Optimized DNI forecast using combinations of nowcasting methods from the DNICast project

Within European Commission’s FP7 DNICast project a nowcasting scheme based on Meteosat Second Generation cloud imagery and cloud movement tracking was further developed. It uses a sectoral approach and answers the question at which time any cloud structure will affect the power plant. It distinguishes between thin cirrus clouds and other clouds, which typically occur in different heights in the atmosphere and move in different directions. Also, their optical properties are very different - especially for the calculation of direct normal irradiance (DNI) as required by concentrating solar power plants. The method is also applied in ESA’s CSP-FoSyS project developing a nowcasting and forecasting system. This paper shortly discusses the method and provides a comparison against an optical flow method. This comparison distinguishes between various cloud types. The study also provides an example how jumpiness and percentiles are part of the nowcasting ‘message’ and how they can be used quantitiatively in a first approach