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The reflectivity values for ASTEC vary from 85% to 94%. The
variability is due to the fact that reflectivity of a given material
is "wavelength dependent".
In other words, certain wavelengths of the solar spectrum are
reflected more than others. Between the various wavelengths of
ultraviolet radiation, visible radiation, and infrared radiation, we
obtain "reflectivity" ranging from 85% to 94%.
It would be too expensive and impractical to determine the
reflectivity of every wavelength in the UV to infrared radiation
band. In practice, the industry has adopted a standard which
consists in taking the average reflectivity.
As for ASTEC, we have taken a more conservative approach by using
only the lowest reflectivity: 85%.
Normal hemispherical reflectivity: 86.9%
Reflectivity for visible radiation: 92.7%
Thermal emissivity (infrared): 90%
Normal emissivity: 92%
Please note that the normal hemispherical reflectivity (86.9%)
represents an average reflectivity for ASTEC #900. When we say that
ASTEC #900 has a reflectivity of 85%, we are being very
conservative.
