Efficacy of aluminium oxide nanofluids in passive cooling of direct absorption-based photovoltaic/thermal system: An experimental approach

Over the last two decades, direct absorption-based Photovoltaic/Thermal system (DAS-PV/T) has emerged as a promising solution considering better thermal management and overall performance enhancement over standalone PV system. However, previous studies reported the testing results either using theoretical models or using laboratory prototypes under controlled conditions or operational parameters. The main bottleneck is that there aren't enough outdoor studies that focuses on thermal performance characterization of direct absorption-based PV/T systems in real-world conditions. Metallic nanoparticles-based nano colloids are proved to be better alternative over conventional cooling fluids such as water, oils or glycols for such DAS-PV/T system. Therefore, for the present work, field experiments are conducted using Al 2 O 3 nanofluids at different mass concentrations ( ξ NF ) and mass flow rates ( Ϻ F ) to assess the energetic and energetic performance of a DAS-PV/T system under actual sun setting conditions. Al 2 O 3 nanofluids are characterized for its optical and morphological properties using UV–vis spectrophotometry and field emission-scanning electron microscopy (FE-SEM) techniques. The outdoor testing results showed that tested DAS-PV/T system achieved a maximum photo-thermal, electrical and overall thermal efficiency at higher ξ NF and Ϻ F of Al 2 O 3 nanofluids over de-ionized (DI) water. Further an average surface temperature of PV cell was recorded about 56.0 ℃ with Al 2 O 3 nanofluids, which was about 4.5 °C lower than bare PV system. Further, a maximum overall energetic and exergetic efficiency of values 27.54% and 26.41% was achieved for tested DAS-PV/T system using Al 2 O 3 nanofluids at ξ NF ∼ 0.0004 wt% and Ϻ F ∼ 0.035 kg/s, respectively. The study concludes that a DAS-PV/T systems is a feasible solution over standalone PV system. • Testing of direct absorption-based PV/T system under solar exposure. • Efficacy of Al 2 O 3 -NFs in PV/T system were analysed experimentally. • Al 2 O 3 -nanofluids showed 4.5 °C lower PV cell temperature against bare system. • A maximum reported energy and exergy efficiencies of 27.5% and 26.4%.