Radiative cooling with solar spectrum reflection

Patent metadata

Field	Value
Publication number	US-11215407-B2
Application number	US-201816136044-A
Country	US
Kind code	B2
Filing date	Sep 19, 2018
Priority date	May 21, 2014
Publication date	Jan 4, 2022
Grant date	Jan 4, 2022

Abstract

Various aspects as described herein are directed to a radiative cooling apparatuses and methods for cooling an object. As consistent with one or more embodiments, a radiative cooling apparatus includes an arrangement of a plurality of different material located at different depths along a depth dimension relative to the object. The plurality of different material includes a solar spectrum reflecting portion configured and arranged to suppress light modes, thereby inhibiting coupling of the incoming electromagnetic radiation, of at least some wavelengths in the solar spectrum, to the object at a range of angles of incidence relative to the depth dimension. Further, the plurality of material includes a thermally-emissive arrangement configured and arranged to facilitate, simultaneously with the inhibiting coupling of the incoming electromagnetic radiation, the thermally-generated electromagnetic emissions from the object at the range of angles of incidence and in mid-IR wavelengths.

First claim

What is claimed is:

1. A method comprising:
exposing an arrangement to the sky, the arrangement including a plurality of different materials located at different depths along a depth dimension, and the arrangement including at least one thermally-emissive layer without patterned holes, and
in response to the exposure, simultaneously reflecting incoming electromagnetic radiation of at least some wavelengths in the solar spectrum and emitting thermally-generated electromagnetic emissions in mid-infrared (IR) wavelengths from an object by the plurality of different materials, and thereby providing radiative cooling of the object below an ambient air temperature with direct sunlight striking the arrangement.

2. The method of claim 1 , wherein the simultaneous reflecting of the incoming electromagnetic radiation is selectively in the atmospheric transparency window.

3. The method of claim 1 , wherein the simultaneous reflecting incoming of electromagnetic radiation and emitting thermally-generated electromagnetic emissions in mid-IR wavelengths from the object by the plurality of different materials further includes:
suppressing light modes, by a solar spectrum reflecting portion of the arrangement, and thereby prohibit coupling of incoming electromagnetic radiation, of at least some wavelengths in the solar spectrum, at a range of angles of incidence relative to the depth dimension; and
facilitating, by the thermally-emissive layer of the arrangement and simultaneously with the prohibition of coupling of the incoming electromagnetic radiation, thermally-generated electromagnetic emissions from the object at the range of angles of incidence and in mid-IR wavelengths.

4. The method of claim 1 , wherein providing the radiative cooling to the object includes cooling the object at least 4 degrees Celsius below the ambient air temperature.

5. The method of claim 1 , further including using a heat exchange interface configured and arranged with the arrangement of the plurality of different materials to conduct heat away from the object by using radiative properties of the plurality of different materials.

6. The method of claim 1 , further including absorbing, by the arrangement, light from 300 nanometers to 4 micrometers and reflect at least 90% of solar power at incidence, while also presenting greater than 20% thermal emissivity from 8 micrometers to longer wavelengths.

7. The method of claim 1 , wherein providing the radiative cooling includes during exposure to direct sunlight, reducing a temperature corresponding with the plurality of different materials from ambient air temperature.

8. The method of claim 1 , wherein the arrangement includes a polystyrene enclosure.

9. The method of claim 1 , wherein the arrangement includes a polyethylene film.

10. The method of claim 1 , further comprising reflecting incoming electromagnetic radiation of at least some wavelengths in the ultraviolet spectrum using a polytetrafluoroethylene material.

11. A method comprising:
suppressing light modes, by a solar spectrum reflecting portion of an arrangement, and thereby prohibiting coupling of incoming electromagnetic radiation, of at least some wavelengths in the solar spectrum, to an object at a range of angles of incident relative to a depth dimension;
facilitating, by a thermally-emissive layer of the arrangement and simultaneously with the prohibit of coupling of the incoming electromagnetic radiation, thermally-generated electromagnetic emissions from the object at the range of angles of incidence and in mid-infrared (IR) wavelengths, wherein the thermally-emissive layer of the arrangement is without patterned holes; and
providing radiative cooling to the object responsive to the simultaneous prohibition of coupling of the incoming solar spectrum electromagnetic radiation and facilitation of thermally-generated electromagnetic emissions.

12. The method of claim 11 , further including exposing the arrangement to the sky, and providing the radiative cooling of the object in response to open thermal emission to the sky.

13. The method of claim 11 , wherein the arrangement includes a plurality of different materials located at different depths along the depth dimension, and the method further includes reflecting at least 90% of incident sunlight, by the plurality of different materials, while emitting in the atmospheric transparency window.

14. The method of claim 11 , wherein providing the radiative cooling to the object includes cooling the object from a temperature greater than an ambient air temperature to the ambient air temperature.

15. The method of claim 11 , wherein providing the radiative cooling to the object includes cooling the object at least 1 degree Celsius relative to an initial temperature.

16. The method of claim 11 , wherein the solar spectrum reflecting portion and the thermally-emissive layer of the arrangement include a plurality of different materials configured and arranged to emit selectively between a wavelength range of 8 and 13 μm and reflect at all other wavelengths.

17. The method of claim 11 , wherein using the solar spectrum reflecting portion to suppress light modes further includes inhibiting coupling of incoming electromagnetic radiation of wavelengths from 300 nanometers to 4 micrometers.

18. The method of claim 11 , wherein the arrangement is part of a radiative cooling apparatus integrated with a roof of a building or structure.

19. The method of claim 11 , wherein providing the radiative cooling includes providing at least 20 Watts/meter at an ambient air temperature of 300 degrees Kelvin, or about 30° C., during direct sunlight.

20. The method of claim 11 , further including providing the arrangement at an angle and adjusting the angle over the daytime based on the angle of the sun.

21. A radiative cooling apparatus comprising:
an arrangement of a plurality of different materials located at different depths along a depth dimension, the plurality of different material being configured and arranged to simultaneously reflect incoming electromagnetic radiation of at least some wavelengths in the solar spectrum and emit thermally-generated electromagnetic emissions in mid-infrared (IR) wavelengths, thereby providing radiative cooling below an ambient air temperature with direct sunlight striking the arrangement;
a heat exchange interface configured and arranged with the arrangement of the plurality of different materials including:
a conductive pipe configured and arranged to pass liquid; and
a plate heat exchanger configured and arranged with the arrangement of the plurality of different materials and the conductive pipe, the plate heat exchanger configured and arranged to cool liquid passing through the conductive pipe.

22. The apparatus of claim 21 , further comprising an object, wherein the object includes at least a portion of a heating, ventilation, and air conditioning (HVAC) system.

Assignees

• Univ Leland Stanford Junior

Inventors

• Raman Aaswath Pattabhi
• Fan Shanhui
• Rephaeli Eden
• Zhu Linxiao
• Anoma Marc A
• Goldstein Eli

Classifications

• F24F5/0089

  Systems using radiation from walls or panels · CPC title

• F28F2245/06

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

• F28F13/18 Primary

  by applying coatings, e.g. radiation-absorbing, radiation-reflecting; by surface treatment, e.g. polishing · CPC title

• Y02A30/272

  Solar heating or cooling · CPC title

• Y02B10/20

  Solar thermal · CPC title