scholarly journals A Real-Time Degradation Model for Hardware in the Loop Simulation of Fuel Cell Gas Turbine Hybrid Systems

2015 ◽  
Author(s):  
Valentina Zaccaria ◽  
Alberto Traverso ◽  
David Tucker
Keyword(s):  
Fuel Cell ◽  
Real Time ◽  
Gas Turbine ◽  
Hybrid Systems ◽  
Current Density ◽  
Gas Turbines ◽  
Hardware In The Loop ◽  
Fuel Utilization ◽  
Time Operation ◽  
The Impact

The theoretical efficiencies of gas turbine fuel cell hybrid systems make them an ideal technology for the future. Hybrid systems focus on maximizing the utilization of existing energy technologies by combining them. However, one pervasive limitation that prevents the commercialization of such systems is the relatively short lifetime of fuel cells, which is due in part to several degradation mechanisms. In order to improve the lifetime of hybrid systems and to examine long-term stability, a study was conducted to analyze the effects of electrochemical degradation in a solid oxide fuel cell (SOFC) model. The SOFC model was developed for hardware-in-the-loop simulation with the constraint of real-time operation for coupling with turbomachinery and other system components. To minimize the computational burden, algebraic functions were fit to empirical relationships between degradation and key process variables: current density, fuel utilization, and temperature. Previous simulations showed that the coupling of gas turbines and SOFCs could reduce the impact of degradation as a result of lower fuel utilization and more flexible current demands. To improve the analytical capability of the model, degradation was incorporated on a distributed basis to identify localized effects and more accurately assess potential failure mechanisms. For syngas fueled systems, the results showed that current density shifted to underutilized sections of the fuel cell as degradation progressed. Over-all, the time to failure was increased, but the temperature difference along cell was increased to unacceptable levels, which could not be determined from the previous approach.

Fuel Cell Temperature Control With a Pre-Combustor in SOFC Gas Turbine Hybrids During Load Changes

2016 ◽  
Author(s):  
Valentina Zaccaria ◽  
Zachary Branum ◽  
David Tucker
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Real Time ◽  
Gas Turbine ◽  
Thermal Stresses ◽  
Inlet Temperature ◽  
System Efficiency ◽  
Temperature Deviation ◽  
Conservation Of Energy ◽  
The Impact

The use of high temperature fuel cells, such as Solid Oxide Fuel Cells (SOFCs), for power generation, is considered a very efficient and clean solution to conservation of energy resources. Especially when the SOFC is coupled with a gas turbine, the global system efficiency can go beyond 70% on natural gas LHV. However, the durability of the ceramic material and the system operability can be significantly penalized by thermal stresses due to temperature fluctuations and non-even temperature distributions. Thermal management of the cell during load following is therefore very critical. The purpose of this work was to develop and test a pre-combustor model for real-time applications in hardware-based simulations, and to implement a control strategy in order to keep cathode inlet temperature as constant as possible during different operative conditions of the system. The real-time model of the pre-combustor was incorporated into the existing SOFC model and tested in a hybrid system facility, where a physical gas turbine and hardware components were coupled with a cyber-physical fuel cell for flexible, accurate, and cost-reduced simulations. The control of the fuel flow to the pre-combustor was proven to be very effective in maintaining a constant cathode inlet temperature during a step change in fuel cell load. After imposing a 20 A load variation to the fuel cell, the controller managed to keep the temperature deviation from the nominal value below 0.3% (2 K). Temperature gradients along the cell were maintained below 10 K/cm. An efficiency analysis was performed in order to evaluate the impact of the pre-combustor on the overall system efficiency.

scholarly journals Hardware-in-the-Loop Operations With an Emulator Rig for SOFC Hybrid Systems

2017 ◽  
Author(s):  
Mario L. Ferrari ◽  
Alessandro Sorce ◽  
Aristide F. Massardo
Keyword(s):  
Fuel Cell ◽  
Real Time ◽  
Hybrid Systems ◽  
Control Strategies ◽  
Experimental Tests ◽  
Outlet Temperature ◽  
Hardware In The Loop ◽  
Set Point ◽  
The Real ◽  
System Components

This paper shows the Hardware-In-the-Loop (HIL) technique developed for the complete emulation of Solid Oxide Fuel Cell (SOFC) based hybrid systems. This approach is based on the coupling of an emulator test rig with a real-time software for components which are not included in the plant. The experimental facility is composed of a T100 microturbine (100 kW electrical power size) modified for the connection to an SOFC emulator device. This component is composed of both anodic and cathodic vessels including also the anodic recirculation system which is carried out with a single stage ejector, driven by an air flow in the primary duct. However, no real stack material was installed in the plant. For this reason, a real-time dynamic software was developed in the Matlab-Simulink environment including all the SOFC system components (the fuel cell stack with the calculation of the electrochemical aspects considering also the real losses, the reformer, and a cathodic recirculation based on a blower, etc.). This tool was coupled with the real system utilizing a User Datagram Protocol (UDP) data exchange approach (the model receives flow data from the plant at the inlet duct of the cathodic vessel, while it is able to operate on the turbine changing its set-point of electrical load or turbine outlet temperature). So, the software is operated to control plant properties to generate the effect of a real SOFC in the rig. In stand-alone mode the turbine load is changed with the objective of matching the measured Turbine Outlet Temperature (TOT) value with the calculated one by the model. In grid-connected mode the software/hardware matching is obtained through a direct manipulation of the TOT set-point. This approach was essential to analyze the matching issues between the SOFC and the micro gas turbine devoting several tests on critical operations, such as start-up, shutdown and load changes. Special attention was focused on tests carried out to solve the control system issues for the entire real hybrid plant emulated with this HIL approach. Hence, the innovative control strategies were developed and successfully tested considering both the Proportional Integral Derivative and advanced approaches. Thanks to the experimental tests carried out with this HIL system, a comparison between different control strategies was performed including a statistic analysis on the results The positive performance obtainable with a Model Predictive Control based technique was shown and discussed. So, the HIL system presented in this paper was essential to perform the experimental tests successfully (for real hybrid system development) without the risks of destroying the stack in case of failures. Mainly surge (especially during transient operations, such as load changes) and other critical conditions (e.g. carbon deposition, high pressure difference between the fuel cell sides, high thermal gradients in the stack, excessive thermal stress in the SOFC system components, etc.) have to be carefully avoided in complete plants.

scholarly journals Fuel utilization effects on system efficiency in solid oxide fuel cell gas turbine hybrid systems

2018 ◽  
Vol 228 ◽  
pp. 1953-1965 ◽  
Author(s):  
Danylo Oryshchyn ◽  
Nor Farida Harun ◽  
David Tucker ◽  
Kenneth M. Bryden ◽  
Lawrence Shadle
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Gas Turbine ◽  
Hybrid Systems ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
System Efficiency ◽  
Fuel Utilization

Fuel Cell Temperature Control With a Precombustor in SOFC Gas Turbine Hybrids During Load Changes

2017 ◽  
Vol 14 (3) ◽  
Author(s):  
Valentina Zaccaria ◽  
Zachary Branum ◽  
David Tucker
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Real Time ◽  
Gas Turbine ◽  
Maximum Temperature ◽  
Inlet Temperature ◽  
System Efficiency ◽  
Temperature Deviation ◽  
Conservation Of Energy ◽  
The Impact

The use of high temperature fuel cells, such as solid oxide fuel cells (SOFCs), for power generation is considered a very efficient and clean solution for conservation of energy resources. When the SOFC is coupled with a gas turbine, the global system efficiency can go beyond 70% on natural gas lower heating value (LHV). However, durability of the ceramic material and system operability can be significantly penalized by thermal stresses due to temperature fluctuations and noneven temperature distributions. Thermal management of the cell during load following is therefore essential. The purpose of this work is to develop and test a precombustor model for real-time applications in hardware-based simulations, and to implement a control strategy to keep constant cathode inlet temperature during different operative conditions. The real-time model of the precombustor was incorporated into the existing SOFC model and tested in a hybrid system facility, where a physical gas turbine and hardware components were coupled with a cyber-physical fuel cell for flexible, accurate, and cost-reduced simulations. The control of the fuel flow to the precombustor was proven to be effective in maintaining a constant cathode inlet temperature during a step change in fuel cell load. With a 20 A load variation, the maximum temperature deviation from the nominal value was below 0.3% (3 K). Temperature gradients along the cell were maintained below 10 K/cm. An efficiency analysis was performed in order to evaluate the impact of the precombustor on the overall system efficiency.

Needs and Approaches for Novel Characterization of Direct Hybrid Fuel Cell/Gas Turbines

2015 ◽  
Author(s):  
David Tucker ◽  
Comas Haynes ◽  
Patrick Geoghegan
Keyword(s):  
Fuel Cell ◽  
Hybrid Systems ◽  
Gas Turbines ◽  
Low Cost ◽  
A Priori ◽  
The United States ◽  
Hardware In The Loop ◽  
Operational Flexibility ◽  
Developmental Needs ◽  
Heat Engines

Solid oxide fuel cell (SOFC)/ gas turbine (GT) hybrid systems possess the capacity for unprecedented performances, such as electric efficiencies nearly twice that of conventional heat engines at variable scale power ratings inclusive of distributed generation. Additionally, these hybrids can have excellent operational flexibility with turndowns possibly as great as 85%. There are, however, developmental needs such as turbomachinery characterization and re-design. A leading example is that of greater propensity to have occurrences of stall-surge given the significantly different operating environment in contrast to conventional heat engines. Additionally, dynamic variation in power generation has to be done with significant a priori insight to avoid thermomechanical threats to cell stack and turbomachinery. State-of-the-art approaches involving hardware-in-the-loop simulation and, ultimately, additive manufacturing are being pursued to enable such characterization and re-design considerations given variable and dynamic operability requirements. Compressor performance in hybrid systems has been characterized at the United States National Energy Technology Laboratory (NETL), inclusive of a capability of feed forward hardware-in-the-loop simulation of hybrid systems under dynamic conditions and a capability of replacing turbine and compressor components at a relatively low cost. This paper highlights some of the simulation results, and the net result is an approach that addresses hybrid system developmental needs for accommodating generation transients.

scholarly journals Fuel Utilization Effects on System Efficiency and Solid Oxide Fuel Cell Performance in Gas Turbine Hybrid Systems

2017 ◽  
Author(s):  
Nor Farida Harun ◽  
Lawrence Shadle ◽  
Danylo Oryshchyn ◽  
David Tucker
Keyword(s):  
Fuel Cell ◽  
Gas Turbine ◽  
Hybrid Systems ◽  
Cell Length ◽  
Inlet Temperature ◽  
Total Efficiency ◽  
Total System ◽  
System Efficiency ◽  
Fuel Utilization ◽  
Fuel Cell Performance

The simulation work presented herein characterizes the performance of a recuperated gas turbine (GT) hybrid systems in response to different levels of fuel utilization (Uf) by the SOFC. The SOFC performance was compared with and without anode recycle (AR), operating at 90% total stack Uf (Uf.stack). A study at 65% Uf was also considered as a reference case for the hybrid power system without anode recycle, i.e. using single-pass cell fuel utilization (Uf.cell). All three cases in this paper were evaluated at design points for a 550 MW hybrid system using coal-derived syngas feed with zero methane. A previously developed one-dimensional (1D) fuel cell model was used to simulate the distributed profile of thermal and electrochemical properties along the fuel cell length. Fuel cell total current density, average solid temperature, and cathode inlet temperature were maintained identical at each fuel utilization to avoid confounding the results with the impacts of SOFC degradation. The maximum system efficiency of 71.1% was achieved by SOFC/GT non-recycle systems at 90% Uf.cell (with 90% Uf.stack). The case at 65% Uf.cell (with 65% Uf.stack) demonstrated 70.7% total efficiency, only 0.4% point lower than at 90% Uf.cell. However, integrating anode recycle to the system significantly reduced the maximum total efficiency to 55.5%. Although the distributed SOFC performance across the cell length for 65% Uf.cell with AR at 90% Uf.stack was similar to the 65% Uf.cell (with 65% Uf.stack), recycling anode off-gas resulted in lower fuel cell Nernst potential that caused further drop in both stack and total system efficiency.

Real-Time Variable Geometry Triaxial Gas Turbine Model for Hardware-in-the-Loop Simulation Experiments

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Tao Wang ◽  
Yong-Sheng Tian ◽  
Zhao Yin ◽  
Da-Yue Zhang ◽  
Ming-Ze Ma ◽  
...  
Keyword(s):  
Real Time ◽  
Gas Turbine ◽  
Working Conditions ◽  
Gas Turbines ◽  
Neural Net ◽  
Hardware In The Loop ◽  
Gas Generator ◽  
Component Level ◽  
Simulation Experiments ◽  
Power Turbine

This paper proposes a hybrid method (HMRC) comprised of a radial basis function (RBF) neural net algorithm and component-level modeling method (CMM) as a real-time simulation model for triaxial gas turbines with variable power turbine guide vanes in matlab/simulink. The sample size is decreased substantially after analyzing the relationship between high and low pressure shaft rotational speeds under dynamic working conditions, which reduces the computational burden of the simulation. The effects of the power turbine rotational speed on overall performance are also properly accounted for in the model. The RBF neural net algorithm and CMM are used to simulate the gas generator and power turbine working conditions, respectively, in the HMRC. The reliability and accuracy of both the traditional single CMM model (SCMM) and HMRC model are verified using gas turbine experiment data. The simulation models serve as a controlled object to replace the real gas turbine in a hardware-in-the-loop simulation experiment. The HMRC model shows better real-time performance than the traditional SCMM model, suggesting that it can be readily applied to hardware-in-the-loop simulation experiments.

A Real-Time Spatial SOFC Model for Hardware-Based Simulation of Hybrid Systems

2011 ◽  
Author(s):  
Dimitri Hughes ◽  
William J. Wepfer ◽  
Kevin Davies ◽  
J. Christopher Ford ◽  
Comas Haynes ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Real Time ◽  
Gas Turbine ◽  
Hybrid Systems ◽  
Power Plants ◽  
Large Scale ◽  
Test Facility ◽  
Heating And Cooling ◽  
Dynamic Hybrid ◽  
The One

Solid oxide fuel cell (SOFC)/ gas turbine (GT) hybrid systems possess the capability to nearly double the efficiency of standard coal-fired power plants which are currently being used for large scale power production. For the purposes of investigating and developing this technology, a SOFC/GT hybrid test facility was developed at the U.S. DOE National Energy Technology Laboratory (NETL) in Morgantown, WV as part of the Hybrid Performance (HyPer) project. The HyPer facility utilizes hardware-in-the-loop technology to simulate coupled SOFC operation with gas turbine hardware in a hybrid arrangement. This paper describes and demonstrates the capabilities of the one-dimensional, real-time operating SOFC model that has been developed and successfully integrated into the HyPer facility. The model presented is designed to characterize SOFC operation over a broad and extensive operating range including inert heating and cooling, standard “on-design” conditions and extreme off-design conditions. The model receives dynamic, system-dependent modeling inputs from facility hardware and calculates a comprehensive set of SOFC operational responses, thus simulating SOFC operation while coupled with a gas turbine. In addition to characterizing SOFC operation, the model also drives the only heat source in the facility to represent fuel cell subsystem release of thermal effluent to the turbine subsystem. Operating parameters such as solid and oxidant stream temperatures, fuel stream compositions, current density, Nernst potential and polarization losses are produced by the model in spatiotemporal manner. The capability of the model to characterize SOFC operation, within dynamic hybrid system feedback, through inert heat up and a step change in load is presented and analyzed.

Accelerated Degradation for Hardware in the Loop Simulation of Fuel Cell-Gas Turbine Hybrid

2014 ◽  
Author(s):  
Maria Abreu-Sepulveda ◽  
David Tucker ◽  
Nor Farida Harun ◽  
Gregory Hackett ◽  
Anke Hagen
Keyword(s):  
Fuel Cell ◽  
Real Time ◽  
Gas Turbine ◽  
Degradation Rate ◽  
Operating Conditions ◽  
Hardware In The Loop ◽  
Electrochemical Degradation ◽  
Term Stability ◽  
Long Term Stability

Solid oxide fuel cells (SOFCs) are a promising technology for clean power generation, however their implementation has been limited by several degradation mechanisms, which significantly reduce its lifetime under constant output power and inhibits the technology for commercialization in the near future. With the purpose of harnessing the capabilities offered by SOFCs, the U.S. DOE-National Energy Technology Laboratory (NETL) in Morgantown, WV has developed the Hybrid Performance (HyPer) project in which a SOFC 1D, real-time operating model is coupled to a gas turbine hardware system by utilizing hardware-in-the-loop simulation (HiLS). More recently, in order to assess the long-term stability of the SOFC part of the system, electrochemical degradation due to operating conditions such as current density and fuel utilization have been incorporated into the SOFC model and successfully recreated in real time for standalone and hybrid operation. The mathematical expression for degradation rate was obtained through the analysis of empirical voltage versus time plots for different current densities and fuel utilizations at 750, 800, and 850°C. Simulation results well reflected the behavior of SOFC degradation rates from which the long-term stability of the cell under various conditions was assessed. Distributed fuel cell parameters are presented for both standalone and hybrid configurations. The incorporation of the electrochemical degradation rate into the SOFC model provides a framework to study more realistically Fuel Cell-hybrid systems and set forth a mechanism to improve the long-term stability of SOFCs through the hybridization of such technology.

Hybrid Gas Turbine and Fuel Cell Systems in Perspective Review

1999 ◽  
Author(s):  
David J. White
Keyword(s):  
Carbon Dioxide ◽  
Fuel Cells ◽  
High Temperature ◽  
Fuel Cell ◽  
Gas Turbine ◽  
Hybrid Systems ◽  
Gas Turbines ◽  
Energy Output ◽  
Net Energy ◽  
Cell Systems

The concept of hybrids combining fuel cell and gas turbine systems is without question neoteric, and probably is less than eight years old. However, this concept is in a sense a logical development derived from the many early systems that embodied the key features of rotating machinery to compress air. It was the introduction of high temperature fuel cells such as the solid oxide fuel cell (SOFC) that allowed the concept of hybrid gas turbine fuel cell systems to take root. The SOFC with an operating temperature circa 1000° C matched well with small industrial gas turbines that had firing temperatures on the same order. The recognition that the SOFC could be substituted for the gas turbine combustor was the first step into the realm of fuel cell topping systems. Fuel cells in general were recognized as having higher efficiencies at elevated pressures. Thus the hybrid topping system where the gas turbine pressurized the fuel cell and the fuel cell supplied the hot gases for expansion over the turbine promised to provide a high level of synergy between the two systems. Bottoming systems using the exhaust of a gas turbine as the working fluid of a fuel cell such as the molten carbonate fuel cell (MCFC) have been identified and are potential future power generation hybrid systems. The MCFC is especially well suited to the bottoming role because of the need to have carbon dioxide present in the inlet air stream. The carbon dioxide in the gas turbine exhaust allows the high temperature blower, normally used to recirculate and inject exhaust products into the inlet air, to be eliminated. Hybrid systems have the potential of achieving fossil fuel to electricity conversion efficiencies on the order of 70% and higher. The costs of hybrid systems in dollars per kilowatt are generally higher than say an advanced gas turbine that is available today but not by much. The net energy output over the life of a hybrid topping system is similar to that of a recuperated gas turbine but possibly lower than a high-efficiency simple-cycle machine, depending on the efficiency of the hybrid. Methodologies to aid in the selection of the hybrid system for future development have to be developed and used consistently. Life cycle analyses (LFA) provide a framework for such selection processes. In particular the concept of net energy output provides a mechanism to assign relative worth to competing concepts.

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