The Effect of Size on Optimization of Solid Oxide Fuel Cell/Gas Turbine Hybrid Cycles

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Michael J. Brear ◽  
Michael J. Dunkley
Keyword(s):  
Fuel Cell ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Solid Oxide ◽  
Total Power ◽  
Specific Power ◽  
Oxide Fuel ◽  
Secondary Importance ◽  
Power Outputs

The coupling of solid oxide fuel cells (SOFCs) and recuperated gas turbines (GTs) in a hybrid system has the potential to lead to efficiencies exceeding 60%. SOFC/GT hybrids have been proposed at power outputs from 20 MW down to power outputs as low as 25 kW. The optimum configuration for high and low power outputs is therefore likely to be significantly different. This paper proposes a simple model of the SOFC/GT hybrid to investigate the desired flow rate and pressure ratio for optimum hybrid efficiency with varying component performance and, hence, varying inferred size. The overall hybrid specific power will be dominated by the fuel cell and is therefore of secondary importance when matching with a gas turbine. The results presented suggest that hybrid cycles with total power output of the order MW or greater are preferable.

The Effect of Size on Optimisation of Solid Oxide Fuel Cell/Gas Turbine Hybrid Cycles

2009 ◽  
Author(s):  
Michael J. Brear ◽  
Michael J. Dunkley
Keyword(s):  
Fuel Cell ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Solid Oxide ◽  
Total Power ◽  
Oxide Fuel ◽  
Component Size ◽  
System Pressure

The integration of high temperature solid oxide fuel cells with gas turbines to form high efficiency, hybrid generators is receiving significant attention within both the academic and industrial communities. Various systems have been proposed or demonstrated, and which cover a range of sizes from low power generators suitable for domestic power generation through to larger systems in the megawatt size range. The performance of such hybrid systems depends on the matching of the fuel cell and gas turbine through optimisation of the system pressure ratio and reactant flow rates. Losses associated with non-ideal cycle components are significant and vary with component size, and must be taken into account if optimal performance is to be achieved. This paper presents an intentionally very simple numerical model of the hybrid system, so that the effect of key component efficiencies on the overall cycle efficiency can be examined easily. These component efficiencies of course scale with size, and the results presented suggest that hybrid cycles with total power output of order several MW are preferable.

Thermodynamic Performance of a Gas Turbine Plant Combined With a Solid Oxide Fuel Cell

2008 ◽  
Author(s):  
Yousef Haseli ◽  
Ibrahim Dincer ◽  
Greg F. Naterer
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Gas Turbine ◽  
Compression Ratio ◽  
Solid Oxide ◽  
Specific Power ◽  
Inlet Temperature ◽  
Oxide Fuel ◽  
Turbine Inlet Temperature ◽  
Energy And Exergy

This paper undertakes a thermodynamic analysis of a high-temperature solid oxide fuel cell, combined with a conventional recuperative gas turbine. In the analysis the balance equations for mass, energy and exergy for the system as a whole and its components are written, and both energy and exergy efficiencies are studied for comparison purposes. These results are also verified with data available in the literature for typical operating conditions, the predictive model of the system is validated. The energy efficiency of the integrated cycle is obtained to be as high as 60.55% at the optimum compression ratio. These model findings indicate the influence of different parameters on the performance of the cycle and irreversibilities therein, with respect to the exergy destruction rate and/or entropy generation rate. The results show that a higher ambient temperature would lead to lower energy and exergy efficiencies, and lower net specific power. Furthermore, the results indicate that increasing the turbine inlet temperature results in decreasing both the energy and exergy efficiencies of the cycle, whereas it improves the total specific power output. However, an increase in either the turbine inlet temperature or compression ratio leads to a higher rate of irreversibility within the plant. It is shown that the combustor and SOFC contribute predominantly to the total irreversibility of the system; about 60 percent of which takes place in these components at a typical operating condition, with 31.4% for the combustor and 27.9% for the SOFC.

Performance Evaluation of Solid Oxide Fuel Cell Engines Integrated With Single/Dual-Spool Turbochargers

2011 ◽  
Vol 8 (6) ◽  
Author(s):  
So-Ryeok Oh ◽  
Jing Sun ◽  
Herb Dobbs ◽  
Joel King
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Control Strategies ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Operating Characteristics ◽  
Load Following ◽  
Fuel Flow

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.

scholarly journals Parametric Study of Fuel Cell and Gas Turbine Combined Cycle Performance

1997 ◽  
Author(s):  
Dawn Stephenson ◽  
Ian Ritchey
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Combined Cycle ◽  
Solid Oxide ◽  
Simple Cycle ◽  
Cycle Performance ◽  
Oxide Fuel ◽  
Combined Cycles

A number of cycles have been proposed in which a solid oxide fuel cell is used as the topping cycle to a gas turbine, including those recently described by Beve et al. (1996). Such proposals frequently focus on the combination of particular gas turbines with particular fuel cells. In this paper, the development of more general models for a number of alternative cycles is described. These models incorporate variations of component performance with key cycle parameters such as gas turbine pressure ratio, fuel cell operating temperature and air flow. Parametric studies are conducted using these models to produce performance maps, giving overall cycle performance in terms of both gas turbine and fuel cell design point operating conditions. The location of potential gas turbine and fuel cell combinations on these maps is then used to identify which of these combinations are most likely to be appropriate for optimum efficiency and power output. It is well known, for example, that the design point of a gas turbine optimised for simple cycle performance is not generally optimal for combined cycle gas turbine performance. The same phenomenon may be observed in combined fuel cell and gas turbine cycles, where both the fuel cell and the gas turbine are likely to differ from those which would be selected for peak simple cycle efficiency. The implications of this for practical fuel cell and gas turbine combined cycles and for development targets for solid oxide fuel cells are discussed. Finally, a brief comparison of the economics of simple cycle fuel cells, simple cycle gas turbines and fuel cell and gas turbine combined cycles is presented, illustrating the benefits which could result.

A Comparative Study on the Options in Combining Solid Oxide Fuel Cell With Gas Turbine

2015 ◽  
Author(s):  
Ji Hye Yi ◽  
Ju Hwan Choi ◽  
Tong Seop Kim
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Gas Turbine ◽  
Pressure Ratio ◽  
Solid Oxide ◽  
Inlet Temperature ◽  
Oxide Fuel ◽  
System Efficiency ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet

Various options in combining a solid oxide fuel cell (SOFC) with a gas turbine (GT) were compared in this study. The combination of an SOFC with either a simple gas turbine or a gas/steam turbine combined cycle was investigated. For each combined system, the effect of using a recuperative heat exchanger was examined. The design parameters of a state-of-the-art gas turbine for central power stations were used. The GT modeling included modulation of turbine coolant flow depending on turbine working conditions. An SOFC temperature of 900°C was used. Given a currently available reference voltage, pressure-dependent SOFC cell voltage was used. The analysis was divided into two parts. In the first part, the turbine inlet temperature of the reference gas turbine was given and the influence of pressure ratio was analyzed. In the second part, the influence of varying turbine inlet temperature was analyzed to search for optimal design conditions. The results showed that the SOFC/GTCC systems would provide considerably higher efficiencies than the SOFC/GT systems. The optimal pressure ratio in terms of system efficiency is over 30 for non-recuperated systems but is around 10 for recuperated systems. Reducing the extra fuel to the gas turbine combustor improves system efficiency, especially in the SOFC/GT systems. With zero extra fuel, efficiencies of all of the four systems exceed 70%, the highest of which is obtained by the recuperated SOFC/GTCC layout.

Environmental assessment of a hybrid system composed of solid oxide fuel cell, gas turbine and multiple effect evaporation desalination system

2020 ◽  
pp. 0958305X2097357
Author(s):  
Sobhan Jehandideh ◽  
Hasan Hassanzade ◽  
Seyyed Ehsan Shakib
Keyword(s):  
Fuel Cell ◽  
Gas Turbine ◽  
Pressure Ratio ◽  
Solid Oxide ◽  
Nox Emission ◽  
Emission Rates ◽  
Oxide Fuel ◽  
Exhaust Temperature ◽  
Desalination Plant ◽  
Compressor Pressure Ratio

This study deals with a solid oxide fuel cell- gas turbine (SOFC-GT) hybrid system coupled with a multi-effect evaporation desalination plant with steam condensation. The environmental evaluation is also done due to the importance of waste energy recovery especially waste heat in power generation systems. The evaporation desalination plant is studied for using the excess heat to produce freshwater. The thermodynamic relationships governing different components of the system are first provided, including fuel cells, heat exchangers, gas turbine, and desalination plant. Next, given the absence of previous research on the environmental effects of cogeneration systems, despite its necessity, the study system is analyzed from an environmental point of view. Accordingly, the impacts of the system performance parameters, including the fuel consumption coefficients, compressor pressure ratio, fuel pre-reforming percentage, and the steam to carbon ratio are investigated on the CO2, CO, and NOx emission rates. Based on the findings, it is concluded that of different species, the impacts of CO, CO2, and NOx emission rates are significant on the environment. Thus, the impacts of pressure ratio and pre-reforming percentage on their emission rates have been studied. The results revealed with increasing the compressor pressure ratio, increasing the fuel consumption coefficients, and decreasing the fuel cell's exhaust temperature, the CO and NOx emission rates and corresponding social costs diminished. On the other hand, with elevation of the ratio of steam to carbon, the recovery rate, the fuel cell's exhaust temperature, the concerned gas emission rates, and corresponding social costs increased.

Comparison of Molten Carbonate and Solid Oxide Fuel Cells for Integration in a Hybrid System for Cogeneration or Tri-Generation

2004 ◽  
Author(s):  
Georgia C. Karvountzi ◽  
Clifford M. Price ◽  
Paul F. Duby
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cells ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Molten Carbonate ◽  
Hybrid Cycle

High temperature fuel cells, such as molten carbonate fuel cells (MCFC) and solid oxide fuel cells (SOFC) can be integrated in a hybrid cycle with a gas turbine and a steam turbine and achieve overall lower heating value (LHV) efficiencies of about 70%. A hybrid cycle designed for cogeneration or tri-generation applications could lead to even higher overall LHV efficiencies. Tri-generation is the combined generation of power, heat and cooling from the same fuel source. The purpose of the present paper is to compare the performance of a 20MW MCFC system and a 20MW tubular SOFC system and assess their potential to cogeneration and tri-generation applications. The system includes a fuel cell, a gas turbine, a multiple pressure heat recovery steam generator (HRSG), a steam turbine and an absorption chiller (for cooling). The systems were designed and sized using GatecycleTM heat balance software by GE Enter Software, LLC. In order to optimize each system we developed curves showing LHV “electric” and “cogeneration” efficiency versus power for different ratios of “MCFC and SOFC fuel cell-to-gas turbines size.” At atmospheric pressure and at 675°C (1247°F) the 20MW MCFC system achieves “electric” efficiency of 69.5%. The SOFC at the same pressure and at 980°C achieves 67.3% “electric” efficiency. The MCFC alone is more efficient (58%) than the SOFC alone (56%). However the SOFC produces more heat than the MCFC leading to slightly higher cogeneration and tri-generation efficiencies. Pressurized operation at 9atm boosts the performance of the SOFC system to higher efficiencies (70.5%). Pressurized operation is problematic for the MCFC due to increased cathode corrosion leading to cathode dissolution as well as sealant and interconnection problems. However we can pressurize the MCFC system independently of the fuel cell with the integration of a gas turbine with a compressor pressure ratio of 10 to 16. Thus we achieve efficiencies close to 69%. In conclusion SOFC is more efficiently integrated in a hybrid configuration with gas turbine and a steam turbine for trigeneration applications when pressurized. MCFC is more efficiently integrated at atmospheric and pressures below 6 atm.

Effect of Fuel Cell Operation Pressure on the Optimization of a Hybrid System SOFC/Turbine for Cogeneration

2004 ◽  
Author(s):  
Georgia C. Karvountzi ◽  
Clifford M. Price ◽  
Paul F. Duby
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Hybrid System ◽  
Heat Balance ◽  
Gas Turbines ◽  
Solid Oxide ◽  
Oxide Fuel

A solid oxide fuel cell (SOFC) integrated in a hybrid system with a gas turbine can achieve lower heating value (LHV) power of efficiencies of about 70%. Given the high operating temperature of the SOFC, it produces high grade heat, and a hybrid system designed for cogeneration may achieve total LHV efficiencies of 78% of 80% without post combustion and 85%–88% with post combustion. The present paper illustrates the optimum integration of a tubular solid oxide fuel cell in a cogeneration cycle with a multiple pressure heat recovery steam generator (HRSG) and a back pressure steam turbine. We considered fuel cells of 7.5 MW, 9 MW, 15 MW, 15 MW, 18 MW, 22.5 MW and 27 MW by scaling up published data for a 1.2 MW tubular solid oxide fuel cell. The operating pressures were 3 and 9atm. We used GateCycle™ heat balance software by GE Enter Software, LLC, to design a 20–40 MW high efficiency cogeneration plant. We performed a calculation of the heat balance of the fuel cell stack in Microsoft® Excel and then we imported the results into GateCycle™. We developed curves showing LHV “electric” efficiency versus power for different ratios of “fuel cell-to-gas turbine size”. Pressurization has a positive impact on the fuel cell polarization curve leading to higher power output. The gain in electric power, however, is offset by the additional power requirement of the compressor at higher pressures. Our analysis shows that an optimum pressure of about 9 atmospheres results in an overall hybrid system power efficiency of about 70% and a LHV “cogeneration” efficiency of about 80%. In conclusion, high efficiencies are obtained by optimization of a hybrid system consisting of pressurized high temperature fuel cells with gas turbines and a steam turbine.

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