Effect of CuO-water-ethylene glycol nanofluids on the performance of photovoltaic/thermal energy system: an experimental study

Abstract

ABSTRACT Nanofluids are widely used today as an excellent heat carrier in various solar energy applications. In the current study, the possibility of using a nanofluid consisting of copper oxide (CuO) nanoparticles added to a blend of water and ethylene glycol (EG) at 75% to 25%, respectively, were investigated. Nano-CuO was added in four mass fractions (0.1, 0.5, 1.0, and 2.0%) using ultrasonic vibration to make sure that a stable emulsion was obtained. The thermophysical properties of the samples prepared in the laboratory were examined, as well as the stability of these samples. The prepared emulsions thermal conductivity continued to rise as the nano-CuO mass fraction added was increased in the base fluid. The increment rate was close to 140% compared to the base fluid. The effect of nanoparticle addition to base fluid on the resulted density was limited to 0.072% (2% of Nano-CuO added). Also, the increase in the viscosity of the nanofluids did not exceed 2.3% when adding 2.0% of the nanoparticles. The results of the stability test of the prepared fluids showed that they have high stability, and the stability of emulsions increases with a decrease in the percentage of adding bulk nanoparticles. A nanofluid with an added mass fraction of 2.0% was examined in a PV/T system installed on the roof of the Solar Energy Laboratory at Sohar University – Oman. The electrical and thermal efficiencies were enhanced by 6.76% and 39.6% respectively when the prepared nanofluid (2.0% nano-CuO) was used due to its better cooling effect compared to the use of the base fluid only. The study presents one of the appropriate solutions to treat the high temperatures of PV modules in Oman and the deterioration of their electrical efficiency.