A new clear sky solar irradiance model

A new broadband parametric clear-sky solar irradiance model is reported in this paper. Constructed as a trade-off between accuracy and accessibility, the model holds some innovative elements, such as: (1) the atmospheric transmittances are inferred by integration of Leckner's spectral ones within three disjointed spectral bands; (2) within each band, the specific aerosol transmittance is expressed as an exponential-decay equation, where the aerosol optical depth formally preserves the Angstro euro m power law, but written at a fixed wavelength; (3) targeting a better capture of the peculiarities of solar radiation extinction by different types of aerosols, the Angstro euro m exponent is innovatively introduced as an input parameter; (4) the directional scattering characteristics of aerosols are considered empirically by including the Ang-stro euro m parameters in the equation of the downward fraction. The new model was tested against two challenging data sets collected from two stations located in Europe and the United States. The results show that the proposed model gives good estimates, comparable to those of REST2, a current benchmark in clear-sky solar irradiance modeling. (c) 2021 Elsevier Ltd. All rights reserved.