Creating an Eco-Friendly Building Coating with Smart Subambient Radiative Cooling

Area of Science:

• Materials Science
• Thermodynamics
• Sustainable Energy

Background:

• Subambient daytime radiative cooling (SDRC) is a promising passive cooling technology.
• Current SDRC systems often require complex, costly, and non-eco-friendly surface designs.
• There is a need for cost-effective and scalable SDRC solutions for buildings.

Purpose of the Study:

• To develop a generic method for upgrading conventional building coatings with self-adaptive SDRC capabilities.
• To investigate the theoretical basis for enhanced SDRC through sky heat exchange, eliminating the need for resonant microstructures and noble metal mirrors.
• To demonstrate the practical performance of the upgraded coating for passive cooling.

Main Methods:

• Combining particle scattering, sunlight-excited fluorescence, and mid-infrared broadband radiation in coating materials.
• Theoretical analysis of heat exchange mechanisms with the sky.
• Experimental validation using an aluminum plate and a scale-model building under direct sunlight.

Main Results:

• The upgraded coating achieved a cooling effect of 6 °C below ambient temperature (7 °C on a scale-model building).
• Demonstrated cooling power of 84.2 W m^-2 under solar intensity.
• Theoretical proof that sky heat exchange enhances daytime cooling and suppresses nighttime overcooling.

Conclusions:

• A novel, generic method effectively imparts self-adaptive SDRC properties to conventional building coatings.
• The developed SDRC approach is cost-effective, eco-friendly, and eliminates the need for specialized microstructures or materials.
• This technology holds significant potential for large-scale application in improving building thermal comfort and energy efficiency.