ASPIRE - a tool to investigate spectral effects on PV device performance

A new model for calculating spectral irradiance from standard meteorological inputs is presented, named ASPIRE (All-sky SPectral IRradiancE). The Bouger law-based transmittance approach for modelling clear-sky spectra has been augmented with an extended empirical process to account for variation with cloud cover. Unlike previous clear-sky models, this new tool separates the effects of air mass from cloud cover within the clearness index by comparing measured solar spectra with the results of clear-sky modelling. The intended use of the ASPIRE model is to allow investigation of spectral effects on PV device output under realistic operating conditions, for which measured spectral irradiance data is rarely available. These investigations are important to refine the energy yield calculations for PV systems operating under seasonally varying spectra, especially wide band gap materials.