Correlation between daily diffuse and global irradiation for the UK

Abstract

The measurements of solar irradiation are available for relatively small number of locations. Again the stations recording diffuse as well as global irradiation are fewer. In the UK only seven stations record both components whereas the latter component is recorded at 26 stations. Hence a correlation is desired which would enable computation of daily diffuse component of global irradiation. The present study serves this need. The traditional method is to develop a correlation between daily diffuse ratio (ratio of diffuse to global irradiation) against clearness index (ratio of global to extraterrestrial irradiation). Hence correlations were first developed for five widespread locations in the UK using 3-year daily data. Comparison of these correlations showed their closeness to each other and hence the possibility for a single correlation for the entire United Kingdom. The correlation developed for the UK was checked by various statistical tests and was found to predict the diffuse component quite accurately.