Worldwide analysis of spectral factors for seven photovoltaic technologies

This work presents a worldwide analysis of the PV spectral factor for seven different PV technologies including crystalline silicon and thin film modules. The annual spectral factor for the analyzed technologies is evaluated at 124 sites which cover widely the most important climatic zones. This dataset allows determining the spatial and geographical distribution of the spectral gains/losses with respect to reference conditions for the analyzed PV technologies. The spectral factors are computed from hourly global tilted spectral irradiances for a whole year using the SMARTS2 spectral solar radiation model with atmospheric inputs from the MACC reanalysis dataset. Overall, it is found that the annual spectral factor for crystalline silicon technologies is rather homogenous worldwide with maxima spectral losses and gains of ≈3% and ≈1%, respectively. The annual spectral factor for thin film devices, on the contrary, displays a latitudinal pattern with spectral losses mainly occurring in northern hemisphere locations and spectral gains occurring in tropical zones. Both spectral gains and losses may reach up to ≈10% in the case of amorphous silicon devices. The correlation analysis between average photon energy (APE) and spectral factor shows high correlation values for thin film devices. However, the data dispersion is large, which discourages the use of APE as a measure of the spectral performance of PV systems.