Cooling without electricity
The US Stanford University is currently testing an innovative cooling technology using radiative sky cooling. Radiative sky cooling is a mechanism that enables cooling to sub-ambient temperatures without electricity or evaporating water. In this approach, heat is passively rejected to outer space by exploiting the fact that Earth’s atmosphere is partially transparent to mid-infrared thermal radiation.
In a 2014 study, Stanford researchers showed the cooling capabilities of a mirror-like optical surface they were testing on the roof of the Packard Building, at Stanford. Further researches published in September 2017 showed that a system involving these surfaces can cool flowing water to a temperature below that of the surrounding air.
Indeed, in the system tested by the researchers, panels covered in the specialized optical surfaces were able to consistently reduce the temperature of water 3 to 5 °C below ambient air temperature over a period of 3 days. In a simulation where their panels covered the roof of a commercial office in the hot climate of Las Vegas, the scientists calculated the panel-cooled system would save 14.3 MWh of electricity, representing a 21% reduction in the electricity used to cool the building.