Experimental evaluation of passive and active cooling methods for high-concentration photovoltaic systems using nanofluids

High-concentration photovoltaic (HCPV) systems require cooling methods to maintain cell efficiency. Passive fin heat sinks and active microchannel heat exchangers are potential cooling solutions. Nanofluids are an emerging coolant that could enhance heat transfer in microchannels. This work experimentally evaluated the performance of a fin heat sink and microchannel heat exchanger for cooling HCPV systems. The study also examined silver nanofluids at 0.0005–0.005 vol% concentrations in the microchannel heat exchanger. A small-scale HCPV system with the fin heat sink was built and tested outdoors under 500–1100 W/m² solar irradiance. An experimental bench was constructed to evaluate the microchannel heat exchanger at 5–15 heat fluxes (W/cm²) and 25–35 °C inlet temperatures using water and a 50/50 water/ethylene glycol base fluid. Silver nanofluids increased heat transfer up to 20% but also increased pressure drop compared to base fluids. The fin heat sink achieved 2.5–3.0 °C/W thermal resistance, while the microchannel heat exchanger exhibited 0.5–1.5 °C/W, a 60–80% reduction. Microchannel cooling shows excellent potential for HCPV systems due to its low thermal resistance. Silver nanofluids increased heat transfer up to 20% but also increased pressure drop compared to base fluids. The pressure drop penalty ranged from 5–15% over the base fluid at the same flow rates. Silver nanofluids can enhance heat transfer but require optimization to balance thermal and hydraulic improvements.