An Approach to DNI Transients Characterization for System Evaluation

Abstract

The direct normal irradiance (DNI) is of utmost importance for concentrated solar power (CSP) plants. For annual yield prediction, a steady-state heat balance is made for each hour of the year or for a smaller time period such as 15 min with the corresponding average DNI value. However, the distribution and short term DNI variations are ignored by this approach. In consequence, there is no information on the transient behavior of the plant and the question remains how the plant is influenced by the DNI disturbance. The paper intends to start a discussion on DNI characterization and its application to CSP. An approach to categorize the DNI behavior from a transient system point of view is presented by using purpose-/system-specific filters. The resulting DNI disturbance or variability classes, respectively, can be used to directly compare different sites and technologies. They might as well be useful for better yield analysis in the future.