Solar irradiance is the fuel of solar power plants. The efficient use of solar radiation requires a detailed estimation of the varying solar resources. For the short-term control of
Mean yearly direct normal radiation (direct radiation through a surface perpendicular to he Sun rays) for the time period 1984-2004 from DLR-ISIS.
solar power plants minute forecasts are needed. Hourly forecasts are necessary to optimize solar energy installations. The analysis of time series that extend over many years is necessary in order to reliably assess the long-term evolution of solar energy yield. At the Institute of Atmospheric Physics we apply our knowledge in Earth observation and radiative transfer modelling to address these issues.
Circumsolar radiation is the direct solar radiation that is scattered by thin ice clouds and aersols into a region closely surrounding the solar disk. It is detected by pyrheliometers while concentrating solar technologies (CST) can only use a concentrator specific fraction of it. Its knowledge is important for the accurate calculation of the expected yield of CST and for their efficient operation. Its intensity is controlled by the optical properties of aerosol and thin ice clouds.
For the optimized operation of concentrating solar power plants and for the efficient power injection into the electricity grid especially fluctuations of the direct and global solar radiation must be forecast. Few minutes up to 1-2 hours forecast horizons are desired. To this end we have combined our knowledge in remote sensing of cloud properties with an algorithm for cloud forecasting with the Meteosat Second Generation (MSG) satellites. This way, we are not only able to forecast the position of clouds, but also their properties in order to determine surface irradiance.
For the design and optimization of solar power plants high spatial and temporal resolution data sets are needed. The SOLEMI service (Solar Energy Mining) rests upon Meteosat satellite data and with its 2.5 km and 30 minutes spatial and temporal resolution it optimally serves this purpose. The SOLEMI area comprises Europe, Africa, East Brasil, West and South Asia as well as a part of Australia. For Europe, Africa and South America data is available from 1991 until now, for all other continents only in the time period 1999-2006.
DLR-ISIS (Irradiance at the Surface Derived from ISCCP Cloud Data) is the first long-term data set (1984-2004) of direct and global solar irradiance. The long time series of 21 years enables the derivation of reliable long term averages, the estimation of the year-to-year irradiance variability, and of the impact of extreme events like volcanic eruptions on surface irradiance. DLR-ISIS is used to determine the yearly irradiance for potential solar power plants sites and the year-to-year variability.