Analysis of spectral irradiance distribution for PV applications at high latitude

Abstract

The spectral distribution of global tilted irradiance measured in Grimstad, Norway, is analyzed in terms of the average photon energy (APE) blue fraction (BF) and useful fraction (UF). The results based on eight months of recorded data show a general shift of the APE, BF, and UF values to higher values than reference AM1.5G spectrum, with 1.63 eV, 0.45, and 0.88 being the average indices, respectively. The statistical coefficient of variation (CV) is used to determine the variation of indices. The CV for APE, BF, and UF are calculated to be 20.1%, 26.1%, and 25.7%, respectively confirming the earlier findings on APE being a more accurate index for the quantification of spectral distribution. Also, the spectral indices were classified in terms of sky conditions using the clearness index and CV. The results show a higher variation of indices in the cloudy sky conditions compared to clear and partially sunny sky conditions.