Experimental study of thermoelectric generator with different numbers of modules for waste heat recovery

Significant amounts of residual heat are contained in the exhaust of internal combustion engines. In this regard, thermoelectric generation is recognized as one of the techniques with development potential, which renders thermoelectric generators an efficient technology among several waste heat recovery devices. This study involved the construction of an experimental thermoelectric generation system. The effects of the heat source temperature, flow, and number of modules on the thermoelectric performance were experimentally studied. The results show that the output power increases with the number of modules under high-flow conditions. At low flow rates, the optimal number of modules ensures that the system delivers the peak output power. The voltage uniformity coefficient can accurately indicate the uniformity of voltage distribution. The voltage uniformity degrades with an increase in air temperature, but the increase in air flow can improve the voltage uniformity. In addition, with the increase in the number of thermoelectric modules, the voltage inhomogeneity of the module decreases. As the air temperature and flow increase, the power consumption of the thermoelectric generator increases. The resistance power consumption accounts for a large proportion, as much as 24.2%, under high-flow and low-temperature conditions. As the number of modules increases, the resistance power consumption of the thermoelectric generator and the proportion thereof increase. The net output performance is closely related to the number of modules, and under all test conditions, 40 modules achieved a maximum net power generation of 25.16 W, and 16 modules achieved a maximum net conversion efficiency of 1.56%. Therefore, it is necessary to plan the number of modules in the system reasonably. This study provides guidance for the design of high-efficiency thermoelectric generators.