Economic and environmental analysis of using metal-oxides/water nanofluid in photovoltaic thermal systems (PVTs)

In the present study, an experimental setup for a PVT system is designed and fabricated to investigate the economic and environmental aspects of using different nano-oxides/water fluids. Selected coolant fluids are: pure water, ZnO/water, Al2O3/water and TiO2/water nanofluids. To make nanofluids, nanoparticles are dispersed in distilled water by 0.2% weight fractions (wt%), separately. Based on the experimental results the amount of annual emission reduction and cost saving are investigated for different coolants. Furthermore, the payback period of the PVTs is compared with that of a conventional PV unit. The results are presented in five different scenarios due to increasing of the electricity price, up to the final price and the government subsidies for the renewable energy sources (1st: 10% annual price increasing, with no subsidy, 2nd: linear increasing price, with no subsidy, 3rd: 10% the annual price increasing, 50% subsidy, 4th: linear price increasing, 50% subsidy and 5th: linear price increasing, 75% subsidy). From the energy viewpoint, by using pure water, PVT/TiO2, PVT/ZnO and PVT/Al2O3, the size reduction of the PVT system in comparison with that of the PV is 21, 32, 33 and 24%, respectively, and from the exergy viewpoint these values are about 5, 6, 7, 6%, respectively.