Systems and methods for radiative cooling and heating

Patent metadata

Field	Value
Publication number	US-2018180331-A1
Application number	US-201715845820-A
Country	US
Kind code	A1
Filing date	Dec 18, 2017
Priority date	Jun 18, 2015
Publication date	Jun 28, 2018
Grant date	—

Abstract

Systems and methods for radiative cooling and heating are provided. For example, systems for radiative cooling can include a top layer including one or more polymers, where the top layer has high emissivity in at least a portion of the thermal spectrum and an electromagnetic extinction coefficient of approximately zero, absorptivity of approximately zero, and high transmittance in at least a portion of the solar spectrum, and further include a reflective layer including one or more metals, where the reflective layer has high reflectivity in at least a portion of the solar spectrum.

First claim

What is claimed is:

1 . A system for radiative cooling, comprising:
a top layer comprising one or more polymers, wherein the top layer has high emissivity in at least a portion of the thermal spectrum, and an electromagnetic extinction coefficient of approximately zero, absorptivity of approximately zero, and high transmittance in at least a portion of the solar spectrum; and a reflective layer, disposed below the top layer, comprising one or more metals, wherein the reflective layer has high reflectivity in at least a portion of the solar spectrum.

2 . The system of claim 1 , wherein the top layer comprises two or more polymers, wherein each polymer has high emissivity in a different portion of the thermal spectrum and an electromagnetic extinction coefficient of approximately zero and high transmittance in at least a portion of the solar spectrum.

3 . The system of claim 1 , wherein the one or more polymers are formulated in a mass ratio, and wherein the mass ratio is selected such that the top layer has a uniform and high emissivity in at least a portion of the thermal spectrum.

4 . The system of claim 1 , wherein the top layer comprises one or more regions comprising one or more arrays including one or more ridges and/or protrusions.

5 . The system of claim 1 , wherein the top layer comprises one or more of poly(dimethyl siloxane), poly(vinylidene fluoride), poly(acrylic acid), and poly(methyl methacrylate).

6 . The system of claim 1 , wherein the top layer can be used for passive radiative cooling in the absence of the reflective layer.

7 . The system of claim 1 , wherein the system can be used for daytime passive radiative cooling.

8 . The system of claim 1 , wherein the reflective layer comprises:
an upper layer including a metal and having reflectivity of greater than about 0.8 and a first electromagnetic penetration depth in a first wavelength range within the solar spectrum; and a second electromagnetic penetration depth in a second wavelength range within the solar spectrum, wherein the second electromagnetic penetration depth is greater than the first electromagnetic penetration depth, and the first and second wavelength ranges are different; a lower layer including a metal and having a lower reflectivity than the upper layer in the first wavelength range and a higher reflectivity than the upper layer in the second wavelength range; wherein the upper layer has a thickness that is approximately greater than or equal to the first penetration depth and less than the second penetration depth.

9 . The system of claim 8 , wherein a reflectivity of the reflective layer in the first wavelength range is greater than the reflectivity of the lower layer in the first wavelength range and a reflectivity of the reflective layer in the second wavelength range is greater than the reflectivity of the upper layer in the second wavelength range.

10 . The system of claim 8 , wherein the upper layer comprises silver and/or the lower layer comprises aluminum.

11 . The system of claim 8 , wherein the thickness of the upper layer is from about 5 nm to about 50 nm.

12 . The system of claim 9 , further comprising a protective layer, disposed above the reflective layer, having a thickness of less than about 10 nm and comprising one or more of aluminum oxide and silicon dioxide.

13 . The system of claim 9 , wherein the system can be used as a standalone reflector to reflect radiation in at least a portion of the solar spectrum.

14 . The system of claim 1 , wherein the reflective layer is deposited by electroplating, thermal vapor deposition, electron-beam deposition, or a sputtering technique.

15 . The system of claim 1 , wherein the top layer further comprises one or more types of nanoparticles, wherein each type of nanoparticles has higher emissivity in at least a portion of the thermal spectrum than the other types of nanoparticles, if present, and the one or more polymers, and wherein the nanoparticles have an electromagnetic extinction coefficient of approximately zero and absorptivity of approximately zero in the solar spectrum.

16 . The system of claim 15 , wherein the one or more polymers and the one or more types of nanoparticles are formulated in a mass ratio, and wherein the mass ratio is selected such that the top layer has a uniform and high emissivity in at least a portion of the thermal spectrum.

17 . The system of claim 15 , wherein the one or more polymers and the one or more types of nanoparticles have refractive indices within 10% of each other in at least a portion of the solar spectrum.

18 . The system of claim 15 , wherein the nanoparticles comprise one or more of calcium carbonate, aluminum oxide, silicon dioxide, and silicon nitride.

19 . The system of claim 15 , wherein the nanoparticles have a diameter of less than about 100 nm.

20 . A system for radiative cooling, comprising a top layer comprising one or more polymers and one or more additives, wherein the one or more polymers have high emissivity in at least a portion of the thermal spectrum, and the one or more additives have reflectivity of greater than about 0.3 in at least a portion of the solar spectrum.

21 . The system of claim 20 , wherein the each of the one or more additives has a different refractive index than the other additives, if present, and the one or more polymers in at least a portion of the solar spectrum.

22 . The system of claim 20 , wherein the one or more additives comprise one or more of titanium dioxide, silicon nitride, zinc oxide, aluminum oxide, silicon dioxide, and air voids.

23 . The system of claim 20 , wherein the one or more polymers comprises one or more of poly(dimethyl siloxane), poly(vinylidene fluoride), poly(acrylic acid), and poly(methyl methacrylate).

24 . The system of claim 20 , wherein each of the one or more additives has a size that is selected to increase back-scattering of incident solar radiation and increase reflectivity in the solar spectrum.

25 . The system of claim 20 , wherein the one or more polymers and the one or more additives are formulated in a mass ratio, and wherein the mass ratio is selected such that the system has a high emissivity in at least a portion of the thermal spectrum and a uniform reflectivity of greater than about 0.5 in at least a portion of the solar spectrum.

26 . The system of claim 20 , wherein the system comprises two or more polymers, wherein each polymer has high emissivity in a different portion of the thermal spectrum than the other polymers and an electromagnetic extinction coefficient of approximately zero and high transmittance in at least a portion of the solar spectrum.

27 . The system of claim 20 , wherein the system comprises one or more regions comprising one or more arrays including one or more ridges or protrusions.

28 . The system of claim 20 , wherein the system has a thickness of from about 5 μm to about 500 μm.

29 . The system of claim 20 , wherein the system further comprises fibers and/or textiles, wherein the fibers and/or textiles comprise one or more of regenerated silk, rayon, nylon, polyethylene, polyester, and polyvinylidene difluoride (PVDF).

30 . A system for radiative cooling, comprising:
a top layer comprising one or more structured polymers, wherein the top layer has high emissivity in at least

Assignees

• Univ Columbia

Inventors

• Yu Nanfang
• Mandal Jyotirmoy
• Overvig Adam
• Shi Norman Nan

Classifications

• B32B2383/00

  Polysiloxanes · CPC title

• B32B2386/00

  Specific polymers obtained by polycondensation or polyaddition not provided for in a single one of index codes B32B2363/00 - B32B2383/00 · CPC title

• F28F2245/06

  having particular radiating, reflecting or absorbing features, e.g. for improving heat transfer by radiation · CPC title

• F24S70/60

  characterised by the structure or construction (absorbing coatings or surface treatment for increasing absorption F24S70/20; auxiliary coatings F24S70/30) · CPC title

• B32B2311/24

  Aluminium · CPC title