Development and performance evaluation of a radiative sky cooling coating with insights from active system modeling

Radiative sky cooling represents a promising zero-energy cooling technology with significant potential for mitigating global warming and reducing building energy consumption. However, existing coatings often suffer from complex fabrication processes, and the key parameters governing their performance under high-temperature conditions remain unclear. In this study, we develop a simple and scalable method for fabricating a novel radiative cooling coating. The obtained coating exhibits low solar absorptance, high infrared emissivity, a porous structure, and excellent hydrophobicity. Its passive and active cooling performance was systematically evaluated through outdoor experiments and simulations based on a state-space model, while key photothermal parameters affecting cooling characteristics at different radiative temperatures were identified. Results show that the coating possesses an average solar absorptance of 6.58% and an average infrared emissivity of 94.27%. In passive daytime outdoor tests in Harbin during September, it achieved a temperature reduction of 11.68 °C compared to commercial white paint. Active cooling simulations revealed that at inlet temperatures of 30 °C and 60 °C, the coating provided cooling power enhancements of 48.90% (176.82 W/m2[jls-end-space/]) and -16.92% (438.41 W/m2[jls-end-space/]), respectively, relative to a commercial radiative cooling film. Parameter sensitivity analysis further indicated that spectral properties are not the sole determining factor for active cooling performance. At 60 °C and in thick coating scenario, the thermal conductivity of the coating surpasses solar absorptance in influence, emerging as a secondary governing parameter. This work provides important insights for optimizing radiative cooling materials tailored to different operational temperature ranges.