Computational investigation of an innovative solar photovoltaic thermal collector with spiral shaped absorber using bifluid coolant

In this work, an innovative solar photovoltaic thermal (PVT) collector is developed that has a spiral shaped absorber tube fitted underneath the PV panel in such a manner that a bifluid cooling system extracts heat from the PV panel. The methodology adopted in the present study is to conduct a detailed computational investigation in order to understand the impact of important operating and environmental parameters such as mass flow rates and solar radiations on the overall performance of the bifluid PVT collector. One of the fluids, i.e., a nanofluid (Al₂O₃ in water) with nanoparticle volumetric fraction 5% is passed through the spiral tube, whereas a rectangular air duct is attached below the PV panel for extracting heat from it and delivering the same to the flowing air, thereby making a bifluid coolant system for the PVT collector. Detailed CFD simulations are performed in ANSYS Fluent 19.2 platform for analyzing the thermal performance of the collector. The effects of mass flow rate variations of each individual fluid and in combination (i.e., bifluid) on the PVT efficiency, i.e., thermal, electrical and overall efficiency are observed. The results indicate that with increase in mass flow rate of the fluids, these efficiencies increase up to a certain level but after that, there is only incremental increase with further increase of the latter. When the fluids are used individually or in combination, higher thermal and electrical efficiency are obtained with nanofluid mass flow rate less than that of air. Further, the bifluid is able to transfer heat effectively from the PV panel with less temperature variation between inlet and outlet. Out of all the combinations of varying mass flow rates of individual fluids and bifluid, the best bifluid combination is such that lead to an overall efficiency of 79% corresponding to nanofluid mass flow rate 0.0247 kg/s and air mass flow rate 0.034 kg/s. The computational model developed in this present study will help in designing and developing a more energy efficient, environment friendly and sustainable PVT technology for effective utilization of solar energy.

Graphical abstract