# US 11,440,291 B2 · Composite material for passive radiative cooling

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- Number: US 11,440,291 B2
- Document ID: US11440291B2
- Status: Granted
- Kind: B2
- Application number: 15/172,304
- Filed: 2016-06-03
- Published: 2016-12-08
- Granted: 2022-09-13
- Earliest claimed: 2015-06-03
- Assignees: P.C. Krause & Associates, Inc.
- Applicants: PC Krause and Associates
- Inventors: Alex Heltzel
- Web page: https://patentgrep.com/patent/US11440291B2

## CPC

- B32B 15/08: of synthetic resin
- H10W 40/10: Arrangements for heating
- B32B 27/20: using fillers, pigments, thixotroping agents
- H10W 40/251: {Organics}
- B32B 2264/1021: Silica
- B32B 2264/303: Average diameter greater than 1µm
- B32B 2307/30: having particular thermal properties
- B32B 2307/40: having particular optical properties
- B32B 2307/416: Reflective
- B32B 2311/08: Silver
- B32B 2311/24: Aluminium
- B32B 2419/00: Buildings or parts thereof
- Y10T 428/31504: Composite [nonstructural laminate]
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A composite material for passive radiative cooling is provided. In some embodiments, the composite material includes a base layer, and at least one emissive layer located adjacent to a surface of the base layer. In some embodiments, the at least one emissive layer is affixed to the surface of the base layer via a binding agent. In some embodiments, the surface of the base layer comprises a reflective substrate comprising an adhesive layer. In some embodiments, the at least one emissive layer is affixed to the base layer via the adhesive layer of the base layer.

## Claims

### Claim 1

A composite material for passive radiative cooling comprising:
a reflective substrate comprising silver; and
at least one thermally-emissive layer comprising a plurality of spherical silica microparticles located adjacent to a surface of the reflective substrate, wherein the at least one thermally-emissive layer is affixed to the surface of the reflective substrate via a polymer binding agent, and wherein each of the plurality of microparticles includes a diameter between about 5 to about 50 μm;
wherein at least some light impinging on the thermally-emissive layer reaches the reflective substrate;
wherein an ideal material exhibits an emissivity=1 in the frequency range of 8 micrometers to 13 micrometers, and is purely reflective at all other frequencies; and
wherein the composite material provides radiative cooling power in excess of the ideal material when the composite material is exposed to a nighttime sky at an ambient temperature of 280 Kelvin, when an equilibrium temperature of the composite material is above 255 Kelvin.

### Claim 2 (depends on 1)

The composite material of claim 1, wherein the binding agent is transparent.

### Claim 3 (depends on 1)

The composite material of claim 1, wherein the binding agent includes a thickness less than or equal to approximately 50 μm.

### Claim 4 (depends on 1)

The composite material of claim 1, wherein each of the plurality of microparticles includes a diameter greater than or equal to 5 μm and less than or equal to 30 μm.

### Claim 5

A composite material for passive radiative cooling comprising:
a reflective substrate comprising silver; and
at least one thermally-emissive layer comprising a plurality of spherical silica microparticles located adjacent to a surface of the reflective substrate, wherein the at least one thermally-emissive layer is affixed to the surface of the reflective substrate via a polymer binding agent, and wherein each of the plurality of microparticles includes a diameter between about 5 to about 50 μm;
wherein at least some light impinging on the thermally-emissive layer reaches the reflective substrate;
wherein an ideal material exhibits an emissivity=1 in the frequency range of 8 micrometers to 13 micrometers, and is purely reflective at all other frequencies;
wherein the composite material provides positive radiative cooling power when exposed to direct sunlight at an ambient temperature of 300 Kelvin, when an equilibrium temperature of the composite material is above 280 Kelvin; and
wherein the composite material provides radiative cooling power in excess of the ideal material when exposed to direct sunlight at an ambient temperature of 300 Kelvin, when the equilibrium temperature of the composite material is between 320 and 330 Kelvin.

### Claim 6 (depends on 5)

The composite material of claim 5, wherein each of the plurality of microparticles includes a diameter greater than or equal to 5 μm and less than or equal to 30 μm.

### Claim 7 (depends on 5)

The composite material of claim 5, wherein the binding agent includes a thickness less than or equal to approximately 50 μm.

### Claim 8 (depends on 5)

The composite material of claim 5, wherein the binding agent is transparent.