Flexible passive radiative cooling inspired by Saharan silver ants

Wu, Wanchun; Lin, Shenghua; Wei, Mingming; Huang, Jinhua; Xu, Hua; Lu, Yuehui; Song, Weijie

doi:10.1016/j.solmat.2020.110512

Cited by 59 publications

(27 citation statements)

References 35 publications

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“…Examples include switchable radiative coolers that reduce their temperature only when they are above a critical temperature [ 24,25 ] and flexible radiative coolers. [ 26,27 ] Moreover, radiative textiles that can cool down a human body [ 28–30 ] and a Janus emitter to reduce the temperature of enclosures [ 31 ] have been demonstrated recently.…”

Section: Introductionmentioning

confidence: 99%

Visibly Transparent Radiative Cooler under Direct Sunlight

Kim

Lee

Son

et al. 2021

Advanced Optical Materials

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Transparency is an important characteristic in practical applications of radiative cooling, but the transmitted sunlight trapped in an inner space is generally the main cause of the increasing temperature. A transparent radiative cooler that can lower a temperature during the daytime by transmitting visible light, reflecting near‐infrared (NIR) light, and radiating thermal energy through the atmospheric window is proposed. In contrast to transparent selective emitters that transmit most of the incoming solar irradiance under direct sunlight and opaque radiative coolers that reflect all solar energy, the proposed cooler achieves transparency and the cooling effect simultaneously by selectively blocking solar absorption in the NIR regime. Outdoor rooftop measurements confirm that the cooler can reduce i) the inner temperature of an absorbing system and ii) its own temperature when combined with commercially available paints. During daytime, the cooler provides a temperature reduction of a maximum 14.4 °C and 10.1 °C for the inner and own temperature, respectively, and of an average 5.2 °C and 4.3 °C, respectively, in comparison to the transparent selective emitter. The proposed cooler can reduce the temperature during the daytime while maintaining transparency, confirming its possibilities in practical applications such as passive diurnal cooling of vehicles or buildings and compatibility with current paint technologies for aesthetic use.

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Section: Introductionmentioning

confidence: 99%

Visibly Transparent Radiative Cooler under Direct Sunlight

Kim

Lee

Son

et al. 2021

Advanced Optical Materials

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“…Daytime radiative cooling inevitably faces the sun, and here, we chose air mass 1.5 (AM1.5) as the solar irradiation condition. 38 The solar energy received by the Earth's surface is mainly concentrated in the visible band (vis, 0.38−0.76 μm) and near-infrared band (NIR, 0.76−2.5 μm), accounting for about 97% of the total solar energy (45% for vis and 52% for NIR, respectively), with energy in the ultraviolet band (UV, 0.2−0.38 μm) probably occupying the remaining 3%, indicating that almost all the solar energy is in these three regions, while the solar energy in the midinfrared band (MIR, 2.5−25 μm) and far-infrared band (FIR, 25−1000 μm) is almost zero and can be neglected. To achieve radiative cooling, first, it is necessary to maximize the reflectivity in the UV−vis− NIR band to eliminate the absorption P solar, and previous studies have shown that a small amount of absorption in the solar region could cause a significant reduction in radiative cooling power.…”

Section: Resultsmentioning

confidence: 99%

In Situ Formation of SiO₂ Nanospheres on Common Fabrics for Broadband Radiative Cooling

Zhang

2021

ACS Appl. Nano Mater.

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Radiative cooling materials are attracting more and more attention because of their intrinsic advantages in energy saving and environmental protection, especially radiative cooling fabrics. In this paper, we used tetraethyl orthosilicate (TEOS) as the silicon source and prepared radiative cooling fabrics by in situ synthesizing SiO 2 microspheres on polyester cloth. The in situ formation of SiO 2 microspheres results in strong bonding with polyester fibers, solving the problem of powder peeling. The fabrics we prepared have a high emissivity of more than 95% in the midinfrared band and a relatively high reflectivity of ∼70% in the visible−near infrared band and can realize effective radiative cooling. The cooling effect would vary with the amount of TEOS added, and the sample with the optimal performance could achieve a maximal temperature drop of 11.2 °C under direct sunlight (10:00 a.m. to 16:00 p.m.) when compared with the surrounding environment. Such cooling fabrics can be made from commonly used fabrics on a large area, suggesting their potential use in fields such as outdoor cooling clothing and refrigerated shipments and thus opened up a way for the preparation and application of radiative cooling fabrics.

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“…Meanwhile, radiative coolers have been studied for onskin electronics to improve thermal comfort because they can provide heat dissipation without requiring external energy. [18][19][20][21][22][23][24] To address the challenge associated with unwanted TES mode conversion in a hot outdoor environment, we investigated a radiative cooling system as a solution for thermal management of the TES. Here, we developed a multi-layered, flexible, and stretchable radiative cooler (m-FSRC) and integrated it with a TES to passively and effectively lower the device temperature through thermal radiation and solar reflection.…”

Section: Introductionmentioning

confidence: 99%

Self‐Cooling Gallium‐Based Transformative Electronics with a Radiative Cooler for Reliable Stiffness Tuning in Outdoor Use

et al. 2022

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Reconfigurability of a device that allows tuning of its shape and stiffness is utilized for personal electronics to provide an optimal mechanical interface for an intended purpose. Recent approaches in developing such transformative electronic systems (TES) involved the use of gallium liquid metal, which can change its liquid-solid phase by temperature to facilitate stiffness control of the device. However, the current design cannot withstand excessive heat during outdoor applications, leading to undesired softening of the device when the rigid mode of operation is favored. Here, a gallium-based TES integrated with a flexible and stretchable radiative cooler is presented, which offers zero-power thermal management for reliable rigid mode operation in the hot outdoors. The radiative cooler can both effectively reflect the heat transfer from the sun and emit thermal energy. It, therefore, allows a TES-in-the-air to maintain its temperature below the melting point of gallium (29.8 °C) under hot weather with strong sun exposure, thus preventing unwanted softening of the device. Comprehensive studies on optical, thermal, and mechanical characteristics of radiative-cooler-integrated TES, along with a proof-of-concept demonstration in the hot outdoors verify the reliability of this design approach, suggesting the possibility of expanding the use of TES in various environments.

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Flexible passive radiative cooling inspired by Saharan silver ants

Cited by 59 publications

References 35 publications

Visibly Transparent Radiative Cooler under Direct Sunlight

Visibly Transparent Radiative Cooler under Direct Sunlight

In Situ Formation of SiO₂ Nanospheres on Common Fabrics for Broadband Radiative Cooling

Self‐Cooling Gallium‐Based Transformative Electronics with a Radiative Cooler for Reliable Stiffness Tuning in Outdoor Use

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Flexible passive radiative cooling inspired by Saharan silver ants

Cited by 59 publications

References 35 publications

Visibly Transparent Radiative Cooler under Direct Sunlight

Visibly Transparent Radiative Cooler under Direct Sunlight

In Situ Formation of SiO2 Nanospheres on Common Fabrics for Broadband Radiative Cooling

Self‐Cooling Gallium‐Based Transformative Electronics with a Radiative Cooler for Reliable Stiffness Tuning in Outdoor Use

Contact Info

Product

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In Situ Formation of SiO₂ Nanospheres on Common Fabrics for Broadband Radiative Cooling