Daytime radiative cooling has recently become an attractive passive approach to address the global energy demand associated with modern technologies, currently accounting for about 15 % of the worldwide energy consumption. By engineering surface properties to maximise the natural blackbody emission to radiate thermal energy in the spectral transparency window of the atmosphere (8 – 13 μm), it has been shown that thermal radiation can be transferred to outer space, resulting in surface cooling, without an external electrical input. One technique used is based on surface phonon-polaritons, i.e., thermally excited surface waves in polar dielectric materials which can be outcoupled into free space. Here, we theoretically investigate new surface morphologies in the form of silica micro-sphere and micro-shell photonic crystals (PCs) using rigorous coupled-wave analysis to achieve cooling of over 73 K below-ambient temperature. Additionally, the effect of impurities in silica is explored by simulating soda-lime glass micro-shells, which in turn, exhibit radiative cooling of 61 K below-ambient temperature.
    Date made available21 May 2021
    PublisherThe Optical Society

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