Optimization and experimentation of concentrating photovoltaic/cascaded thermoelectric generators hybrid system using spectral beam splitting technology

Abstract

The concentrating photovoltaic-thermoelectric (PV-TE) hybrid system by using spectrum splitting technology had been considered to be a promising system. The IR-wavelength light, which can’t generally be converted by solar cells, can be separated from the full solar spectrum in this system and then be appropriately converted by thermoelectric generators based on Seebeck effect. The overall system efficiency might be improved due to the additional contribution of thermoelectric generation. In this paper, a prototype PV-TE hybrid system and a numerical model for the evaluation of the whole system are presented. In order to convert IR-wavelength light into electricity sufficiently, we proposed the cascaded thermoelectric module for thermoelectric generation, which consists of two individual TE stages. These are middle-temperature thermoelectric materials, CoSb3 and low-temperature thermoelectric materials, Bi2Te3 which are configured in tandem. The numerical model was established to optimize thermoelectric module geometries and the optical concentration ratio. In addition, such a novel PV/cascaded TE generators hybrid system had been constructed and experimentally researched in practical conditions. Meanwhile, the effects of the direct normal irradiation (DNI) on the temperature of the thermoelectric module and the overall output power of the hybrid system are experimentally investigated. The optimized results showed that the DNI, optical concentration ratio and the height ratio of two TE stages could significantly affect the performances of this hybrid system. The TE subsystem efficiency ηTE can reach to 8%, the PV subsystem efficiency ηPV can reach to 44%, and total hybrid system efficiency ηPV-TE can reach to 35% under the conditions that DNI = 1000 W/m2, optical concentration ratio CF = 1000, optimized height ratio of two TE stages τ = 0.6. The experimental research results revealed that output power of PV and TE subsystem could reach to 22 W and 1.9 W respectively.