Synergistic Passive Cooling of Photovoltaics: A Numerical Study on CombiningRadiative Cooling and Hydrogel-based Evaporative Cooling

Evaporative cooling using hygroscopic composite hydrogels and radiative cooling are widely studied passive thermal management strategies for photovoltaic (PV) modules.This work explores a synergistic approach that integrates evaporative cooling through a hygroscopic hydrogel on the back side with radiative cooling on the front side of PV modules.A highly accurate heat and mass transfer model is developed and validated to simulate three configurations: radiative cooling only; evaporative cooling only on the back side; and the combined use of both techniques.Results demonstrate that the hybrid configuration achieves the best cooling performance, yielding an average temperature reduction of 3.2 °C and power generation efficiency (PCE) increase by 1.2%, which corresponds to a 500% and 26% relative improvement in PCE compared to the radiative-cooling-only and evaporative-coolingonly cases, respectively.Notably, radiative cooling has only a minor influence on the hydrogel's absorption and desorption dynamics, increasing nighttime water absorption by about 1%, while the enhanced radiation extends the duration of the positive temperature reduction effect by 10%.Radiative cooling can be considered as a supplementary method coupled with PV modules, where evaporative cooling serves as the primary passive cooling mechanism.