Radiative-Cooling Air Conditioning

 

There is a surprisingly new addition to air conditioning from nanotechnology, radiative cooling.  Radiative-cooling panels pointing straight up into the sky can tap a vast freely available heat sink only slightly above absolute zero. The radiative panels emit more energy in infrared (heat waves) than they absorb in visible. Their emission frequency band is optimized to be in the band that best penetrate the atmosphere so that energy can dissipate out into space.  On clear nights, heat radiates even more strongly out to the cold of outer space. 

Researchers at the University of California Berkeley are developing even more exotic roof coatings that radiatively cool in hot weather and absorb light for heat in cold weather.  Such variable cooling/absorbing roof coatings could theoretically reduce American electrical use by 10%.

Radiative cooling will not replace air conditioning, but it can reduce the needed size and energy use of air conditioners needed for a given climate.  That will be a crucial technology upgrade just for cooling the developing world where people are applying increased incomes for cooling comfort.  Furthermore, if global warming is as bad as some predict, better cooling technology might be needed to keep air conditioning affordable.

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