Scalable and durable dual-layer radiative cooling paint using a spray-coating method

Passive daytime radiative cooling (PDRC) offers a sustainable solution for reducing space cooling energy demand. However, achieving high cooling performance alongside scalability and durability remains a key challenge in PDRC. In this study, we propose a scalable and durable dual-layer radiative cooling paint (DRCP), composed of a bottom PDMS/TiO₂ layer and a top PDMS/Al₂O₃ layer, fabricated using a spray-coating method. The particle size and layer thickness were determined via Monte Carlo simulations based on Mie scattering theory to maximize solar reflectance across the entire solar spectrum. The fabricated DRCP achieved a solar-weighted reflectance of 91.7% and an average emissivity of 95.9%, resulting in a peak subambient cooling temperature of −3.2 °C under 1060 W/m² solar irradiance. Thermal durability was confirmed through 40 thermal cycles and a 30-day outdoor exposure test; over 99.7% of the initial solar-weighted reflectance was restored after water rinsing. EnergyPlus simulations demonstrated annual cooling energy savings of up to 44.6 GJ in hot desert climates. These findings highlight the potential of DRCP as a scalable, durable, and energy-efficient PDRC solution for real-world applications.