Hybrid passive cooling of PV modules: A numerical study on evaporative and radiative integration

Elevated temperatures degrade photovoltaic (PV) modules efficiency and lifespan, making effective thermal management essential. Among passive cooling strategies, standalone evaporative cooling suffers from humidity sensitivity and water depletion, while radiative cooling alone provides only modest cooling power. This study investigates a synergistic hybrid approach integrating front-side radiative cooling with back-side evaporative cooling via a hygroscopic hydrogel layer. A refined heat and mass transfer model was developed and validated. Comparative simulations of radiative-only, evaporative-only, and hybrid configurations reveal that the hybrid design is predicted to achieve an average temperature reduction of 3.9°C and a 1.5% relative efficiency improvement under moderate humidity, corresponding to a 6.5 fold increase over the 0.2% gain from radiative cooling alone and a 25% improvement over the 1.2% gain from evaporative cooling alone. Crucially, the analysis uncovers a strong differential sensitivity to ambient humidity, as evaporative cooling power decreases by 2.3 W/m 2 per 1% increase in relative humidity, nearly 2.5 times greater than the 0.94 W/m 2 decline observed for radiative cooling. In high humidity environments, the cooling capacity drops to approximately 30% of that under moderate humidity. In low humidity regions, evaporative cooling produces a high peak reduction of 9.9 °C but rapid water depletion limits the average reduction to 3.3 °C. Notably, the hybrid configuration prolongs the duration of positive cooling by ∼10% across different humidity conditions. These findings reveal a synergistic interplay where evaporative cooling drives primary heat rejection and radiative cooling provides a stable baseline, establishing a theoretical foundation for next-generation passive photovoltaic cooling.