Reference Solar Spectra and Their Generation Models

Abstract

Reference solar spectra are used in many solar applications. Utilizing a reference solar spectrum in a unified manner is necessary for reliable evaluation for each application. Since reference solar spectra have been updated only recently, the most recent spectra have not yet been uniformly adopted for some applications. To improve this situation, understanding the evolution and details of reference solar spectra is important. However, there have been few reports on reference solar spectra and their generation models. This paper reviews the evolution of reference solar spectra and their generation models, particularly ASTM G173-03 and CIE 241:2020 reference solar spectra and their Simple Model for the Atmospheric Radiative Transfer of Sunshine (SMARTS) generation model. In addition, the key points in the SMARTS model that affect the calculation accuracy of the spectral irradiance are explained. Moreover, the issue of further comparing the SMARTS model with a rigorous model is revealed. The information presented will help users to understand the newly updated reference solar spectra and correctly use the SMARTS model in practice.