EXTENSION OF THE SPECTRAL SOLAR IRRADIANCE MODEL FOR CLEAR SKIES BY BIRD ET AL. TO ALL WEATHER CONDITIONS

Bird et al.’s spectral solar irradiance model, Spectral2, accurately estimates spectral solar irradiance for clear skies. Since the model estimates spectral solar irradiance for global as well as direct and diffuse, it can easily be extended to the spectral irradiance calculation for tilted surfaces with various azimuth. This paper describes a method for extending Spectral2 to all-weather conditions. We use data observed at Tsukuba and Naganuma in 2015 from NEDO's database for the extension and examine the accuracy including observed data at Gifu, Tosu and Okinoerabu. We name the proposed model Spec_allsky.