Radiative cooling resource maps for the contiguous UnitedStates

• Published in: Journal of renewable and sustainable energy 2019-05, Vol.11 (3)
• Main Authors: Li Mengying, Peterson, Hannah B, Coimbra Carlos F M
• Format: Article
• Language: English
• Subjects: Absorptance; Absorptivity; Air conditioners; Air conditioning; Atmospheric windows; Blackbody; Cooling; Cooling effects; Emittance; Optical properties; Optical thickness; Reflectance; Sky; Solar reflectors; Temperature; Water vapor; Weather
• ISSN: 1941-7012

Passive cooling devices take advantage of the partially transparent properties of theatmosphere in the longwave spectral band from 8 to 13 μm(the so-called “atmospheric window”) to reject radiation to outer space. Spectrallydesigned thermophotonic devices have raised substantial attention recently for theirpotential to provide passive and carbon-free alternatives to air conditioning. However,the level of transparency of the atmospheric window depends on the local content of watervapor in the atmosphere and on the optical depth of clouds in the local sky. Thus, theradiative cooling capacity of solar reflectors not only depends on the optical propertiesof their surfaces but also on local meteorological conditions. In this work, detailedradiative cooling resource maps for the contiguous United States are presented with thegoal of determining the best climates for large-scale deployment of passive radiativecooling technologies. The passive cooling potential is estimated based on ideal opticalproperties, i.e., zero shortwave absorptance (maximum reflectance) and blackbody longwaveemittance. Both annual and season-averaged maps are presented. Daytime and nighttimecooling potential are also computed and compared. The annual average cooling potentialover the contiguous United States is 50.5 m−2. The southwestern United Stateshas the highest annual averaged cooling potential, over 70 W m−2, due to itsdry and mostly clear sky meteorological conditions. The southeastern United States has thelowest potential, around 30 W m−2, due to frequent humid and/or overcastweather conditions. In the spring and fall months, the Arizona and New Mexico climatesprovide the highest passive cooling potential, while in the summer months, Nevada and Utahexhibit higher potentials. Passive radiative cooling is primarily effective in the westernUnited States, while it is mostly ineffective in humid and overcast climateselsewhere.