Solar Irradiance Ramp Forecasting Based on All-Sky Imagers

Solar forecasting constitutes a critical tool for operating, producing and storing generated power from solar farms. In the framework of the International Energy Agency's Photovoltaic Power Systems Program Task 16, the solar irradiance nowcast algorithms, based on five all-sky imagers (ASIs), are used to investigate the feasibility of ASIs to foresee ramp events. ASIs 1-2 and ASIs 3-5 can capture the true ramp events by 26.0-51.0% and 49.0-92.0% of the cases, respectively. ASIs 1-2 provided the lowest (<10.0%) falsely documented ramp events while ASIs 3-5 recorded false ramp events up to 85.0%. On the other hand, ASIs 3-5 revealed the lowest falsely documented no ramp events (8.0-51.0%). ASIs 1-2 are developed to provide spatial solar irradiance forecasts and have been delimited only to a small area for the purposes of this benchmark, which penalizes these approaches. These findings show that ASI-based nowcasts could be considered as a valuable tool for predicting solar irradiance ramp events for a variety of solar energy technologies. The combination of physical and deep learning-based methods is identified as a potential approach to further improve the ramp event forecasts.