produced by the TEG. The analysis of the influence of the number of thermoelectric modules and influence of electric currents on the produced electrical power was investigated. Different operating points of hot inlet gas airflow rate and of cold inlet source temperature were tested. Both experimental and numerical results show the necessity to optimize the position and the number of TE modules and the electrical currents.