To cite this version:Christelle Rigollier, Mireille Lefèvre, Lucien Wald. The method Heliosat-2 for deriving shortwave solar radiation from satellite images. Solar Energy, Elsevier, 2004, 77 (2), pp.159-169.

This paper presents a clear-sky model, which has been developed in the framework of the new digital European Solar Radiation Atlas (ESRA). This ESRA model is described and analysed with the main objective of being used to estimate solar radiation at ground level from satellite images with the Heliosat method. Therefore it is compared to clear-sky models that have already been used in the Heliosat method. The diffuse clear-sky irradiation estimated by this ESRA model and by other models has been also checked against ground measurements, for different ranges of the Linke turbidity factor and solar elevation. The results show that the ESRA model is the best one with respect to robustness and accuracy. The r.m.s. error in the estimation of the hourly diffuse irradiation ranges from 11 Wh.m-2 to 35 Wh.m-2 for diffuse irradiation up to 250 Wh.m-2. The good results obtained with such a model are due to the fact that it takes into account the Linke turbidity factor and the elevation of the site, two factors that influence the incoming solar radiation. In return, it implies the knowledge of these factors at each pixel of the satellite image for the application of the Heliosat method.

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This data set of TL is unique in the world and attention has been paid to the means of disseminating the resulting information. A World Wide Web site "Helioserve" has been established, which offers an access to the database through a standard HTML interface. The customers of the Helioserve site are professionals, in research or industry. The database outputs are used as inputs into their own models for atmospheric optics. The site Helioserve comprises also a numerical simulation aspect, which provides to the customer, estimates of the clear sky radiation by running the clear sky model of the ESRA. The TL values requested by the model can be supplied by either the database using an internal query, or the customer himself, or can be set to default values.

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