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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. Structurally colored films capable of full‐time sub‐ambient radiative cooling are prepared from a composite of cellulose nanocrystals and ethylcellulose. The distinct nanostructure within each layer allows for selective reflection of visible light generating color, whilst maintaining a broadband solar reflection. Finally, by demonstrating roll‐to‐roll fabrication, the potential for commercial production from this low‐cost and sustainable feedstock is substantiated.

Radiative cooling passively removes heat from objects via emission of thermal radiation to cold space. Suitable radiative cooling materials absorb infrared light while they avoid solar heating by either reflecting or transmitting solar radiation, depending on the application. Here, we demonstrate a reflective radiative cooler and a transparent radiative cooler solely based on cellulose derivatives manufactured via electrospinning and casting, respectively. By modifying the microstructure of cellulose materials, we control the solar light interaction from highly reflective (> 90%, porous structure) to highly transparent (≈ 90%, homogenous structure). Both cellulose materials show high thermal emissivity and minimal solar absorption, making them suitable for daytime radiative cooling. Used as coatings on silicon samples exposed to sun light at daytime, the reflective and transparent cellulose coolers could passively reduce sample temperatures by up to 15 °C and 5 °C, respectively.

Radiative cooling is a natural process to cool down surfaces through the rejection of thermal radiation using the outer space as a cold sink, taking advantage of the transparency of the atmospheric windows (8–14 μm), which partially matches the infrared radiation band. With the development of new materials that have a high reflectivity of solar radiation, daytime radiative cooling can be achieved. This phenomenon depends on the optical properties of the surface and the local weather conditions. In this research, climatological data from 1791 weather stations were used to present detailed nighttime and all-day radiative cooling maps for the potential implementation of radiative cooling-based technologies. The paper offers a parametric study of the variation of the potential as a result of decreasing the solar reflectivity. The results show that southern Europe is the region with the highest potential while northern Europe holds more hours of available radiative cooling. After varying the solar reflectivity from 1 to 0.5 the average power reduces from 60.18 to 45.32 W/m2, and energy from 527.10 to 264.87 kWh/m2·year. For solar reflectivity lower than 0.5, all-day radiative coolers behave as nighttime radiative coolers, but power and energy values improve significantly for high values of solar reflectivity. Small variations of solar reflectivity have greater impacts on the potential at higher reflectivity values than at lower ones.

The Arctic is notable as a region where the greatest rate of increase in precipitation associated with global warming is anticipated. The Arctic precipitation simulated by the Coupled Model Intercomparison Project Phase 6 models showed a strong increasing trend since the 1980s. We found that the forcing factor of the trend is a combination of the continued strengthening of greenhouse gas forcing and the leveling off of aerosol forcing dominated in earlier periods. From an energetic perspective, we found that the increased atmospheric radiative cooling and reduced sensible heat transport from lower latitudes contributed equally to the recent increase in Arctic precipitation. The combination of these two energetic factors suggests a doubling of the Arctic amplification factor for precipitation relative to that for temperature. Future Arctic precipitation will change in proportion to the temperature change, and the fractional contributions of the energetic factors will remain stable across various scenarios. Plain Language Summary The Arctic region is inherently a low‐precipitation area. However, because of global warming, precipitation is expected to increase substantially in the Arctic region compared with the global average when viewed as a percentage change from the original precipitation. This severely affects climate change in the Arctic environment. The latest climate model simulations show that there has been a rapid increase in precipitation in the Arctic region in recent decades. The driving factors behind the rapid increase are the effects of the accelerating growth of greenhouse gas concentrations, which were previously suppressed by the increasing anthropogenic aerosol emissions before the 1980s. Based on the heat budget of the atmosphere, we identified important factors contributing to these precipitation changes. These include enhanced radiative cooling (responding locally to increased air temperature) and reduced heat transport from lower latitudes due to greater temperature increases at higher latitudes. Future precipitation will change in proportion to the temperature change while maintaining consistent fractional contributions across different scenarios. Key Points Trends in Arctic precipitation in the recent and future decades are examined from multimodel simulations The recent rapid increase is driven by accelerating greenhouse gas concentrations and plateauing growth in anthropogenic aerosol emissions Increased radiative cooling and reduced poleward sensible heat transport equally contributed to the Arctic precipitation changes

Thanks to recent advances in nanophotonics and scalable manufacturing of metamaterials, radiative sky cooling has emerged as a “self-reliant” cooling technology with various potential applications. However, not every region across the globe is well suited for the adoption of radiative cooling technologies, depending on the local climate, population density, cooling demand, air conditioning saturation, economic prosperity, etc. Because the atmospheric downward longwave radiation, especially the portion from the atmospheric window (8–13 µm), is substantially affected by weather conditions, the performance of a well-designed radiative cooler can be vastly different across regions and seasons. Here, we first map the global radiative sky cooling potential in the form of net cooling power density. We then further evaluate it based on the global population density and cooling demand. In terms of the adjusted potential, we show that geographically and demographically “transitional” regions, located between wet and dry climates as well as sparsely and densely populated regions, are better suited for the adoption of radiative cooling technologies because of their temperate climate and moderate population density. Even in densely populated and humid regions, the cumulative impact and other accompanying benefits must not be ignored.

Radiative thermal management technologies that utilize thermal radiation from nano/microstructure for cooling and heating have gained significant attention in sustainable energy research. Passive radiative cooling and solar heating operate continuously, which may lead to additional heating or cooling energy consumption due to undesired cooling or heating during cold nighttime/winters or hot daytime/summers. To overcome the limitation, recent studies have focused on developing radiative thermal management technologies that can toggle radiative cooling on and off or possess switchable dual cooling and heating modes to realize sustainable and efficient thermal management. This review will explore the fundamental concepts of radiative thermal management and its switching mechanisms, utilizing novel systems composed of various materials and nano/microstructures. Additionally, we will delve into the potential future research directions in radiative thermal management technologies.

Radiative cooling, taking advantage of the coldness of the sky, has a potential to be a sustainable alternative to meet cooling needs. The performance of a radiative cooling device is fundamentally limited by the emissivity of the sky, therefore depends heavily on the regional weather conditions. Although the sky emissivity is known to increase with the dew point temperature, the feasibility of radiative cooling remains elusive in the equatorial tropical climate, where the weather is humid, cloudy, and constantly changing. It is pointed out that a high degree of thermal insulation of the radiative cooling system can be effective under such extreme weather conditions. A new method to characterize dynamic sky conditions is presented, namely to measure the sky window emissivity in the zenith direction. It is shown that a sub‐ambient cooling up to 8 °C is possible during daytime and that the cloud base is not a complete blackbody and can be used as a heat sink for radiative cooling. The feasibility of radiative cooling in hot and humid climates has been elusive, due to the opaqueness of the sky and the high cloud coverage. To overcome these compromising environmental factors, various heat gain channels are meticulously suppressed and 8 degrees temperature reduction from ambient is demonstrated during the daytime under the cloudy sky of Singapore.

Broadband passive daytime radiative cooling (PDRC) materials exhibit sub-ambient surface temperatures and contribute highly to mitigating extreme urban heat during the warm period. However, their application may cause undesired overcooling problems in winter. This study aims to assess, on a city scale, different solutions to overcome the winter overcooling penalty derived from using PDRC materials. Furthermore, a mesoscale urban modeling system assesses the potential of the optical modulation of reflectance (ρ) and emissivity (ε) to reduce, minimize, or reverse the overcooling penalty. The alteration of heat flux components, air temperature modification, ground and roof surface temperature, and the urban canopy temperature are assessed. The maximum decrease of the winter ambient temperature using standard PDRC materials is 1.1 °C and 0.8 °C for daytime and nighttime, respectively, while the ρ+ε-modulation can increase the ambient temperature up to 0.4 °C and 1.4 °C, respectively, compared to the use of conventional materials. Compared with the control case, the maximum decrease of net radiation inflow occurred at the peak hour, reducing by 192.7 Wm−2 for the PDRC materials, 5.4 Wm−2 for ρ-modulated PDRC materials, and 173.7 Wm−2 for ε-PDRC materials; nevertheless, the ρ+ε-modulated PDRC materials increased the maximum net radiation inflow by 51.5 Wm−2, leading to heating of the cities during the winter.

Polylactic acid (PLA) fabrics exhibit significant sunlight reflectivity and high emissivity within the atmospheric window, making them suitable as the foundational material for this study. This research involves the modification of one side of the fabric with hydrophilic agents and titanium dioxide (TiO2), while the opposite side is treated with MXene and subsequently coated with polydimethylsiloxane (PDMS) to inhibit oxidation of the MXene. Through these surface modifications, a thermal management fabric based on PLA was successfully developed, capable of passively regulating temperature in response to environmental conditions and user requirements. The study discusses the optimal concentrations of TiO2 and MXene for the fabric, and characterizes and evaluates the functional surface of the PLA. Surface morphology analyses and tests indicate that the resulting functional PLA fabrics possess excellent ultraviolet (UV) resistance, favorable air permeability, high sunlight reflectivity on the TiO2-treated side, and superior photothermal conversion capabilities on the MXene-treated side. Furthermore, photothermal effect tests conducted under a light intensity of 1000 W/m2 reveal that the MXene-treated fabric exhibits a heating effect of approximately 25 °C, while the TiO2-treated side demonstrates a cooling effect exceeding 5 °C. This study developed PLA functional fabrics with heating and cooling capabilities.

This is the second of two large‐eddy simulation studies on the mechanisms of mesoscale cellular organization in drizzling (open cells) and nondrizzling marine stratocumulus (closed cells). This study uses a hard nudging approach which maintains fixed horizontal‐mean temperature and humidity profiles for a well‐mixed boundary layer with a constant boundary layer depth. For the case studied, closed cells develop and broaden by 32 hr to an aspect ratio of 25. Simulations show that the closed‐cell mesoscale cellular convection is driven by positive feedback from cloud‐induced mesoscale perturbations of longwave radiative cooling. A conceptual model for closed‐cell stratocumulus as a mesoscale wavelength hydrodynamic instability in which mesoscale moist and dry anomalies spontaneously grow is presented. In simulations in which long‐wavelength sinusoidal moisture anomalies are initially imposed, these anomalies evolve into amplifying closed cells. The cell structure is visualized with a compositing approach based on sorting grid columns by their mesoscale‐smoothed total water path. A thermally direct mesoscale circulation pattern develops in the interior of the boundary layer with buoyant mesoscale updrafts, thicker cloud, and a slightly higher capping inversion in the moister columns. There is a mesoscale flow of above‐inversion air down the slightly sloping capping inversion from the moist to the dry regions, reinforced by cloud top radiative cooling. This strengthens the mesoscale anomalies by preferentially cooling and drying the already dry regions. The sloping inversion flow is not driven as efficiently if the radiative cooling is artificially horizontally homogenized, partly disrupting this positive feedback and the resulting closed‐cell development. Key Points Closed‐cell organization of stratocumulus is a convective instability that amplifies mesoscale column humidity anomalies Cell broadening is induced by longwave radiative cooling of air sinking down sloping cloud tops Turbulent kinetic energy is transferred from mesoscale to smaller scales rather than vice versa