Expanding the applicability of daytime radiative cooling: Technological developments and limitations

Ulpiani, Giulia; Ranzi, Gianluca; Feng, Jie; Santamouris, M.

doi:10.1016/j.enbuild.2021.110990

Cited by 37 publications

(17 citation statements)

References 158 publications

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“…As outlined in the Section 1, the feasibility of their ALT properties is also controversially debated until now. 4 − 7 Our improved understanding of the reflection mechanism of a DCR enabled us to reassess their contribution to radiative cooling. Our simplified mode-to-mode conversion analysis indicates a potential positive effect ( S3 , Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

“… 4 , 5 An experimental proof of the feasibility of such a filter has not been shown, and a complete theoretical analysis is also missing, especially with a full description of the mode-to-mode conversion. 6 , 7 Further progress in this direction requires a thorough understanding of the optical properties of a suitable ALT filter, which, furthermore, should cover a broad wavelength range and work independently of the light polarization. Ultimately, for transitioning into a potential application, such an ALT filter needed to be simple and scalable to manufacture.…”

Section: Introductionmentioning

confidence: 99%

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Reflection Mechanism of Dielectric Corner Reflectors: The Role of the Diffraction of Evanescent Waves and the Goos–Hänchen Shift

2022

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Nano- and microstructures have been developed for asymmetric light transmission (ALT) filters operating in a wide wavelength range. One of the most straightforward structures with ALT properties is a dielectric corner reflector (DCR) comprising a one-dimensional grating of a triangular shape on one surface. The DCR possesses strong reflection only for one-way light illumination due to multiple total internal reflections (TIRs) inside the triangular grating. For triangular structures being much larger than the wavelength of light, the reflection properties are expected to be fully described by geometrical optics. However, geometrical optics do not account for the Goos–Hänchen (GH) shift, which is caused by the evanescent wave of the TIR. In this work, the reflection mechanism of DCRs is elucidated using the finite element method and a quantitative model built by considering the GH shift. The reduction in reflection of the DCR is dominated by diffraction of the evanescent wave at the corner of the triangular structure. Our model is based on simple mathematics and can optimize the DCR geometry for applications addressing a wide wavelength range such as radiative cooling.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Reflection Mechanism of Dielectric Corner Reflectors: The Role of the Diffraction of Evanescent Waves and the Goos–Hänchen Shift

2022

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“…[1] Radiative cooling is a promising future technology for passive cooling and renewable energy harvesting. [2][3][4][5][6][7][8][9] Highly emissive material is usually adopted in radiative coolers (RC) to spontaneously cool a surface by radiating thermal heat in the atmospheric transparent window within 8-13 µm, hence excessive heat can be dissipated to outer space without energy consumption or pollutant emission. [10][11][12][13][14][15][16][17] However, in real conditions, the fixed high infrared emittance in broadband mid-infrared is bound to bring unwanted thermal effects.…”

Section: Introductionmentioning

confidence: 99%

“…[40][41][42][43][44] Among all, asymmetric infrared transmission and reflection is the promising breakthrough required for an all-season and all-terrain sustainable passive cooling/heating technology. [2,45,46] The underlying principle of optimized radiative thermoregulation can be interpreted as follows. Under counter radiation of the sky, without an asymmetric shielding, intensive atmospheric emission results in massive heat load absorption by RC.…”

Section: Introductionmentioning

confidence: 99%

A Dual‐Mode Infrared Asymmetric Photonic Structure for All‐Season Passive Radiative Cooling and Heating

Liu

Song

et al. 2022

Adv Funct Materials

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Radiative cooling is a revolutionary sustainable thermoregulating technology in favor to fight against global warming and urban heat island effects. However, the conventional designed high infrared emissive coolers do not function satisfactorily under atmospheric counter radiation (cloudy, humid, reduced sky access conditions) nor for all‐season thermal requirement (cooling and/or heating). Dual‐mode asymmetric photonic mirror (APM) consisted of silicon‐based diffractive gratings is presented, approaching an all‐season and all‐terrain optimized radiative thermal regulation. Based on the mechanism of asymmetric diffraction through high refractive index contrast mediums, the designed APM establishes an asymmetric radiative heat transfer channel for cooling and heating. An average infrared asymmetry of 20% for outgoing and incoming radiation is achieved by the fabricated APM. The remarkable cooling power of APM surpasses 80% over the standalone radiative cooler (RC) for counter radiation conditions. Under cloudy sky, the cooling‐APM achieves 8 °C lower than RC standalone, while the heating‐APM 5.7 °C higher, which presents prominent advantages over conventional coolers for different thermal management needs. The proposed dual‐mode infrared asymmetric photonic structure is promising to overcome shortcomings of conventional radiative cooling and offers breakthrough developments in future energy‐saving thermal management system.

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“…Cellulose materials emit thermal radiation, and when facing the sky, the emitted radiation escapes the earth through the atmospheric transparent window (8-13 µm) and ends up in the ultracold universe (Fig. 1A) (35). The emitted heat exceeds the adsorbed solar heat resulting in a net cooling effect at zero energy cost.…”

Section: Introductionmentioning

confidence: 99%

Radiative Cooling Sorbent towards High Performance All Weather Ambient Water Harvesting

Zhu

Zhang²,

Zhang

et al. 2022

Preprint

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Emerging atmospheric water harvesting (AWH) technologies promise water supply to underdeveloped regions that have no access to liquid water resources. The prevailing AWH systems, including condensation- or sorption-based, mostly rely on a single mechanism and thus have a limited range of working conditions and inferior performance. In this study, we synergistically integrate multiple mechanisms, including thermosorption effect, radiative cooling, and multiscale cellulose-water interactions, and demonstrate a low-cost (~ 4 USD kg− 1) and high performance (up to 6.75 L kg− 1 day− 1 in field tests) AWH system requiring zero active energy input. The proposed system consists of a highly scalable and sustainable cellulose scaffold impregnated with hygroscopic deliquescent lithium chloride (LiCl) salt. Cellulose scaffold and coated LiCl synergistically interact with water at different scales from molecular, to nanometer, and micrometer scales, providing a fast harvesting rate and high yield over a wide operation range. Iterating radiative cooling and solar heating workflow achieves simultaneous enhancement of water capture and release through the so-called temperature-swing strategy. The captured water in return facilitates radiative cooling due to the intrinsically high infrared (IR) emissivity of the LiCl-cellulose composite. With our simple yet effective material design, the AWH working range extends to lower than ~ 10% relative humidity (RH), and the water uptake in the controlled lab test reaches 16 kg kg− 1 at 90% RH (sample at 19°C, i.e. 6°C below 25°C ambient temperature). In addition, we propose a theoretical model capable of elucidating the experimental water uptake curves and demonstrating the synergy among cellulose-LiCl-water-energy interaction. The promising performance emphasizes the potential of involving multiple AWH mechanisms and points to an alternative pathway to stimulate future improvement.

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Expanding the applicability of daytime radiative cooling: Technological developments and limitations

Cited by 37 publications

References 158 publications

Reflection Mechanism of Dielectric Corner Reflectors: The Role of the Diffraction of Evanescent Waves and the Goos–Hänchen Shift

Reflection Mechanism of Dielectric Corner Reflectors: The Role of the Diffraction of Evanescent Waves and the Goos–Hänchen Shift

A Dual‐Mode Infrared Asymmetric Photonic Structure for All‐Season Passive Radiative Cooling and Heating

Radiative Cooling Sorbent towards High Performance All Weather Ambient Water Harvesting

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