Dynamic simulation results for a thermal energy storage (TES) unit used in a parabolic trough concentrated solar power (CSP) system are presented. A two-tank-direct method is used for the thermal energy storage. While previous works have been focused largely on controlling the outlet temperature of the solar collector as a single unit, this work emphasizes the storage component, its interaction with the other components of the system, and how it can be leveraged to control power output in addition to collector outlet temperature. The use of storage gives the system the ability to provide power at a constant rate despite significant disturbances in the amount of solar radiation available. It can also shift times of power generation to better match times of consumer demand. By contrast, a CSP system without storage undergoes large fluctuations in power output, particularly during intermittent cloud cover. Adding a storage system increases the solar share of the power plant by as much as 47% for a base load thermal power output of 1 MW. This reduces the supplementary fuel requirement by as much as 43%. (C) 2011 Elsevier Ltd. All rights reserved.