Authors:

Ricardo Andrews Huertas

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As global temperatures continue to rise, developing alternative cooling technologies that reduce energy usage is necessary. Radiative cooling in systems can be enhanced by increasing solar spectrum reflectance and atmospheric sky window emissivity. These permit the reflection of solar irradiation and the emission of thermal energy to deep space, respectively. Radiative cooling technologies so far have been used for applications such as housing, vehicle cooling, and water harvesting. However, there remains room to use our understanding of radiative cooling to further reduce environmental impact by developing biodegradable and multifunctional radiative cooling materials. Thus, we propose nanocomposite radiative cooling films composed of a naturally occurring, biodegradable matrix and a hexagonal boron nitride (hBN) nanoparticle reinforcement that also serves to improve solar reflectance. The resulting films are inspired by biological systems via their composition and biodegradability. To develop more optimized films, the effects of varying hBN volume concentration on solar reflectance and mechanical durability are studied. Reflectance is lower, and absorptance is higher with a higher volume fraction of matrix material due to less reinforcement. Transmittance trends are influenced by increased porosity in films with decreasing reinforcement volume, causing scattering at material-pore interfaces. Decreasing the volume fraction of nanoplatelet-shaped reinforcement material makes films more ductile and flexible, potentially reducing mechanical properties like yield strength and toughness. The results could help to achieve below-ambient cooling with biodegradable films for application in buildings, fabrics, wearables, aerospace, and automotive industries. Keywords: Global Warming; Radiative Cooling; Hexagonal Boron Nitride; Sky Window; Solar Spectrum

Source:

Purdue University / 2024

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Co-authors:

Ricardo Andrews Huertas