Photovoltaic thermal solar air heater under external recycle: A performance study

The photovoltaic thermal (PV/T) systems are promising techniques for cooling photovoltaic modules and performance improvement. The heat-exchanging fluid removes the heat from the PV module, which can be utilized in the low-temperature application, including space heating. In the present study, a photovoltaic thermal system based on a double pass air collector under recycling is theoretically investigated for its overall performance and analysis. An analytical model explaining the different temperatures and heat transfer characteristics of the proposed PV/T system is developed and employed to study the effects of different recycling ratios at varying mass flow rates, the area covered by the PV module (packing factor), solar irradiation, and varying duct depth on thermal, electrical, and combined efficiency. The analytical model utilizes an iterative solution to work out the governing energy balance equations describing the complex heat and mass exchanges. The results show that the new design collector encloses photovoltaic cells under recycling, reduces the PV surface temperature from 97 degrees C (without cooling) to 45 degrees C (with cooling) at 0.15 kg/sec mass flow rate of air and recycle ratio of 1.8 and, thereby improves the electrical efficiency from 12% to 16%, which is 13% more increment than a non-recycling case. The influences of the identified parameters, which may vary with the proposed design performance, are presented in detail.