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CTU UCEEB: By Photographing the Sky, We Can Predict the Intensity of Solar Irradiance with Higher Precision

18.09.2018

Experts of the University Centre for Energy-Efficient Building of the Czech Technical University are developing a special device, so-called skyscanner, which photographs the sky and predicts the production of electric energy by photovoltaic panels as much as several hours in advance based on the photographs taken. The skyscanner can be found on the UCEEB building in Buštěhrad or in the Fenix office center in Jeseník as early as today.

The information about the intensity and amount of solar radiation is very important for a battery repository charged by a PV system. The reason is that the values of solar irradiation are lower when clouds in the sky are covering the sun. Hence, PV panels or solar collectors cannot then produce enough electric energy. Low-energy buildings or buildings with almost-zero energy consumption (nZEB) which use PV panels for their operation can efficiently control, and therefore decrease the take-off of electricity at high tariff rate from the distribution network thanks to the prediction of solar radiation. Hence, the prediction of irradiation can save considerable costs of electricity.

Experts from the Laboratory of Photovoltaic Systems and Energetics developed three systems of prediction of irradiation in total. The first one is PV Forecast, providing the prediction of irradiation several days in advance. The second one is PV Nowcast, one-day prediction using irradiation sensors, and the third one is the newest developed system, the Skyscanner which predicts the intensity of solar irradiance in hourly time horizon based on sky photography. The shorter the prediction is, the more exact the values of irradiation are.

Skyscanner is suitable for short-term predictions with the corresponding local characteristics. It is basically a wide-angle camera for photographing the sky that is suitable for outdoor use. Thanks to it, it is possible to evaluate the cloudiness, cloud types and their velocity. Approximately every ten seconds, the cameras photograph the sky and the photographs are then sent to CTU server where they are evaluated by the system.

At present, one of the skyscanner cameras is located on the CTU UCEEB building.  Another camera was installed on the Fenix office building in Jeseník at the beginning of September. The experts are planning installations of cameras in other places in the Czech Republic in future. The bottom line of the purpose of creation and development of the skyscanner is to facilitate the service of prediction of irradiation, focused on users of low-energy buildings, that is as precise as possible, and also not only to make the production and consumption of electric energy more efficient but to decrease the dependence and load of the electric distribution network at the same time, too. The reach of the skyscanner camera is as much as four kilometers; therefore, the prediction of solar irradiance could be watched by several objects at the same time.

Skyscanner, fotografie oblohy Zařízení skyscanner