SOFC powerplants have many potential attributes which make them suitable for distributed generation applications. Power densities for SOFCs are very promising. Power densities possibilities of 20 watts per square centimeter have been reported to be possible. Westinghouse Electric is the leader in tubular SOFC technology. Several completely packaged and self-contained generators, up to nominal 25-kW size, have been manufactured and tested by Westinghouse Electric. A manufacturing facility currently produces these generators. In the US, several planar designs are also under development. Organizations developing planar designs include IGT, Celamalec, Ztek, TMI, and Allied Signal Aerospace. One of the most promising developments in SOFC powerplants is the conceptual development of very high efficiency fuel cell gas turbine powerplants. Combination of SOFC and turbine has the potential for enormous synergies

Williams, M.C.

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Paper Number:DOE/FETC/C-97/7281Title:U.S. Solid Oxide Fuel Cell Powerplant Development and CommercializationAuthors:M.C. WilliamsConference:Fifth International Symposium on Solid Oxide Fuel CellsConference Location:Aachen, GermanyConference Dates:June 2-5, 1997Conference Sponsor:Electrochemical SocietyDisclaimerThis report was prepared as an account of work sponsored by anagency of the United States Government.  Neither the United StatesGovernment nor any agency thereof, nor any of their employees,makes any warranty, express or implied, or assumes any legal liabilityor responsibility for the accuracy, completeness, or usefulness of anyinformation, apparatus, product, or process disclosed, or representsthat its use would not infringe privately owned rights.  Referenceherein to any specific commercial product, process, or service by tradename, trademark, manufacturer, or otherwise does not necessarilyconstitute or imply its endorsement, recommendation, or favoring bythe United States Government or any agency thereof.  The views andopinions of authors expressed herein do not necessarily state or reflectthose of the United States Government or any agency thereof.U.S. SOLID OXIDE FUEL CELL POWERPLANTDEVELOPMENT AND COMMERCIALIZATIONDr. Mark C. WilliamsFuel Cells Product ManagerU.S. Department of EnergyFederal Energy Technology Center (FETC)Morgantown, WV  26507-0880ABSTRACTSolid Oxide Fuel Cell (SOFC) powerplants have many potential attributeswhich make them suitable for distributed generation applications.  Powerdensities for SOFC’s are very promising.  Power densities possibilities of2.0 watts per square centimeter have been reported to be possible.  Westing-house Electric is the leader in tubular SOFC technology.  Several completelypackaged and self-contained generators, up to nominal 25-kilowatt (kW) size,have been manufactured and tested by Westinghouse Electric.  Amanufacturing facility currently produces these generators.  In the U.S.,several planar designs are also under development.  Organizations developingplanar designs include the Institute of Gas Technology (IGT), Ceramatec,Ztek, Technology Management Incorporated (TMI), and Allied SignalAerospace Corporation.  One of the most promising developments in SOFCpowerplants is the conceptual development of very high efficiency fuel cell gasturbine powerplants.  The combination of the SOFC and turbine has thepotential for enormous synergies.INTRODUCTIONSOFC powerplants offer the potential for ultra-high energy conversion efficiencylevels and ultra-low emissions levels--a combination attractive in energy markets world-wide.  Because of this, organizations in the U.S., such as the Department of Energy’s(DOE’s) FETC, user groups, the Environmental Protection Agency, the Department ofCommerce, National Institute of Standards and Technology, the Department of Defense,the Gas Research Institute, and the Electric Power Research Institute are funding thispromising technology.Because of the DOE and industrial investment in the 1980's and 1990's, fuel cellssuch as the phosphoric acid fuel cell, are now crossing the commercial threshold.  DOE andpredecessor agencies have funded the development of fuel cell systems since the 1970's.In the last few years, focus has shifted in the U.S. to the advanced fuel cell types, includingSOFC’s.  These systems offer higher efficiencies, the potential for lower capital cost, andbecause of higher operating temperatures, are more suitable for cogeneration than lower-temperature fuel cells.Solid Oxide Fuel Cells StatusIn the U.S., several SOFC technology configurations are being developed.  Since theSOFC may be operated over a wide range of temperatures, several lower-temperatureconfigurations with alternative materials are being considered.  While alternative electro-lytes and electrodes are b ing investigated, most developers are using the oxygen ion-conducting, solid-state device composed of a nickel-zirconia cermet anode, yittria-stabilizedzirconia electrolyte, a strontium-doped lanthanum manganite cathode, and a doped lantha-num chromite interconnect (1).  The solid-state electrolyte of yittria-stabilized z rconiaoxide is characterized by ionic conduction.  The solid-state character of the SOFC elec-trolyte means there are few constraints on design.Power densities for SOFC’s are promising.  Power density possibilities of 2.0 wattsper square centimeter on hydrogen at 1,000 EC have been reported for SOFC’s by theLawrence Berkeley Laboratory.  The high-power density with thin-layered componentscould make the SOFC the highest power density fuel cell.Westinghouse Electric is the leader in tubular SOFC technology.  The WestinghouseElectric tubular configuration is shown in Figure 1.  Several completely packaged and self-contained generators, up to n minal 25-kW size, have been manufactured and tested byWestinghouse Electric.  A 4-megawatt (MW)/year manufacturing facility currently pro-duces the cells (tubes), bundles, and generators.  The length of the tubes has been scaledup to a nominal 2 meters in length.  The porous air support tube has recently been elimi-nated.  The cell is now supported by the air electrode.  The Westinghouse Electric tech-nology has been validated to a far greater extent than any other SOFC technology.  Multi-ple tube tests have been successfully conducted for almost 70,000 hours, with less than1 percent per 1,000 hours degradation.  Pressurized operation to 15 atmospheres of thetubular SOFC has recently been demonstrated at Ontario-Hydro.  This pressurizationtesting is a key aspect of the eventual integration of the SOFC with the gas turbine.  A100-kW generator test, in the Netherlands, is also planned for the 1996-1997 timeframe(2-6).  Westinghouse is marketing its products under the name of SureCELL .RSeveral planar designs are also under development.  Organizations developing planardesigns include IGT, Ceramatec, Ztek, TMI, and Allied Signal Aerospace Corporation.These developers hold strong patent positions on cell designs, which is essential for low-cost manufacturing.Solid Oxide Fuel Cell Tubular DesignFuelFlowAirFlowElectrolyteInterconnectionAirElectrodeFuel ElectrodeM95000849WSchematic of Active Component Tri-Layer of IMHEX SOFCManifoldingHoleDenseElectrolyte(Thin Film)Porous Anode(Tape Cast)Porous Cathode(Screen Printed)M95000851EFigure 1.  Westinghouse Tubular ConfigurationFigure 2.  IGT IMHEX ConfigurationIGT is developing an 800 EC, intermediate-temperature, internally manifolded planardesign.  This trilayer IGT design, shown in Figure 2, has, according to IGT, the advantagesof more effective gas flow patterns, more compact design and cell stacking, more efficientcurrent and voltage transfer from cell to cell, and more cost-effective manufacture (7).  TheIGT design is an internally manifolded fuel cell design using pressed metallic plates calledIMHEX .  Because the IMHEX  design has no external gaskets and seals, only compres-R Rsion seals are necessary to obtain good sealing.  The ceramic bipolar separator plates in theSOFC’s currently under development are the single most expensive component.  Thesemake up more than 80 percent of the total m terials and fabrication costs of the cellcomponents (8).  IGT replaces the ceramic separator plates with nickel-based metallic sepa-rator plates, thus lowering cost significantly.  Since at 800 EC the zirconia electrolyte willhave high-internal resistance losses, IGT is using the provskite gadolinium-doped bariumcerium oxide, and glass/ceramic composite seals, which could sidestep most of the prob-lems associated with glass-only or cement-only manifold seals.The Ceramatec design, CPn , consists of stacks and a fuel processor and places someRcells in a series, rather than in parallel, to obtain greater efficiency.  Ceramatec has attaineda power density of 0.18 watts per centimeter square (167 watts per square foot) and acurrent density of 250 milliamperes per square centimeter (230 amperes per square foot).Ceramatec has tested a 1.4-kW module and has a limited partnership with Babcock andWilcox (9-10) for the commercialization of the technology.  This partnership is SOFCo.Ztek uses a radial design stacked into two-stack modules, which are then combinedinto arrays.  Ztek, along with Tennessee Valley Authority, has completed testing a 1-kWstack (11-12).TMI uses an Interscience Radial Flow design in which each cell is made up of fourlayers, with sealing being achieved through the use of rings, which also form the internalfuel and air manifolds (see Figure 3).  Small stack testing from 1- to 10-cell stacks has beenperformed.  Power densities around 0.08 watts per square centimeter (75 watts per squarefoot) have been attained (13).  One of the promising features of TMI’s SOFC developmentapproach is use of sulfur-tolerant anodes.Allied Signal Aerospace Corporation is developing the monolithic and flat planardesigns and is now using tape calendaring to produce a thin-electrolyte, reduced-temperature fuel cell with a potentially low manufacturing cost (14-15).It is often difficult to determine if the SOFC materials and their electrochemical andphysical properties, per se, or if the individual SOFC designs contribute more to perfor-mance, as measured by power density, efficiency, longevity (or durability), cost, pack-agability, and system integrability.IRF SOFC Exploded Schematic with FlowsM95000850WAir AirLanthanum StrontiumManganiteYttria-StabilizedZirconiaGlassMetal AlloyGlassNickel-ZirconiaCermetFuelFigure 3.  TMI Radial ConfigurationHigh-Efficiency SOFC Gas Turbine PowerplantsOne of the most promising developments in SOFC powerplants is the conceptualdevelopment of very high efficiency fuel cell gas turbine powerplants (16-23).  The combi-nation of the SOFC and turbine has the potential for enormous synergies, in that it offersa solution to two important problems:  the low efficiency and relatively high nitrogen oxide(NO ) emissions of small gas turbines and the high cost of small SOFC powerplants.xBecause of the synergistic effects leading to the higher efficiencies and lower emis-sions achieved by combining a fuel cell and a gas turbine into a power generation system,many potential system configurations have been developed.  Studies have indicated that thiscombination has the potential to increase the overall efficiency for the conversion of naturalgas into electricity to over 70 percent.  These systems are the logical extension of SOFCand gas turbine development and represent the most promising fossil energy powerplantsever conceived.  Figure 4 shows that the efficiency expected from high efficiency fuel cellgas turbine powerplants is higher than either system by itself.One promising configuration is the SOFC topper shown in Figure 5.  By allowing thefuel cell in this powerplant to serve as the combustor for the gas turbine and the gas turbineto serve as the balance of plant for the fuel cells, the combined efficiency is raised to the Gas Turbine/Fuel CellM96001975WFuelCellACGas TurbinesRecuperatorIntercoolerAirTCCStackComb.(NG-GT/FC)Figure 4.  Powerplant EfficienciesFigure 5.  SOFC Topper60 percent range, even at sizes of less than 3 to 10 MW, and NO  emissions are essentiallyxeliminated.Potential Markets for the SOFCThe SOFC can expect to play a role in the world power market.  By the year 2010,it is estimated that approximately 130 gigawatts (GW) of new generating capacity will beinstalled in the U.S., while in world markets and within a much closer timeframe, nearly550 GW of generating capacity will be added (24).  Fuel cell commercialization opportuni-ties in the U.S. market are focused in several areas:  repowering, central powerplants,industrial generators, and commercial/residential generators.The worldwide market for additional electric generation capacity dwarfs the domesticmarket.  Nearly 550,000 MW of new capacity will be added by 2002.  Estimates of plantrepowering installations between 1999 and 2010 range from 15 percent to approximately65 percent of the installed generating capacity.  Most repowering will occur in centralpowerplants:  fuel cell installations of 100 MW or more are targeted to his market,powered initially by natural gas and later by coal gas.The market for additional industrial capacity by 2010 is estimated at 3 GW, and themarket for additional commercial/residential capacity at 6 GW.  These markets are targetedfor early entry and will be a proving ground for natural-gas fuel cell powerplants sized from500 kW to 20 MW.In the U.S., SOFC’s have many potential attributes which make them suitable fordistributed generation applications (24).  These include low emissions, high efficiency, pro-duction of high-grade waste heat, modularity, reliability, unmanned operation, and fuelflexibility, to name a few.  These smaller applications favor SOFC’s for their high-efficiency, low-emission, and load-following capabilities.  In addition, the attractiveness ofeconomical and reliable on-site power generation may significantly expand the market forsmall-scale commercial and industrial powerplants.  The Clean Air Act mandatessignificantly reduced emissions of sulfur and nitrogen compounds from existingpowerplants and sets strict limits on emissions from new sources.  In the short term, theserestrictions may encourage the use of under-utilized fuels, particularly natural gas, byelectric power producers.References 1. Fuel Cells - A Handbook (Revision 3), Report Number DOE/METC-94/1006. 2. E. Ray, Tubular Solid Oxide Fuel Cell Development Program.  Proceedings of the'94 Contractor's Review Meeting, DOE/METC-94/1010, pp. 3-8. 3. E. Ray, Tubular Solid Oxide Fuel Cell Development Program, Proceedings of the 95Contractor's Review Meeting, DOE/METC 95/1020, pp. 9-14. 4. E. Ray and S. Veyo, Tubular Solid Oxide Fuel Cell Demonstration Activities, Pro-ceedings of the '94 Contractor's Review Meeting, DOE/METC-94/1010, pp. 9-14. 5. E. Ray and S. Veyo, Tubular Solid Oxide Fuel Cell Demonstration Activities, Pro-ceedings of the 94 Contractor's Review Meeting, DOE/METC 94/1010, pp. 9-14. 6. S. Veyo, A. Kusunoki, S. Takeuchi, S. Kaneko, and H. Yokoyama, A Solid OxideFuel Cell Power System - 1992/93 Field Operation, presented at the 56th Annual Meetingof the American Power Conference, Chicago, April 1994. 7. L. G. Marianowski, F. C. Schora, R. J. Petri, and M. G. Lawson, Fully InternalManifolded Fuel Cell Stack.  U.S. Patent No. 5,227,256, July 13, 1993. 8. K. Krist and J. D. Wright, Proceedings of the Third International Symposium onSOFC's, S. C. Singhal and H. Iwahara, Editors, pp. 782-791, 1993. 9. E. A. Barringer, A. Khandar, and A. Yagiela, Development and Demonstration ofa 50-kW Planar SOFC Power Generation System, a white paper for EPRI, GRI, andUtilities, November 1994.10. R. Privette, et al., Status of SOFCo SOFC Technology Development, Fuel Cell Semi-nar, Orlando, November 1996, in Proceedings of Fuel Cell Seminar, pp. 40-43.11. M. Hsu, D. Nathanson, and E. Hoag, Ztek's Radiant Thermal Integration Programfor Efficient and Cost-Effective Electric Utility Powerplants.  An EPRI/GRI Fuel CellWorkshop on Fuel Cell Technology Research and Development, 20, 1994.12. M. Hsu, et al., Ztek's Ultra-High Efficiency Fuel Cell/Gas Turbine System for Distrib-uted Generation, Fuel Cell Seminar, Orlando, November 1996, in Proceedings Fuel CellSeminar, pp. 183-186.13. M. Petrick, T. Cable, and R. Ruhl, Stack Development Status of the InterscienceRadial Flow (IRF) SOFC.  An EPRI/GRI Fuel Cell Workshop on Fuel Cell TechnologyResearch and Development, 19, 1994.14. N. Minh, W. Wentzel, and R. Gibson, Tape-Calendaring Monolithic and Flat PlateSOFC's.  Proceedings of the Third International Symposium on SOFC's, S. C. Singhal andH. Iwahara, Editors, pp. 801-809, 1993.15. N. Minh, et al., Allied Signal SOFC Technology, Fuel Cell Seminar, Orlando,November 1996, in Proceedings Fuel Cell Seminar, pp. 40-43.16. M. Williams and C. Zeh, Editors, Proceedings of the Workshop on Very High Effi-ciency FC/GT Power Cycles, October, 1995.17. D. Archer, M. Williams, and J. Wimer, FC/GT Systems - Power Generation WithHeat and Fuel Recovery.  Proceedings of the Workshop on Very High Efficiency FC/GTPower Cycles, pp. 33-40, October, 1995.18. M. C. Williams, E. L. Parsons, and P. Micheli, Engineering a 70% Efficient IFCFC,Proceedings 9th Fuel Cell Contractor’s Meeting, Poster 10, pp. 121-129, 1995.19. P. Micheli, M. Williams, and F. Sudhoff, Dual Fuel Cell Tandem Cycles.  U.S.Patent 5,541,014.20. D. Archer, J. Wimer, and M. Williams, Power Generation by Combined Fuel Cell andGas Turbine Systems, GT/FC Workshop, October 19, 1996, in Proceedings 1996 Fuel CellContractor’s Meeting.21. D. Archer, J. Wimer, and M. C. Williams, Power Generation by Combined Fuel Celland Gas Turbine Systems.  1996 IECEC Meeting, Florida.  IECEC Proceedings, 2: pp. 1117-1122, 1996.22. L. Rath, P. Lee, and F. Sudhoff, Configuration and Performance of Fuel Cell Com-bined Cycle Options.  Proceedings of the Workshop on Very High Efficiency FC/GT PowerCycles, pp. 21-32, October, 1995.23. M. Williams and C. Zeh, Editors, Proceedings of the Second Workshop on Very HighEfficiency FC/GT Power Cycles, 1996 (in press).24. EIA, 1996 Energy Outlook.25. M. C. Williams, Fuel Cell Market Applications, Proceedings of 11th U.S./KoreanWorkshop, October 1-6, pp. 259-276, 1995.

U.S. solid oxide fuel cell powerplant development and commercialization

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U.S. solid oxide fuel cell powerplant development and commercialization

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