The Eye2Sky cloud camera network
In north-western Germany, between Oldenburg, the North Sea coast and the Dutch border, the Institute of Networked Energy Systems is operating a one-of-a-kind cloud camera network, Eye2Sky. Once the setup process has been completed, the network will consist of 37 stations, 28 of which are already in operation (as of 6/2021). A cloud camera – also known as an All-Sky-Imager (ASI) – is at the heart of each station. This is a standard webcam fitted with a fisheye lens, together with a ventilation and heating system which ensures optimum image quality even in case of bad weather. A third of the stations are equipped with a so-called “rotating shadowband irradiometer” (RSI, see photo) as well as further radiation and meteorological sensors, e.g. for temperature and humidity.
The RSI enables the measurement of various solar radiation components (global, diffuse, direct, 30° tilt angle) at one-second intervals. In addition, so-called “ceilometers” at two locations in the network use lasers to determine the height of clouds. The entire network spans an area of 110x100 km. In the rural area to the west of Oldenburg, the stations are sparsely positioned, while in the Oldenburg urban area they are much closer together, with 14 stations located here. The high level of density enables observation of cloud cover by means of several different cameras, from a variety of perspectives. This enables particularly precise solar radiation forecasts for the urban area.
Using the WOBAS algorithm developed by the DLR Institute of Solar Research in Almería, very precise short-term solar radiation forecasts can be made using the data collected by the cameras and measuring stations (see ASI video of all active cameras). Unlike with satellite-based forecasts, a spatial resolution of 50 metres and a temporal resolution of 30 seconds is possible.
The cameras have a limited range which varies depending on the height of the clouds. This currently enables forecasts up to approx. 1 hour in advance. Given the limited range but the high resolution, it may be helpful to combine the forecast provided by the cloud camera network with a satellite forecast for the short-term forecast and/or a numerical weather forecast. The different systems’ advantages can thus be exploited, as in the current European research project Smart4RES and the research project HyForPV.
Fig. : Eye2Sky map - as of 27 January 2021
The high-resolution solar radiation forecast enables precise calculations of the intensity of solar radiation at “street or neighborhood level”. For instance, the movement of a large cloud across the city of Oldenburg and its impact on the feed-in of solar electricity to the local power network can be calculated and predicted.
Please contact the competent project manager directly if you are interested in the cloud camera network or sample data. You will be provided with data where possible.