LSTM and RBFNN Based Univariate and Multivariate Forecasting of Day-ahead Solar Irradiance for Atlantic Region in Canada and Mediterranean Region in Libya

Abstract

For optimal functioning, grid-connected photovoltaic (GCPV) systems need day-ahead power forecasting, as this ensures overall enhanced management in areas such as reliability, scheduling, and efficiency in energy trading. Solar irradiation forecasts are especially important for obtaining photovoltaic (PV) power production predictions, given that that PV output represents a function of solar irradiation. Recently, the Long Short-Term Memory (LSTM) model is being increasingly applied in solar irradiance forecasting, but the performance of LSTM is still relatively unknown. The present paper explores how meteorological and geographical (i.e., exogenous) and past records of solar irradiance (i.e., endogenous) variables may be incorporated as input features in day-ahead solar irradiance forecasting models that use deep learning models. In this study, the results for the LSTM model are compared to those for the Radial Basis Function neural network (RBFNN) in relation to both multivariate time series forecasting (MTSF) and univariate time series forecasting (UTSF). The results of the comparisons show that the UTSF_LSTM model performs better than other models with regard to minimum forecasting errors. Our results have also been validated with data from a region that features different climatic conditions from those originally tested. Overall, the outcome of these investigations clearly indicate the superiority of the proposed UTSF_LSTM method when compared to the UTSF_RBFNN, MTSF_RBFNN, or MTSF_LSTM developed models with regard to the coefficient of determination (R2) and the Root Mean Square Error (RMSE).