Time Specific Irradiances Derived from Geostationary Satellite Images

Hourly time/site specific irradiances derived from geostationary satellite images are more accurate than irradiances from a ground measurement station when the distance from the station exceeds 25 km. The scatter plot comparing two stations in Long Island, NY distant from 25 km, is similar to the scatter plot comparing satellite derived irradiance against anyone of the stations. The plot on the lower right shows the degradation of station extrapolation error as a function of station distance. The accuracy of the satellite is illustrated by the thick horizontal line.