Synchronous Radiative Cooling and Thermal Insulation in SiO2/Poly(vinyl alcohol) Composite Aerogel for Energy Savings in Building Thermal Management

Daytime passive radiative cooling is an effective way to reduce energy consumption for building cooling. However, overcooling might occur in radiative cooling at low-temperature which presents limitations in thermal management. Herein, a new SiO2/poly(vinyl alcohol) composite aerogel with nanomicro–multistage porous structure for thermal insulation and radiative cooling was fabricated by a non-solvent-assisted freeze-drying strategy. In the fabrication process, the nonsolvent (acetone) for poly(vinyl alcohol) was utilized to control the proportion and size of the macro-porous structure inside the SiO2/poly(vinyl alcohol) composite aerogel, making the thermal conductivity of the aerogel decreased to 0.0390 W/mK while spontaneously increasing its solar reflectance and infrared (8–13 μm) emissivity to 93.70% and 98.19%, respectively. The composite aerogel achieved sub-ambient cooling of up to 14.1 °C during the day and above-ambient warming of 3.8 °C at night, avoiding nighttime overcooling. The SiO2/poly(vinyl alcohol) composite aerogel demonstrates adaptive thermal management compared to commercial insulation materials, making it suitable for intelligent thermal management of energy-saving buildings.