Modeling and thermodynamic optimization of a solar-driven two-stage multi-element thermoelectric generator

In this article, a finite-time thermodynamic model of solar-driven two-stage multi-element thermoelectric generator is developed. Considering external heat transfers, radiation loss of collector, Joule heat and Fourier heat leakage, analytical formulas for heat balance equations, power and efficiency are derived. Working tem-peratures of thermoelectric device are obtained by solving four equations simultaneously, and basic performance of the system is explored. Performance optimization is executed by adjusting electrical current, thermoelectric element distribution and heat exchanger inventory distribution. The optimal allocations for different total thermoelectric element numbers are given by the enumeration method. Influences of various factors on maximal power and efficiency are analyzed, and the upper bounds of power and efficiency are given. Results show that an optimal collector temperature exists to achieve optimal performance for this solar power device. Power and efficiency show the same variation trend, and the efficiency is maximal when power reaches its maximum. The system performance is optimal when external heat transfers and inner structure parameters are optimal. At this time, the corresponding junction temperatures reach their optimal values, the total thermal conductance should be divided in a half to two heat exchangers, and the corresponding thermoelectric element is allocated nearly half to upper generator.