Performance Analysis of a Combination System of Concentrating Photovoltaic/Thermal Collector and Thermoelectric Generators

Abstract

Thermoelectric (TE) modules utilize available temperature differences to generate electricity by the Seebeck effect. The current study investigates the merits of employing thermoelectrics to harvest additional electric energy instead of just cooling concentrating photovoltaic (CPV) modules by heat sinks (heat extractors). One of the attractive options to convert solar energy into electricity efficiently is to laminate TE modules between CPV modules and heat extractors to form a CPV-TE/thermal (CPV-TE/T) hybrid system. In order to perform an accurate estimation of the additional electrical energy harvested, a coupled-field model is developed to calculate the electrical performance of TE devices, which incorporates a rigorous interfacial energy balance including the Seebeck effect, the Peltier effect, and Joule heating, and results in better predictions of the conversion capability. Moreover, a 3D multiphysics computational model for the HCPV-TE/T water collector system consisting of a solar concentrator, 10 serially connected GaAs/Ge photovoltaic (PV) cells, 300 couples of bismuth telluride TE modules, and a cooling channel with heat-recovery capability, is implemented by using the commercial FE–tool Comsol Multiphysics®. A conjugate heat transfer model is used, assuming laminar flow through the cooling channel. The performance and efficiencies of the hybrid system are analyzed. As compared with the traditional photovoltaic/thermal (PV/T) system, a comparable thermal efficiency and a higher 8% increase of the electrical efficiency can be observed through the PV-TE hybrid system. Additionally, with the identical convective surface area and cooling flow rate in both configurations, the PV-TE/T hybrid system yields higher PV cell temperatures but more uniform temperature distributions across the cell array, which thus eliminates the current matching problem; however, the higher cell temperatures lower the PV module's fatigue life, which has become one of the biggest challenges in the PV-TE hybrid system.