Abstract
Passive daytime radiative cooling (PDRC) technologies that both reflect sunlight and pump heat out of objects on Earth into cold outer space, have attracted considerable attention in recent years. However, conventional PDRC materials face numerous limitations, including costly and complex fabrication methods, as well as performance losses due to surface contamination and humid climates. Here, we present a new radiative cooling structure consisting of a hydrophobic SiO2 nanosphere top layer, a polymethyl methacrylate (PMMA) middle layer, and a metallic Ag bottom layer. The hydrophobic SiO2 nanospheres layer provides a low surface energy nanoscale textured surface for self-cleaning, with a maximum surface contact angle of 151°. The as-prepared film has a high solar reflectivity (∼96.6 %) and a strong broadband infrared emittance (∼88 %). The calculated net cooling power at 27 °C can reach 106.9 W·m−2 and the predicted subambient cooling is 15 °C at night and 10 °C during the day in the dry environment. The outdoor experiments are carried out in a hot and humid city (Xiamen, China) and realize a promisingly subambient cooling of ∼6 °C at night and even ∼3.5 °C during a sunny summer day. These findings could have a substantial impact on energy consumption habits in hot and humid regions around the world.
Published Version
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