Cover shields for sub-ambient radiative cooling: A literature review

Zhang, Ji; Yuan, Jianjuan; Liu, Junwei; Zhou, Zhi‐Hua; Sui, Jiyuan; Xing, Jincheng; Zuo, Jian

doi:10.1016/j.rser.2021.110959

Cited by 65 publications

(27 citation statements)

References 94 publications

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“…Similarly, the temperature difference Δ T of Sample 1 and Sample 2 are 7.6 and 8.1 °C, respectively (Figure S7, Supporting Information), with an estimated net cooling power of 130.35 and 138.17 W m –2 , respectively, under the same non‐radiative heat losses of h cc = 12 W m –2 K –1 . More importantly, in the ideal limit of no convection and conduction losses ( h cc = 0 W m –2 K –1 ), [ 42,43 ] the model returns a remarkable 32.9 °C temperature drop in the daytime temperature for Sample 3, suggesting that the designed radiative cooler should retain a high cooling potential if additional IR‐transparent insulation is applied to it. [ 43,44 ] In comparison, an ideal sample (null absorption between 0.25 and 2.5 µm and unit emissivity between 2.5 and 25 µm, see Figure S8, Supporting Information) shows an 11.6 °C temperature drop, while the bulk SiO 2 cannot be cooled as its curve value is negative at equilibrium.…”

Section: Resultsmentioning

confidence: 99%

Iridescent Daytime Radiative Cooling with No Absorption Peaks in the Visible Range

Ding

Pattelli

Xü

et al. 2022

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Traditional cooling technologies suffer from several limitations: basically, they all rely on electricity, have high energy needs, and discharge waste heat into the surrounding environment which in turn contributes to global warming and the urban heat island effect. [2][3][4] For these reasons, the recent development of passive radiative sky cooling materials is attracting a growing interest due to its environmentally friendly nature and energy-free working principle. [5] In recent years, hundreds of candidate materials have been proposed, offering a range of passive cooling performances during daytime hours and even under direct sunlight. Two essential requirements for sub-ambient radiative cooling under direct sunlight are a high reflectivity above 90% in the solar spectral range (0.25-2.5 µm), and a strong, preferably selective emissivity in the atmospheric transparency window (8-13 µm). [6,7] This demanding combination of optical properties is generally achieved through both the selection of specific materials with appropriate absorption bands and the micro and nanoengineering of coatings. These materials can be generally divided into four main categories, namely dielectric multilayer films, [8][9][10][11][12] organic-inorganic composite materials, [13][14][15] Coatings for passive radiative cooling applications must be highly reflected in the solar spectrum, and thus can hardly support any coloration without losing their functionality. In this work, a colorful daytime radiative cooling surface based on structural coloration is reported. A designed radiative cooler with a bioinspired array of truncated SiO 2 microcones is manufactured via a self-assembly method and reactive ion etching. Complemented with a silver reflector, the radiative cooler exhibits broadband iridescent coloration due to the scattering induced by the truncated microcone array while maintaining an average reflectance of 95% in the solar spectrum and a high thermal emissivity (ε) of 0.95, owing to the reduced impedance mismatch provided by the patterned surface at infrared wavelengths, reaching an estimated cooling power of ≈143 W m -2 at an ambient temperature of 25 °C and a measured average temperature drop of 7.1 °C under direct sunlight. This strong cooling performance is attributed to its bioinspired surface pattern, which promotes both the aesthetics and cooling capacity of the daytime radiative cooler.

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Section: Resultsmentioning

confidence: 99%

Iridescent Daytime Radiative Cooling with No Absorption Peaks in the Visible Range

Ding

Pattelli

Xü

et al. 2022

Small

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“…Generally, it required larger areas of radiative coolers to produce a sufficient cooling capacity, which inevitably resulted in the improved cost. [ 4,136–138 ] Therefore, it is highly urgent to develop the facile strategies to further enhance radiative cooling performance. [ 139,140 ] Some reports have revealed that aerogel materials can markedly reduce nonradiative heat exchange, resulting in great temperature drop with the ambient.…”

Section: Discussionmentioning

confidence: 99%

Micro‐Nano Porous Structure for Efficient Daytime Radiative Sky Cooling

Liu

Tang

Jiang

et al. 2022

Adv Funct Materials

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CO 2 in 2050. [5] Due to the second law of thermodynamics, cooling is generally more challenging than heating. Conventional vapor-compression cooling not only results in excessive energy consumption, accelerating the depletion of fossil fuels, but also degrades the atmospheric ozone, leading to notorious environmental issues. Therefore, developing novel and pollutionfree cooling technology has become an urgent demand in the following decades.Radiative sky cooling (RSC) can harvest the coldness of the universe via the 8-13 µm atmospheric window without any pollution and energy consumption, which has witnessed great progress in the last few years. [6][7][8] Since the first demonstration of daytime radiative cooling via multilayer photonic structure by Fan and co-workers in 2014, this facile cooling technology has drawn worldwide attention. [9,10] With the joint efforts, RSC technology has achieved striking advances in building cooling, [4,11] photovoltaic cooling, [12][13][14] cryogenic cooling, [15,16] RSC driving thermoelectricity, [17][18][19] atmospheric water harvesting, [20,21] personal thermal management [3,22,23] and wearable devices. [24][25][26] For building cooling, the pioneering reports by Goldstein et al. and Zhao et al. have demonstrated that building-integrated RSC modules can provide continuous day-and-night cooling and can potentially save 32%-45% of the electricity consumption for cooling in summer. [4,11] For photovoltaic cooling, selective photonic cooler can lower the temperature of solar panels by over 5.7 K and afford the greater cooling

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“…A polyethylene (PE) film is commonly used as the cover, and this makes the conventional RC emitter not durable. Thus, a durable cover shield for the RC itself is now one of the pursued topics in the RC research [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…It is also worth mentioning that the roof SC-RC ventilation implemented in this strategy has a notable difference from the conventional RC emitter, i.e., we eliminate the convection cover. This elimination of convection cover aims to avoid the use of short-lived material and thus make this SC-RC system more durable because most of the RC emitter materials are more durable than the commonly used cover material such as polyethylene (PE) [48][49][50].…”

Section: Introductionmentioning

confidence: 99%

Performance evaluation of combined solar chimney and radiative cooling ventilation

Suhendri

et al. 2022

Building and Environment

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Cover shields for sub-ambient radiative cooling: A literature review

Cited by 65 publications

References 94 publications

Iridescent Daytime Radiative Cooling with No Absorption Peaks in the Visible Range

Iridescent Daytime Radiative Cooling with No Absorption Peaks in the Visible Range

Micro‐Nano Porous Structure for Efficient Daytime Radiative Sky Cooling

Performance evaluation of combined solar chimney and radiative cooling ventilation

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