Estimation of Solar Irradiance Under Cloudy Weather Based on Solar Radiation Model and Ground-Based Cloud Image

The estimation of solar radiation plays an important role in different fields such as heating, agriculture and energy. At present, most studies focus on clear-sky models; it is relatively difficult to quantify the obstruction of radiation by clouds, which makes the calculation of irradiance in cloudy weather more challenging. This paper proposes a method for calculating solar irradiance in cloudy weather, which consists of two parts: radiation and cloud. In the radiation part, clear-sky radiation and the distribution of all-sky irradiance under different haze conditions are studied. In the cloud part, a cloud transmittance model based on ground-based cloud images is studied. Then, combined with the radiation model, the calculation of Global Horizontal Irradiance (GHI) in cloudy weather is achieved. After testing, rRMSE of the clear-sky model for calculating Direct Normal Irradiance (DNI) and GHI is 4.48% and 5.62% respectively, the rRMSE of the all-sky model is 2.28%, and the rRMSE of the cloudy irradiance model is 16.74%.