Intra-day Variability Quantification from Ground-based Measurements of Global Solar Irradiance

Abstract

Worldwide electricity production has switched from fossil fuel combustion to renewable energy sources and solar power generation has increased significantly in recent years, particularly in the form of photovoltaic (PV) power. Solar radiation is mainly influenced by the process of sunlight interaction with clouds. Being able to quantify the variability of solar irradiance due to clouds is crucial for better integration of the energy generated in the power grid by reducing the uncertainties in solar irradiance forecasts. Our objective is the characterization of a given solar site by quantifying the variability of solar irradiance caused by clouds. To do so, we provide a classification scheme of clouds conditions classes based on the daily clear sky index K c , and the hourly intraday variability I´(K c ) defined by the standard deviation of the variations of the clear sky index. As a result of irradiance classification, we obtained nine classes identified as the overcast, mixed, and clear sky conditions and subdivided into three categories: low, medium, and high variability. We used the solar irradiance data set measured at the high precision meteorological station installed in Benguerir, Morocco, for the period from 01/01/2018 to 31/12/2018.