Durable radiative cooling against environmental aging

Abstract

To fight against global warming, subambient daytime radiative cooling technology provides a promising path to meet sustainable development goals. To achieve subambient daytime radiative cooling, the reflection of most sunlight is the essential prerequisite. However, the desired high solar reflectance is easily dampened by environmental aging, mainly natural soiling and ultraviolet irradiation from sunlight causing yellowish color for most polymers, making the cooling ineffective. We demonstrate a simple strategy to use titanium dioxide nanoparticles, with ultraviolet resistance, forming hierarchical porous morphology via evaporation-driven assembly, which guarantees a balanced anti-soiling and high solar reflectance, rendering anti-aging cooling paint based coatings. We challenge the cooling coatings in an accelerated weathering test against simulated 3 years of natural soiling and simulated 1 year of natural sunshine, and find that the solar reflectance only declined by 0.4% and 0.5% compared with the un-aged ones. We further show over 6 months of aging under real-world conditions with barely no degradation to the cooling performance. Our anti-aging cooling paint is scalable and can be spray coated on desired outdoor architecture and container, presenting durable radiative cooling, promising for real-world applications.

Recent progress in organic-based radiative cooling materials: fabrication methods and thermal management properties

“…For example, the refractive index of most organic materials in the visible range is limited at around 1.5, 84 which is lower than most metal oxides such as BaSO 4 (1.63) 85 Al 2 O 3 (1.77), 86 ZnO (2), 87,88 and TiO 2 (2.7). 89 Furthermore, the unique Si-O, Si-O-Si bonds of SiO 2 and its phonon-polariton resonance can make it used as the filler of high IR emissivity polymer. 47 By combining these materials and tuning the size distribution of inorganic fillers, the spectral reflectance and emissivity of radiative cooling materials can thus be further regulated.…”

Droplet interface in additive manufacturing: From process to application

“…Due to their unique surface microstructure and excellent superhydrophobic properties, 4,8,[73][74][75][76][77][78][79][80] it is difficult for rain, ice, and snow to adhere to the self-cleaning surfaces, which enables a wide range of essential applications in architectural glass, car, and aircraft windscreens, satellite dishes, high-voltage power lines, and locomotive and aircraft paintings. [81][82][83][84][85][86][87][88][89][90][91] Distinct from conventional methods with limited capability in preparation of a self-cleaning surface, AM fabricates functional surfaces with high self-cleaning efficiency by fully implementing self-cleaning mechanisms owing to its high degree of design and fabrication freedom. As shown in Figure 6b, the surface with a micropillar array was prepared by creating a mold with projection micro stereolithography (PμSL), a vat photopolymerization 3D printing method, and combining it with a template replication process.…”

“…A self‐cleaning surface is a surface from which dust or other pollutants would fall off under the influence of only gravity or natural external forces imposed by rain or wind (Figure 6a). Due to their unique surface microstructure and excellent superhydrophobic properties, 4,8,73–80 it is difficult for rain, ice, and snow to adhere to the self‐cleaning surfaces, which enables a wide range of essential applications in architectural glass, car, and aircraft windscreens, satellite dishes, high‐voltage power lines, and locomotive and aircraft paintings 81–91 …”

All-day passive radiative cooling using common salts

“…Even with encapsulant PE sheets, humidity could easily penetrate the SAP and interact with the salt aerogels as PE has a high water vapor transmission rate. [43] With recent PDRC works demonstrating continued optimal performance of emitter materials in outdoors environments, [45,46] we sought to improve the longevity of these salt aerogels. Na 4 Fe(CN) 6 is a well-known anti-caking agent and has been used to stop coarsening of salts from ambient moisture.…”