Improving time series prediction of solar irradiance after sunrise: Comparison among three methods for time series prediction

Short-term prediction for renewable energy outputs up to 6 h is important especially for preparing backup power plants such as thermal power plants and hydro power plants to keep the voltage and the frequency in a power grid constant. However, short-term prediction of solar irradiance for the morning is especially difficult because measurements of solar irradiance before sunrise are zeros and useless for the prediction. Here we propose to use recently derived infinite-dimensional delay coordinates for predicting solar irradiance after sunrise based on a time series before the sunrise. As a result, one can make time series prediction by taking into account the long history of previous changes of solar irradiance. We demonstrate that the examined short-term time series prediction has effectively predictive skills because its prediction errors are smaller by about 85% best compared with the 24 h clear sky index persistence.