Modeling and Simulation of the Dynamic Operating Behavior of a High Solar Share Gas Turbine System

Solar gas turbine (GT) systems provide the opportunity to utilize solar heat at a much higher temperature than solar thermal power plants based on steam turbine cycles. Therefore, GT technology has the potential to improve the efficiency of future solar thermal power plants. Nevertheless, to achieve mature technology for commercial application, further development steps are required. Knowledge of the operational behavior of the solar GT system is the basis for the development of the systems control architecture and safety concept. The paper addresses dynamic simulation of high solar share GT systems, which are characterized by primary input of solar heat to the GT. To analyze the dynamic operating behavior, a model with parallel arrangement of the combustion chamber and the solar receiver was set up. By using the heaviside step function, the system dynamics were translated into transfer functions which are used to develop controllers for the particular system configuration. Two operating conditions were simulated to test the controller performance. The first case is the slow increase and decrease of solar heat flow, as part of a regular operation. The second case is an assumed rapid change of solar heat flow, which can be caused by clouds. For all cases, time plots of critical system parameters are shown and analyzed. The simulation results show much more complex system behavior compared to conventional GT systems. This is due to the additional solar heat source, large volumes, and stored thermal energy as well as the time delay of energy transportation caused by the piping system.