Solar Thermal Cogeneration System Using a Cylindrical Thermoelectric Module

Abstract

We propose a solar thermal cogeneration system using a cylindrical thermoelectric module for efficient solar energy convergence. Numerical simulations are presented to evaluate the system efficiency compared with a conventional pillar-type thermoelectric cogeneration system. We consider the effects of thermal radiation, contact resistances, and heat flux in the connecting wire, which significantly affect the system efficiency. Compared with the pillar-type device, the cylindrical device can achieve a higher heat flux and lower thermal radiation loss from the sides. In particular, the thermal radiation loss from the sides becomes negligible in a scaled-up cylindrical device. When the areas of the light-absorbing layer are the same in both devices, the power efficiencies, which are defined as power extracted from the module over input heat to the module, are comparable, but the system efficiency, which is defined as extracted heat from the module over input heat to the module, of the cylindrical device is higher than that of the pillar-type device. In the case of the unileg cylindrical device, where the hot side is connected to the cold side by the Cu wire, the system efficiency increased but the power efficiency decreased owing to the heat flux through the Cu wire. On the other hand, the p-n couple cylindrical device can overcome the trade-off and achieve system efficiency as high as 91.6%, including 8.1% power efficiency.