Abstract
Over the years, solar collecting systems have gained interest in renewable energy. This study investigated improving the efficiency of the working fluid in thermal solar systems by using nanofluids with three concentrations of alumina, 0.1, 0.3, and 0.5 wt%. The UV-vis absorbance, electronic conductivity, and thermal transfer properties of the nanofluids were analyzed, and the thermal changes with exposure to solar radiation in an experimental collector system were measured by pyranometer. The electronic conductivity, thermal conductivity, and UV-vis absorbance increased with the alumina concentration. Moreover, the temperatures of the nanofluids increased more under solar irradiation than that of distilled water. This implies that the alumina nanofluids absorb solar energy more efficiently than water. The findings of this study suggest that the use of both alumina nanofluids and nanoparticles will improve the efficiency of thermal solar power systems.
Highlights
Solar energy can be directly utilized in the form of either photovoltaic or thermal energy.The conversion efficiency of solar photovoltaic energy from solar cells using polysilicon materials has reached 24%, which, when compared with the maximum theoretical conversion efficiency for solar photovoltaics of 29%, suggests that the photovoltaic conversion efficiency has reached its maximum.Solar thermal energy, in contrast, has received comparatively little attention.The utilization of solar thermal energy can be divided into low, medium, and high-temperature areas
Kim et al [19] confirmed that thermal conductivity increased with nanofluid concentration and showed that the efficiency of the nanofluids improved in the order of multi-walled carbon nanotubes (MWCNTs), CuO, Al2 O3, TiO2, and SiO2 based on their thermal performance in a U-type solar collector
Alumina nanofluids were prepared at concentrations of 0.5, 0.3, and 0.1 wt%, and distilled water (DW) was tested for comparison
Summary
Solar energy can be directly utilized in the form of either photovoltaic or thermal energy. Kim et al [19] confirmed that thermal conductivity increased with nanofluid concentration and showed that the efficiency of the nanofluids improved in the order of multi-walled carbon nanotubes (MWCNTs), CuO, Al2 O3 , TiO2 , and SiO2 based on their thermal performance in a U-type solar collector. Studied the thermal properties of alumina nanofluids for use as a new phase-change material in cooling systems and concluded that the addition of alumina nanoparticles alone reduced the solidification time of the fluid and improved the performance of the refrigeration system. Tong et al [25] analyzed the thermal performance of enclosed-type evacuated U-tube solar collectors using a MWCNT nanofluid as the working fluid and demonstrated that the heat transfer coefficient between the tube and working fluid is higher than that of water. The heat transfer characteristics according to alumina nanofluid concentration when applied to an actual solar collector system by analyzing the solar heat absorption characteristics of the nanofluids with a good dispersibility according to their concentration and performance in a real environment were examined
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