A model for the estimation of global spectral solar irradiance under all-sky conditions for Nakhon Pathom station, Thailand

Abstract

In this work, a model was developed to estimate global spectral solar irradiance under all-sky conditions using data from the Nakhon Pathom station, Thailand. This model expresses the global spectral solar irradiance under all-sky conditions as the multiplication of two functions. The global spectral irradiance under clear sky conditions from the calculation and the cloud correction factor are considered in the model. The cloud correction factor is a function of the cloud index from Himawari satellite data and the ratio of global spectral irradiance under all sky conditions and clear sky conditions. The global spectral irradiance was measured at Nakhon Pathom station using a spectroradiometer (EKO, MS-710) from 2017 to 2019. Model validation was computed using the 2020 dataset. The global solar spectral irradiance from measurements and calculated from the model were found to be in reasonable agreement, with discrepancies in mean bias difference and root mean squared difference of 4.85% and 14.21%, respectively.