Durable and Scalable Superhydrophobic Colored Composite Coating for Subambient Daytime Radiative Cooling

Abstract

Passive daytime radiative cooling without any energy input has attracted significant attention due to its ability to spontaneously radiate heat into cold outer spaces. However, the distinctive structure and optical properties made radiative cooling materials white in appearance, which limits their use in actual application. In this study, poly(dimethylsiloxane) (PDMS), poly-(ethyl cyanoacrylate) (PECA), polystyrene (PS), and pigments that selectively absorb visible light with high emissivity were adopted to fabricate a colored superhydrophobic radiative cooling coating through spraying and nonsolvent-induced phase separation. The asfabricated yellow, red, and green PS/PDMS/PECA composite coatings exhibited high solar reflectivities of 92.8, 89.8, and 86.6% with strong infrared emissivities of 95.4, 95.3, and 96.3%, respectively, which correspondingly realized a subambient temperature reduction of 5.3, 3.5, and 2.5 °C. The self-cleaning property of the coating caused by superhydrophobicity helps protect the coating from contamination, favoring a stable outdoor cooling performance. Additionally, the composite coating was resistant to different chemical immersions, ultraviolet (UV) irradiation, sand impact, water impact, and sandpaper abrasion, which might improve the applicability of the material and promote the cooling materials toward large-area production for practical application.

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

“…Energy efficiency optimization of building envelope materials will have a huge influence on the energy mix. In order to demonstrate the superiority of the SiO 2 /PVA aerogel as a building envelope material in practical applications, simulation was conducted of the annual energy consumption of four different types of building envelopes (building baseline, thermal-insulation-only, radiative-cooling-only, and composite aerogel) for various provinces and cities in China . It was found that the average energy-saving efficiency of the SiO 2 /PVA composite aerogel in 10 cities in China reached 26.24% (Figure a,b), which is better than that of thermal-insulation-only and radiative-cooling-only materials.…”

“…The heat conduction and heat convection from ambient radiation ( P ( cond + conv ) ) is P false( c o n d + c o n v false) false( T , T a m b false) = h c c false( T a m b − T false) where A is the nonradiative heat transfer coefficient, with typical values in the range 0–12 W/m 2 . , …”

“…The heat conduction and heat convection from ambient radiation ( P ( cond + conv ) ) is where A is the nonradiative heat transfer coefficient, with typical values in the range 0–12 W/m 2 . , …”

Scalable, Waterproof, Breathable, and Flexible Polyolefin-Elastomer/Polyethylene Glycol@Zinc Oxide Microfibrous Fabrics for Daytime Radiative Cooling Clothing

“…Microfibrous structures are composed of fibers with diameters of 0.5–10 μm and dense pores with sizes of 10–1000 μm, beneficial not only for air penetration but also for strongly reflecting incident photons, resulting in excellent breathability and 99% opacity. Moreover, various strategies, including laminating, coating, and direct-spinning processes, were used to embed the particles into the microfibrous structures, and multilayered fabric/membrane composites and coated textiles have been reported for the promising potential of radiative cooling fabric. However, these exciting composite textiles are still tricky to industrialize due to the complex preparation processes and uncertified safety of the coating agents.…”