Abstract
In order to integrate a substantial amount of fluctuating solar energy into the power grid, accurate irradiance prediction systems are required to estimate the power output of solar power plants. This study presents a simple statistical approach to predict irradiance on the basis of regional numerical weather prediction data that is forecasted up to three days by the Japan Meteorological Agency. Annual irradiance forecasts of individual sites in the Hokuriku region demonstrate a root mean square error of 0.43-0.45MJ/m2 for the intra-day forecast, increasing to about 0.51MJ/m2 for the two-days-ahead forecast. Furthermore, we calculated error indexes under different conditions to estimate the magnitude of the influence of different assumptions on the results.
