Reducing photovoltaic-thermal module temperature with iron, copper oxide

An international group of scientists proposed to use copper oxide (CuO) and iron oxide (Fe2O3) nanofluids to cool down the operating temperatures of photovoltaic-thermal (PVT) systems.

”The current study offers an energy and exergy assessment for a PVT system considering the thermodynamic laws using CuO and Fe2O3 nanofluids at different volume fractions, circulated in a heat exchanger placed at the rear of the PV module,” the researchers said, noting that their analysis was based on a 2D numerical model developed with MATLAB software.

The experimental setup consisted of a 50 W PV module and a 50 W PVT module relying on a heat exchanger made from serpentine tubes placed on a copper absorbing plate. In between, the group used a thermal grease with high thermal conductivity and thickness, while the heat exchanger was covered with an insulation layer. The rear side of the PVT was also covered with an aluminium sheet to minimize heat dissipation.

“A cooling water tank with a capacity of 35 liters is used to cool the exit nanofluid coming from the outlet by circulating into a coil placed in the water tank to dissipate the temperature of the nanofluid,” said the group. “The PV module and PVT systems were fixed at a tilt angle of 14.8 degrees on the top roof-open area.”

Both the CuO and the Fe2O3 were first synthesized and then added to deionized (DI) water to create the nanofluid. In both cases, the nanofluid contained the CuO and Fe2O3 at 0.2% and 0.3% volume fractions. The system was measured at Miskolc City, northeastern Hungary, from 8:30 to 15:00. The conditions and the systems were recreated in the numerical model for compression.

“Good agreement was observed between numerical calculations and experimental measurements, with slight deviations due to the uncertainties of measurements and assumptions of the numerical model,” they said. “The successfully synthesized Fe2O3 NRs and Cuo NPs have improved the effectiveness of nanofluids, which positively decreased the temperature of PV cells and improved the energy and exergy.”

For both nanofluids, the best results were obtained at volume fractions of 0.3%. CuO was able to reduce the PV cell temperature by 23.49% and Fe2O3 by 34.58%. They have also increased the electrical efficiency by about 9.21% and 10.30% respectively. “The PV temperature was reduced as the nanomaterial’s suspension increased in the host fluid, increasing the electrical exergy efficiency by about 9.2% and 11.18% when cooled with CuO and Fe2O3 nanofluids, respectively, more than the cooling by water, which achieved 6.12%,” they emphasized.

“Circulating CuO and Fe2O3 nanofluids in the heat exchanger has increased the temperature absorption from the rear side of the PV module, incrementing the thermal efficiency by about 38.92% and 43.3% while cooling by DI water enhanced the efficiency by 23% only,” the academics concluded. “Cooling by nanofluids has influenced the energy losses and entropy generation more than cooling by water. The highest increase in exergy destruction was 26.06%, while entropy generation was reduced by 68.15% when cooling by Fe2O3 nanofluid. In contrast, the cooling by CuO nanofluid has increased the exergy destruction and decreased entropy generation by 15.43% and 51.72%.”

The findings of the research were presented in the paper “Experimental and numerical study of a photovoltaic/thermal system cooled by metal oxide nanofluids,” published in the Alexandria Engineering Journal. The group comprised academics from Hungary’s University of Miskolc, Iraq’s Southern Technical University, University of Misan and University for Oil and Gas.