Numerical and Experimental Investigation of Photovoltaic/Thermal Systems: Parameter Analysis and Determination of Optimum Flow

The emergence of photovoltaic/thermal (PV/T) technology has effectively solved the problem of high temperature and low electrical efficiency of photovoltaic cells, and significantly improved the utilization rate of solar energy. At present, improving the thermoelectric performance of PV/T systems is a research hotspot. The effects of operating parameters such as inlet temperature, solar radiation, ambient temperature, and coolant mass flow rate, are investigated through numerical simulations. An experimental platform is built to verify the effectiveness of the three-dimensional numerical model. It is found that when the solar radiation changes from 800 W/m2 to 1000 W/m2, the increase rate in thermal efficiency will obviously slow down. When the coolant mass flow rate is increased from 60 to 320 L/h, the thermal efficiency is raised by 8.24%. For each 40 L/h increase in mass flow rate, the electrical efficiency increased by 0.047%. However, when the mass flow rate is too large, the increase in electrical and thermal efficiency gradually decreases. Orthogonal experiments and analysis of variance (ANOVA) are used to study the effects of each parameter and parameter combination on overall efficiency. The results show that ambient temperature has the greatest effect, followed by inlet temperature. Finally, the mathematical model of overall efficiency is established, and the coolant mass flow control formula is proposed. This formula can determine the optimal flow rate according to different environmental conditions, so that the system can operate under the optimal flow rate at all times and maximize the thermoelectric efficiency. Experimental results show that flow control increases the overall energy gain by 2.5% compared with the optimal constant mass flow.