Experimental and theoretical performance investigation of asymmetric photovoltaic/thermal hybrid solar collectors connected in series

In this study five asymmetric hybrid solar collectors with flat plate receiver connected in series are investigated experimentally and mathematically through analytical expressions deriving from heat transfer and thermodynamics fundamentals. The main objective of this study is to evaluate the collectors' performance in terms of thermal energy and exergy production under various operating conditions thus the experiments are performed at open circuit mode regarding their electrical part and with water as working fluid. Concerning the theoretical analysis, the developed model combines optical, thermal and flow analysis for the determination of both first and second law efficiencies and it is validated against experimental data with an acceptable agreement being observed. Following the model validation, the performance of the collectors is analyzed in terms of thermal and exergy efficiency, thermal losses and absorber temperature. After the thermal analysis, the mathematical model is further developed so as to take into account the electrical production for the overall performance evaluation of the compound parabolic PVT solar collectors. Among the main findings, the final experimental results proved that these solar collectors connected in series work efficiently throughout the year as they are able to produce about 2.2 kW useful energy in summer, 2.8 kW in spring and 2.6 kW in autumn.