Experimental study of an optimally designed photovoltaic/thermal collector in variable outdoor and working conditions

Performance of photovoltaic/thermal (PV/T) collectors greatly depend on their design, ambient and load conditions. Hence, various arbitrarily designed PV/T collectors in literature have shown different efficiencies and may not perform best at different load and ambient conditions. Meanwhile, a previously published theoretical study has achieved an optimal design by multi-objective optimization of both thermal and electrical efficiencies to provide a superior performance at variable outdoor and load conditions. The objective of the present study is to fabricate and test this design experimentally in variable outdoor and loading conditions at different flow rates. At first, a practical approach is presented for fabrication of this PV/T collector according to the available tube arrangement specifications. Then, the PV/T collector is experimentally analyzed in a test rig which is capable of operating in real outdoor conditions at three cooling configurations of closed, open, and semi-open loop under varying flow rates of 90, 187, and 240 L/h. The experimental results demonstrated that the optimal performance, considering combined electrical-thermal efficiency, was achieved at a water flow rate of 187 L/h across different cooling configurations, in agreement with theoretical predictions. Among these, the semi-open configuration, which closely simulates real-world operating conditions of PV/T collectors, delivered the highest performance, with maximum and average overall efficiencies of 74.5 % and 67.1 %, respectively, at the flow rate of 187 L/h.