Assessment of alumina/water nanofluid in a glazed tube and sheet photovoltaic/thermal system with geothermal cooling

Abstract

This article presents evaluation of alumina/water nanofluid (NF) in a glazed tube and sheet photovoltaic/thermal (PV/T) system with ground-coupled heat exchanger (GCHE) in semi-arid region of Pilani, Rajasthan (India). Conventionally in the literature, the cooling performance of NF is reported compared to the normal fluid cooling under equal Reynolds number (Re) comparison criterion. However, according to many researchers, equal pumping power-based evaluation is more pragmatic and is explored here. The first law of thermodynamics analysis is invoked to appropriately assess the replacement of water with NF in the PV/T system coupled with GCHE. Nanoparticle concentration is varied from 0.5% to 6% by volume fraction and the Re from 3000 to 9000. Temperature of PV panel, temperature difference in PV/T outlet and inlet, electrical efficiency, thermal efficiency and Bejan number in PV as well as in GCHE are computed using a validated mathematical model for both equal Re and equal pumping power evaluation criteria. The performance of PV/T system with NF is found superior under equal Re comparison. The improvement observed are reduction in PV panel temperature by 2 °C, reduction in temperature difference in PV/T outlet and inlet by 6 °C, rise in electrical efficiency by 0.1% and a rise in thermal efficiency by 4%. However, the performance of PV/T system with NF is found inferior under equal pumping power evaluation criterion.