DLRIPA             Solar Energy                       


Irradiance at the Surface derived from ISCCP cloud data

The DLR-ISIS data set gives an overview of the available total solar irradiance worldwide (global hemispherical irradiance, GHI). Many solar energy applications, especially concentrating solar power plants, require knowledge of the beam irradiance (direct normal irradiance, DNI). DLR-ISIS provides both solar flux components for all regions on Earth and can be used to estimate technical potentials for solar energy systems. Its long temporal coverage over more than 21 years makes it possible to derive stable longterm averages, to evaluate the variability of irradiance from year to year and to study the effect of extreme atmospheric conditions on the irradiance at the surface, e.g. after a volcano eruption. The analysis of the long-term variability of DNI contributed to the approval of several 50 MW solar thermal power plants in Southern Spain.

The 3-hourly temporal resolution of ISIS enables the study of daily cycles. However, the spatial resolution of 280 km by 280 km is too coarse for site selection.  For detailed siting of solar power plants we recommend using data with higher resolution, e.g. those from the SOLEMI-service.