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.

Assessment of the Potential of Combined Micro Gas Turbine and High Temperature Fuel Cell Systems

2002 ◽  
Author(s):  
Dieter Bohn ◽  
Nathalie Po¨ppe ◽  
Joachim Lepers
Keyword(s):  
Fuel Cells ◽  
High Temperature ◽  
Fuel Cell ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Advanced Materials ◽  
Cell Systems ◽  
Micro Gas Turbine ◽  
Technological Assessment

The present paper reports a detailed technological assessment of two concepts of integrated micro gas turbine and high temperature (SOFC) fuel cell systems. The first concept is the coupling of micro gas turbines and fuel cells with heat exchangers, maximising availability of each component by the option for easy stand-alone operation. The second concept considers a direct coupling of both components and a pressurised operation of the fuel cell, yielding additional efficiency augmentation. Based on state-of-the-art technology of micro gas turbines and solid oxide fuel cells, the paper analyses effects of advanced cycle parameters based on future material improvements on the performance of 300–400 kW combined micro gas turbine and fuel cell power plants. Results show a major potential for future increase of net efficiencies of such power plants utilising advanced materials yet to be developed. For small sized plants under consideration, potential net efficiencies around 70% were determined. This implies possible power-to-heat-ratios around 9.1 being a basis for efficient utilisation of this technology in decentralised CHP applications.

A New Concept for High Temperature Fuel Cell Hybrid Systems Using Supercritical Carbon Dioxide

2009 ◽  
Vol 6 (2) ◽  
Author(s):  
D. Sánchez ◽  
R. Chacartegui ◽  
F. Jiménez-Espadafor ◽  
T. Sánchez
Keyword(s):  
Carbon Dioxide ◽  
Fuel Cells ◽  
High Temperature ◽  
Fuel Cell ◽  
Supercritical Carbon Dioxide ◽  
Hybrid Systems ◽  
Cell Hybrid ◽  
Gas Turbines ◽  
Solid Oxide ◽  
Molten Carbonate

Hybrid power systems based on high temperature fuel cells are a promising technology for the forthcoming distributed power generation market. For the most extended configuration, these systems comprise a fuel cell and a conventional recuperative gas turbine engine bottoming cycle, which recovers waste heat from the cell exhaust and converts it into useful work. The ability of these gas turbines to produce useful work relies strongly on a high fuel cell operating temperature. Thus, if molten carbonate fuel cells or the new generation intermediate temperature solid oxide fuel cells are used, the efficiency and power capacity of the hybrid system decrease dramatically. In this work, carbon dioxide is proposed as the working fluid for a closed supercritical bottoming cycle, which is expected to perform better for intermediate temperature heat recovery applications than the air cycle. Elementary fuel cell lumped-volume models for both solid oxide and molten carbonate are used in conjunction with a Brayton cycle thermodynamic simulator capable of working with open/closed and air/carbon dioxide systems. This paper shows that, even though the new cycle is coupled with an atmospheric fuel cell, it is still able to achieve the same overall system efficiency and rated power than the best conventional cycles being currently considered. Furthermore, under certain operating conditions, the performance of the new hybrid systems beats that of existing pressurized fuel cell hybrid systems with conventional gas turbines. From the results, it is concluded that the supercritical carbon dioxide bottoming cycle holds a very high potential as an efficient power generator for hybrid systems. However, costs and balance of plant analysis will have to be carried out in the future to check its feasibility.

Optimization of a MCFC/Turbine Hybrid System for Cogeneration

2003 ◽  
Author(s):  
Georgia C. Karvountzi ◽  
Clifford M. Price ◽  
Paul F. Duby
Keyword(s):  
Fuel Cells ◽  
High Temperature ◽  
Fuel Cell ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Hybrid System ◽  
Heat Balance ◽  
Gas Turbines ◽  
Cogeneration Plant ◽  
Hybrid Cycle

High temperature fuel cells can be integrated in a hybrid cycle with a gas turbine and achieve lower heating value (LHV) efficiencies of about 70%. A hybrid cycle designed for cogeneration applications could lead to even higher LHV efficiencies such as 78% to 80% without post combustion and 85%–90% with post combustion. The purpose of the present paper is to optimize the integration of a high temperature fuel cell in a cogeneration cycle. We used Gatecycle™ heat balance software by GE Enter Software, LLC, to design a 20–80 MW high efficiency cogeneration plant. Since Gatecycle™ does not have an icon for the fuel cell, we calculated the heat balance for the fuel cell stack in Microsoft® Excel and we imported the results into Gatecycle™. We considered a 8.5 MW, a 17 MW and a 34 MW fuel cell by scaling up of the commercially available 3MW molten carbonate fuel cell (MCFC). Our goal was to evaluate the optimum ratio between the fuel cell size and gas turbine size using a family of curves we developed showing LHV “electric” efficiency versus power for different ratios of “fuel cell–to–gas turbines size”. Similar curves showing LHV “cogeneration” efficiency are also presented. In addition configurations with a back pressure steam turbine and with a condensing steam turbine are evaluated. The influence of steam generation pressure in the overall system efficiency is discussed, as well as the performance of the hybrid system for different temperatures (0°F–80°F) and elevations (0 ft–3000 ft). Our conclusion is that high temperature fuel cells in a hybrid configuration with gas turbines could be successfully integrated into a cogeneration plant to achieve very high efficiencies.

Comparison of a Multi-Megawatt High Temperature Fuel Cell System With Reciprocating Engines and Aero-Derivative Gas Turbines

2008 ◽  
Author(s):  
Georgia C. Karvountzi ◽  
Paul F. Duby
Keyword(s):  
Fuel Cells ◽  
High Temperature ◽  
Fuel Cell ◽  
Gas Turbine ◽  
Hybrid System ◽  
Gas Turbines ◽  
Cell System ◽  
Combined Cycle ◽  
Simple Cycle ◽  
Fuel Cell System

High temperature fuel cells can be successfully integrated in a simple cycle or in a combined cycle configuration and achieve lower heating value (LHV) efficiencies greater than gas turbines and reciprocating engines. A simple cycle fuel cell system reaches 50 to 51% LHV efficiencies. A fuel cell system integrated with gas and steam turbines in a hybrid system could lead to LHV efficiencies of 70% to 72%. An aero-derivative gas turbine that is the most efficient simple cycle gas turbine achieves 40% to 46% thermal efficiency and a new generation reciprocating engine 39% to 42%. Upon integration in a combined cycle configuration with steam injection, aero-derivative gas turbines potentially reach LHV efficiencies of 55% to 58%. The purpose of the present paper is to compare initially the performance of a stand alone fuel cell with a stand alone gas turbine and a stand alone reciprocating engine. Then the fuel cell is integrated in a hybrid system and it is compared with a gas turbine combined cycle plant. The system sizes explored are 5MW in the stand alone case, and 20MW, 30MW, 60MW, 100MW and 200MW in the hybrid / combined cycle case. The performance of the hybrid system was reviewed under different ambient temperatures (0° F–90° F) and site elevations (0 ft–3000 ft). High temperature fuel cells are more efficient and have lower emissions than gas turbines and reciprocating engines. However fuel cells cannot be used for peak power generation due to long start-up time or load following applications.

Near-Zero CO2 Emissions Power Plant Based on High Temperature Fuel Cells

2019 ◽  
Author(s):  
Roberto Carapellucci ◽  
Roberto Cipollone ◽  
Davide Di Battista
Keyword(s):  
Carbon Dioxide ◽  
Fuel Cells ◽  
High Temperature ◽  
Fuel Cell ◽  
Power Plant ◽  
Energy Conversion ◽  
Gas Turbine ◽  
Co2 Emissions ◽  
Cathode Side ◽  
Energy Conversion Systems

Abstract The recent awareness on the environmental issues related to global warming is leading to the search for always more efficient energy conversion systems and, mainly, with very low carbon dioxide emissions. In fact, they are strictly related to the combustion reaction of fossil fuels which is the main process of the actual power generation technology. In this regard, fuel cells are energy conversion systems which are characterized by higher efficiency and near-zero CO2 emissions. Their novel integration with conventional power plants participates to the concept of the decarbonization of the economy. In this work, the integration of two high temperature fuel cells (HTFC) with a gas turbine power plant has been proposed and investigated, thanks to the combination of a physical model of the fuel cells and a numerical one of the components involved in the gas turbine cycle. In the layout studied, fresh air is compressed, pre-heated and used in a Solid Oxide Fuel Cell (SOFC), where the high operating temperature and the exothermic process give exhaust gases at very high temperatures, suitable for an expansion in a turbine. After the expansion, the gases are rich of CO2 and, so, they can be sent to the cathode side of a Molten Carbonate Fuel Cell (MCFC). Hence, the so-defined integrated plant is composed by three power units: a turbine, a SOFC and a MCFC; operating pressure, fuel need, oxygen and carbon dioxide utilizations in the fuel cells are parameterized in order to optimize the whole plant and find additional room of energy exploitation. Moreover, the MCFC acts as an active device for carbon separation, introducing further environmental benefits.

The Thermodynamic Evaluation and Optimization of Fuel Cell Systems

2006 ◽  
Vol 3 (2) ◽  
pp. 155-164 ◽  
Author(s):  
N. Woudstra ◽  
T. P. van der Stelt ◽  
K. Hemmes
Keyword(s):  
Heat Transfer ◽  
Fuel Cells ◽  
High Temperature ◽  
Fuel Cell ◽  
Energy Conversion ◽  
System Optimization ◽  
Fuel Conversion ◽  
Cell Systems ◽  
Electrochemical Conversion ◽  
Conversion Efficiencies

Energy conversion today is subject to high thermodynamic losses. About 50% to 90% of the exergy of primary fuels is lost during conversion into power or heat. The fast increasing world energy demand makes a further increase of conversion efficiencies inevitable. The substantial thermodynamic losses (exergy losses of 20% to 30%) of thermal fuel conversion will limit future improvements of power plant efficiencies. Electrochemical conversion of fuel enables fuel conversion with minimum losses. Various fuel cell systems have been investigated at the Delft University of Technology during the past 20 years. It appeared that exergy analyses can be very helpful in understanding the extent and causes of thermodynamic losses in fuel cell systems. More than 50% of the losses in high temperature fuel cell (molten carbonate fuel cell and solid oxide fuel cell) systems can be caused by heat transfer. Therefore system optimization must focus on reducing the need for heat transfer as well as improving the conditions for the unavoidable heat transfer. Various options for reducing the need for heat transfer are discussed in this paper. High temperature fuel cells, eventually integrated into gas turbine processes, can replace the combustion process in future power plants. High temperature fuel cells will be necessary to obtain conversion efficiencies up to 80% in the case of large scale electricity production in the future. The introduction of fuel cells is considered to be a first step in the integration of electrochemical conversion in future energy conversion systems.

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.

Performance Analysis on SOFC-HCCI Engine Hybrid System

2012 ◽  
Author(s):  
Sung Ho Park ◽  
Young Duk Lee ◽  
Sang Gyu Kang ◽  
Kook Young Ahn
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Hybrid Systems ◽  
Hybrid System ◽  
Gas Turbines ◽  
Waste Heat ◽  
Metal Catalyst ◽  
Molten Carbonate ◽  
Hcci Engine ◽  
Ci Engines

Fuel cell systems are currently regarded as a promising type of energy conversion system. Various types of fuel cell have been developed and investigated worldwide for portable, automotive, and stationary applications. In particular, in the case of large-scale stationary applications, the high-temperature fuel cells known as the molten carbonate fuel cell (MCFC) and the solid oxide fuel cell (SOFC) have been used as a power source due to their higher efficiency compared to low-temperature fuel cells. Because SOFCs have many advantages, including a high power density, low corrosion, and operability without a metal catalyst, many efforts to develop a SOFC hybrid system have been undertaken. SOFC hybrid systems with a gas turbine or engine show improved system efficiency through their utilization of waste heat and unreacted fuel. Especially, the internal combustion engine has the advantage of robustness, easy maintenance, and a low cost compared to gas turbines, this type is more adaptable for use in a hybrid system with a SOFC. However, the engine should be operated stably at a high air fuel ratio because the SOFC anode exhaust gas has a low fuel concentration. The homogeneous charge compression ignition (HCCI) engine has both the advantages of SI and CI engines. Moreover, the lean burn characteristics of the HCCI engine make it a strong candidate for SOFC hybrid systems. The objective of this work is to develop a novel cycle composed of a SOFC and a HCCI engine. In order to optimize the SOFC-HCCI hybrid system, a system analysis is conducted here using the commercial software Aspen Plus®. The SOFC model is validated with experimental data. The engine model is developed based on an empirical equation that considers the ignition delay time. The performance of the hybrid system is compared with that of a SOFC stand-alone system to confirm the optimization of the system. This study will be useful for the development of a new type of hybrid system which uses a fuel cell and an optimized system.

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.

Power Cycle Integration and Efficiency Increase of Molten Carbonate Fuel Cell Systems

2005 ◽  
Vol 3 (4) ◽  
pp. 375-383 ◽  
Author(s):  
Petar Varbanov ◽  
Jiří Klemeš ◽  
Ramesh K. Shah ◽  
Harmanjeet Shihn
Keyword(s):  
Fuel Cells ◽  
High Temperature ◽  
Fuel Cell ◽  
Gas Turbines ◽  
Waste Heat ◽  
Combined Cycle ◽  
Molten Carbonate Fuel Cell ◽  
Steam Turbines ◽  
Molten Carbonate ◽  
Carbonate Fuel Cell

A new view is presented on the concept of the combined cycle for power generation. Traditionally, the term “combined cycle” is associated with using a gas turbine in combination with steam turbines to better utilize the exergy potential of the burnt fuel. This concept can be broadened, however, to the utilization of any power-generating facility in combination with steam turbines, as long as this facility also provides a high-temperature waste heat. Such facilities are high temperature fuel cells. Fuel cells are especially advantageous for combined cycle applications since they feature a remarkably high efficiency—reaching an order of 45–50% and even close to 60%, compared to 30–35% for most gas turbines. The literature sources on combining fuel cells with gas and steam turbines clearly illustrate the potential to achieve high power and co-generation efficiencies. In the presented work, the extension to the concept of combined cycle is considered on the example of a molten carbonate fuel cell (MCFC) working under stationary conditions. An overview of the process for the MCFC is given, followed by the options for heat integration utilizing the waste heat for steam generation. The complete fuel cell combined cycle (FCCC) system is then analyzed to estimate the potential power cost levels that could be achieved. The results demonstrate that a properly designed FCCC system is capable of reaching significantly higher efficiency compared to the standalone fuel cell system. An important observation is that FCCC systems may result in economically competitive power production units, comparable with contemporary fossil power stations.

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