A numerical model and comparative investigation of a thermoelectric generator with multi-irreversibilities

Taking into account inner and external multi-irreversibilities, a complete numerical model of commercial thermoelectric generator with finned heat exchangers is established by combining thermodynamics with heat transfer theory. A significant novelty is that physical properties, geometric dimensions, temperature parameters and flow parameters are all considered in the model. The inner effects include Seebeck effect, Fourier effect, Joule effect and Thomson effect. The irreversibilities include the heat transfer through the air gap (proposed and evaluated first time), the thermal and electrical resistance of the conducting strips, and the multiform external thermal resistances. Based on the numerical model, the performances of a typical commercial thermoelectric generator are simulated. Hot water at 60-100 oC and cold water at 27 oC are employed as heat source and sink of the generator module which consists of 127 thermoelectric elements. The results show that the maximum power output of 0.13 W and the maximum efficiency of 0.87% are available from the generator. The open circuit voltage is 1.80 V and the short circuit current is 0.28 A, respectively. The effects of external irreversibilities on the performance of the thermoelectric generator are analyzed by comparing this irreversible model with the exo-reversible model. The numerical model and calculation method can be applied to the performance prediction and optimization of thermoelectric generators with finned heat exchangers. The simulation results can be used as feasibility and effectiveness reference by employing low-grade energy or waste heat for power generation. -- Highlights: → A complete numerical model of commercial thermoelectric generator with finned heat exchangers is established by combining thermodynamics with heat transfer theory. → The performances of a typical commercial thermoelectric generator are simulated. → The temperature difference and voltage output are linear function of the electrical current output approximately. → The power and efficiency are both parabolic-like functions of the electrical current output. The Fourier heat leakage is the main loss among the inner effects.