Enhanced passive radiative cooling

Researchers have described the synergistic effect of silica aerogel and titanium dioxide in porous polyurethane composite coating with enhanced passive radiative cooling performance.

Global warming increasing the demands of space refrigeration equipment such as air conditioners and fans. However, these cooling methods often increase the energy consumption and greenhouse gas emission. To cut off this vicious cycle, coatings with passive radiative cooling capacity are suggested to be an efficient way. Image source: mohamed_hassan - Pixabay (symbol image).

Passive daytime radiative cooling is a promising technology that can mitigate the increasing issues of global warming and urban heat island effects. In a new work, a series of porous polyurethane (PPU) composite coatings containing silica aerogel (SA) and/or titanium dioxide (T) were prepared. A PPU-SA10@T10 composite coating showed an interleaving porous structure, and the incorporated SA and T fillers were uniformly stacked in the pore cavities.

Superior hydrophobicity

Taking advantages of the strong light-back scattering and molecular oscillation functions, the solar reflectance, thermal emittance in the atmospheric transparency window, and the net cooling power of the PPU-SA10@T10 coating reached 0.917, 0.973, and 87.8 W/m2, respectively, which results in a sub-ambient cooling of 7.8 °C at midday under a solar irradiance of ∼640 W/m2. Moreover, the PPU-SA10@T10 coating possessed well balanced mechanical properties and superior hydrophobicity (water contact angle was 121.7°).

The study has been published in Progress in Organic Coatings, Volume 183, October 2023.

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