Multi-surface passive cooling articles
Passive cooling article ( 120 ) includes a plurality of first elements ( 122 ) defining a high absorbance in the atmospheric window wavelength range and defining high average reflectance in the solar wavelength range and a plurality of second elements ( 124 ) defining a low absorbance in the atmospheric window wavelength range and defining high average reflectance in the solar wavelength range, wherein the plurality of first ( 122 ) and second ( 124 ) elements are interspersed to form a major structure having a first major surface ( 130 ) comprising the first element outer surfaces ( 126 ) and the second element outer surfaces ( 128 ), wherein the first element outer surfaces ( 126 ) face a first direction toward a first end region ( 136 ) of the major structure ( 130 ) and the second element outer surfaces ( 128 ) face a second direction toward a second end region ( 136 ) of the major structure. The article ( 120 ) may be applied to a substrate ( 104 ), for example, on a generally vertical surface of a vehicle or stationary structure.
1. A passive cooling article comprising:
a plurality of first elements defining first element outer surfaces, the plurality of first elements defining a first absorbance of greater than or equal to 0.6 in an atmospheric window wavelength range from 8 to 13 micrometers and defining a first average reflectance of greater than or equal to 80% in a solar wavelength range from 0.4 to 2.5 micrometers; and
a plurality of second elements defining second element outer surfaces, the plurality of second elements defining a second absorbance of less than or equal to 0.5 in the atmospheric window wavelength range and defining a second average reflectance of greater than or equal to 60% in the solar wavelength range;
wherein the plurality of first elements and the plurality of second elements are interspersed to form a major structure having a first major surface comprising the first element outer surfaces and the second element outer surfaces and a second major surface opposing the first major surface;
wherein the major structure has a first end region and a second end region, wherein the first element outer surfaces face a first direction toward the first end region and the second element outer surfaces face a second direction toward the second end region;
wherein the plurality of second elements comprises one or more of the following: a dense polyethylene layer, a dense polyethylene copolymer layer, a microporous polyethylene layer, a microporous polyethylene copolymer layer, a fluoropolymer layer defining a thickness less than or equal to 10 micrometers, a coating comprising metal, an infrared mirror film at least partially defining the second absorbance in the atmospheric window wavelength range, a graphic layer at least partially defining the second absorbance in the atmospheric window wavelength range, a graphic layer at least partially covered by an infrared mirror film at least partially defining the second absorbance in the atmospheric window wavelength range, and a metal layer at least partially defining the first reflectance in the solar wavelength range;
wherein at least some of the plurality of first elements comprises first supporting layers and first outer layers, the first outer layers at least partially defining the first absorbance and at least partially covering an outer surface of the first supporting layers to at least partially define the first element outer surfaces, wherein at least some of the plurality of second elements comprises second supporting layers and second outer layers, the second outer layers at least partially defining the second absorbance and at least partially covering an outer surface of the second supporting layers to at least partially define the second element outer surfaces; and
wherein the passive cooling article is a composite film, each of the first and second outer layers and first and second supporting layers being a film layer of the composite film.
2. The article of claim 1 , wherein the plurality of first elements defines the first absorbance in a mid-infrared wavelength range from 4 to 20 micrometers.
3. The article of claim 1 , wherein a first vector normal to at least a portion of the first element outer surfaces defines an interelement angle with a second vector normal to at least a portion of the second element outer surfaces, wherein the interelement angle is greater than or equal to 15 degrees and less than or equal to 165 degrees.
4. The article of claim 3 , wherein a major surface vector normal to at least a portion of the second major surface defines a first element angle with the first vector, wherein the first element angle is greater than or equal to 15 degrees and less than or equal to 75 degrees.
5. The article of claim 4 , wherein the major surface vector defines a second element angle with the second vector, wherein the second element angle is greater than or equal to 15 degrees and less than or equal to 75 degrees.
6. The article of claim 1 , wherein the plurality of first elements comprises one or more of the following: a dense fluoropolymer layer, a microporous fluoropolymer layer, a dense polyester layer at least partially covered by a dense fluoropolymer layer, a microporous polyester layer at least partially covered by a dense fluoropolymer layer, a multilayer optical film at least partially defining the first reflectance in the solar wavelength range, and a metal layer at least partially defining the first reflectance in the solar wavelength range.
7. The article of claim 6 , wherein the graphic layer comprises one or more of the following: a polyvinyl chloride layer, a polyethylene copolymer layer, a microporous polyethylene copolymer layer, and a microporous polyethylene at least partially covered by a dense polyethylene copolymer layer.
8. The article of claim 1 , wherein the first supporting layers, the second supporting layers, or both comprise reflectors defining the respective average reflectances.
9. The article of claim 8 , wherein at least some of the reflectors define diffuse reflectors.
10. The article of claim 1 , wherein the first supporting layers, the second supporting layers, or both comprise a polymer layer that is a microporous polymer layer, a multilayer optical film, or a graphic layer.
11. The article of claim 10 , wherein the first outer layers comprise a multilayer optical film at least partially defining the first absorbance and the first average reflectance.
12. The article of claim 11 , wherein the first outer layers comprise a microporous fluoropolymer layer at least partially defining the first absorbance and the first average reflectance.
13. The article of claim 10 , wherein the second outer layers comprise a microporous layer at least partially defining the second absorbance and the second average reflectance, wherein the microporous layer comprises a polyethylene or a polyethylene copolymer.
14. The article of claim 1 , wherein the second outer layers comprise infrared mirror films at least partially defining the second absorbance and the plurality of second elements further comprises graphic layers, wherein the infrared mirror films at least partially cover the graphic layers, wherein the graphic layers together define a visual graphic.
15. The article of claim 14 , wherein the infrared mirror films define an average transmittance less than 30% in a visible wavelength range from 0.3 to 0.8 micrometers.
16. The article of claim 1 , wherein the plurality of first elements comprise an array of inorganic particles having an effective D 90 particle size of at most 50 micrometers.
17. The article of claim 1 , wherein at least some of the first or second outer surfaces define an array of discrete surface nanostructures, each discrete surface nanostructure defining height and width dimensions each less than 1 micrometer.
18. The article of claim 1 , wherein the first and second supporting layers are integral parts of a single continuous layer.
19. An apparatus comprising:
a substrate capable of being cooled comprising at least a portion of a substrate surface configured to be exposed to solar energy; and
the article of claim 1 covering at least the portion of the substrate surface to reflect solar energy directed toward the substrate surface.
20. The apparatus of claim 19 , wherein the substrate surface comprises a vertical surface of a vehicle or a stationary structure and the second element outer surfaces face a direction toward a ground surface.