“…Although the large variety of cloud characteristics (opacity, motion, height, spatial distribution) makes these cloud-induced fluctuations difficult to predict, solar irradiance forecasting techniques have been successfully developed (a comprehensive overview is given in Inman et al, 2013, andHeinemann, 2012). The spectrum comprises numerical weather models (NWPs) (Perez et al, 2013), satellite-based forecasts using cloud motion vectors (Kühnert et al, 2013;Lorenz et al, 2004;Hammer et al, 1999), statistical methods based on machine learning (Wolff et al, 2013) and time series analysis (Reikard, 2009) predominantly developed for intra-day and day-ahead forecasts. For very short term forecasts with time horizons of up to 30 min, both NWP and satellite image-based models lack spatial and temporal resolution regarding cloud-induced small-scale variability (Inman et al, 2013).…”