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Last updated - Dernière modification 21/11/08 Mines ParisTech - Armines |
Methods for assessing radiation (global, direct, diffuse) on horizontal or inclined planes from the HelioClim Database of Solar Radiation
Global Radiation on Horizontal Plane (GHI)
The images taken by the satellite Meteosat, are processed by the means of the method Heliosat-2. The HelioClim database provides global irradiance and irradiation on a horizontal surface.
Diffuse and Direct Radiation on Horizontal Plane
By using split algorithms, one may derive the direct and diffuse components from the global radiation on a horizontal plane. The algorithms used are those of the European Solar Radiation Atlas (2000).
Diffuse and Direct Radiation on Inclined Plane and Plane Normal to Sun Rays (DNI)
Once the direct and diffuse components known for a horizontal plane, one may derive the direct and diffuse components on any inclined plane. The algorithms used are those of the European Solar Radiation Atlas (2000).
The computation for the direct component is based on pure geometry. The DNI (direct normal irradiance) is the direct radiation reaching a plane always facing the sun. More on the method for assessing the DNI and comparison with ground measurements.
The computation of the diffuse component is based on empirical models. More on the method to compute the irradiance on tilted surfaces.