Evaluation of the variation in surface solar irradiance in Japan

Abstract:

Surface solar irradiance varies on a wide range temporal scale. To install and operate solar power generation systems not only the intensity of solar irradiance at ground but also variation in sola irradiance has to be considered. Ground-based observation of solar irradiance can provide information about the variation on shorter temporal scale. In this study variation within a day is investigated. Solar irradiance data with 1minute interval is used. To evaluate the variation in solar irradiance we use three variables: mean, standard deviation and sample entropy. These variables represent availability of solar irradiance at the surface, strength of variation, and manner of fluctuation respectively. The characteristics of variation in surface solar irradiance is investigated using three variables. The cluster analysis is performed to divide 47 observation stations in Japan into groups with similar variation features. We found that 3, 6, and 9 clusters are suitable for classifying the 47 sites. The results of cluster analysis clarified characteristics of monthly mean values for three variables of variation in solar irradiance.