Fundamental thermodynamics of fuel cell, engine, and combined heat and power system efficiencies

2002 ◽  
Vol 216 (6) ◽  
pp. 407-417 ◽  
Author(s):  
F J Barclay
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Gas Turbines ◽  
Equilibrium Diagram ◽  
Equilibrium Constants ◽  
Calorific Value ◽  
Combined Heat And Power ◽  
Chemical Exergy ◽  
Chp System ◽  
The Right

At the 2001 Grove Symposium on Fuel Cells attended by representatives of the world-wide fuel cell industry, fuel cells and fuel cells integrated with gas turbines were discussed. Combined heat and power (CHP) aspects were also discussed. Without exception, efficiency figures were irrationally based on the measured, Carnot-limited, lower calorific value (CV) of the fuel in energy units J. The rational basis, on the other hand, is the fuel chemical exergy (work units, Ws) calculated via an equilibrium diagram. In Joules experiment 1 Ws ≫ 1 J, where the irreversible ≫ must not become an = sign. A misnomer like potential energy (exergy) fits on the left of the diagram, CV on the right. Moreover credence was also given, at the symposium, to the popular misconception that a CHP system has an efficiency of the order of 80 per cent. An essential precursor to reading the paper is to grasp the theory of chemical equilibrium and equilibrium constants [3] as an aid to exploring the equilibrium diagram mentioned above.

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.

Techno-Economic Optimal Design of Solid Oxide Fuel Cell Systems for Micro-Combined Heat and Power Applications in the U.S.

2010 ◽  
Vol 7 (3) ◽  
Author(s):  
Robert J. Braun
Keyword(s):  
Life Cycle ◽  
Fuel Cell ◽  
Life Cycle Cost ◽  
Combined Heat And Power ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Chp System ◽  
System Configurations ◽  
System Designs ◽  
The U.S

A techno-economic optimization study investigating optimal design and operating strategies of solid oxide fuel cell (SOFC) micro-combined heat and power (CHP) systems for application in U.S. residential dwellings is carried out through modeling and simulation of various anode-supported planar SOFC-based system configurations. Five different SOFC system designs operating from either methane or hydrogen fuels are evaluated in terms of their energetic and economic performances and their overall suitability for meeting residential thermal-to-electric ratios. Life-cycle cost models are developed and employed to generate optimization objective functions, which are utilized to explore the sensitivity of the life-cycle costs to various system designs and economic parameters and to select optimal system configurations and operating parameters for eventual application in single-family, detached residential homes in the U.S. The study compares the results against a baseline SOFC-CHP system that employs primarily external steam reforming of methane. The results of the study indicate that system configurations and operating parameter selections that enable minimum life-cycle cost while achieving maximum CHP-system efficiency are possible. Life-cycle cost reductions of over 30% and CHP efficiency improvements of nearly 20% from the baseline system are detailed.

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 Energy Conversion Analysis of a Novel Solar Thermochemical System Coupled With Fuel Cells

2015 ◽  
Author(s):  
Ian Vinck ◽  
Nesrin Ozalp
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Energy Conversion ◽  
Calorific Value ◽  
Electricity Production ◽  
Thermal Reactor ◽  
Hydrogen Fuel Cell ◽  
Combined System ◽  
Concentrated Solar Energy ◽  
Byproduct Formation

Fossil fuels have been the main supply of power generation for use in manufacturing, transportation, residential and commercial sectors. However, environmentally adverse effects of fossil fuel conversion systems combined with pending shortage raise major concerns. As a promising approach to tackle these challenges, this paper presents a novel energy conversion system comprising of a solar thermal reactor coupled with hydrogen fuel cell and carbon fuel cell for electricity generation. The system uses concentrated solar energy for high temperature heat which upgrades the calorific value of the feedstock by 8%. The paper describes the components and characteristics of the proposed concept and models the energy flow of this system. A comparison based on unit mass feedstock supply is made with conventional Brayton cycles for electricity production. The results show that the extent of acetylene byproduct conversion in the solar reactor is of crucial importance to ensure competitiveness. Depending on the fuel cells efficiency and even more on the extent of byproduct formation, the results show that the overall chemical-to-electrical efficiency of this combined system ranges from 35 to 58%.

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.

Greenhouse Gas Reduction Potential With Combined Heat and Power With Distributed Generation Prime Movers

2012 ◽  
Author(s):  
Scott J. Curran ◽  
Timothy J. Theiss ◽  
Michael J. Bunce
Keyword(s):  
Fuel Cells ◽  
Natural Gas ◽  
Distributed Generation ◽  
Gas Turbines ◽  
Reduction Potential ◽  
Combined Heat And Power ◽  
Ghg Reduction ◽  
Prime Movers ◽  
Electrical Generation ◽  
The U.S

Pending or recently enacted greenhouse gas regulations and mandates are leading to the need for current and feasible GHG reduction solutions including combined heat and power (CHP). Distributed generation using advanced reciprocating engines, gas turbines, microturbines and fuel cells has been shown to reduce greenhouse gases (GHG) compared to the U.S. electrical generation mix due to the use of natural gas and high electrical generation efficiencies of these prime movers. Many of these prime movers are also well suited for use in CHP systems which recover heat generated during combustion or energy conversion. CHP increases the total efficiency of the prime mover by recovering waste heat for generating electricity, replacing process steam, hot water for buildings or even cooling via absorption chilling. The increased efficiency of CHP systems further reduces GHG emissions compared to systems which do not recover waste thermal energy. Current GHG mandates within the U.S Federal sector and looming GHG legislation for states puts an emphasis on understanding the GHG reduction potential of such systems. This study compares the GHG savings from various state-of-the-art prime movers. GHG reductions from commercially available prime movers in the 1–5 MW class including, various industrial fuel cells, large and small gas turbines, micro turbines and reciprocating gas engines with and without CHP are compared to centralized electricity generation including the U.S. mix and the best available technology with natural gas combined cycle power plants. The findings show significant GHG saving potential with the use of CHP. Also provided is an exploration of the accounting methodology for GHG reductions with CHP and the sensitivity of such analyses to electrical generation efficiency, emissions factors and most importantly recoverable heat and thermal recovery efficiency from the CHP system.

Evaluation of Energy, Environmental, and Economic Characteristics of Fuel Cell Combined Heat and Power Systems for Residential Applications

2003 ◽  
Vol 125 (3) ◽  
pp. 208-220 ◽  
Author(s):  
M. Burak Gunes ◽  
Michael W. Ellis
Keyword(s):  
Life Cycle ◽  
Fuel Cell ◽  
Thermal Energy ◽  
Life Cycle Cost ◽  
Energy Use ◽  
Combined Heat And Power ◽  
Environmental Benefits ◽  
Design Parameters ◽  
Single Family ◽  
Chp System

Residential combined heat and power (CHP) systems using fuel cell technology can provide both electricity and heat and can substantially reduce the energy and environmental impact associated with residential applications. The energy, environmental, and economic characteristics of fuel cell CHP systems are investigated for single-family residential applications. Hourly energy use profiles for electricity and thermal energy are determined for typical residential applications. A mathematical model of a residential fuel cell based CHP system is developed. The CHP system incorporates a fuel cell system to supply electricity and thermal energy, a vapor compression heat pump to provide cooling in the summer and heating in the winter, and a thermal storage tank to help match the available thermal energy to the thermal energy needs. The performance of the system is evaluated for different climates. Results from the study include an evaluation of the major design parameters of the system, load duration curves, an evaluation of the effect of climate on energy use characteristics, an assessment of the reduction in emissions, and a comparison of the life cycle cost of the fuel cell based CHP system to the life cycle costs of conventional residential energy systems. The results suggest that the fuel cell CHP system provides substantial energy and environmental benefits but that the cost of the fuel cell sub-system must be reduced to roughly $500/kWe before the system can be economically justified.

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.

Dynamic Simulation of a Solid Oxide Fuel Cell System for Micro Combined Heat and Power Application

2013 ◽  
Vol 336-338 ◽  
pp. 695-699 ◽  
Author(s):  
Ying Wei Kang ◽  
Wei Huang ◽  
Yang Xue ◽  
Guang Yi Cao ◽  
Heng Yong Tu
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Thermal Inertia ◽  
System Optimization ◽  
Combined Heat And Power ◽  
Cell System ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Dynamic Simulations ◽  
Chp System

In the past decade, developing solid oxide fuel cell (SOFC) systems for micro combined heat and power applications (micro-CHP, 1-10 kWe) is one of the hot spots in the world energy field. To meet the requirements for system optimization and control design of SOFC micro-CHP systems, in this paper a dynamic model of an SOFC micro-CHP system is developed, based on which dynamic simulations are also carried out. Simulation results show that the present model can reflect the behavior of the SOFC micro-CHP system quite well; the influence of one component on another is an important factor to determine system dynamic behavior; as the system comprises many components and concerns different physical and chemical processes, it has dynamic processes with several kinds of time scales; for the air preheating need, the heat-exchange area of air pre-heater is quite big, which leads to its big thermal inertia, and causes the dynamic process lasting for several ten thousands of seconds.

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