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As a sustainable alternative to using virgin polymer, we propose the use of recycled polymer for the fabrication of passive radiative cooling materials to tackle both the increasing demand for cooling systems and to upcycle plastic waste. Using recycled acrylic sheets as the binder for BaSO4 thorough sol–gel method, a sustained 1.2 °C sub-ambient temperature during daytime and 3 °C sub-ambient temperature during nighttime was achieved under the hot and humid conditions of the tropical climate. The coating achieved 97.7 % solar reflectance and 95 % infrared emittance. Separately, when porosity is introduced to recycled acrylic sheets through a phase inversion method, a near-ambient temperature during noontime and sustained sub-ambient temperature of 2.5 °C during nighttime was achieved (with 96.7 % solar reflectance). Comparable performances are also obtained using recycled polyvinyl chloride (PVC) pipe and expanded polystyrene (EPS) foam. [ABSTRACT FROM AUTHOR]

As a sustainable alternative to using virgin polymer, we propose the use of recycled polymer for the fabrication of passive radiative cooling materials to tackle both the increasing demand for cooling systems and to upcycle plastic waste. Using recycled acrylic sheets as the binder for BaSO4 thorough sol–gel method, a sustained 1.2 °C sub-ambient temperature during daytime and 3 °C sub-ambient temperature during nighttime was achieved under the hot and humid conditions of the tropical climate. The coating achieved 97.7 % solar reflectance and 95 % infrared emittance. Separately, when porosity is introduced to recycled acrylic sheets through a phase inversion method, a near-ambient temperature during noontime and sustained sub-ambient temperature of 2.5 °C during nighttime was achieved (with 96.7 % solar reflectance). Comparable performances are also obtained using recycled polyvinyl chloride (PVC) pipe and expanded polystyrene (EPS) foam.

Daytime radiative cooling (DRC) materials offer a sustainable approach to thermal management by exploiting net positive heat transfer to deep space. While such materials typically have a white or mirror‐like appearance to maximize solar reflection, extending the palette of available colors is required to promote their real‐world utilization. However, the incorporation of conventional absorption‐based colorants inevitably leads to solar heating, which counteracts any radiative cooling effect. In this work, efficient sub‐ambient DRC (Day: −4 °C, Night: −11 °C) from a vibrant, structurally colored film prepared from naturally derived cellulose nanocrystals (CNCs), is instead demonstrated. Arising from the underlying photonic nanostructure, the film selectively reflects visible light resulting in intense, fade‐resistant coloration, while maintaining a low solar absorption (≈3%). Additionally, a high emission within the mid‐infrared atmospheric window (>90%) allows for significant radiative heat loss. By coating such CNC films onto a highly scattering, porous ethylcellulose (EC) base layer, any sunlight that penetrates the CNC layer is backscattered by the EC layer below, achieving broadband solar reflection and vibrant structural color simultaneously. Finally, scalable manufacturing using a commercially relevant roll‐to‐roll process validates the potential to produce such colored radiative cooling materials at a large scale from a low‐cost and sustainable feedstock. [ABSTRACT FROM AUTHOR]

Textiles with radiative cooling/warming capabilities provide a green and effective solution to personal thermal comfort in different climate scenarios. However, developing multiple-mode textiles for wearing in changing climates with large temperature variation remains a challenge. Here a Janus textile is reported, comprising a polyethersulfone (PES)-Al 2 O 3 cooling layer optically coupled with a Ti 3 C 2 T x warming layer, which can realize sub-ambient radiative cooling, solar warming, and active Joule heating. Owing to the intrinsically high refractive index of PES and the rational design of the fiber topology, the nanocomposite PES textile features a record high solar reflectance of 0.97. Accompanied by an infrared (IR) emittance of 0.91 in the atmospheric window, sub-ambient cooling of 0.5-2.5 °C is achieved near noontime in humid summer under ≈1000 W m -2 solar irradiation in Hong Kong. The simulated skin covered with the textile is ≈10 °C cooler than that with white cotton. The Ti 3 C 2 T x layer provides a high solar-thermal efficiency of ≈80% and a Joule heating flux of 66 W m -2 at 2 V and 15 °C due to its excellent spectral selectivity and electrical conductivity. The switchable multiple working modes enable effective and adaptive personal thermal management in changing environments., (© 2023 Wiley-VCH GmbH.)

While radiative cooling has been proven successful in mid-latitude regions to achieve sub-ambient temperatures, the same performance could not be achieved in tropical regions due mainly to the higher solar irradiance and atmospheric radiation. Herein, for the first time, the criteria to achieve sub-ambient temperatures in the challenging conditions of tropical daytime is recommended based on the solar reflectance and infrared emittance of an effective broadband radiative cooler. Briefly, the total solar reflectance of the material should be above 97% with an infrared emittance of over 80% to achieve sub-ambient temperatures. To illustrate, the feasibility of daytime radiative cooling under Singapore's tropical climate is investigated using a radiative cooler that meets these criteria. By having a solar reflectance of 98.4% and infrared emittance of 95% within the 8–13 μm spectrum, sustained daytime sub-ambient temperature of 2 °C can be achieved under direct exposure to solar intensity of 1000 W/m2 and downwelling atmospheric radiation of 450 W/m2. The simulated cooling power limit was around 35 W/m2, with the potential to provide over 30 MJ/m2 of cooling energy per month. • For the first time, the criteria to achieve sub-ambient in tropical daytime is recommended. • The solar reflectance should be above 97% with emittance of 80% to be effective. • The BK coating has solar reflectance and infrared emittance (8–13 μm) of 98.4% and 95%, respectively. • A daytime sub-ambient temperature of 2 °C was achieved for the first time. • Simulated upper limit of daytime radiative cooling power is around 35 W/m2. [ABSTRACT FROM AUTHOR]

Sub-ambient radiative cooling has drawn abundant research interest, due to its great energy saving potential. However, the challenge of lacking suitable wind cover material seriously impedes its actual application. To address the challenge, the radiative cooling model with wind cover should be developed firstly. In this work, an accurate radiative cooling model considering the solar and mid-infrared transmissivity of wind cover is developed systematically. Subsequently, the radiative cooling experiments with the polyethylene film wind cover of different thickness are designed to validate the accuracy of the developed model. The experimental results demonstrate that wind cover has a significant impact on radiative cooling performance and the developed model has a high accuracy, with an average relative error of below 3%. Additionally, the developed model is used to investigate the radiative cooling performance in different areas. The modeling results indicate that radiative cooling has a great potential in arid areas. More significantly, feasible breakthrough route towards the rigid wind cover is discussed. The results indicate that the minimum target transmissivity of ultra-white glass and zinc selenide wind covers gradually improve with the increase of humidity. Our work provides a platform to address the challenge of lacking suitable wind cover and promotes the actual application of radiative cooling technology. Accurate radiative cooling model considering the spectral profiles of wind cover is developed systematically. Image 1 • An accurate wind cover model towards the actual application of sub-ambient radiative cooling is developed. • The developed radiative cooling model has a relative error of below 3%. • Radiative cooling performance in different areas is explored with the developed model. • Feasible breakthrough routes to address the challenge of lacking suitable wind cover materials are discussed. [ABSTRACT FROM AUTHOR]

With the breakthrough of daytime radiative cooling, more and more efforts have been devoted to this promising clean energy technology. However, there still lacks systematic research on the impact of wind cover on radiative cooling performance. This work firstly reviews the existing wind cover material and non-radiative heat exchange models. Subsequently, the great impact of the wind cover on cooling performance is demonstrated theoretically and experimentally. The results indicate that in the high temperature and humidity area, the difference of daytime maximum temperature drop with and without wind cover can reach about 2.3 K, while the nighttime difference is significantly greater. Additionally, the tilt strategy and wind cover strategy are employed to achieve a maximum daytime average temperature drop of 4.2 K in Tianjin, China. Furthermore, this work continues to investigate the impact of the wind cover on radiative cooling potential of various areas in China, and the results reveal that wind cover has a greater impact on the radiative cooling potential in Northwest China and 85% of China's areas can achieve radiative cooling performance with wind cover. This work provides a detailed evaluation of radiative cooling potential with and without wind cover in China. • The impact of wind cover on radiative cooling performance is demonstrated theoretically and experimentally. • The existing wind cover material and non-radiative heat exchange model are reviewed. • The tilt strategy and wind cover strategy can improve the cooling performance significantly. • The distribution of radiative cooling potential with and without wind cover in China is drawn. [ABSTRACT FROM AUTHOR]