EXPERIMENTAL AND NUMERICAL STUDY OF OXIDE/WATER-NANOFLUIDS AS OPTICAL FILTER AND COOLANT IN A PV/T PANEL
In this paper, in order to realize the full spectrum utilization of solar radiation and improve the efficiency of a PV/T (Photovoltaic/Thermal) panel, oxide/water nanofluid used as spectrum splitting fluid and coolant for a PV/T panel is investigated experimentally and numerically. Firstly, to obtain the spectrum splitting property of nanofluids, the nanoparticles including Silica (SiO2), Titanium dioxide(TiO2) and Zinc-Oxide(ZnO) were dispersed in base fluid (deionized water) with diverse volume fractions. A spectrophotometer was used to measure the transmittance of nanofluids under different volume fractions, nanoparticle kinds and liquid optical thicknesses. Furthermore, Rayleigh model and Mie scattering model were used to evaluate the radiative characteristics of nanofluid. It is found that the experimental results were in good agreement with the theoretical results when the volume fraction is smaller. In addition, an optimal nanofluid matching the Si-PV spectral was selected as the working-fluid for the PV/T panel. The solar cell temperature, photoelectric efficiency and total solar radiation utilization efficiency were evaluated. The study indicated that nanofluids containing small number of nanoparticles have flexible radiative properties, which can keep PV/T panels working at lower temperature and collecting the extra heat generated by low frequency radiation (1100~2500nm). The selected nanofluid is highly transparent to visible solar light and its nearby spectrum (380~1100nm), and the low frequency radiation can be highly absorbed. The experimental results show that the temperature of the PV/T panel is less than a traditional PV panel. The total utilizing of solar radiation is more than 70%, which is much higher than a bare PV panel.