This standard contains the information necessary for determining the performance and functional characteristics of active indirect thermal energy storage systems based on sensible heat and liquid storage media, in solar thermal power plants using parabolic-trough collector technology. The standard includes general characterization procedures for testing energy storage system charge and discharge, as well as reporting the results. Test performance requirements are given and the instrumentation necessary for them, as well as data acquisition and processing methods and methods for calculating the results and their uncertainties.