Optical-to-thermal reliability mapping of a soiled high-concentration photovoltaic system with ferrofluid-based hotspot mitigation

This study evaluates how Fresnel-lens soiling and ferrofluid-based microchannel cooling influence the thermal safety and energy output of a highly concentrated photovoltaic system under desert conditions. An integrated optical, thermal, and electrical framework is developed in which Monte Carlo ray tracing generates non-uniform irradiance maps for clean and soiled lens conditions, which are then coupled with a conjugate heat-transfer model of a multijunction solar cell with microchannel heat sinks. The analysis considers a geometric concentration of 1500 suns, water-based Fe₃O₄ ferrofluids with nanoparticle volume fractions of 2.5%-10.0%, and mass flow rates of 0.001-0.008 kg/s. The results indicate that the clean lens, by increasing the mass flow rate, suppresses hot spots, reducing the maximum cell temperature from 197.70 °C to 69.54 °C at 2.5% volume fraction and from 371.44 °C to 71.92 °C at 10.0% volume fraction. Whereas electrical efficiency improves from 39.72% to 41.60% at 2.5% volume fraction, while P_net-el remains within 233.22-243.96 W. However, for the dusty lens, a 60% transmittance loss reduces the optical efficiency from 81.46% to 32.58%, lowering the incident power from 800.52 W to 320.21 W. Although the reduced optical load lowers operating temperature and slightly increases electrical efficiency from 41.08% to 42.05% at 2.5% volume fraction, net electrical power decreases substantially to 96.47-98.47 W. These results show that optimal desert operation requires coordinated control of Fresnel lens cleanliness, coolant volume fraction, and mass flow rate.