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キーワード:
cellulose
high mid-infrared emittance
low solar absorption
radiative cooling
scattering
Cellulose films
Conductive films
Nanotechnology
Solar radiation
Temperature
Thick films
Advanced science
Ambients
CO 2 reduction
Energy
Energy savings
Energy-savings
Midinfrared
Nanofabrication process
Solar irradiances
Energy conservation
Cooling
Materials
Sun Light
要旨:
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 (Formula presented.) 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. © 2022 The Authors. Advanced Science published by Wiley-VCH GmbH
