Optimization and load-following characteristics of 5kw-class tubular solid oxide fuel cell/gas turbine hybrid systems

This study investigates the performance and operating characteristics of 5kW-class solid oxide fuel cell and gas turbine (SOFC/GT) hybrid systems for two different configurations, namely single- and dual- spool gas turbines. Both single and dual spool turbo-chargers are widely used in the gas turbine industry. Even though their operation is based on the same physical principles, their performance characteristics and operation parameters vary considerably due to different designs. The implications of the differences on the performance of the hybrid SOFC/GT have not been discussed in literature, and will be the topic of this paper. Operating envelops of single and dual shaft systems are identified and compared. Performance in terms of system efficiency and load following is analyzed. Sensitivities of key variables such as power, SOFC temperature, and GT shaft speed to the control inputs (namely, fuel flow, SOFC current, generator load) are characterized, all in an attempt to gain insights on the design implication for the single and dual shaft SOFC/GT systems. Dynamic analysis are also performed for part load operation and load transitions, which shed lights for the development of safe and optimal control strategies.

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Development of a Dynamic Cathode Ejector Model for Solid Oxide Fuel Cell-Gas Turbine Hybrid Systems

Journal of Fuel Cell Science and Technology ◽

10.1115/1.4003774 ◽

2011 ◽

Vol 8 (5) ◽

Cited By ~ 4

Author(s):

James D. Maclay ◽

Jacob Brouwer ◽

G. Scott Samuelsen

Keyword(s):

Fuel Cell ◽

Solid Oxide Fuel Cell ◽

Gas Turbine ◽

Hybrid Systems ◽

Solid Oxide ◽

Theoretical Development ◽

Oxide Fuel ◽

Simulink Model ◽

Fuel Cell Cathode ◽

Good Agreement

Solid oxide fuel cell-gas turbine (SOFC-GT) hybrid systems are attractive for future power generation with ultra-low criteria pollutant and greenhouse gas emissions. One of the challenges for SOFC-GT systems is to sufficiently pre-heat incoming air before it enters the fuel cell cathode. An ejector for cathode exhaust recirculation has the benefits of reliability, low maintenance, and cost compared to either recuperators or cathode recirculation blowers, which may be also be used for air pre-heating. In this study, a dynamic Simulink model of an ejector for cathode exhaust recirculation to pre-heat incoming fuel cell air has been developed. The ejector is to be utilized within a 100 MW SOFC-GT dynamic model operating on coal syngas. A thorough theoretical development is presented. Results for the ejector were found to be in good agreement with those reported in literature.

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

Applied Energy ◽

10.1016/j.apenergy.2018.07.004 ◽

2018 ◽

Vol 228 ◽

pp. 1953-1965 ◽

Cited By ~ 29

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

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Designing Solid Oxide Fuel Cell Gas Turbine Hybrid Systems Using Exergy Analysis

ASME 2006 Fourth International Conference on Fuel Cell Science, Engineering and Technology, Parts A and B ◽

10.1115/fuelcell2006-97084 ◽

2006 ◽

Cited By ~ 2

Author(s):

K. J. Bosch ◽

N. Woudstra ◽

K. V. van der Nat

Keyword(s):

Fuel Cell ◽

Natural Gas ◽

Solid Oxide Fuel Cell ◽

Gas Turbine ◽

Hybrid Systems ◽

Exergy Analysis ◽

Operating Conditions ◽

Solid Oxide ◽

Oxide Fuel ◽

Exergy Losses

In conventional gas turbine systems combustion results in high exergy losses (∼30%) of fuel exergy input. Replacing the combustor with a high temperature fuel cell, like the Solid Oxide Fuel Cell (SOFC), will significantly reduce these exergy losses. As the SOFC electrochemically converts the natural gas, exergy losses are far lower (∼10%) compared to combustion. Natural gas entering a SOFC system has to be reformed first to hydrogen and carbon monoxide by steam reforming. Here it is chosen to use the heat generated by the fuel cell to drive the endothermic reforming reactions: internal reforming. The SOFC-GT system has the advantage that both fuel cell and gas turbine technology contribute to power production. In earlier work [1] several fuel cell system configurations with PEMFC, MCFC or SOFC, were analyzed studying the exergy flows. Here is focused on the SOFC-GT configuration, to get a detailed understanding of the exergy flows and losses through all individual components. Several configurations, combining the SOFC with the GT are possible. The selected operating conditions should prevent carbon deposition. Systems studies are performed to get more insight in the exergy losses in these combined systems. Exergy analysis facilitates the search for the high efficient SOFC-GT hybrid systems. Using exergy analysis, several useful configurations are found. Exergy losses are minimized by varying pressure ratio and turbine inlet temperature. Sensitivity studies, of equivalent cell resistance and fuel cell temperature, show that total system exergy efficiencies of more than 80% are conceivable, without using a bottoming cycle.

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A Thermodynamic Analysis of Tubular Solid Oxide Fuel Cell Based Hybrid Systems

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.1499728 ◽

2002 ◽

Vol 125 (1) ◽

pp. 59-66 ◽

Cited By ~ 25

Author(s):

A. D. Rao ◽

G. S. Samuelsen

Keyword(s):

Fuel Cell ◽

Natural Gas ◽

Solid Oxide Fuel Cell ◽

Gas Turbine ◽

Hybrid Systems ◽

Hybrid Plant ◽

Solid Oxide ◽

Oxide Fuel ◽

Cost Of Electricity ◽

Analysis Strategy

The goals of a research program recently completed at the University of California, Irvine were to develop analysis strategy for solid oxide fuel cell (SOFC) based systems, to apply the analysis strategy to tubular SOFC hybrid systems and to identify promising hybrid configurations. A pressurized tubular SOFC combined with an intercooled-reheat gas turbine (SureCell™ cycle) is chosen as the base cycle over which improvements are sought. The humid air turbine (HAT) cycle features are incorporated to the base cycle resulting in the SOFC-HAT hybrid cycle which shows an efficiency of 69.05 percent while the base cycle has an efficiency of 66.23 percent. Exergy analysis identified the superior efficiency performance of the SOFC component. Therefore, an additional cycle variation added a second SOFC component followed by a low pressure combustor in place of the reheat combustor of the gas turbine of the SOFC-HAT hybrid. The resulting dual SOFC-HAT hybrid has a thermal efficiency of 75.98 percent. The single SOFC-HAT hybrid gives the lowest cost of electricity (3.54¢/kW-hr) while the dual SOFC-HAT hybrid has the highest cost of electricity (4.02¢/kW-hr) among the three cycles with natural gas priced at $3/GJ. The dual SOFC-HAT hybrid plant cost is calculated to be significantly higher because the fraction of power produced by the SOFC(s) is significantly higher than that in the other cases on the basis of $1100/kw initial cost for the SOFC. The dual SOFC-HAT hybrid can only be justified in favor of the single SOFC-HAT hybrid when the price of natural gas is greater than $14/GJ or if a severe carbon tax on the order of $180/ton of CO2 is imposed while natural gas price remains at $3/GJ.

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