References Lds
1. Physical and Thermodynamic Properties of Elements and Compounds, Girdler Catalysts, Chemetron Corporation, Catalysts Division. 2. J. M. Smith, H. C. Van Ness, Introduction to Chemical Engineering Thermodynamics, Third Edition, McGraw-Hill, 1975. 3. Chemistry Principles and Applications, M.J. Sienko, R.A. Plane, McGraw-Hill, New York, NY, 1979. 4. D.B. Stauffer, J.S. White, JH. Hirschenhofer, An ASPEN SP MCFC Performance User Block, DOE Contract DE-AC21-89-MC25177, Task 7, July 1991. 5. D.B....
Effect of Impurities 1
The concentrations of impurities entering the PAFC are very low relative to diluents and reactant gases, but their impact on performance is significant. Some impurities e.g., sulfur compounds originate from fuel gas entering the fuel processor and are carried into the fuel cell with the reformed fuel, whereas others e.g., CO are produced in the fuel processor. Carbon Monoxide The presence of CO in a H2-rich fuel has a significant effect on anode performance because CO affects Pt electrodes...
Effects of Cell Life Cfp
The endurance of the cell stack is of primary concern for SOFCs. As SOFC technology has continued to approach commercialization, research in this area has increased and improvements made. The Siemens Westinghouse state-of-the-art tubular design has been validated by continuous electrical testing of over 69,000 hours with less than 0.5 voltage degradation per 1,000 hours of operation. This tubular design is based on the early calcia-stabilized zirconia porous support tube PST . In the current...
Natural Gas Fueled Pressurized SOFC System
This natural gas fuel cell power system is based on a pressurized TSOFC combined with a combustion turbine developed by Siemens Westinghouse 52 . Most TSOFC power plant concepts developed to date have been based on atmospheric operation. However, as shown in 53. The referenced Siemens Westinghouse publication presented the cycle concept and overall performance values. Neither specific stream information nor assumptions were presented. The stream data and assumptions presented here were...
Figure Advanced WaterCooled PAFC Performance
The atmospheric pressure on-site short stack consisting of 32 cells obtained an initial performance of 0.65 volts cell at 200 ASF 215 mA cm2 or 0.139 W cm2. The performance degradation rate was less than 4 mV 1000 hours during the 4500 hour test. Single cells tested at atmospheric conditions achieved a 500 hour performance of approximately 0.75 volts cell at 225 ASF 242 mA cm or 0.182 W cm . The results from this program represent the highest performance of full-size phosphoric acid cells and...
Codes Standards
A summary of existing and pending fuel cell related codes and standards is presented in Table 11-2. More detailed descriptions are provided subsequently based on their specific area of Table 11-2 Summary of Related Codes and Standards Table 11-2 Summary of Related Codes and Standards Performance Test Code - Will provide test procedures, methods and definitions for the performance characterization of fuel cell power systems. Standards coordinating committee - fuel cells, photo-voltaics,...
nnini i iimu iirn W O C
Figure 8-3 Cross Section in the Axial Direction of the of an Early Tubular Configuration for SOFCs 8 , Figure 2, p. 256 Figure 8-4 Cross Section in the Axial Direction of the Series-Connected Cells of an Early Bell and Spigot Configuration for SOFCs 15 , Figure 24, p. 332 Figure 8-4 Cross Section in the Axial Direction of the Series-Connected Cells of an Early Bell and Spigot Configuration for SOFCs 15 , Figure 24, p. 332 Figure 8-5 Cross Section of Present Tubular Configuration for SOFCs 2...
Summary of Equations for AFC
The preceding sections described parametric performance based on various referenced data at differing cell conditions. It is suggested that the following set of equations be used unless the reader prefers other data or rationale. Pressure Vp mV .15 T oK log P2 P1 1 atm P 100 atm 4-4 Temperature Vt mV 4.0 T2-T1 Temperature VT mV 0.7 T2-Ti Current Density Vj mV .18 J for T 63oC, at 100 mA cm2 4-5 for T gt 63oC, at 100 mA cm2 4-6 for J 40-100 mA cm2 operating in O2 4-8 with 9 N KOH at 55-60oC. for...
Electrochemical Society Extended Abstract Fall Meeting 1976 Las Vegas
1. R.H. Arendt, J. Electrochem. Soc., 129, 942, 1982. 2. H.C. Maru, L.G. Marianowski, Extended Abstracts, Abstract 31, Fall Meeting of the Electrochemical Society, October 17-22, 1976, Las Vegas, NV, Pg. 82, 1976. 3. J. Mitteldorf, G. Wilemski, J. Electrochem. Soc., 131, 1784, 1984. 4. H.C. Maru, A. Pigeaud, R. Chamberlin, G. Wilemski, in Proceedings of the Symposium on Electrochemical Modeling of Battery, Fuel Cell, and Photoenergy Conversion Systems, edited by J.R. Selman and H.C. Maru, The...
Effect of Impurities Gxd
Gasified coal is expected to be the major source of fuel gas for MCFCs, but because coal contains many contaminants in a wide range of concentrations, fuel derived from this source also contains a considerable number of contaminants. A critical concern with these contaminants is the concentration levels that can be tolerated by MCFCs without suffering significant degradation in 32 See Table 11.1 for contaminant levels found in fuel gases from various coal gasification processes. performance or...
Effects of Current Density Cvc
The voltage level of a SOFC is reduced by ohmic, activation, and concentration losses, which increase with increasing current density. The magnitude of this loss is described by the following equation that was developed from information in the literature 36,29,37,38,39,40 where J is the current density mA cm at which the cell is operating. The latest AES cells by Siemens Westinghouse exhibit the following performance Figure 8-15 Voltage-Current Characteristics of an AES Cell 1.56 cm Diameter,...
References
1. A.J. Appleby, F.R. Foulkes, Fuel Cell Handbook, Van Nostrand Reinhold, New York, NY, 1989. 2. Report of the DOE Advanced Fuel-Cell Commercialization Working Group, Edited by S.S. Penner, DOE ER 0643, prepared by the DOE Advanced Fuel Cell Working Group AFC2WG or the United States Department of Energy under Contract No. DEFG03-93ER30213, March 1995. 3. K. Kordesch, J. Gsellmann, S. Jahangir, M. Schautz, in Proceedings of the Symposium on Porous Electrodes Theory and Practice, Edited by H.C....
Natural Gas Processing
The major constituents of pipeline gas are methane, ethane, propane, CO2, and, in some cases, N2. Sulfur containing odorants mercaptans, disulfides, or commercial odorants are added for leak detection. Because neither fuel cells nor commercial reformer catalysts are sulfur tolerant, the sulfur must be removed. This is usually accomplished with a zinc oxide sulfur polisher and the possible use of a hydrodesulfurizer, if required. The zinc oxide polisher is able to remove the mercaptans and...
Effect of Pressure 1
The dependence of reversible cell potential on pressure is evident from the Nernst equation. For a change in pressure from P1 to P2, the change in reversible potential AVp is given by where the subscripts a and c refer to the anode and cathode, respectively. In an MCFC with the anode and cathode compartments at the same pressure i.e., P1 P1,a P1,c and P2 P2,a P2,c P2 I P2 AVp mV 20 ln I 46 log Thus, a tenfold increase in cell pressure corresponds to an increase of 46 mV in the reversible cell...
Effect of Reactant Gas Composition and Utilization 1
The voltage of MCFCs varies with the composition of the reactant gases. The effect of reactant gas partial pressure, however, is somewhat difficult to analyze. One reason involves the water gas shift reaction at the anode due to the presence of CO. The other reason is related to the consumption of both CO2 and O2 at the cathode. Data 55,64,65,66 show that increasing the reactant gas utilization generally decreases cell performance. As reactant gases are consumed in an operating cell, the cell...
Uf H
where H2,in and H2,out are the mass flow rates of H2 at the inlet and outlet of the fuel cell, respectively. However, hydrogen can be consumed by various other pathways, such as by chemical reaction i.e., with O2 and cell components and loss via leakage out of the cell. These pathways increase the apparent utilization of hydrogen without contributing to the electrical energy produced by the fuel cell. A similar type of calculation is used to determine the oxidant utilization. For the cathode in...
SOFC System Cost Structure
The main difference in SOFC stack cost structure as compared to PEFC cost relates to the simpler system configuration of the SOFC-based system. This is mainly due to the fact that SOFC stacks do not contain the type of high-cost precious metals that PEFCs contain. This is off-set in part by the relatively complex manufacturing process required for the manufacture of the SOFC electrode electrolyte plates and by the somewhat lower power density in SOFC systems. Low temperature operation enabled...
Coal Fueled SOFC System Vision
The coal fueled solid oxide fuel cell power system presented here is based on work performed for the Department of Energy's Vision 21 Program 57 to develop of high efficiency, low emission, fuel flexible including coal processes. This cycle is a coal-fueled version of the Siemens Westinghouse TSOFC cycle presented in Section 9.3.5 consists of a Destec gasifier, cascaded SOFCs at two pressure levels, an integrated reheat gas turbine, and a reheat steam turbine bottoming cycle. The high-pressure...
Fuel Cells Doe Metc 86 0241
1. N.Q. Minh, Ceramic Fuel Cells, J. Am. Ceram. Soc., p. 76 3 563-88, 1993. 2. Courtesy of Siemens Westinghouse. 3. T.H. Etsell, S.N. Flengas, J. Electrochem. Soc, p. 118, 1890 1971 . 4. A.O. Isenberg, in Proceedings of the Symposium on Electrode Materials and Processes for Energy Conversion and Storage, edited by J.D.E. Mclntyre, S. Srinivasan and F.G. Will, The Electrochemical Society, Inc., Pennington, NJ, 1977, p. 682. 5. A.O. Isenberg, in Proceedings of the Symposium on Electrode Materials...
Capital Cost Development
There is a need for an easily understood, flexible, and reasonably accurate methodology for rapidly estimating the cost of conceptual fuel cell power plants. One method proposed for estimating the cost of fuel cell power plants is to calculate distributive bulk costs as a function of the equipment cost using established factors based on conventional generating technologies. When applied in such a way as to compensate for the differences associated with a fuel cell plant, this approach can yield...
Sulfur Requirements
Present formula gasolines contain approximately 300 ppm. No. 2 fuel oil contains 2,200 to 2,600 ppm by weight of sulfur. Even pipeline gas contains sulfur-containing odorants mercaptans, disulfides, or commercial odorants for leak detection. Metal catalysts in the fuel reformer can be susceptible to sulfur poisoning and it is very important that sulfur in the fuel reformate be removed. Some researchers have advised limiting the sulfur content of the fuel in a stream reformer to less than 0.1...
Cell Configuration Options
As with the other cell types, it is necessary to stack SOFCs to increase the voltage and power being produced. Because there are no liquid components, the SOFC can be cast into flexible shapes Figure 8-1 . In the early 1960s, experimental SOFCs with a planar geometry were evaluated, but this geometry presented a problem for building cell stacks because of difficulties with fabricating large flat, thin cells and obtaining adequate gas seals. A tubular configuration i.e., cylindrical design...
Equilibrium Constants
Figure 11-1 presents the temperature dependence of the equilibrium constants for the water gas shift reaction, the carbon deposition Boudouard reaction reaction, 600 700 800 900 1000 1100 1200 1300 Temperature K Figure 11-1 Equilibrium Constants Partial Pressures in MPa for a Water Gas Shift, b Methane Formation, c Carbon Deposition Boudouard Reaction , and d Methane Decomposition J.R. Rostrup-Nielsen, in Catalysis Science and Technology, Edited by J.R. Anderson and M. Boudart, Springer-Verlag,...
Efficiency Calculations
Example 10-11 LHV, HHV Efficiency and Heat Rate Calculations Given a 2.0 MWAC fuel cell cycle operating on 700 lb hr of methane, what is a the HHV65 thermal input of the methane gas, b the LHV thermal input, c the HHV electric efficiency, d the LHV electric efficiency, and e the HHV Heat Rate Assume the higher and lower heating value of methane as 23,881 and 21,526 Btu lb respectively. a The HHV thermal input of the methane gas is HHV Thermal Input 700lb h CH4 2W Btu, HHVIfiM l 16.716 MMBtu h,...
Actual Performance
Large, complex computer models are used to characterize the actual operation of fuel cells based on minute details of cell component design physical dimensions, materials, etc. along with physical considerations transport phenomena, electrochemistry, etc. . These codes, often proprietary, are needed in the design and development of fuel cells, but would be cumbersome and time consuming for use in system analysis models. Simpler approaches are normally used for system studies. One approach, for...
Figure Overview of subsystems and components for SOFC and PEM systems
Figure 1-14 shows a simplified layout for an SOFC-based APU. The air for reformer operation and cathode requirements is compressed in a single compressor and then split between the unit operations. The external water supply shown in figure 1-14 will most likely not be needed the anode recycle stream provides water. Unreacted anode tail gas is recuperated in a tail gas burner. Additional energy is available in a SOFC system from enthalpy recovery from tail gas effluent streams that are typically...
Summary of Equations for PAFC
The preceding sections provide parametric performance based on various referenced data at differing cell conditions. It is suggested that the following set of equations be used unless the reader prefers other data or rationale. Figure 5-7 is provided as reference PAFC performances at 8.2 atm and ambient pressure. 18. Assumes graph operating conditions not provided are the same as associated text of Ref. 15. Temperature AVj mV 1.15 T2 - Ti Oxidant 1 atm lt P lt 10 atm 177 C lt T lt 218 C -11.1...
Alkaline Fuel Cell
The Alkaline Fuel Cell AFC was one of the first modern fuel cells to be developed, beginning in 1960. The application at that time was to provide on-board electric power for the Apollo space vehicle. Desirable attributes of the AFC include its excellent performance on hydrogen H2 and oxygen O2 compared to other candidate fuel cells due to its active O2 electrode kinetics and its flexibility to use a wide range of electrocatalysts, an attribute which provides development flexibility. The AFC...
Practical Thermodynamics
A logical first step in understanding the operation of a fuel cell is to define its ideal performance. Once the ideal performance is determined, losses can be calculated and then deducted from the ideal performance to describe the actual operation. Section 2.1.1 is a description of the thermodynamics that characterize ideal performance. Actual performance is addressed in Section 2.1.2. Section 2.1.3 provides a lead-in to the development of equations in Section 3 through Section 8 that quantify...
Natural Gas Fueled Internally Reformed MCFC System
Fuel Cell Energy expects to have its initial market entry MCFC power systems available in the year 2001, with mature megawatt class units projected to be available in 2004. These units will be produced in various sizes. Preliminary cycle information was received from FCE for a nominal 3 MW power plant. This cycle is presented in Figure 9-9 and is described below. Figure 9-9 Natural Gas Fueled MCFC Power System Figure 9-9 Natural Gas Fueled MCFC Power System Natural gas is cleaned of its sulfur...
References Cud
1. Communications with IFC, September 21, 1998. 2. J. Hirschenhofer, Latest Progress in Fuel Cell Technology, IEEE-Aerospace and Electronic Systems Magazine, 7, November 1992. 3. J. Hirschenhofer, Status of Fuel Cell Commercialization Efforts, American Power Conference, Chicago, IL, April 1993. 4. J. Appleby, in Proceedings of the Workshop on the Electrochemistry of Carbon, Edited by S. Sarangapani, J.R. Akridge and B. Schumm, The Electrochemical Society, Inc., Pennington, NJ, p. 251, 1984. 5....
Automotive Design Calculations
The total power, P, needed from a vehicle's power system must be sufficient for vehicle acceleration, aerodynamic drag losses, rolling resistance, changes in elevation, and auxiliary power for vehicle accessories 20,21 . These power terms are, respectively P mav 0.5 CdAfv3 mgCRV mgv sin P. Where P total power W m vehicle mass kg a vehicle acceleration m sec2 v vehicle velocity m sec CD aerodynamic drag coefficient Af vehicle area normal to direction of travel m g gravitation constant 9.8 m sec2...
Development Components
The primary focus of ongoing research is to improve the performance of the cell and lower its cost. The principal areas of development are improving cell membranes, handling the CO in the fuel stream, and refining electrode design. There has been an effort to incorporate system requirements into the fuel cell stack in order to simplify the overall system. This work has included a move toward operation with zero humidification at ambient pressure and direct fuel use. The Dow Chemical Company has...
Ideal Performance
The ideal performance of a fuel cell depends on the electrochemical reactions that occur with different fuels and oxygen as summarized in Table 2-1. Low-temperature fuel cells PEFC, AFC, and PAFC require noble metal electrocatalysts to achieve practical reaction rates at the anode and cathode, and H2 is the only acceptable fuel. With high-temperature fuel cells MCFC, ITSOFC, and SOFC , the requirements for catalysis are relaxed, and the number of potential fuels expands. Carbon monoxide poisons...
System Configuration and Technology Issues
Based on the system requirements discussed above, fuel cell APUs will consist of a fuel processor, a stack system and the balance of plant. Figure 1-13 lists the components required in SOFC and PEM based systems. The components needed in a PEM system for APU applications are similar to that needed in residential power. The main issue for components for PEM-based systems is the minimization or elimination of the use of external supplied water. For both PEM and SOFC systems, start-up batteries...
Gibbs Free Energy and Ideal Performance
The maximum electrical work Wel obtainable in a fuel cell operating at constant temperature and pressure is given by the change in Gibbs free energy AG 12 of the electrochemical reaction, where n is the number of electrons participating in the reaction, F is Faraday's constant 96,487 coulombs g-mole electron , and E is the ideal potential of the cell. If we consider the case of reactants and products being in the standard state, then 10. Constraints can limit the degree of part load operation...
References Wsb
1. Impact of Catalysis on Clean Energy in Road Transportation, P.G. Gray and J.C. Frost Johnson Matthey, Energy amp Fuels, Vol. 12, No. 6, pp. 1121 - 1129, 1998. 2. Private communication with Argonne National Laboratory, Argonne IL, August 2000. 3. Fuel Processing for Fuel Cell Power Systems, S. Ahmed, R. Kumar, and M. Krumpelt, ANL, Fuel Cells Bulletin, Elsevier Scientific, Ltd., ISSN 1464-2859, No. 12, September 1999. 4. Fuel Choices for Fuel Cell Powered Vehicles, J. Holmes, statement before...
Natural Gas Fueled MultiStage Solid State Power Plant System
The Fuel Cell system presented below is based on an innovative solid state fuel cell system developed by U.S.DOE 54 . Conventional fuel cell networks, in order to effectively use the supplied fuel, often employ fuel cell modules operating in series to achieve high fuel utilization55 or combust the remaining fuel for possible thermal integration such as cogeneration steam or a steam bottoming cycle. Both of these conventional approaches utilize fuel cell modules at a single state-of-the-art...
Cost of Electricity
Three major contributors are considered in the computation of the COE for a fuel cell power plant 1 capital cost, 2 fuel cost and 3 operation and maintenance costs. The cost of electricity MWh can be calculated using these parameters as follows where 0.125 is a capital recovery rate excluding taxes and insurance , CC is the capital cost kW , FC is the fuel cost 106 Btu , 3.412 is the theoretical heat rate for 100 efficiency 3412 Btu kWh divided by 1000 for units consistency, ss is the...
Natural Gas Fueled PEFC System
A natural gas PEFC power plant configuration is shown in Figure 9-7 and is a slight simplification of a cycle published in 1997 by a Ballard Researcher 48 . In light of the PEFC sensitivity to CO, CO2 and methane, the fuel processing represents a significant portion of the cycle. Natural gas fuel enters a fuel compressor and a fuel cleanup device. The reference document does not describe the cleanup device, but it is assumed to be a sulfur polisher to prevent poisoning of the fuel cell...
References Vlx
1. A.J. Appleby, E.B. Yeager, Energy, pg. 11, 137, 1986. 2. S. Gottesfeld, T. Zawodzinski, PEFC Chapter in Advances in Electrochemical Science and Engineering, Volume 5, edited by R. Alkire, H. Gerischer, D. Kolb, C. Tobias, pp. 197-301, 1998. 3. W.T. Grubb, Proceedings of the 11th Annual Battery Research and Development Conference, PSC Publications Committee, Red Bank, NJ, p. 5, 1957 U.S. Patent No. 2,913,511, 1959. 4. H. Grune, 1992 Fuel Cell Seminar Program and Abstracts, The Fuel Cell...
Pafc
Europe The Energetic Utility of Milan, the National Agency for Energy, New Technology and Environment ENEA , and Ansaido Ricerche designed, built, and tested 1.3 MWe PAFC system in Milan. The powerplant had an actual capacity of 930 kW and an energy efficiency of 38 LHV . It has operated for over 5,000 hours. Japan Fuji Electric has developed a 100 kWe on-site system. To date, they have tested a 50 kW power plant using innovative cell design that improves electrolyte management. They tested...
Efficiency Comparison to Heat Engines
It is commonly expressed that a fuel cell is more efficient than a heat engine because it is not subject to Carnot Cycle limitations, or a fuel cell is more efficient because it is not subject to the second law of thermodynamics. These statements are misleading. A more suitable statement for understanding differences between the theoretical efficiencies of fuel cells and heat engines11 is that if a fuel cell is compared to an equivalent efficiency heat engine, the fuel cell is not limited by...
Summary of Equations for MCFC
The preceding sections provide parametric performance based on various referenced data at different operating conditions. It is suggested that the following set of equations could be used for performance adjustments unless the reader prefers other data or correlations. Figure 6-15 is provided as reference MCFC performance. AVT mV 2.16 T2 - T1 AVj mV 1.40 T2 - T1 AVT mV 0.25 T2 - T1 AVJ mV -1.21 AJ AVJ mV -1.76 AJ Life Effects AVlifetime mV -5mV 1000 hours 1 atm lt P lt 10 atm 6-19 575 C lt T lt...
Thermodynamic Considerations
Example 10-13 Production of Cogeneration Steam in a Heat Recovery Boiler HRB Given 10,000 lb hr of 700 F cycle exhaust gas passing through a heat recovery boiler HRB a How much 150 psia, 400 F steam can be produced b How much heat is transferred from the gas to the steam c What is the exhaust temperature of the gas leaving the HRB and d Sketch the T-Q temperature-heat diagram for the HRB. Assume a gas side mean heat capacity of 0.25 Btu lb, F, an evaporator pinch temperature of 30 F, a...
Partial Oxidation Description
As the name implies, partial oxidation, or POX, is the partial, or incomplete, combustion of a fuel. A substoichiometric amount of air, or oxygen, is used. This partial oxidation process is highly exothermic and raises the reactants to a high temperature. The resulting high temperature reaction products, still in a reduced state, are then quenched through the introduction of superheated steam. The addition of the steam promotes the combined water-gas shift and steam reforming reactions, which...
Polarization Activation Tafel and Concentration
To determine actual cell performance, three losses must be deducted from the Nernst potential activation polarization, ohmic polarization, and concentration polarization. Definition of the ohmic polarization is simply the product of cell current and cell resistance. Both activation polarization and concentration polarization required additional description for basic understanding. Activation Polarization It is customary to express the voltage drop due to activation polarization by a...