Mathematical and experimental evaluation of thermal and electrical efficiency of PV/T collector using different water based nano-fluids

The high temperature of PV modules is one of the major factors that affect the PV system performance. The PV/T collector is proposed mainly to recover the heat of the high PV module temperature using conventional working fluids (water/air). Nanofluids (NFs) would help enhance the heat transfer/heat removal. The effect of NFs on enhancing the electrical/thermal efficiency of the PV/T collector besides the fluid's outlet temperature were investigate theoretically and experimentally. Fluent simulation tool together with energy balance equations were used. Three rounds of analysis were performed. Firstly, the optimal design of “sheet and tube” thermal absorber was determined using water as the base fluid. Secondly, the PV/T performance aspects using three types of NFs (CuO, SiO2, and ZnO) and water, were compared. Thirdly, the life cycle cost analysis/profit gain were applied to examine the feasibility of the grid connected PV/T-NF. The results showed that the optimal design of the PV/T thermal absorber requires 11 rectangular tubes per module, and the optimal rectangular tube dimensions are 24 mm (width) and 15 mm (depth). The results also revealed that the NF-SiO2 showed outstanding enhancement compared to other types of NFs and water. In addition, the results revealed that using NF- SiO2 in the PV/T collector reduced the PV module temperature from 65 °C to 45 °C and increased the outlet temperature from 35 °C to 44 °C, leading to an electrical and thermal efficiency enhancement of 12.70% and 5.76% respectively at a solar irradiance of 1000 W/m2. Payback analysis and profit gain of grid connected PV/T- NF (SiO2) system, grid connected PV/T- water system, and (grid connected PV + solar thermal) system were found (8 yrs, 10218.137 $; 11 yrs, 5518.518 $; 15 yrs, 3816.873 $), respectively. This indicated that the grid connected PV/T-NF (SiO2) system is economically feasible compared to the other systems despite the additional initial cost of the expensive NFs and the customized heat exchanger.