25 November 1992 Solar-reflecting material for radiative cooling applications: ZnS pigmented polyethylene
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Proceedings Volume 1727, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XI: Selective Materials, Concentrators and Reflectors, Transparent Insulation and Superwindows; (1992); doi: 10.1117/12.130498
Event: Optical Materials Technology for Energy Efficiency and Solar Energy, 1992, Toulouse-Labege, France
Abstract
Plastic foils containing nonabsorbing pigments can display a high reflectance of solar radiation combined with a high transmittance in the atmospheric window region in the thermal infrared. Such foils can be applied as selective covers enabling radiative cooling of an underlying material during the night and avoiding heating in direct sunlight during the day. The foils could be used for condensing water or cooling food, buildings, etc. We have prepared ZnS pigmented polyethylene foils with various thicknesses and volume fractions of pigments. The optical properties of the foils were compared with theory, and good agreement was achieved for pigment volume fractions up to 0.1. The optimum solar reflectance of the foil is 0.825 for the available pigment powder; but should be 0.88 if heating were to be avoided at noon with the sun in its zenith. The cooling power for a radiator covered with the best sample is 52 Wm-2 at night, and the equilibrium temperature of a radiator is 12 K below the ambient temperature. Heating of the radiator is avoided 18 hours per day, and the radiator temperature at noon is 8 K above the ambience.
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Torbjorn M.J. Nilsson, Gunnar A. Niklasson, Claes-Goeran Granqvist, "Solar-reflecting material for radiative cooling applications: ZnS pigmented polyethylene", Proc. SPIE 1727, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XI: Selective Materials, Concentrators and Reflectors, Transparent Insulation and Superwindows, (25 November 1992); doi: 10.1117/12.130498; https://doi.org/10.1117/12.130498
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KEYWORDS
Reflectivity

Transmittance

Zinc

Absorption

Optical properties

Solar radiation

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