Radiative heating and cooling with spectrally selective surfaces

Ambient radiative properties are examined. For the temperatures of interest in connection with natural heating and cooling, the Planck spectrum is confined to the wavelength range from 3 to 50 micrometers. Solar radiation is limited to the range from 0.25 to 3 micrometers. A surface may, therefore, have different properties with respect to solar and thermal radiation. Attention is given to surfaces with high solar absorptance and low thermal emittance, surfaces for radiative cooling to low temperatures, transparent heat mirrors, and green leaves. An extensive list of literature references concerning the different surface types is provided. The importance of spectral selectivity for efficient photothermal conversion of solar energy was pointed out several decades ago. Recently the interest in solar energy applications had led to an active development of selective surfaces. Practical solar energy collectors use surfaces consisting of black chrome, black nickel, electrolytically colored anodic alumina, and copper oxide.