Design and Off-Design Predictions of a Combined SOFC and Gas Turbine System

Pålsson, Jens; Selimovic, Azra

doi:10.1115/2001-gt-0379

Cited by 15 publications

(8 citation statements)

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“…To control the fuel cell temperature at low power the gas turbine would have to operate at speeds less than its minimum speed for sustentation. This limitation has also been reported by [10] for topping SOFC/GT hybrid systems.…”

Section: Steady State System Analysissupporting

confidence: 57%

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Control Design for a Bottoming Solid Oxide Fuel Cell Gas Turbine Hybrid System

Mueller

Jabbari

Brouwer

et al. 2006

Journal of Fuel Cell Science and Technology

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A bottoming 275 kilowatt planar solid oxide fuel cell (SOFC) gas turbine (GT) hybrid system control approach has been conceptualized and designed.Based on previously published modeling techniques, a dynamic model is developed that captures the physics sufficient for dynamic simulation of all processes that affect the system with time scales greater than ten milliseconds. The dynamic model was used to make system design improvements to enable the system to operate dynamically over a wide range of power output (15 to 100% power). The wide range of operation was possible by burning supplementary fuel in the combustor and operating the turbine at variable speed for improved thermal management.The dynamic model was employed to design a control strategy for the system. Analyses of the relative gain array (RGA) of the system at several operating points gave insight into input/output (I/O) pairing for decentralized control. Particularly, the analyses indicate that for SOFC/GT hybrid plants that use voltage as a controlled variable it is beneficial to control system power by manipulating fuel cell current and to control fuel cell voltage by manipulating the anode fuel flowrate. To control the stack temperature during transient load changes, a cascade control structure is employed in which a fast inner loop that maintains the GT shaft speed receives its setpoint from a slower outer loop that maintains the stack temperature. Fuel can be added to the combustor to maintain the turbine inlet temperature for the lower operating power conditions. To maintain fuel utilization and to prevent fuel starvation in the fuel cell, fuel is supplied to the fuel cell proportionally to the stack current. In addition, voltage is used as an indicator of varying fuel concentrations allowing the fuel flow to be adjusted accordingly. Using voltage as a sensor is shown to be a potential solution to making SOFC systems robust to varying fuel compositions.The simulation tool proved effective for fuel cell/GT hybrid system control system development. The resulting SOFC/GT system control approach is shown to have transient load-following capability over a wide range of power, ambient temperature, and fuel concentration variations.

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Section: Steady State System Analysissupporting

confidence: 57%

“…In the current system, this is accomplished by operating the turbine at variable speeds. Such design has been investigated systematically and shown beneficial for hybrid systems by many [3][4][5][9][10].…”

Section: System Configurationmentioning

confidence: 99%

Control Design for a Bottoming Solid Oxide Fuel Cell Gas Turbine Hybrid System

Mueller

Jabbari

Brouwer

et al. 2006

Journal of Fuel Cell Science and Technology

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“…However, a large number of studies have showed that hybrid systems may suffer from many safety constraints in the operations of load variation or partial load scenarios because of high nonlinear multivariable and strong coupling [14][15][16][17][18]. These constraints can be classified into two categories: 1) from the matching and coupling characteristics between components [14,17,18] and 2) from the security of components themselves [15,16,18]. The instability phenomenon of compressor surge or choke might appear because of too low or too high air when operation points deviate from the designed point.…”

Section: Introductionmentioning

confidence: 99%

Determination of safe operation zone for an intermediate-temperature solid oxide fuel cell and gas turbine hybrid system

Xing

et al. 2016

Energy

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This paper proposes a novel approach to determine the safe zone for an intermediate-temperature solid oxide fuel cell and gas turbine hybrid system. The approach first ensures the compressor safety and then determines the overall system safe zone by analyzing the unsafe characteristics of main components. Safe performance of the hybrid system fueled with biomass gas at all operations is analyzed. Finally, the map of safe zone is obtained to avoid component malfunctions and system performance deterioration. Results show that the hybrid system can achieve a high efficiency 60.78%, which is an interesting reference for distributed power stations. Under all operations, two unbalanced energy zones exist, which may cause the short supply of O2 or fuel for electrochemical reaction. The lower the rotational speed, the narrower the zone of carbon deposition takes place in the reformer or turbine inoperation caused by too low inlet temperature. However, the phenomenon of fuel cell thermal cracking due to over-temperature will be exacerbated. System layout also affects component safety especially for the fuel cell. In the safe zone, the system has a characteristic of high efficiency

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“…Off-design operation of a Solid Oxide Fuel Cell Hybrid System was analysed previously inter alia by Chan et al (2002Chan et al ( , 2003; Costagama et al (2001); Freeh et al (2005); Kimijima and Kasagi (2002); Marsano et al (2004); Milewski et al (2007);Miller et al (2007); Palsson and Selimovic (2001); Stiller (2006); Stiller et al (2005;2006); Thorstensen (2001).…”

Section: Introductionmentioning

confidence: 99%

Triple-layer based control strategy for molten carbonate fuel cell – hybrid system

Milewski¹,

Miller²

2012

Chemical and Process Engineering

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Based on mathematical modelling and numerical simulations, a control strategy for a Molten Carbonate Fuel Cell Hybrid System (MCFC-HS) is presented. Adequate maps of performances with three independent parameters are shown. The independent parameters are as follows: stack current, fuel mass flow and compressor outlet pressure. Those parameters can be controlled by external load, fuel valve and turbine-compressor shaft speed, respectively. The control system is purposed to meet many constraints: e.g. stack temperature, steam-to-carbon ratio, compressor surge limitation, etc. The aim is to achieve maximum efficiency of power generated within these constraints. Governing equations of MCFC-HS modelling are given. An operational line of the MCFC-GT system is presented which fulfils several constraints (temperature difference, cell temperature, etc.) The system is able to achieve efficiency of more than 62% even in part-load operation.

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Design and Off-Design Predictions of a Combined SOFC and Gas Turbine System

Cited by 15 publications

References 0 publications

Control Design for a Bottoming Solid Oxide Fuel Cell Gas Turbine Hybrid System

Control Design for a Bottoming Solid Oxide Fuel Cell Gas Turbine Hybrid System

Determination of safe operation zone for an intermediate-temperature solid oxide fuel cell and gas turbine hybrid system

Triple-layer based control strategy for molten carbonate fuel cell – hybrid system

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