Effect of thermal resistance and infrared transparency on radiative cooling efficiency

Le résumé fourni par la source

Radiative cooling materials that reflect sunlight and emit infrared light to the cold sky can lower the surface temperatures of building envelopes, reducing cooling energy usage by buildings. Over the last decade, various structures, such as thin films/coatings and thick infrared-transparent/opaque foams, have been developed for these applications. Understanding the influence of thermal resistance and infrared transparency of radiative cooling materials, along with the thermal resistance of the substrate to which they are applied, is vital for optimizing their energy savings potential. Herein, we employed a heat transfer model that integrates conduction, convection, and radiation to investigate the energy savings of radiative cooling materials with varying roof and material thermal resistances. Our results suggest that radiative cooling materials are most effective on roofs with low thermal resistance, like metal roofs, and increasing roof thermal resistance reduces their energy-saving effect. Thermally insulating infrared-transparent radiative cooling foams can significantly boost energy savings by minimizing convection and radiation losses. Conversely, compared to thin film, thermally insulating infrared-opaque foams can enhance or reduce energy savings depending on whether their surface temperatures are above or below room temperature. Throughout summer, infrared-transparent foam consistently achieves the highest energy savings, whereas infrared-opaque foam shows the least. This work provides guidance for the practical application and structural design of radiative cooling materials.

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