Reflective and transparent cellulose-based passive radiative coolers

Gamage, Sampath; Banerjee, Debashree; Alam, Md. Mehebub; Hallberg, T.; Åkerlind, Christina; Sultana, Ayesha; Shanker, Ravi; Berggren, Magnus; Crispin, Xavier; Kariis, Hans; Zhao, Dan; Jonsson, Magnus P.

doi:10.1007/s10570-021-04112-1

Cited by 49 publications

(42 citation statements)

References 37 publications

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“…The cooling wood achieved continuous subambient conditions during the day and night (Figure 4b). Similarly, other cellulose‐based materials [ 35,41–48 ] as efficient IR emitters have been explored for PDRC. Tian et al.…”

Section: Development Of Advanced Pdrc Devicesmentioning

confidence: 99%

“…The cooling wood achieved continuous subambient conditions during the day and night (Figure 4b). Similarly, other cellulose-based materials [35,[41][42][43][44][45][46][47][48] as efficient IR emitters have been explored for PDRC. Tian et al [41] designed scalable cellulose-based composites with strong solar reflectance and mid-IR emittance, and a subambient cooling performance of 5 °C under sunlight was achieved.…”

Section: Spectral Design In the Mid-ir Rangementioning

confidence: 99%

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Recent Progress in Daytime Radiative Cooling: Advanced Material Designs and Applications

Zhang

Wang

et al. 2022

Small Methods

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the terrestrial radiation with a temperature of ≈300 K at the Earth's surface is concentrated at wavelengths ranging from 2.5 to 50 µm. Meanwhile, the combined effects from all atmospheric components result in that the special atmospheric window between 8 and 13 µm that is highly transparent. Hence, most terrestrial areas can effectively radiate heat through the transparent atmospheric window to the cold universe to maintain a relatively stable temperature. To this end, radiative coolers should have high emissivity in the transparent atmospheric window (8-13 µm), which is transparent in this region and allows infrared (IR) light to pass through. In this regard, various materials and structures have been designed in the past few decades and have exhibited promising passive cooling performance at night. [8,9] However, during the daytime, the Sun heats the radiative coolers, which seriously compromises the cooling effect. To resolve this problem, the cooler should radiate more heat to the cold universe while reflecting sunlight to avoid solar heating. Fan and co-workers [10] first designed multilayer photonic materials and achieved daytime radiative cooling to a temperature below ambient conditions when subjected to direct sunlight. Since then, various materials have been demonstrated to realize subambient daytime radiative cooling and have shown great potential for practical applications. [11][12][13] Before some reviews have summarized these developments in radiative cooling, [14][15][16][17] but the limited net cooling power and instability of radiative cooling hinder its practical wide applications. In this review, by summarizing the state-of-the-art research and development in passive daytime radiative cooling (PDRC), we first propose three critical components for PDRC: 1) spectral design in the mid-IR range, 2) structure design for enhancing solar reflectance, and 3) thermal management. Second, we introduce various applications of PDRC, such as building cooling, solar cell cooling, water harvesting, clothing, and electricity generation (Figure 1). Finally, the remaining challenges and opportunities of PDRCs are also discussed. Fundamental Mechanisms of PDRC PDRC ConceptBased on Kirchhoff's law, an object with a temperature higher than 0 K continuously exchanges heat with other objects by absorbing Passive daytime radiative cooling (PDRC) is emerging as a promising cooling technology. Owing to the high, broadband solar reflectivity and high mid-infrared emissivity, daytime radiative cooling materials can achieve passive net cooling power under direct sunlight. The zero-energy-consumption characteristic enables PDRC to reduce negative environmental issues compared with conventional cooling systems. In this review, the development of advanced daytime radiative cooling designs is summarized, recent progress is highlighted, and potential correlated applications, such as building cooling, photovoltaic cooling, and electricity generation, are introduced. The remaining challenges and opportunities of PDRCs are also in...

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Section: Development Of Advanced Pdrc Devicesmentioning

confidence: 99%

Section: Spectral Design In the Mid-ir Rangementioning

confidence: 99%

Recent Progress in Daytime Radiative Cooling: Advanced Material Designs and Applications

Zhang

Wang

et al. 2022

Small Methods

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“…Such efficient thermal-regulating aerogel coolers, simultaneously acting as a thermal insulator and a daytime passive radiative cooler, integrate dual functions in one design. The development of such CNC aerogel coolers is based on four key points: (1) strong solar reflectance throughout the solar spectrum (0.25–2.5 μm); (2) high and selective infrared emittance in the mid-infrared region (8–13 μm) because of the presence of C–O–C and C–O bonds in cellulose; , (3) construction of aerogels with ultralow thermal conductivity to reduce thermal convection from ambient surroundings to the inner space; and (4) mechanical robustness to meet the increasing demand for harsh conditions. The first two requirements are satisfied by using sustainable CNCs and a silane agent as building blocks.…”

mentioning

confidence: 99%

Dynamically Tunable All-Weather Daytime Cellulose Aerogel Radiative Supercooler for Energy-Saving Building

et al. 2022

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A passive cooling strategy without any electricity input has shown a significant impact on overall energy consumption globally. However, designing tunable daytime radiative cooler to meet requirement of different weather conditions is still a big challenge, especially in hot, humid regions. Here, a novel type of tunable, thermally insulating and compressible cellulose nanocrystal (CNC) aerogel coolers is prepared via chemical cross-linking and unidirectional freeze casting process. Such aerogel coolers can achieve a subambient temperature drop of 9.2 °C under direct sunlight and promisingly reached the reduction of ∼7.4 °C even in hot, moist, and fickle extreme surroundings. The tunable cooling performance can be realized via controlling the compression ratio of shape-malleable aerogel coolers. Furthermore, energy consumption modeling of using such aerogel coolers in buildings in China shows 35.4% reduction of cooling energy. This work can pave the way toward designing high-performance, thermal-regulating materials for energy consumption savings.

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“…This reduction represents a gain in net cooling power of at least 17 W m −2 , despite the fact that our films are two and one order of magnitude thinner than the reported structural materials. Very recently, Gamage et al., [ 45 ] demonstrated reflective and transparent radiative coolers based on cellulose derivatives manufactured via electrospinning and casting. Our 300 µm‐thick films exhibit comparable optical properties in the visible and mid‐IR with respect to their 275 µm‐thick film.…”

Section: Resultsmentioning

confidence: 99%

Highly‐Scattering Cellulose‐Based Films for Radiative Cooling

et al. 2022

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Passive radiative cooling (RC) enables the cooling of objects below ambient temperature during daytime without consuming energy, promising to be a game changer in terms of energy savings and CO2 reduction. However, so far most RC surfaces are obtained by energy‐intensive nanofabrication processes or make use of unsustainable materials. These limitations are overcome by developing cellulose films with unprecedentedly low absorption of solar irradiance and strong mid‐infrared (mid‐IR) emittance. In particular, a cellulose‐derivative (cellulose acetate) is exploited to produce porous scattering films of two different thicknesses, L ≈ 30 µm (thin) and L ≈ 300 µm (thick), making them adaptable to above and below‐ambient cooling applications. The thin and thick films absorb only ≈5%${\approx}5\%$ of the solar irradiance, which represents a net cooling power gain of at least 17 W m−2, compared to state‐of‐the‐art cellulose‐based radiative‐cooling materials. Field tests show that the films can reach up to ≈5 °C below ambient temperature, when solar absorption and conductive/convective losses are minimized. Under dryer conditions (water column = 1 mm), it is estimated that the films can reach average minimum temperatures of ≈7–8 °C below the ambient. The work presents an alternative cellulose‐based material for efficient radiative cooling that is simple to fabricate, cost‐efficient and avoids the use of polluting materials.

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Reflective and transparent cellulose-based passive radiative coolers

Cited by 49 publications

References 37 publications

Recent Progress in Daytime Radiative Cooling: Advanced Material Designs and Applications

Recent Progress in Daytime Radiative Cooling: Advanced Material Designs and Applications

Dynamically Tunable All-Weather Daytime Cellulose Aerogel Radiative Supercooler for Energy-Saving Building

Highly‐Scattering Cellulose‐Based Films for Radiative Cooling

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