Apparatus and method for radiative cooling

Abstract

A system and method for operating a selective emitter is provided. One embodiment comprises a heat sink that absorbs heat from an ambient environment, a heat pipe comprising a cooling portion thermally coupled to the heat sink, a wick portion and a heat dissipation portion, and a selective emitter that is thermally coupled to the cooling portion of the heat pipe. The selective emitter converts absorbed heat into radiative energy that is emitted out through the Earth's atmosphere.

Therefore, having thus described the invention, at least the following is claimed: 
     
         1 . A selective emitter radiative cooler, comprising:
 a heat sink that absorbs heat from an ambient environment;   a heat pipe comprising:
 a cooling portion; 
 a wick portion; and 
 a heat dissipation portion, 
 wherein the cooling portion is thermally coupled to the heat sink; 
   a selective emitter that converts absorbed heat into radiative energy that is emitted out through an atmosphere of the Earth, comprising:
 a substrate defined by a radiation emitting surface that emits the radiative energy and an opposing external surface that is thermally coupled to the cooling portion of the heat pipe, 
   wherein heat that is absorbed at the cooling portion of the heat pipe from the heat sink is transferred to the heat dissipation portion of the heat pipe via the intervening wick portion, and   wherein the transferred heat is absorbed by the selective emitter from the heat dissipation portion of the heat pipe so that the absorbed heat is converted into the radiative energy.   
     
     
         2 . The selective emitter radiative cooler of  claim 1 , wherein an orientation of the intervening wick portion of the heat pipe is perpendicular to an orientation of the radiation emitting surface of the selective emitter. 
     
     
         3 . The selective emitter radiative cooler of  claim 1 , wherein an orientation of the intervening wick portion of the heat pipe is substantially horizontal to an orientation of the radiation emitting surface of the selective emitter. 
     
     
         4 . The selective emitter radiative cooler of  claim 1 , wherein an orientation of the intervening wick portion of the heat pipe is at a predefined angle to an orientation of the radiation emitting surface of the selective emitter. 
     
     
         5 . The selective emitter radiative cooler of  claim 1 , wherein an orientation of the radiation emitting surface of the selective emitter is substantially horizontal with respect to the Earth's surface. 
     
     
         6 . The selective emitter radiative cooler of  claim 1 , wherein a wavelength of the emitted radiative energy is within a wavelength range from eight to thirteen μm. 
     
     
         7 . The selective emitter radiative cooler of  claim 1 , further comprising:
 an enclosure that encloses at least the heat sink and the cooling portion of the heat pipe,   wherein a fluid residing in the enclosure is cooled as the cooling portion of the heat pipe absorbs heat.   
     
     
         8 . The selective emitter radiative cooler of  claim 7 , wherein the cooled fluid is pumped from proximity to the heat sink to a location wherein the cooled fluid is used for cooling purposes. 
     
     
         9 . The selective emitter radiative cooler of  claim 7 , further comprising a plurality of selective emitters, where the external surface of each of the plurality of selective emitters is thermally coupled to the heat dissipation portion of the heat pipe. 
     
     
         10 . A method of operating a selective emitter that comprises a substrate defined by a radiation emitting surface that emits the radiative energy and an opposing external surface, the method comprising:
 absorbing heat using a heat sink that absorbs heat from an ambient environment;   transferring the absorbed heat through a heat pipe, the heat pipe comprising:
 a cooling portion; 
 a wick portion; and 
 a heat dissipation portion, 
 wherein the cooling portion is thermally coupled to the heat sink such that the heat is absorbed from the heat sink by the cooling portion of the heat pipe; 
   transferring the absorbed heat from the cooling portion to a heat dissipation portion of the heat pipe via the intervening wick portion;   transferring the absorbed heat from the heat dissipation portion of the heat pipe to the opposing external surface of the selective emitter that is thermally coupled to the heat dissipation portion;   converting the transferred heat received by the selective emitter into radiative energy; and   emitting the radiative energy from the radiation emitting surface of the selective emitter out through an atmosphere of the Earth.   
     
     
         11 . The method of  claim 10 , wherein an orientation of the intervening wick portion of the heat pipe is perpendicular to an orientation of the radiation emitting surface of the selective emitter. 
     
     
         12 . The method of  claim 10 , wherein an orientation of the intervening wick portion of the heat pipe is substantially horizontal to an orientation of the radiation emitting surface of the selective emitter. 
     
     
         13 . The method of  claim 10 , wherein an orientation of the intervening wick portion of the heat pipe is at a predefined angle to an orientation of the radiation emitting surface of the selective emitter. 
     
     
         14 . The method of  claim 10 , wherein an orientation of the radiation emitting surface of the selective emitter is substantially horizontal with respect to the Earth's surface. 
     
     
         15 . The method of  claim 10 , wherein a wavelength of the emitted radiative energy is within a wavelength range from eight to thirteen μm. 
     
     
         16 . The method of  claim 10 , further comprising:
 cooling a fluid residing an enclosure that encloses at least the heat sink and the cooling portion of the heat pipe.   
     
     
         17 . The method of  claim 16 , further comprising:
 pumping the cooled fluid from proximity to the heat sink to a location wherein the cooled fluid is used for cooling purposes.