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.1

This paper describes the experimental validation of two different transient models of the hybrid fuel cell/gas turbine facility of the U.S. DOE-NETL at Morgantown. The first part of this work is devoted to the description of the facility, designed to experimentally investigate these plants with real components, except the fuel cell. The behavior of the SOFC is obtained with apt volumes (for the stack and the off-gas burner) and using a combustor to generate similar thermal effects. The second part of this paper shows the facility real-time transient model developed at the U.S. DOE-NETL and the detailed transient modeling activity using the TRANSEO program developed at TPG. The results obtained with both models are successfully compared with the experimental data of two different load step decreases. The more detailed model agrees more closely with the experimental data, which, of course, is more time consuming than the real-time model (the detailed model operates with a calculation over calculated time ratio around 6). Finally, the TPG model has been used to discuss the importance of performance map precision for both compressor and turbine. This is an important analysis to better understand the steady-state difference between the two models

Fuel cell hybrid power systems have potential for the highest electrical power generation efficiency. Fuel cell gas turbine hybrid systems are currently under development as the first step in commercializing this technology. The dynamic interdependencies resulting from the integration of these two power generation technologies is not well understood. Unexpected complications can arise in the operation of an integrated system, especially during startup and transient events. Fuel cell gas turbine systems designed to operate under steady state conditions have limitations in studying the dynamics of a transient event without risk to the more fragile components of the system. A 250kW experimental fuel cell gas turbine system test facility has been designed at the National Energy Technology Laboratory (NETL), U.S. Department of Energy to examine the effects of transient events on the dynamics of these systems. The test facility will be used to evaluate control strategies for improving system response to transient events and load following. A fuel cell simulator, consisting of a natural gas burner controlled by a real time fuel cell model, will be integrated into the system in place of a real solid oxide fuel cell. The use of a fuel cell simulator in the initial phases allows for the exploration of transient events without risk of destroying an actual fuel cell. Fuel cell models and hybrid system models developed at NETL have played an important role in guiding the design of facility equipment and experimental research planning. Results of certain case studies using these models are discussed. Test scenarios were analyzed for potential thermal and mechanical impact on fuel cell, heat exchanger and gas turbine components. Temperature and pressure drop calculations were performed to determine the maximum impact on system components and design. Required turbine modifications were designed and tested for functionality. The resulting facility design will allow for examination of startup, shut down, loss of load to the fuel cell during steady state operations, loss of load to the turbine during steady state operations and load following.

The dynamic interdependencies created during the integration of fuel cell and a gas turbine in a hybrid power generation system are not well understood. Because these systems are new, there are risks that unexpected complications might arise during both steady state operation and transient events. A 250kW experimental fuel cell gas turbine simulation facility has been constructed at the National Energy Technology Laboratory (NETL), U.S. Department of Energy to examine the effects of transient events on the dynamics of these systems. A natural gas burner controlled by a real-time fuel cell model is used in the facility to simulate the thermal output of a solid oxide fuel cell during transient events. Pressure vessels are used for simulating the cathode and post combustion volumes, and are integrated into the system with a modified turbine and the fuel cell simulator. Preliminary results of system characterization are presented and discussed in context of the test scenarios proposed for experimental evaluation of thermal and mechanical transient impact on fuel cell and the gas turbine systems.