US 11,873,440 B2
Spectral and angular emission control based temperature sensitive radiative cooling device
Jonghwa Shin, Seoul (KR); and Suwan Jeon, Seoul (KR)
Assigned to KOREA ADVANCED INSTITUTE OF SCIENCE AND TECHNOLOGY, Daejeon (KR)
Filed by KOREA ADVANCED INSTITUTE OF SCIENCE AND TECHNOLOGY, Daejeon (KR)
Filed on Apr. 15, 2021, as Appl. No. 17/231,619.
Claims priority of application No. 10-2020-0045888 (KR), filed on Apr. 16, 2020; and application No. 10-2021-0045129 (KR), filed on Apr. 7, 2021.
Prior Publication US 2021/0341233 A1, Nov. 4, 2021
Int. Cl. C09K 5/00 (2006.01)
CPC C09K 5/00 (2013.01) [F28F 2245/06 (2013.01)] 11 Claims
 
1. A radiative cooling device that is sensitive to an ambient atmosphere temperature,
wherein an angle-dependent emissivity spectrum in the infrared range changes depending on the relative high and low of the temperature of the radiative cooling device with respect to the ambient atmosphere temperature,
wherein as for the radiative cooling device in parallel with a ground surface, the angle-dependent emissivity spectrum is represented by Equation 1, and
as for the radiative cooling device not in parallel with the ground surface, the angle-dependent emissivity spectrum is represented by Equation 2:
ε(λ,Ω,T;Ωsun,Tamb,α)=0.5×[1+sgn(IBB(λΩ,T)−Isun(λ,Ωsun,Tamb,α)−Iatm(λ,Ω,Tamb,α))];  [Equation 1]
ε(λ,Ω,T;Ωsun,Tamb,α,R,Ωrotation)=0.5×[1+sgn(IBB(λΩ,T)−R(Isun(λ,Ωsun,Tamb,α)+Iatm(λ,Ω,Tamb,α))−(1−R)Iground(λ,Ωsun,Tamb,α,Ωrotation))];  [Equation 2]
in the Equation 1 and the Equation 2,
ε(Δ,Ω,T) represents an angle-dependent emissivity spectrum in the infrared range depending on a temperature T of the radiative cooling device,
Ωsun represents an incident angle of sunlight,
Tamb is a temperature of the ambient atmosphere,
α represents an environmental factor,
R represents a reflectivity of an ambient environment,
Ωrotation represents a tilt angle of the radiative cooling device,
IBB(λ,Ω,T) represents an angle-dependent spectral radiance corresponding to the temperature T,
Isun(λ,Ωsun,Tamb,α) represents an angle-dependent spectral radiance of the sun,
Iatm, (λ,Ω,Tamb, α) represents an angle-dependent spectral radiance of the atmosphere,
Iground(λ, Ωsun, Tamb,α,Ωrotation) represents an angle-dependent spectral radiance of the ambient environment, and
the Ω includes the azimuth angle and the zenith angle in a spherical coordinate system based on an axis perpendicular to the ground surface.