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.

This paper examines the arrangement of a solid oxide fuel cell (SOFC) within a coal gasification cycle, this combination generally being called an integrated gasification fuel cell cycle. This work relies on a previous study performed by the National Energy Technology Laboratory (NETL) that details thermodynamic simulations of integrated gasification combined cycle (IGCC) systems and considers various gasifier types and includes cases for 90% $CO2$ capture (2007, “Cost and Performance Baseline for Fossil Energy Plants, Vol. 1: Bituminous Coal and Natural Gas to Electricity,” National Energy Technology Laboratory Report No. DOE/NETL-2007/1281). All systems in this study assume a Conoco Philips gasifier and cold-gas clean up conditions for the coal gasification system (Cases 3 and 4 in the NETL IGCC report). Four system arrangements, cases, are examined. Cases 1 and 2 remove the $CO2$ after the SOFC anode. Case 3 assumes steam addition, a water-gas-shift (WGS) catalyst, and a Selexol process to remove the $CO2$ in the gas cleanup section, sending a hydrogen-rich gas to the fuel cell anode. Case 4 assumes Selexol in the cold-gas cleanup section as in Case 3; however, there is no steam addition, and the WGS takes places in the SOFC and after the anode. Results demonstrate significant efficiency advantages compared with IGCC with $CO2$ capture. The hydrogen-rich case (Case 3) has better net electric efficiency compared with typical postanode $CO2$ capture cases (Cases 1 and 2), with a simpler arrangement but at a lower SOFC power density, or a lower efficiency at the same power density. Case 4 gives an efficiency similar to Case 3 but also at a lower SOFC power density. Carbon deposition concerns are also discussed.

The National Energy Technology Laboratory (NETL, U.S., D.O.E.) in Morgantown, West Virginia has successfully designed and is operating a fuel cell/turbine hybrid test facility. With the successful operation of this test facility, it is now possible to model, test and evaluate the effect of pressure and temperature transients important to the design and operation of a fuel cell/gas turbine hybrid system and provide a means of quantifying mitigation methods to address adverse impacts of such transients to the operation, safety and efficiency of these systems. This paper deals exclusively with the Simulink, lumped parameter model and its relationship to controls development. Presented in detail are the development, structure and methodology of this Simulink process model as related to the Hybrid Performance (Hyper) test facility in use at NETL. Thus far the model simulates only the test facility, which presently does not have a fuel cell, but a large plenum is used to represent the cathode air volume. Future work will insert fuel cell models developed by NETL. Components of the model are presented and described in detail. Two case studies are presented based on the effect of load shed transients on system performance. These case studies are 1.) Speed controlled load shedding, 2.) Speed set point changing.

A dynamic process model of a steam turbine, including partial arc admission operation, is presented. Models were made for the first stage and last stage, with the middle stages assumed to have a constant pressure ratio and efficiency. A condenser model is also presented. The paper discusses the function and importance of the steam turbine's entrance design and the first stage. The results for steam turbines with a partial arc entrance are shown and compare well with experimental data available in the literature; in particular, the “valve loop” behavior as the steam flow rate is reduced. This is important to model correctly since it significantly influences the downstream state variables of the steam, and thus the characteristic of the entire steam turbine, e.g., state conditions at extractions, overall turbine flow, and condenser behavior. The importance of the last stage (the stage just upstream of the condenser) in determining the overall flow rate and exhaust conditions to the condenser is described and shown via results.

A dynamic model is developed for a microgas turbine (MGT), characterized by an intrinsic free-spool configuration, coupled to large volumes. This is inspired by an experimental facility at the National Energy Technology Laboratory (NETL) called hybrid performance (Hyper), which emulates a hybrid MGT and Fuel Cell system. The experiment and model can simulate stable and unstable operating conditions. The model is used to investigate the effects of different volumes on surge events, and to test possible strategies to safely avoid or recover from unstable compressor working conditions. The modeling approach is started from the Greitzer lumped parameter approach, and it has been improved with integration of empirical methods and simulated components to better match the real Hyper plant layout and performance. Pressure, flowrate, and frequency plots are shown for the surge behavior comparing two different volume sizes, for cases where gas turbine shaft speed is uncontrolled (open loop) and controlled (closed-loop). The ability to recover from a surge event is also demonstrated.

A generic training simulator of a natural gas combined cycle (NGCC) was modified to match operations at a real plant. The objective was to use the simulator to analyze cycling operations of the plant. Initial operation of the simulator revealed the potential for saturation conditions in the final high pressure superheater (HPSH) as the attemperator tried to control temperature at the superheater outlet during gas turbine loading and unloading. Subsequent plant operational data confirmed simulation results. Multiple simulations were performed during loading and unloading of the gas turbine to determine operational strategies that prevented saturation and increased the approach to saturation temperature. The solutions included changes to the attemperator temperature control setpoints and strategic control of the steam turbine (ST) inlet pressure control valve.