Characterization of Air Flow Management and Control in a Fuel Cell Turbine Hybrid Power System Using Hardware Simulation

Air flow management and control in a fuel cell gas turbine hybrid power system is evaluated using the Hybrid Performance (Hyper) hardware simulation facility at the National Energy Technology Laboratory (NETL), U.S. Department of Energy. The Hyper facility at NETL is a hardware simulation of a fuel cell gas turbine hybrid power system capable of emulating systems in the range of 300kW to 900kW. The hardware portion is comprised of a modified single-shaft gas turbine, a high performance exhaust gas recuperator, several pressure vessels that represent the volumes and flow impedances of the fuel cell and combustors, and the associated integration piping. The simulation portion consists of a real time fuel cell model that is used to control a natural gas burner which replicates the thermal output of a solid oxide fuel cell. Thermal management in the fuel cell component of the hybrid system, especially during an imposed load transient, is improved through the control of cathode air flow. This can be accomplished in a fuel cell turbine hybrid by diverting air around the fuel cell system. Two methods for air flow control are presented in the paper. In this paper, the use of bleed air by-pass and cold air by-pass are characterized quantitatively in terms of compressor inlet flow, process limits, system efficiency and system performance.