Thermal Modeling and Life Prediction of Water Cooled Hybrid Concentrating Photovoltaic/Thermal Collectors

Abstract

In this paper, a multiphysics, finite element computational model for a hybrid concentrating photovoltaic/thermal (CPV/T) water collector is developed. The collector consists of a solar concentrator, 18 single junction germanium cells connected in series, and a water channel cooling system with heatrecovery capability. The electrical characteristics of the entire module are obtained from an equivalent electrical model for a single solar cell. A detailed thermal and electrical model is developed to calculate the thermal and electrical characteristics of the collector at different water flow rates. These characteristics include the system temperature distribution, outlet water temperature and the thermal and electrical efficiencies. The model is used to study the effect of flow rate on the efficiencies. It is found that both efficiencies improve as the flow rate increases up to a point (0.03 m/s), and after that point remain at relatively constant levels. However, as the flow rate increases the outlet water temperature decreases, reducing the quality of the extracted thermal energy. In addition to the thermal and electrical modeling, finite element analysis is used to estimate the fatigue life of the module based on the different temperature profiles obtained from the thermal model at flow rates of 0.01 m/s and 0.03 m/s. Results show that for the higher flow rate, the outlet water temperature decreases, but the fatigue life improves. Based on the fatigue life model predictions, it is shown that the thickness of die attach layer must be increased for high outlet temperature applications of the hybrid CPV/T collector.