Eye2Sky – a network of all-sky imager and meteorological measurement stations for high resolution nowcasting of solar irradiance

The Eye2Sky network is a measurement network in north-western Germany consisting of 29 all-sky imagers (ASI) and 12 meteorological and solar irradiance measurement stations. Since 2018, the network collects high temporal and spatial resolution data for meteorological and especially solar energy related applications. Quality control schemes have been developed for the different sensors and are applied to the data in order to ensure a high quality. Quality controlled minute-resolution measurements (1 year) and ASI images (4 months) in the year 2022 are published for open access. Eye2Sky data is used in the development of new technologies and methodologies for accurate solar irradiance forecasts, facing the demand for grid integration of high shares of photovoltaic-generated power. The ASIs used in Eye2Sky record 180 ° field of view hemispherical sky images from fish-eye lensed cameras. Accompanied with local point measurements of solar irradiance components (global, direct and diffuse) a very short-term forecast of the solar resource is possible. A single ASI can provide such so-called nowcasts as minutely updated information. Nowcasts with a temporal resolution in the intra-minute range and a spatial resolution of a few meters are possible. Depending on the prevailing cloud dynamics the spatial coverage can be several kilometers and the maximum forecast horizon varies in the intra-hour range. The used ASI based approach shows superior forecasting results for the next minutes ahead compared to single ASI systems and traditional methods based on lower resolved satellite images or numerical weather prediction models. Eye2Sky, a unique network with multiple ASIs in a regional domain (about 110 km × 100 km coverage), enables an increased spatial coverage and an extended forecast horizon requested by many applications. In this article, the Eye2Sky network, its data and the quality control procedures are described. The potential of the network for solar energy applications and research topics is introduced.