33. Bi-fluid Photovoltaic/Thermal PV/T Solar Collector with Three Modes of Operation: Experimental Validation of a Theoretical Model

This chapter discusses theoretical and indoor experimental studies of a bi-fluid type photovoltaic/thermal (PV/T) solar collector. Two-dimensional steady-state analysis was developed and computer simulations were performed using MATLAB. Experiments were conducted for steady-state analysis under the solar simulator at Solar Energy Research Lab UiTM, Perlis, Malaysia, and under real sky conditions of Northern Peninsular Malaysia, to validate the model. The solar collector and the test rig facilities were fabricated to be suitable for mathematical validation purposes in both indoor and outdoor testing. For indoor collector testing, at an average wind speed of 1 m/s and average solar radiation of 700 W/m², the air and water mass flow rate was varied from 0.0074 to 0.09 kg/s and 0.0017 to 0.0265 kg/s respectively. The thermal efficiency increased as the mass flow rate increased. At a mass flow rate of 0.0262 and 0.0066 kg/s for air and water respectively, the thermal efficiency curves tended to plateau, which marked the optimum point of the fluid flow. For the simultaneous mode of fluid operation, testing was conducted with air and water fixed at a flow rate of 0.0262 and 0.0066 kg/s respectively, while the fluids’ mass flow rate was varied according to the range used during the independent mode. The range of the computed efficiencies for the simultaneous mode were higher than for the independent mode. In this study, collector outdoor testing was conducted for each mode of operation on a typical day in January in Perlis, Northern Peninsular Malaysia. Based on the outdoor monitoring analysis for simultaneous mode, the performance of the collector was also higher overall than the independent mode. The test was conducted by monitoring the performance of the collector with the air mass flow rate and water mass flow rate fixed at 0.0262 and 0.0066 kg/s respectively. Theoretical analysis was also performed and then validated against the experimental results by a direct comparison of the plotted curves and using mean absolute percentage error (MAPE) analysis. For the air, water and simultaneous modes, by taking into account both indoor and outdoor collector testing, the theoretical and experimental curves were found to be in good agreement, and the computed MAPE values for the fluids’ output temperature were less than 2 %. Thus, the two-dimensional mathematical model was proven valid. The PV/T collector designed in this study has a variety of applications because it can be operated in three different modes of fluid operation, and the theoretical model is useful in modelling all three modes without further modification.