A New High Frequency Global-to-direct Irradiance Conversion Methodology

Overview & Synopsis

In order to accurately simulate the behavior of a solar thermal power plant, it is necessary to carry out an adequate evaluation of the available solar resource. To that end, it is important to know the cumulative Direct Normal solar Irradiation (DNI) values and their dynamic behavior. Only by knowing this information with accuracy, it will be possible to predict the solar thermal power plant behavior and to establish an adequate operation strategy. Sites with high cumulative DNI values are not necessarily the best locations for solar thermal power plants. Variability of the solar resource and its impact on the management of the plant may cause that sites with similar or lower DNI values can present a higher electricity production. Current solar radiation models based on hourly data series do not allow fairly evaluating the plant behavior or analyzing with the required detail different possible operation strategies. So as to overcome this limitation and to have a more accurate knowledge of the solar resource it is necessary to increase the sampling frequency of the data, what will enable to simulate with higher accuracy certain aspects of the operation like transient effects. For that purpose, this paper presents a new global-to-direct irradiance conversion methodology, based on 1-minute frequency series, which will improve results of solar thermal power plants simulations.