RANGE OF FORECAST ERRORS OF GLOBAL IRRADIANCE BY THE JAPAN METEOROLOGICAL AGENCY NUMERICAL WEATHER PREDICTION MODEL FOR THE PV POWER FORECAST

摘要

To forecast the photovoltaic (PV) power production, global horizontal irradiance (GHI) obtained from a numerical weather prediction (NWP) model are useful. In Japan, the Japan meteorological Agency (JMA) has been developed an operational NWP (that is, meso-scale model, MSM) with the horizontal grid spacing of 5km. In this study, the range of forecast errors of the GHI is investigated on seasonal and annual changes. In addition, we compared forecast errors between a station and a relatively large area of the Kanto region in the main island, Japan. Validation results of hourly GHI forecasts showed that overestimations of GHI forecasts were found in relatively higher clear sky conditions while underestimations of those were found in relatively lower clear sky conditions. In clear sky or rainy conditions, ranges of forecast errors tend to be relatively smaller, suggesting that the GHI values are well forecasted in these conditions. Seasonal analysis of the range of forecast errors showed that underestimations of the GHI were significant in summer at a point station. From results for a relatively large area of the TEPCO (Tokyo Electric Power Company) region, we confirmed that ranges of forecast errors tended to be decreased by a spatial- smoothing effect.