Performance and reliability analysis of hybrid concentrating photovoltaic/thermal collectors with tree-shaped channel nets' cooling system

Excess temperatures on concentrating photovoltaic (PV) modules can lead to a decrease in electrical efficiency and irreversible structural damage. Therefore, designing an appropriate cooling system becomes necessary for the lifetime and performance of concentrating PV (CPV) modules. The basic design considerations for cooling systems include low and uniform cell temperatures, minimal pumping power, high PV efficiencies, and system reliability. In this paper, a 3-D multiphysics computational model for a hybrid concentrating photovoltaic/thermal (HCPV/T) water collector is developed. The collector consists of a solar concentrator, 40 silicon cells connected in series, and a multichannel liquid cooling system with heat-recovery capability. A conjugate heat transfer model is used, assuming laminar flow through either parallel or tree-shaped branching cooling channels. The temperature distributions within the PV cells are determined for different cooling strategies. Comparisons are made by considering the thermal and electrical performances, such as PV cell temperature, electrical efficiency, and outlet water temperature, between a system incorporating tree-shaped channel networks and one having straight parallel channel cooling arrays. For identical convective surface area and pumping pressures in both configurations, the tree-shaped branched channel cooling networks yield lower PV cell temperatures and more uniform temperature distributions within the PV cells. Additionally, a finite-element mechanical analysis is used to estimate the fatigue life of the PV modules based on the temperature profiles obtained from both cooling channel configurations under a specified pumping pressure. The model results predict that the fatigue life of the module with the branched channels is almost twice that of the module with straight channels.