Coating to cool a surface by passive radiative cooling
Disclosed herein in is a radiative cooling formulation including a solvent for providing a viscosity of a radiative cooling material for application onto a surface to be passively cooled. The radiative cooling formulation includes a binder for the radiative cooling material's integrity and bonding to the surface to be passively cooled. The radiative cooling formulation includes a polymer, which, in combination with the binder, provides one or more properties in the radiative cooling material, including a reflectance of or greater than 55% in a wavelengths range of 0.3 to 2.5 microns and a first thermal emissivity peak value greater than 0.85 at a first wavelength in a range of 8 to 13 microns (μm). For example, the polymer is a latex material including a styrene based copolymer.
1 . An apparatus comprising:
a substrate;
a radiative cooling material on the substrate, the radiative cooling material comprising:
a medium for providing a viscosity for application of the radiative cooling material onto a surface to be passively cooled;
a binder for the radiative cooling material's integrity and bonding to the surface to be passively cooled, wherein the binder comprises a latex;
a solar reflector material embedded in the binder, the solar reflector material comprising particles of barium sulfate (BaSO 4 ) wherein at least half of the particles of BaSO 4 are smaller than 2 microns (μm); and
a polymer in combination with the binder for providing properties including a first thermal emissivity peak value greater than 0.85 at a first wavelength in a range of 8 to 13 microns (μm).
2 . The apparatus of claim 1 , wherein the polymer is formed from a non-styrene material.
3 . The apparatus of claim 1 , wherein the binder comprises a dispersion of one or more polymers in the medium.
4 . The apparatus of claim 3 , wherein the binder comprises nanoparticles having a particle size from about 10 nm to 500 nm dispersed in the medium, and wherein the dispersion is about 80% by weight of the radiative cooling material.
5 . The apparatus of claim 1 , wherein the polymer comprises a styrene based copolymer being about 15% by weight of the radiative cooling material.
6 . The apparatus of claim 5 , wherein the styrene based copolymer is a latex material formed by:
a surfactant;
a medium (or media);
a plurality of monomers; and
an initiator.
7 . The apparatus of claim 6 , wherein the plurality of monomers comprises at least one of:
an acrylate; or
a methacrylic acid.
8 . A method of manufacturing the apparatus of claim 1 , the method comprising:
physically mixing:
an aqueous medium for providing a viscosity for application of the radiative cooling material onto a surface to be passively cooled;
a binder for the radiative cooling material's integrity and bonding to the surface to be passively cooled, wherein the binder comprises a latex;
a solar reflector material embedded in the binder, the solar reflector material comprising particles of barium sulfate (BaSO 4 ) wherein at least half of the particles of BaSO 4 are smaller than 2 microns (μm); and
a polymer in combination with the binder for providing properties including a first thermal emissivity peak value greater than 0.85 at a first wavelength in a range of 8 to 13 microns (μm).
9 . The method of claim 8 , wherein the aqueous medium in total is about 30% by weight of the radiative cooling material, accounting for respective media or solvents in the binder and the polymer.
10 . The method of claim 8 , wherein the binder comprises a dispersion of one or more polymers in the aqueous medium.
11 . The method of claim 10 , wherein the binder comprises nanoparticles having a particle size from about 10 nm to 500 nm dispersed in the aqueous medium, and wherein the dispersion is about 80% by weight of the radiative cooling material.
12 . The method of claim 8 , wherein the polymer comprises a styrene based copolymer about 15% by weight of the radiative cooling material.
13 . The method of claim 12 , wherein the styrene based copolymer is a latex material formed by one or more of:
a surfactant;
a medium or media;
a plurality of monomers; and
an initiator.
14 . The method of claim 8 , wherein the binder comprises a solar reflector material.