Chapter 9 - Nowcasting solar irradiance for effective solar power plants operation and smart grid management

Abstract

The equilibrium of the electricity grid is very often changing due to demand fluctuations and it is further threatened by the fluctuation in the output of solar power plants. With the aim of increasing the share of solar electricity in the energy mix, near real-time forecasting of the solar power production represents a key issue for smart-control of the grid. Since the accuracy of forecasting of the performance of a solar plant is strongly conditioned by the accuracy of forecasting of the solar resource, this chapter deals with solar irradiance forecasting. First, a brief introduction to solar radiation and its inherent variability is presented. Then, the performance of solar irradiance forecasting models at time horizons within an hour is analyzed in-depth. The present limitations and perspectives are discussed. A survey on the metrics used to quantify the forecasts accuracy is also presented. As a case study, the accuracies of three models, different in nature and complexity, are evaluated from different perspectives: (1) forecast time horizon, (2) forecast precision, and (3) influence of the solar irradiance variability on forecast accuracy. The study is conducted with high-quality radiometric data recorded at high frequency on the Solar Platform of the West University of Timisoara, Romania.