Effects of different electrical arrangements and Thomson effect on the system performance as well as the optimum allocation of thermocouples in a self-driven two-stage TEC & TEG

Abstract

In this study, four different electrical arrangements of a two-stage thermoelectric cooler (TEC) driven by a two-stage thermoelectric generator (TEG) are analyzed, and the best combination is identified in terms of maximum cooling capacity and coefficient of performance (COP). The results demonstrate that the inclusion of the Thomson effect increases the maximum COP and cooling capacity and shifts the optimum thermocouple ratio towards a lower value. Simple regression equations are developed for quick and accurate prediction of optimum thermocouples ratio for maximum cooling capacity and maximum COP conditions. As observed, the optimum thermocouple ratio is a strong function of total thermal conductance, source and sink temperatures, thermocouple ratio in stages of TEG and TEC and the type of electrical arrangement. The best combination is further confirmed by analyzing the variation of exergetic efficiency with the total thermocouple ratio. Although both the arrangement, i.e. TEG in parallel and TEC in series and TEG in series and TEC in series, yield comparable COP, TEG in parallel and TEC in series is quite advantageous from the cooling capacity point of view. In the absence of the Thomson effect, TEG in parallel TEC in series yields the best COP and cooling capacity.