Construction of robust silica-hybridized cellulose aerogels integrating passive radiative cooling and thermal insulation for year-round building energy saving

Passive radiative cooling (PRC) is a promising carbon reduction technology that radiates heat into the universe through atmospheric transparency window (ATW) to cool objects below ambient temperature with zero energy consumption. However, so far the cooling efficiencies of most PRC designs are inevitably restrained by inadequate optical properties and parasitic heat gains from ambient air. These defects are overcome by developing aerogel coolers with functional integration of low absorption of solar irradiance, strong mid-infrared emittance, and high thermal insulation in one design. In particular, cross-linked silica-hybridized cellulose acetate is exploited to construct robust aerogels with well-arranged nano/micro porous structures, representing a solar reflectance up to ∼96 % and an ATW emissivity of ∼97 %. Such aerogels can realize a subambient temperature drop of ∼9.15 °C during the daytime and maintain their remarkable cooling performance even in cloudy, moist, and windy climates. The aerogel coolers also show excellent anti-aging, self-cleaning, and compression resistance, making them adaptable for long-term cooling applications. The year-round energy consumption simulations demonstrate that an average total energy saving of 13.87 kW m−2 per year can be promisingly achieved in China when the aerogel coolers are integrated on building roofs. This work paves a new way to manufacture more cost-effective and sustainable cooling materials for efficient building energy conservation in the future.