Colourful phase change material-incorporated flexible film for efficient passive radiative cooling.

Passive radiative cooling involves the emission of thermal radiation into cold space and the reflection of solar radiation, which aims to cool and lower the temperature of objects. However, currently most radiative coolers have a white appearance which restricts their potential applications. We develop a coloured bilayer radiative cooling membrane using polyvinylidene fluoride/tetraethoxysilane (PVDF/TEOS) fibres, with incorporation of phase change materials (PCMs) and active dyes through a simple and large-area electrospinning process. In comparison to traditional emitters, PCM-incorporated colourful coolers provide energy storage capacity and colourful appearances. Our phase-transition-based colourful flexible film (PCFF) achieves a total solar reflectance of 0.81 and a mid-infrared (8-13µm) emissivity of 0.85 with superior mechanical strength and good hydrophobicity. We experimentally demonstrate that our PCFF can significantly reduce the temperature of objects exposed to direct sunlight, with a cooling effect of up to 9 °C compared to commercial fabrics of similar materials and colours. Our work provides a promising starting point for the design and manufacture of colourful and flexible thermal control films.

Diatomite-Based Recyclable and Green Coating for Efficient Radiative Cooling.

Radiative cooling is a promising strategy to address energy challenges arising from global warming. Nevertheless, integrating optimal cooling performance with commercial applications is a considerable challenge. Here, we demonstrate a scalable and straightforward approach for fabricating green radiative cooling coating consisting of methyl cellulose matrix-random diatomites with water as a solvent. Because of the efficient scattering of the porous morphology of diatomite and the inherent absorption properties of both diatomite and cellulose, the aqueous coating exhibits an excellent solar reflectance of 94% in the range of 0.25-2.5 µm and a thermal emissivity of 0.9 in the range of 8-14 µm. During exposure to direct sunlight at noon, the obtained coating achieved a maximum subambient temperature drop of 6.1 °C on sunny days and 2.5 °C on cloudy days. Furthermore, diatomite is a naturally sourced material that requires minimal pre-processing, and our coatings can be prepared free from harmful organic compounds. Combined with cost-effectiveness and environmental friendliness, it offers a viable path for the commercial application of radiative cooling.