Editing Radiative cooling (section)

== Types ==
[[File:Erbe.gif|thumb|upright=1.35|Earth's longwave thermal [[Earth's energy budget#Outgoing energy|radiation]] intensity, from clouds, atmosphere and surface]]The three basic types of radiant cooling are direct, indirect, and fluorescent:

* '''Direct radiant cooling''' - In a building designed to optimize direct radiation cooling, the building roof acts as a heat sink to absorb the daily internal loads. The roof acts as the best heat sink because it is the greatest surface exposed to the night sky. Radiate heat transfer with the night sky will remove heat from the building roof, thus cooling the building structure. Roof ponds are an example of this strategy. The roof pond design became popular with the development of the Sky thermal system designed by Harold Hay in 1977. There are various designs and configurations for the roof pond system but the concept is the same for all designs. The roof uses water, either plastic bags filled with water or an open pond, as the heat sink while a system of movable insulation panels regulate the mode of heating or cooling. During daytime in the summer, the water on the roof is protected from the solar radiation and ambient air temperature by movable insulation, which allows it to serve as a heat sink and absorb the heat generated inside through the ceiling. At night, the panels are retracted to allow nocturnal radiation between the roof pond and the night sky, thus removing the stored heat. In winter, the process is reversed so that the roof pond is allowed to absorb solar radiation during the day and release it during the night into the space below.<ref name="givoni1">{{cite book |last=Givoni |first=Baruch |title=Passive and Low Energy Cooling of Buildings |publisher=John Wiley & Sons, Inc. |year=1994 |isbn=978-0-471-28473-4 |edition=1st |location=New York, NY}}</ref><ref>{{cite journal |last1=Sharifi |first1=Ayyoob |last2=Yamagata |first2=Yoshiki |date=December 2015 |title=Roof ponds as passive heating and cooling systems: A systematic review |journal=Applied Energy |volume=160 |pages=336–357 |bibcode=2015ApEn..160..336S |doi=10.1016/j.apenergy.2015.09.061}}</ref>
* '''Indirect radiant cooling''' - A heat transfer fluid removes heat from the building structure through radiate heat transfer with the night sky. A common design for this strategy involves a plenum between the building roof and the radiator surface. Air is drawn into the building through the plenum, cooled from the radiator, and cools the mass of the building structure. During the day, the building mass acts as a heat sink.
* '''Fluorescent radiant cooling''' - An object can be made [[fluorescent]]: it will then absorb light at some wavelengths, but radiate the energy away again at other, selected wavelengths. By selectively radiating heat in the [[Infrared window|infrared atmospheric window]], a range of frequencies in which the atmosphere is unusually transparent, an object can effectively use [[outer space]] as a heat sink, and cool to well below ambient air temperature.<ref>{{cite journal |last1=Raman |first1=Aaswath P. |last2=Anoma |first2=Marc Abou |last3=Zhu |first3=Linxiao |last4=Rephaeli |first4=Eden |last5=Fan |first5=Shanhui |date=November 2014 |title=Passive radiative cooling below ambient air temperature under direct sunlight |journal=Nature |language=en |volume=515 |issue=7528 |pages=540–544 |bibcode=2014Natur.515..540R |doi=10.1038/nature13883 |issn=1476-4687 |pmid=25428501 |s2cid=4382732}}</ref><ref>{{cite web |last1=Burnett |first1=Michael |date=November 25, 2015 |title=Passive Radiative Cooling |url=http://large.stanford.edu/courses/2015/ph240/burnett1/ |website=large.stanford.edu}}</ref><ref>{{cite journal |last1=Berdahl |first1=Paul |last2=Chen |first2=Sharon S. |last3=Destaillats |first3=Hugo |last4=Kirchstetter |first4=Thomas W. |last5=Levinson |first5=Ronnen M. |last6=Zalich |first6=Michael A. |date=December 2016 |title=Fluorescent cooling of objects exposed to sunlight – The ruby example |journal=Solar Energy Materials and Solar Cells |volume=157 |pages=312–317 |doi=10.1016/j.solmat.2016.05.058 |doi-access=free|bibcode=2016SEMSC.157..312B }}</ref>