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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Condition-based maintenance (CBM) appears to be a key element in modern maintenance practice. Research in diagnosis and prognosis, two important aspects of a CBM program, is growing rapidly and many studies are conducted in research laboratories to develop models, algorithms and technologies for data processing. In this context, we present a new evolving clustering algorithm developed for prognostics perspectives. E2GK (Evidential Evolving Gustafson-Kessel) is an online clustering method in the theoretical framework of belief functions. The algorithm enables an online partitioning of data streams based on two existing and efficient algorithms: Evidantial c-Means (ECM) and Evolving Gustafson-Kessel (EGK). To validate and illustrate the results of E2GK, we use a dataset provided by an original platform called PRONOSTIA dedicated to prognostics applications.

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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