Abstract
The sun radiates heat to earth in the day. At night the reverse happens when the warmer earth radiates heat to the cold night sky. Roofs of buildings radiate heat day and night at a rate of up to 75 watts per square meter.
The sun radiates heat to earth in the day. At night the reverse happens when the warmer earth radiates heat to the cold night sky. Roofs of buildings radiate heat day and night at a rate of up to 75 watts per square meter.
Consumes no electricity:
It consumes no electricity and has great potential to be explored for cooling of buildings, vehicles, solar cells, and even thermal power plants. Radiative sky cooling has been explored in the past few decades but limited to nighttime use only
Radiate heat day and night:
Roofs of buildings radiate heat day and night. During the day, this is offset by solar radiation gains on
The roofs; however, at night this heat loss has the ability to cool air. Cooling a building by long-wave.
Radiation to the night sky has long been identified as a potentially productive means to reduce space
Cooling energy in buildings but the technology has not been commercially available.
. As the energy situation and environmental issues become more and more severe in the 21st century radiative sky cooling can be explored for energy saving in buildings and vehicles, mitigating the urban heat island effect, achieving more efficient power generation, and even fighting against the global warming problem.
Invention:
In India before the invention of artificial refrigeration technology, ice making by nocturnal cooling was common. The apparatus consisted of a shallow ceramic tray with a thin layer of water, placed outdoors with a clear exposure to the night sky. The bottom and sides were insulated with a thick layer of hay. On a clear night the water would lose heat by radiation upwards.