Superhydrophobic waste paper-based aerogel as a thermal insulating cooler for building

Daytime subambient radiative cooling is a most promising alternative to electricity-free building cooling. However, optical performance degradation arising from surface contamination and inevitable parasitic heat gain still pose unprecedented challenges to cool building at subambient temperatures. This paper proposed a superhydrophobic cellulose aerogel cooler (SHB-CAC) as building envelope by integrating self-cleaning capacity, passive daytime radiative cooling and thermal insulation to reduce environmental heat gain. The SHB-CAC demonstrates high solar reflectance (93%) and long-wave infrared emittance (91%), accomplishing a temperature drop of 8.5 degrees C lower than the ambient under sunlight of 800 W/m(2) in the outdoor experiment. Notably, the SHB-CAC possesses low thermal conductivity (28 mW/(m.K)) that suppresses parasitic heat gain from warmer surrounding and reduces cooling energy consumption. The self-cleaning property resulting from superhydrophobicity protects SHB-CAC from water wetting and dust contamination but also maintains its good surface radiation capacities under different humidity environment. A building energy simulation was conducted and results showed that 43.4% of cooling energy on average could be saved compared to the building baseline consumption, if SHB-CAC was widely used in China, indicating that the strategy of optical and thermal conductivity management of cooler has the potential to reduce the energy consumption of buildings. (C) 2022 Elsevier Ltd. All rights reserved.

Automated summary

A superhydrophobic cellulose aerogel cooler is proposed in this study, which can reduce environmental heat gain to the level needed for building insulation and effectively lower cooling energy consumption through its self-cleaning property and solar reflection capabilities.