In this study, the use of metal-oxides/water nanofluids as coolants in photovoltaic thermal units (PVT) is investigated experimentally and numerically. The considered nanoparticles include Aluminum-oxide (Al2O3), Titanium-oxide (TiO2) and Zinc-oxide (ZnO) all dispersed in deionized water as base fluid, with 0.2% by weight (wt%). To investigate the reliability of the measurements, an uncertainty analysis is performed for the experimental data. The t-statistic indicator is used to verify that the results of the numerical model are statistically significant. The electrical efficiency for the PVT system is calculated based on the measured temperature of the photovoltaic surface and the fluid outlet. The energy balance equations for various parts of the PVT system are solved using numerical simulations. Both numerical and experimental results show that the TiO2/water and ZnO/water nanofluids present a better performance in terms of the electrical efficiency compared to that of the Al2O3/water nanofluid and deionized water. In terms of the thermal performance of the system, the ZnO/water nanofluid is found to have the highest thermal efficiency compared to deionized water and the other two nanofluids. Finally, the numerical model is used to investigate the effect of nanoparticles mass fraction, ranged from 0.05 to 10 wt%, on electrical and thermal performance of the PVT system.

Keywords