A radiative cooling structural material

Li, Tian; Zhai, Yao; He, Shuaiming; Gan, Wentao; Wei, Zhiyuan; Heidarinejad, Mohammad; Dalgo, Daniel; Mi, Ruiyu; Zhao, Xinpeng; Song, Jianwei; Dai, Jiaqi; Chen, Chaoji; Aili, Ablimit; Vellore, Azhar; Martini, Ashlie; Yang, Ronggui; Srebric, Jelena; Yin, Xiaobo; Hu, Liangbing

doi:10.1126/science.aau9101

Cited by 905 publications

(642 citation statements)

References 55 publications

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“…Therefore, to obtain a reasonable comparison between different designs from the material aspect, as shown in Figure S6, we theoretically calculated the stagnation temperature and net cooling power for all designs in the same environmental conditions. The ambient temperature was set as 300 K, and a AM1.5 solar irradiation was assumed to directly shine on the emitters, including our proposed emitter, the ideal emitters and other ones, 5,[7][8][9][10] which have demonstrated sub-ambient daytime cooling effect in outdoor tests. The ideal selective emitter indicates an emitter with unity emittance only at the atmospheric window from 8 to 13 m, while the ideal broadband emitter represents the one with unity emittance in the whole mid-infrared region from 4 to 25 m.…”

Section: Part IV Comparison Between Our Proposed Emitter With Ideal mentioning

confidence: 99%

“…5 Selective thermal emission within the infrared atmospheric window (8-13 m) is required for efficient radiative cooling, while a low solar absorptance is needed to minimize solar heating during the daytime. Due to the supreme optical property of selective emission in the infrared region, the bulk materials of plastic, 6,7 oxide, 8,9 nitride, 10,11 and composite materials of pigmented paints 12,13 as well as gaseous materials 14,15 were the main objectives searched to achieve radiative cooling from the 1960s to 1990s. The coolers were usually composed of a layer of the bulk material with alumina/silver (Al/Ag) coated as the back reflector.…”

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confidence: 99%

“…[21][22][23] However, the complexity and high cost in fabricating photonic structures significantly limit their wide applications. Later, radiative emitters with a simple fabrication process and the possibility of scalable manufacture, including a TPX layer embedded with glass nanoparticles, 24 combinations of a fused silica layer and a PDMS film, 20 and complete delignification and densification of wood, 25 were proposed for demonstration of daytime radiative cooling effect. All of these emitters occupy broadband high infrared emission and low solar absorptance in the meanwhile.…”

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confidence: 99%

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Bulk material based selective infrared emitter for sub-ambient daytime radiative cooling

Yang

Long

Meng

et al. 2020

Solar Energy Materials and Solar Cells

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Through passively emitting excess heat to the outer space, radiative cooling has been demonstrated as an efficient way for energy saving applications. Selective surface with unity emittance only within the atmospheric window as well as zero absorption within the solar spectrum is sought to achieve the best sub-ambient radiative cooling performance during the daytime. In this work, we proposed a bulk radiative cooler consisting of a 1-mm-thick lithium fluoride crystal coated with silver backing, which exhibits a solar absorptance of 4.7% and nearly ideal infrared selectivity with high emission exactly within the atmospheric transmission band (i.e., 8-13 m).Excellent daytime cooling performance was demonstrated in an outdoor test with stagnation temperature below the ambient temperature by 5 ℃ under solar irradiance above 900 W/m 2 and a net cooling power of about 60 W/m 2 when the cooler is in thermal equilibrium with the ambient. As a bulk material with the highest ultraviolet-visible-near infrared transmittance, lithium fluoride crystal has been widely employed as the optical windows and mirrors in various applications. The proposed simple selective infrared emitter based on lithium fluoride would open up an innovative way to radiatively cool optical systems.

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Section: Part IV Comparison Between Our Proposed Emitter With Ideal mentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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Bulk material based selective infrared emitter for sub-ambient daytime radiative cooling

Yang

Long

Meng

et al. 2020

Solar Energy Materials and Solar Cells

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“…Wood has been used to build structures such as bridges, house, towers, and furniture from ancient times to present day . Compared with the manufacturing processes of steel, concrete, and other construction materials, wood processing not only reduces the energy consumption but also results in a positive contribution to the carbon footprint due to its green and environmentally friendly characteristics . Despite these attractive features, wood still faces challenges in the modern construction industry because of its high fire risk.…”

Section: Introductionmentioning

confidence: 99%

Fire‐Resistant Structural Material Enabled by an Anisotropic Thermally Conductive Hexagonal Boron Nitride Coating

Gan

Chen

Wang

et al. 2020

Adv Funct Materials

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Fire retardant coatings have been proven effective at reducing the heat release rate (HRR) of structural materials during burning; yet effective methods for increasing the ignition temperature and delay time prior to burning are rarely reported. Herein, a strong, fire‐resistant wood structural material is developed by combining a densification treatment with an anisotropic thermally conductive flame‐retardant coating of hexagonal boron nitride (h‐BN) nanosheets to produce BN‐densified wood. The thermal management properties created by the BN coating provide fast, in‐plane thermal diffusion, slowing the conduction of heat through the densified wood, which improves the material's ignition properties. Compared with densified wood without the BN coating, a 41 °C enhancement in ignition temperature (Tig), a twofold increase in ignition delay time (tig), and a 25% decrease in the maximum HRR of BN‐densified wood can be achieved. As a proof of concept for scalability, the pieces of the BN‐densified wood are fabricated with a length larger than 25 cm, width greater than 15 cm, and thickness more than 7 mm. The improved thermal management, fire resistance, mechanical strength, and scalable production of BN‐densified wood position it as a promising structural material for safe and energy‐efficient buildings.

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“…In optics and photonics, harnessing the interaction between light and disordered photonic structures recently inspires the rapid and amazing development of the field of "disordered photonics" [10,11], in which focusing [12,13] and imaging [14] through some seemingly scrambled media were successfully demonstrated. Moreover, enormous applications can be achieved by using disordered media with engineered micro/nano-structures, such as spontaneous emission control [15], random lasers [16][17][18] and radiative cooling [19][20][21], etc.…”

Section: Introductionmentioning

confidence: 99%

Near-resonant light transmission in two-dimensional dense cold atomic media with short-range positional correlations

Wang

Zhao

2020

J. Opt. Soc. Am. B

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Light propagation in disordered media is a fundamental and important problem in optics and photonics. In particular, engineering light-matter interaction in disordered cold atomic ensembles is one of the central topics in modern quantum and atomic optics. The collective response of dense atomic gases under light excitation, which crucially depends on the spatial distribution of atoms and the geometry of the ensemble, has important impacts on quantum technologies like quantum sensors, atomic clocks and quantum information storage.Here we analyze near-resonant light transmission in two-dimensional dense ultracold atomic ensembles with short-range positional correlations. Based on the coupled-dipole simulations under different atom number densities and correlation lengths, we show that the collective effects are strongly influenced by those positional correlations, manifested as significant shifts and broadening or narrowing of transmission resonance lines. The results show that mean-field theories like Lorentz-Lorenz relation are not capable of describing such collective effects. We further investigate the statistical distribution of eigenstates, which are significantly affected by the interplay between dipole-dipole interactions and position correlations. This work can provide profound implications on collective and cooperative effects in cold atomic ensembles as well as the study of mesoscopic physics concerning light transport in strongly scattering disordered media. simplest hard-sphere-type correlation which exists in densely packed hard spheres [32] can usually increase the transport mean free path of light [33,34]. Screened Coulomb potential induced positional correlations in nanoparticle colloidal suspensions were found to induce strongly negative asymmetry factor [35,36]. Recently, some unexpected optical properties like optical transparency [37], enhanced absorption [38] and isotropic photonic band gaps [39][40][41][42] were discovered in 2D and 3D disordered media with certain structural correlations, e.g., the stealthy hyperuniform media. Therefore, structural correlations offer a great opportunity for tailoring the optical properties of disordered materials, with promising applications like structural coloration [43,44], bright white paints [45] and solar energy harvesting [38,[46][47][48][49], etc.Despite these fascinating advancements, however, it is still not fully understood how structural correlations affect optical properties of disordered media, even for an ideally simple system composed of randomly distributed spherical scatterers [45,[50][51][52][53]. In particular, the interplay between structural correlations and near-field as well as far-field electromagnetic interactions among scatterers is still not very clear [50,51,54], especially near single scatterer internal resonances (like Mie resonances for dielectric nanoparticles) at high packing density [55][56][57][58][59].On the other hand, the last three decades have witnessed the rapid development of laser cooling and trapping of atoms to r...

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A radiative cooling structural material

Cited by 905 publications

References 55 publications

Bulk material based selective infrared emitter for sub-ambient daytime radiative cooling

Bulk material based selective infrared emitter for sub-ambient daytime radiative cooling

Fire‐Resistant Structural Material Enabled by an Anisotropic Thermally Conductive Hexagonal Boron Nitride Coating

Near-resonant light transmission in two-dimensional dense cold atomic media with short-range positional correlations

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