SURVEILLANCE OF PHOTOVOLTAIC SOLAR ENERGY SYSTEMS USING METEOSAT DERIVED IRRADIANCES Annette Hammer 1 , Detlev Heinemann 1 , Carsten Hoyer 1 , Peter Toggweiler 2 , Urs Br ¨ ugger 2 , Christian Reise 3 , Edo Wiemken 3 , Hans Georg Beyer 4 , Vincent van Dijk 5 , Jethro Betcke 5 1 Dept. of Energy and Semiconductor Research, University of Oldenburg, D-26111 Oldenburg, Phone +49-441-798-3543, Fax +49-441-798-3326, email: Detlev.Heinemann@uni-oldenburg.de 2 Enecolo AG, Lindhof 235, CH-8617 M¨ onchaltorf 3 Fraunhofer Insitute for Solar Energy Systems, Oltmannstraße 5, D-79100 Freiburg 4 University of Applied Sciences Magdeburg, Breitscheidstraße 2, D-29114 Magdeburg 5 Department of Science, Technologyand Society, Utrecht University, Padualaan 14, NL-3584 CH Utrecht ABSTRACT In this paper, we describe a surveillance procedure for grid connected photovoltaic (PV) systems. The site specific solar irradiation data will be derived from satellite images rather than from ground based measure- ments. No additional hardware installation will be necessary on site. On the basis of hourly irradiance time series, monthly values of PV system yield will be calculated and distributed automatically towards the system operators. He or she may then compare the estimated power production to the real production meter reading. First tests reveal an overall accuracy of about 10 % for that period of a year offering 90 % of the annual solar irradiation. 1 INTRODUCTION Photovoltaic (PV) Systems generate electricity from sunlight. In grid- connected systems, a fraction (or all) of the generated power is fed to the local utility network. A large number these systems is in operation in Europe today, and a strong increase is expected for the near future. Today, the installed PV power of small systems increases with remarkable rates in some countries, e. g. with some 10 MW p per year in Germany. Generally, these PV systems in a power range from 1 to some 10 kW p do not include any long term surveillance mechanism. As most system operators are no PV specialists, system faults (component failures) or decreasing performance (e. g. due to increasing shading by growing vegetation) will not be recognized. At least two negative effects would be related to a bad performance of numerous PV systems: the overall energy production 1