Enhanced passive radiative cooling
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.
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.