bluuebunny/crossref_metadata_2025 huggingface dataset:
U.S. DOE Fossil Energy Fuel Cell Program
Authors: Surdoval Wayne
Published: May 2007

The U.S. Department of Energy's Office of Fossil Energy's National Energy Technology Laboratory, in partnership with private industry, educational institutions, and national laboratories, is leading the research, development, and demonstration of high efficiency, fuel flexible solid oxide fuel cells (SOFCs) and coalbased SOFC power generation systems for stationary markets. This Fuel Cell Program has three parts: Solid State Energy Conversion Alliance (SECA) cost reduction, SECA fuel cell coalbased systems, and advanced SECA systems. The SECA cost reduction goal is to have SOFCs capable of being mass manufactured at $400 per kilowatt by 2010. Concurrently, the scale-up, aggregation, and integration of the technology will progress in parallel leading to prototype validation of megawattclass products by 2012 with potential testing at FutureGen. The SECA coal-based and advanced systems goals are the development of megawatt-class fuel cell power systems that will enable affordable, reliable, efficient, and environmentally-friendly electrical power from coal.
SOFC Related Research and Development within the Framework Programme of the European Union
Authors: Rietveld Bert
Published: May 2007

This paper provides an overview of current SOFC related projects funded by the European Commission by any of their programmes. Projects presented concern basic or generic activities for developing materials and components; application related development activities for stationary and transport systems, as well as projects aiming for cost reduction of SOFC manufacturing processes. Additionally, an activity on establishing pre-normative, harmonised SOFC test procedures is reported.
Development of SOFC Residential Cogeneration System at Osaka Gas and Kyocera
Authors: Suzuki Minoru , Sogi Tadayuki , Higaki Katsumi , Ono Takashi , Takahashi Naruto , Shimazu Kenji , Shigehisa Takashi
Published: May 2007

At 2004, Osaka Gas Co., Ltd. and Kyocera Corporation launched joint development of SOFC residential cogeneration system, aiming for the commercialization. To demonstrate the technical achievement, we installed SOFC residential cogeneration system in a house and carried out operation. At rated power, ac 1kW, net ac efficiency and hot water heat recovery efficiency were 49% (LHV) and 34%(LHV), respectively. The mean net ac efficiency of each day, that is total efficiency of 24 hours, ranged 42-48 % (LHV), when the mean net ac power of SOFC were 480-680W. We demonstrated that this system is good for decreasing CO2 emission. At the end of 2006, we developed new SOFC power generation unit. It was reduced its size nearly half in the volume, in order to fit Japanese house in the city.
Coal Based Solid Oxide Fuel Cell Technology Development
Authors: Minh Nguyen
Published: May 2007

Solid oxide fuel cell (SOFC) technology has been under development at General Electric (GE) for multi-MW integrated gasification fuel cell (IGFC) power plants. Current efforts at GE concentrate on three main areas: system design and analysis, stack technology development, and prototype system demonstration. The system design and analysis effort involves assessment of various IGFC system concepts and development of suitable designs with the goal of 50% system efficiency (coal HHV to AC power). The stack technology development effort addresses issues concerning stack design (including sealing), performance improvement, cell manufacturing and scaleup, and degradation/life under IGFC operating conditions. The prototype system demonstration effort focuses on building and testing of small (3-10 kW) prototypes to demonstrate operation with desired performance characteristics
Support Structures for SOFCs Operating at High Power Density and Fuel Utilization
Authors: Aruliah Sathia , Amarasinghe Sudath , Love Jonathan , Ratnaraj Raj , Summergreene Annette , Watts Merrill
Published: May 2007

CFCL has developed both electrolyte-supported cells for all- ceramic stacks and anode-supported cells for ceramic-metal stacks. The support structure in the anode-supported cell is critical to the functionality of the ceramic-metal stack. The support structure has been optimised to achieve continuous operation at high efficiency using internal steam reforming of methane at high fuel utilisations. Optimisation of the Ni- cermet (Ni-YSZ) support is described in this paper with results of testing related to CFCL's anode supported cells.
Development of Intermediate-temperature SOFC Modules and Systems
Authors: Shibata Makoto , Murakami Naoya , Akbay Taner , Eto Hiroyuki , Hosoi Kei , Nakajima Hiroaki , Kano Jiro , Nishiwaki Futoshi , Inagaki Toru , Yamasaki Satoru
Published: May 2007

Mitsubishi Materials Corporation and The Kansai Electric Power Co., Inc. have been jointly developing intermediate- temperature SOFCS as stationary power generation units since 2001. High performance cells based on lanthanum gallate electrolyte and a unique seal-less cell-stack design enable high efficiency operation. The 4th generation module with internal manifolds was developed and the electrical efficiency of 54% HHV on DC output was achieved in 2005. The first long- term durability test using town gas for fuel over 4000hrs was ended recently and its voltage degradation rate was about 0.5%/1000hrs. In parallel to 1kW module development efforts, scaling-up of the module toward 10kW-class has been successfully done and the electrical efficiency of 50% HHV on DC output was achieved in 2006. Fabrication of the 10kW-class CHP system is under progress and will be finished by the end of FY2006. The field test of this system is scheduled in FY2007.
Characterization of SOFC Short Stacks and Stacks for Mobile Applications
Authors: Lang Michael , Auer Corinna , Eismann Andreas , Schiller Günter , Szabo Patric
Published: May 2007

The paper concentrates on the investigation of SOFC short stacks and stacks for mobile applications. A lightweight stack design was used, which is based on stamped metal sheet bipolar plates with anode supported cells (ASC). The stacks were electrochemically characterized mainly by long-term measurements, by current-voltage measurements and by impedance spectroscopy. The stacks were operated at different temperatures, varying fuel gas compositions, different flow rates and under dynamical electrical loading cycles. Their influence on the electrochemical performance of the short stacks is outlined. The fuel utilizations and the different power densities, i.e. area specific, gravimetric and volumetric ones, are presented. The nature of losses, e.g. ohmic and polarization resistances, were examined by combining the results of the current-voltage curves and the impedance spectra. Moreover, the degradation rates were determined from the long-term measurements. After operation, the stacks were examined by light microscopy and SEM in order to analyze possible degradation mechanisms.
Stack Testing Summary - Versa Power Systems
Authors: Dueck Jason , Benhaddad Sofiane , Brown Casey , Grande Oliver , Kelsall James , Machacek Todd , Nelson Jeff , Thompson Scott , Wood Tony
Published: May 2007

Versa Power Systems' stack development is based on a consistent, repeatable testing methodology focused on increasing the durability and endurance of the stack while simultaneously decreasing the stack manufacturing cost. Standard tests are repeated on every stack to allow for comparison of various stack configurations and material systems. These standard tests are also used as a qualification step to maximize the usefulness of long-term stack in-test stand and stack in system testing. Statistical analysis of the test results provides an opportunity for process improvement and optimization. Testing has been performed at Versa Power Systems (Calgary, Canada), Cummins Power Generation (Minneapolis, MN), Gas Technology Institute (Chicago, IL), U.S. National Energy Technology Laboratory (Morgantown, WV), U.S. Naval Undersea Warfare Center (Newport, RI), the U.S. Air Force Lab (Panama City, FL) and Imperial College (London, England) with a minimum variation in results. These results are presented and discussed.
The Components of a Rolls-Royce 1 MW SOFC System
Authors: Agnew G. D. , Collins R. D. , Jörger Michael B. , Pyke S. H. , Travis Rowland
Published: May 2007

Progress at Rolls-Royce Fuel Cell Systems (RRFCS) continues towards demonstration of a 250 kW generator module for launch of a 1 MW pressurized SOFC hybrid system for stationary power generation. This paper describes recent progress on demonstration of the SOFC system, both as individual components - core cell and stack technology, the turbogenerator, packaging, and, crucially, the progress on building these components together into a functional hybrid Generator Module and system. The establishment of a truly global engineering team with skills and experience across the range of technologies required has been crucial to the development of the overall system with a view to cost effective manufacture, system simplicity and realistic fuel availability. Efficiency and key system components are discussed, together with design evolution as the technology moves towards a commercial product.
Operational Experience of an IT-SOFC / Battery Hybrid System for Automotive Applications
Authors: Brett Daniel J. , Aguiar Patricia , Brandon Nigel P. , Coop Ian , Dueck Jason , Galloway Roy C. , Grande Oliver , Hayes Gary W. , Lillie Ken , Mellors Chris , Thompson Scott , Tilley Roger , Wood Tony
Published: May 2007

Testing of a 300 W stack, supplied by Versa Power Systems Ltd., and a sodium - metal chloride (ZEBRA) battery has been performed with a view to assessing the feasibility of combining an intermediate temperature solid oxide fuel cell with a high temperature battery for automotive traction applications. Field testing of a self-compressed stack is demonstrated including consideration of the mechanical robustness of the technology. The battery system, comprising novel cell technology, is tested under pulse discharge and standard driving cycle conditions. Based on modeling studies previously performed, the performance results obtained and the reliability of the respective technologies, development of a full-scale prototype is considered viable and ultimately commercially relevant.
Design of 500 W Class SOFC Stack with Homogeneous Cell Performance
Authors: Bucheli Olivier , Molinelli Michele , Zähringer Thomas , Thorn Emily , Diethelm Stefan , Wuillemin Zacharie , Nakajo Arata , Autissier Nordahl , van Herle Jan
Published: May 2007

Our planar SOFC stacking technology uses unprofiled metallic interconnects (MIC) and thin cells of tape cast anode supported YSZ. The key element is the gas diffusion layer (GDL) between cell and MIC, which consists of so-called SOFConnex{trade mark, serif}. Using square cells with internal manifolds, 0.5 W/cm2 stack power density (800{degree sign}C) can be obtained on short stacks. However, this open design configuration limits (i) the assembly of large stacks and (ii) the durability of operation. A new design, inspired from modeling work, led to oblong-shaped cells, assembled in a closed stack casing with external air manifolding and fuel recovery manifolding, avoiding postcombustion. While stack power density remains similar, the operation at increased fuel utilization has become more stable in the 2nd design. Furthermore, a correlation of performance homogeneity during stack testing was drawn to assembly quality control. A 36-cell stack in dilute H2 at 800 {degree sign}C achieved 625 Wel (28% LHV efficiency, 0.35 W/cm2) under continuous polarisation, with all 6 clusters of 6 cells showing coincident i-V-output.
Investigation on Degradation in Long-Term Operations of Four Different Stack/Modules
Authors: Yokokawa Harumi , Watanabe Takao , Ueno Akira , Hoshino Koji
Published: May 2007

Investigation on degradation of performance during long term operations of four different SOFC stacks/modules has been initiated in the NEDO SOFC project from 2005FY to 2007FY. Four stack/modules with different designs and materials have been tested for about 5000 h and have been dissected for post- operation examination. In addition to normal visual and microscopic inspection, SIMS was used as strong tool of detecting those mass transfer phenomena which may lead to degradations. Examinations were made first on those stack materials which were operated for 24 h. Impurity levels in the cell components were detected and extent of the interdiffusion across the interface of the cell components was determined. Further analyses were made by using SIMS on those stack materials operated for around 5000 h.
JPOWER's Prototype 150kW-Class SOFC Cogeneration System Development (SOFIT)
Authors: Nakatomi Hitoshi , Komiyama Norio , Takahashi Yasuhiro , Omata Kouji , Haga Tsuyoshi , Kikuchi Tetsuo , Sasatsu Hiroshi
Published: May 2007

Electric Power Development Co., Ltd. (JPOWER) started Tubular Type SOFC system development in collaboration with Mitsubishi Heavy Industries, Ltd. (MHI) in 1991. Stability of our improved structure featured with higher durability and lower cost has been verified using the 5kW-class Cartridge with 104 cell-tubes and 25kW-class Sub-module which consists of 4 Cartridges. As our new SOFC module structure was well established through great success in 5kW-class Cartridge and 25kW-class Sub-module test in collaboration with MHI, the prototype 150kW-class atmospheric SOFC co-generation system (SOFIT) development was planned by JPOWER. The system was installed at JPOWER's R&D Center in Chigasaki in 2006, and its verification test is started in January 2007. Our main purpose is definitely to verify and evaluate system durability and operation ability through more than 10,000 hours operation.
Development of Anode Supported Micro-Tubular SOFC Stack for APU Application
Authors: Lee Seung-Bok , Yun Ki-Seok , Lim Tak-Hyoung , Song Rak-Hyun , Shin Dong-Ryul
Published: May 2007

We developed a 700W anode-supported tubular SOFC stack for APU application. For this purpose, we have first designed single cell by optimization of current collecting method, brazing method and the length of tubular cell, and then we have fabricated high power single cell. After that we designed fuel manifold by adopting simulation method to uniformly supply fuel gas and oxygen gas to the inside and to the outside of single cells, respectively. Finally, by stacking the bundles of cells in series electrical connection, we can construct a 700W anode-supported micro-tubular SOFC stack having power density of 0.38W/cm2 at 750oC
Operating Characteristics of Advanced 500W Class Anode-supported Flat Tubular SOFC stack in KIER
Authors: Lim Tak-Hyoung , Kim Gwan-Yeong , Park Jae-Layng , Song Rak-Hyun , Lee Seung-Bok , Shin Dong-Ryul
Published: May 2007

KIER has been developing the anode supported flat tubular SOFC stack for the intermediate temperature (700~800oC) operation. For this purpose, we have first fabricated anode supported flat tubular cells by the optimization between the current collecting method and the induction brazing process. After that we designed the compact fuel & air manifold by adopting the simulation technique to uniformly supply fuel & air gas and the unique seal & insulation method to make the more compact stack. For making stack, the prepared anode-supported flat tubular cells with effective electrode area of 90 cm2 connected in series with 12 modules, in which one module consists of two cells connected in parallel. The performance of stack in 3 % humidified H2 and air at 800 oC shows maximum power of 507 W. Through these experiments, we obtained basic & advanced technology of the anode-supported flat tubular cell and established the proprietary concept of the anode-supported flat tubular SOFC stack in KIER
The Electrical Performance of a 5-Cell Planar SOFC Stack
Authors: DiGiuseppe Gianfranco
Published: May 2007

In this paper the electrochemical performance of a 5-cell planar SOFC stack is reported and discussed. Voltage-current density curves were measured at two temperatures and at different fuel utilizations. The temperature and fuel utilization effects on the individual cell's performance is discussed. A fuel sensitivity analysis is reported as well, and its effect at different current level is discussed. Finally the lifetime performance of the stack is discussed where the voltage-time profile is shown.
Planar LT-SOFC, Stack and Fuel Processor Development at IPPE
Authors: Ruzhnikov Vladimir , Khramushin Nikolai , Gulevich Andrei , Privezentsev Vitaly
Published: May 2007

Institute for Physics and Power Engineering (IPPE) has been developing planar SOFCs and power systems, based on them, since 1996. The R&D works include SOFC material investigations, SOFC and stack design and technology, single cells and stacks tests, small-scale SOFC power system design development. Currently our efforts have been concentrated mainly on development of the LT- SOFC with thin-film electrolyte and electrodes on porous stainless steel supporting plate with operating temperature of about 600OC. The stack design and technology are being developed on the base of the LT-SOFC. Simultaneously the fuel processor on the base of microchannel reactors technology for the stack is being developed too. The status of R&D works on the IT-SOFC, stack and fuel processor at IPPE and some results are discussed in this paper.
Development of Autothermal Reforming Catalyst for SOFC System Powered by Kerosene
Authors: Sugiura Yukihiro , Mizuno Yasushi , Sadakane Osamu , Anzai Iwao
Published: May 2007

A SOFC system powered by kerosene has been developed. This system consists of desulfurization, reforming section, SOFC and air pre-heater. We designed a thermal self-sustainable SOFC system by using kerosene. The heat balance between SOFC and reforming section can be controlled to change Uf mainly. But we have developed the autothermal reforming catalyst to have some choices for the thermal self-sustainable SOFC system.
Development of Anode-supported Planar SOFC using Inexpensive and Simple Processing Technique
Authors: Basu Rajendra , Das Sharma A , Dutta A , Mukhopadhyay J , Maiti H S.
Published: May 2007

In the anode-supported planar SOFC, conventionally the porous anode support is fabricated first, over which a thin layer of electrolyte (5-50 µm) is developed to form the half-cell. Additionally, functional layers in the anode side (AFL) and cathode side (CFL) are used. The present contribution reports use of inexpensive and simple processing techniques to fabricate anode-supported planar SOFC where no AFL is used. The process involves room temperature lamination of several layers of tapecast NiO-YSZ together with a top layer of YSZ followed by co-firing. The half cells thus fabricated, having thin electrolyte (~ 20µm), are screen-printed with La(Sr)MnO3 (LSM)-YSZ CFL and LSM cathode layer . Single cells of dimensions up to 10 cm × 10 cm × 1.5 mm have been fabricated. Coupon cells show high current density between 1.0 and 1.5A/cm2 at 8000C at 0.7V. The electrochemical performances of these cells are size independent and show excellent repeatability.
Characterization of Cathode Chromium Incorporation during Mid-Term Stack Operation under Various Operational Conditions
Authors: Menzler Norbert H. , de Haart L. G. , Sebold Doris
Published: May 2007

As part of the Real-SOFC Integrated Project of the European Commission, four SOFC stacks each with 2 planar anode-supported cells were operated for durations of up to 3000 h under varying fuel and electrical load conditions. The variations comprised the external applied current density (0.3 or 0.5 A/cm²) and the fuel gas (hydrogen or methane). All stacks were operated galvanostatically at a temperature of 800 {degree sign}C and a fuel utilization of 40%. A pronounced difference in degradation behaviour was observed between the two stacks operated at 0.5 A/cm² and those operated at 0.3 A/cm². The latter displayed linear behaviour of the voltage with time over the full duration of operation. The degradation rate was always below 1%/kh. From the start, the two stacks operated at 0.5 A/cm² showed an increased degradation rate (> 2%/kh). Post-test characterization of the cathode with respect to chromium poisoning was performed on cells from all four stacks. Segments of the cells were cut by sawing and examined. On the one hand, polished samples for SEM characterization were prepared for microstructural and EDX investigations, and, on the other hand, the cathode was removed and chemically characterized with respect to compositional changes due to the incorporation of species from the surrounding components.
Metal Supported SOFCs
Authors: Tucker Michael , Lau Grace , Jacobson Craig P. , DeJonghe Lutgard C. , Visco Steven J.
Published: May 2007

Metal-supported thin-film YSZ SOFCs with infiltrated Ni and LSM catalysts are operated in the temperature range 650-750{degree sign}C. A five-layer structure consisting of porous metal support/porous YSZ interlayer/dense YSZ electrolyte film/porous YSZ interlayer/porous metal current collector is prepared at 1300{degree sign}C in reducing atmosphere. The cell is sealed and joined to a cell housing/gas manifold using a commercially-available braze. The porous YSZ interlayers are then infiltrated with Ni and LSM catalyst precursor solutions at low temperature prior to cell testing. Maximum power densities of 285mW/cm2 and 712mW/cm2 were achieved at 700{degree sign}C, with air and oxygen as oxidant, respectively.
Performance and Reliability Improvement of Planar SOFC Stack with Advanced Design of Unit Cell and Sealing
Authors: Lee Jong-Ho , Kim Hyoungchul , Kim Hae-Ryoung , Son Ji-Won , Kim Joosun , Lee Hae-Weon , Song Huesup
Published: May 2007

Commercialization of SOFC technology requires the development of high performance SOFC stack, combined with an engineering focus on stack reliability and cost. Recently KIST was successful to greatly improve the performance and reliability of SOFC stack based on newly developed 10x10 cm2 anode- supported cells and glass-based compression-seal gaskets. In this study, a novel design of SOFC unit cells with higher thermo-mechanical stability and better electrochemical performance has been introduced and its evaluation results are discussed in terms of its electrical property, structural property and unit cell performance. We also address the key factors and the latest progress in sealing technique in a view point of sealing capability and thermal-cycle stability.
Fabrication and Performance Evaluation of Multi-Cell Arrayed Planar SOFC Stack
Authors: Kim Hyoungchul , Jung Hwa Young , Jung Hoon-Gi , Kim Joosun , Lee Jong-Ho , Lee Hae-Weon , Song Huesup
Published: May 2007

In recent days, SOFC technology has been developed in order to accomplish high power capacity system and satisfy economic requirements. We have been developing the anode supported planar SOFCs with large active area by employing various multi- cell array and compressive sealing system. The 4-cell and 2- cell array systems, which were equivalent to 10 cm × 10 cm unit cell in active area, were operated successfully to achieve high power density of 0.46 W/cm2 and 0.45 W/cm2 at 750oC respectively. By means of enhanced compressive sealant, especially, this equivalent cell system was assembled without any aid of auxiliary anchoring parts. Our results provide a feasible alternative for realization of planar SOFCs of high power capacity by increasing active area with currently available fabrication techniques.
Manufacturing of Anode-Supported SOFC's: Processing Parameters and their Influence
Authors: Ramousse Severine , Menon Mohan , Brodersen Karen , Knudsen Jesper , Rahbek Uffe , Larsen Peter H.
Published: May 2007

Commercialization of SOFC technology is strongly relying on the establishment of low cost, highly reliable and reproducible manufacturing processes. A major challenge in the production chain is the manufacture of single cells. Anode-supported planar SOFC's are layer structured, where each layer contains a complex microstructure. Successful manufacture of such a cell and the achievement of optimal final properties are very much dependant on each of the processing steps and their interdependence. Therefore, in order to improve the cell performance as well as reducing the processing costs, it is necessary to consider the process chain holistically. Several thousand anode-supported SOFCs are manufactured annually at the Risoe National Laboratory in collaboration with Topsoe Fuel Cell A/S. As a result a large database exists, which enables a statistical analysis of the various controlling parameters. In the present work, some of the critical manufacturing elements are discussed along with their impact on product quality.
New High Efficient Thermal Spray Solutions for Perovskite Coatings and Dense Thin Electrolytes Using TriplexPro-200 APS and LPPS-Thin Film Technology
Authors: Hoehle Hans-Michael , Refke Arno , Gindrat Malko
Published: May 2007

The production of protective coatings on metallic SOFC interconnects using LaSrMnO (LSM) in an industrial scale requires an economically efficient process in order to obtain high quality and reliable coatings. The TriplexProTM-200 gun is a new advanced plasma spray torch with three electrodes which provides all the features necessary to apply this type of coatings following the requested productivity and quality for a mass production in an Atmospheric Plasma Spray (APS) process. The LPPS-Thin Film technology uses a high power plasma torch operated in a low pressure environment. This low ambient pressure produces a large plasma jet with unconventional properties allowing the production of thin and dense ceramic coatings. Thus, the technology is best suited to deposit very dense electrolyte layers of Yttria Stabilized Zirconia (YSZ) for improved cell performance. Moreover, the large plasma plume in the LPPS-TF process allows a very efficient coating production on large areas.
Operation of High Temperature Steam Electrolyzer Module
Authors: Hartvigsen Joseph J. , Elangovan S , O'Brien James E. , Stoots Carl M. , Herring J S.
Published: May 2007

A nominally 4-kW planar solid oxide stack module was operated in electrolysis mode. The module consisted of two 60-cell stacks with an integrated steam generator. The tests included both steam electrolysis to produce hydrogen and steam-carbon dioxide co-electrolysis to produce syngas. The initial performance of the module matched the performance of a 10-cell short stack. Fairly rapid initial degradation, attributed primarily to thermal imbalance from the heat duty of steam generator was noted. Reducing the heat duty of the steam generator within the thermal enclosure significantly improved the performance stability. The production of hydrogen and syngas was verified using dew point sensor and gas chromatograph.
Double Layer-Type Electrodes for Reversible Solid Oxide Fuel Cells
Authors: Uchida Hiroyuki , Watanabe Sohta , Tao Yohei , Osada Norikazu , Watanabe Masahiro
Published: May 2007

We have developed double layer-type (catalyst layer/current collecting layer) electrodes for reversible SOFCs operating at medium-temperature. As the H2 catalyst layer (anode for SOFC and cathode for steam electrolysis) interfaced with YSZ solid electrolyte, mixed conducting samaria-doped ceria (CeO2)0.8 (SmO1.5)0.2 particles were employed in combination with Ni metal electrocatalysts (10 to 20 vol.% of nanometer-size Ni) highly dispersed on their surfaces. The current collecting porous layer of Ni-SDC cermet (60 vol.% of micrometer-size Ni) was formed on the catalyst layer. The H2-electrode with 10 vol.% Ni in the catalyst layer exhibited high performance, due to the effective enhancement of the reaction rate by increasing both the active reaction sites and the electronic conductance.
Long-term and Redox Stability of Electrolyte Supported Solid Oxide Fuel Cells Under Various Operating Conditions
Authors: Mosch Sindy , Trofimenko Nikolai , Kusnezoff Mihail , Betz Thomas , Kellner Marco
Published: May 2007

The electrolyte supported cells satisfy the requirements for the application in the solid oxide fuel cell such as mechanical stability, long-term stability during operation at temperatures <1000{degree sign}C, thermal cycling and very low degradation during repeated anode reduction/oxidation cycles. Nevertheless an enhancement of the power density at T=800-850{degree sign}C should be achieved to increase the power density level towards anode supported cells. The electrolyte supported solid oxide fuel cells on dense 8YSZ or 10Sc1CeSZ tapes (50x50x0.150 mm) with screen printed nickel oxide and yttria stabilized zirconia cermet anode (NiO/YSZ) and lanthanum strontium manganite and yttria stabilized zirconia composite cathode (uLSM/YSZ) were sintered in co-firing. The long-term tests (over 1000 hours) were carried out at 850{degree sign}C at constant load of 550 mA/cm2 (H2:H2O:N2=40:5:55, fuel utilization uf=50%) for 8YSZ based MEA and 650 mA/cm2 (H2:H2O=50:50, uf=23%) for 10Sc1CeSZ based MEA. During the redox cycle the cells were unloaded and fully oxidized by air for 120-180 min. Up to 10 redox cycles were performed. The field emission scanning electron microscopy (FESEM) was used to characterize the microstructural changes that occurred after long-term and redox cycles experiments. Changes of polarization resistance of the cells during the experiments were analyzed by impedance spectroscopy.
Degradation Behavior at Interface of LSCF Cathodes and Rare Earth Doped Ceria
Authors: Sakai Natsuko , Kishimoto Haruo , Yamaji Katsuhiko , Horita Teruhisa , Brito Manuel E. , Yokokawa Harumi
Published: May 2007

The reaction and interdiffusion characteristics at the interface of rare earth doped ceria (M0.2Ce0.8O1.9, M = Gd, La) and perovskite- type cathode materials (La0.8Sr0.2CoO3, La0.8Sr0.2FeO3, and La0.8Sr0.2(Co, Fe)O3) were investigated, and their effect on the long-term reliability of SOFC performance was discussed. A secondary phase formed at the interface by the reaction of rare earth component in ceria and transition metal components in perovskite. A significant diffusion of transition metals (cobalt or iron) and strontium from perovskite to ceria was observed, whereas little diffusion of cerium was observed in perovskites. The iron content in perovskite and the type of rare earth in ceria strongly affect the stability of secondary phase and extent of impurity diffusion in ceria. Strontium component exhibited the tendency of the fast grain boundary diffusion in ceria.
Residual Stress Analysis in Lanthanum Gallate-based Cell before and after Fuel Cell Operation
Authors: Yoshida Hiroyuki , Deguchi Hiroshi , Inagaki Toru , Hashino Koji , Kawano Mitsunobu , Hosoi Kei , Horiuchi Masaki
Published: May 2007

The distribution of residual stress in the cells with the practical size of 120mm in diameter was measured by X-ray from synchrotron radiation at Super Photon ring 8 GeV (SPring-8). The residual stress was determined by the constant penetration depth method. When NiO-samaria doped ceria (SDC) was sintered on (La,Sr)(Ga,Mg,Co)O3-d (LSGMC), the tensile stresses resided in NiO and SDC, and the compressive stress was resided in LSGMC. The reduction of the anode by hydrogen decreased tensile stresses in the anode. The residual stresses in the electrodes did not change at any X-ray penetration depth.
High Power SOFC using LaGaO3 Based Oxide Electrolyte Film Prepared on Porous Metal Substrate
Authors: Ishihara Tatsumi , Yan Jingwang , Matsumoto Hiroshige
Published: May 2007

SOFC single cell was fabricated on the porous metal substrate which is prepared by thermal reduction method. After reduction of the NiO-Fe3O4 mixed oxide at 873K for 5h, it was found that the porous metal substrate is successfully obtained. Thus obtained metal porous substrate has 30 % in porosity and ca. 15cc/min for H2 permeation rate, which is enough permeation rate for hydrogen. Pulsed laser ablation techniques were used for the preparation of LSGM film on top of thus obtained porous metal. In order to prevent the reaction between Ni and LSGM, thin film of SDC was deposited between Ni-Fe substrate and LSGM electrolyte. Sm0.5Sr0.5CoO3 is applied by the screen printing techniques. Thus obtained SOFC shows the almost theoretical OCV and the maximum power density is achieved a value of 1.6 and 0.5 W/cm2 at 973 and 773 K, respectively.
A Model for Solid Oxide Fuel Cell (SOFC) Stack Degradation
Authors: Virkar Anil
Published: May 2007

Several solid oxide fuel cells (SOFC) are connected in series to form a stack. If a single cell (or a few cells) in a stack exhibits higher resistance than rest of the cells, stack failure often initiates at such a cell. The cell is then driven by, and exhibits lower voltage than rest of the cells, and often even a negative voltage. The objective of this paper is to present a model for stack degradation when one of the cells exhibits a negative voltage. The existence of low level electronic conduction plays central role in degradation. It is shown that if a cell exhibits a negative voltage, oxygen chemical potential within the electrolyte can exceed that in oxidant, or can drop below that in fuel. This can lead to high internal oxygen partial pressure resulting in cracking and delamination, or very low oxygen partial pressure leading to local electrolyte decomposition.
Influence of Fuel Contaminants on SOFC Operation: Effect on Performance and Degradation Mechanisms
Authors: Mougin Julie , Ravel Serge , de Vito Eric , Petijean Marie
Published: May 2007

SOFCs can be operated with biosyngas, but this fuel contains inorganic species, which act as contaminants for SOFCs. One of the most active is H2S, but salts like KCl can also affect SOFCs. Experiments have been performed to evaluate the interaction between SOFC anode material and these species. A synthetic gas representative of biosyngas containing H2S and KCl was circulating over Ni-YSZ pellets at 800{degree sign}C. It is shown that both H2S and KCl affect the Ni-YSZ anode by forming surface deposits. When KCl is present, K is detected at the surface. In the case of H2S, nickel sulfides are locally formed. In addition SOFCs have been operated with hydrogen containing H2S. The electrochemical behaviour of the SOFC confirms an effect of H2S, showing degradation even for the lowest H2S level tested. This degradation is partly irreversible, which is consistent with the formation of nickel sulfides.
Multiphysics Concepts and Foundations for Durability and Accelerated Characterization of Solid Oxide Fuel Cells
Authors: Reifsnider Kenneth , Ju Gang , Huang Xinyu
Published: May 2007

For Solid Oxide Fuel Cells (SOFCs), durability is often thought of in terms of resistance to mechanical failure, such as cracking of constituents or seals. However, loss of performance due to changes with time and operation history may be driven by changes in porosity, microstructure, chemical constituents, diffusion, transport, or interfacial characteristics. The present paper will examine some of these multiphysics-based degradation modes, and will compare multiphysics modeling with observed changes in SOFC performance. The paper will conclude with a discussion of a multiphysics modeling foundation for considering time- dependent and history dependent performance (especially for cyclic histories) for the purpose of design and as a methodology for accelerated characterization.
Anode Supported Tubular Cell Fabrication and Performance
Authors: McPhee William A. , Menard Peter D. , Gatto Nickolas S. , Sammes Nigel M. , Reifsnider Kenneth
Published: May 2007

The use of an anode supported design for Solid Oxide Fuel Cells (SOFCs) allows the thickness of the electrolyte layer to be reduced to below 20 um, reducing the ohmic losses in the electrolyte layer and allowing operation at temperatures of 700-800ºC. This work was based on cells with a NiO-8YSZ anode, 8YSZ electrolyte and a LSM cathode for intermediate temperature SOFCs. The cells were typically ≈0.7 cm in diameter with an active area of ≈34 cm2. Engineering problems with manufacturing of anode tubes, sealing cells in the hot zone and current collection were solved. Several design and manufacturing changes were made to improve the performance of the cells. This gave a peak performance to date of 0.18 W cm-2 at 750ºC on dry hydrogen. The methodology for performance improvement will be presented. Balance of plant and cell monitoring for a small stack will also be discussed.
Improvement in Mechanical Properties of Anode-Supported Planar SOFC
Authors: Basu Rajendra , Kumar S S. , Mukhopadhyay A K. , Maiti H S.
Published: May 2007

In anode supported SOFC, anode substrate provides the major mechanical support. This work is devoted to establish the improvement in mechanical properties of the tapecast, laminated Ni-YSZ anode substrate. The tested configuration consists of a dense, ~ 20μm YSZ coating on a 1-2mm thick porous Ni-YSZ cermet. The porosimetry data showed an increase of pore volume, uniform reduction of NiO to Ni and a very gradual shift in the unimodal pore size distribution. The bi- axial strength data of 1.5 mm Ni-YSZ anode with and without YSZ electrolyte coating were typically about 90 and 85 MPa respectively which were much higher than those reported (60 MPa) in literature. Also Weibull modulus (15) was higher for these structures compared to those (10) reported earlier. For YSZ coating, the young's modulus data (218 GPa) measured by nano-indentation method matched well with that of dense YSZ electrolyte.
Effect of Anode Support Thickness on the Performance of Tubular SOFCs
Authors: Son Hui-Jeong , Lim Tak-Hyoung , Lee Seung-Bok , Shin Dong-Ryul , Song Rak-Hyun , Kim Sung-Hyun
Published: May 2007

The performance of anode-supported tubular SOFC was investigated in terms of the thickness of anode support. Considering the geometry of single cell, it can be readily known that the concentration polarization across the anode- support is the most significant factor to determine the performance of the cell. For this purpose, we fabricated single cells having different anode-support thickness of 1mm and 2mm for both cells the cathode layer ((La0.85Sr0.15)0.98MnO3) and electrolyte layer (8mol%yttria-stabilized zirconia) were coated at the same condition. The cell performance was increased with decreasing anode-support wall thickness. The single cell having wall thickness of 1mm showed a power density of 0.42mW/cm2 at 0.7V and 700oC. From the analysis of impedance spectra, it was concluded that the total polarization of the anode supported tubular SOFC was mainly governed by the concentration polarization caused by the mass transport though the anode- support.
Effect of GDC Electrolyte Thickness on the Performance of Anode Supported Micro Tubular SOFC
Authors: Otake Takanori , Yokoyama Misuzu , Nagai Kohki , Ukai Kenji , Mizutani Yasunobu
Published: May 2007

An anode supported micro tubular SOFC has been studied because it has the high energy density and the thermal shock resistance. In this study, the relationship between the performance of the micro tubular cells and the thickness of the GDC electrolyte was examined at temperatures between 500 and 650 degrees C. The performance of the cell with 15.5μm thickness electrolyte was higher than the cell with 40μm thickness electrolyte at lower temperatures, but lower at higher temperatures. At lower temperatures, the ormic loss is dominant in the voltage drop, but at higher temperatures, the leakage of electron through the GDC electrolyte is main reason for the voltage drop.
Direct-Flame Solid-Oxide Fuel Cell (DFFC): A Thermally Self-Sustained, Air Self- Breathing, Hydrocarbon-Operated SOFC System in a Simple, No-Chamber Setup
Authors: Vogler Marcel , Barzan Daniel , Kronemayer Helmut , Schulz Christof , Horiuchi Michio , Suganuma Shigeaki , Tokutake Yasue , Warnatz Jürgen , Bessler Wolfgang G.
Published: May 2007

We present a combined experimental and modeling study of a direct-flame type solid oxide fuel cell (DFFC). The operation principle of this system is based on the combination of a flame with an SOFC in a simple, no-chamber setup. Experiments were performed using 13-mm-diameter planar SOFCs with Ni-based anode, samaria-doped ceria electrolyte and cobaltite cathode. At the anode, a 7-mm-diameter flat-flame burner provided methane/air rich premixed flames. The cell performance reaches power densities of up to 200 mW/cm2. A detailed analysis of the electrical efficiency is carried out. Observed system efficiencies are below 0.5%. Equilibrium calculations of the flame exhaust gas were performed. From the simulations, both H2 and CO were identified as species that are available as fuel for the SOFC.
Anode Polarization Effects in Single Step Co-fired Solid Oxide Fuel Cells
Authors: Yoon Kyung J. , Gopalan Srikanth , Pal Uday B.
Published: May 2007

SOFCs were fabricated employing a single step co-firing process and electrochemically characterized in the temperature range of 700-800oC with humidified hydrogen (3% H2O) and air. Voltage-current density characteristics (V-i) at 800oC in hydrogen-water vapor mixtures with compositions ranging from 3% to 73% water vapor have been obtained to simulate the effect of practical fuel utilization on the performance of single cells. The V-i plots obtained in hydrogen containing 3% water vapor were curve-fittd with a model to obtain the ohmic resistance of the cell, the exchange current density and the cathodic and anodic limiting current densities. The V-i curves obtained in other fuel compositions were successfully modeled by varying only the exchange current density and a physical interpretation of the anodic reaction was proposed.
Cell Performance of Microtubular SOFCs with Sc-Doped Zirconia Electrolyte under Pressurized Conditions
Authors: Nishino Hanako , Hashimoto Shin-Ichi , Liu Yu , Asano Koichi , Mori Masashi , Funahashi Yoshihiro , Fujishiro Yoshinobu
Published: May 2007

n this study, we fabricated anode-supported solid oxide fuel cell (SOFC) tubes of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) - Ce0.8Gd0.2O1.9 (CGO) cathode / CGO buffer layer / (ZrO2)0.89 (Sc2O3)0.1(CeO2)0.01 (ScSZ) electrolyte / Ni-ScSZ anode. The power generation test of the SOFC was carried out at 0.1 - 0.7 MPa at 650{degree sign}C. Using wet H2-N2 mixture gas and air, the maximum power density at 0.1 MPa was 0.68 W cm-2 (@2.6 A cm-2, Uf = 78%). With increase operating pressure, the performance has been improved, and the power density finally became over 1.48 W cm-2 (@2.8 A cm-2, Uf = 86%). It was conformed by current interruption method that both of the polarization resistance and ohmic resistance reduced under the pressurized condition.
Polarization Properties of an Intermediate Temperature Operated Ceramic Reactor in Power Generating Mode
Authors: Hashimoto Shin-Ichi , Nishino Hanako , Liu Yu , Asano Koichi , Takei Katsuhito , Mori Masashi , Funahashi Yoshihiro , Fujishiro Yoshinobu
Published: May 2007

It is known that a small tubular design enables SOFCs to have high thermal shock resistance and rapid startability. In this study, we fabricated anode-supported micro-tubular SOFCs which were introduced a Sc-doped ZrO2 electrolyte. The cell dimensions were 1.8 mm in diameter and 500 mm in length. And the cell configuration was (La,Sr) (Fe,Co)O3 - Gd doped CeO2 (CGO) cathode /CGO buffer layer /Sc-doped ZrO2 electrolyte (ScSZ) / Ni-ScSZ anode. The power generating test and the polarization measurement of this micro tubular cell have done at 650oC. The maximum power density of this cell was ca. 0.7Wcm-2 (2.6Acm-2, 0.26V) at 650oC, and the polarization resistance was higher than the ohmic resistance.
An Electrolyte-supported SOFC Stack Fabricated by Slip Casting Technique
Authors: Sui Jing , Liu Jiang
Published: May 2007

Cone-shaped YSZ electrolyte cylinders with a wall thickness of less than 0.2mm have been fabricated using slip casting technique. Single solid oxide fuel cell (SOFC) units have been made by applying La0.6Sr0.4Co0.2Fe0.8O3 (LSCF)- Ce0.9Gd0.1O1.95 (GDC) cathode material on the outside of the cylinders and NiO- GDC anode on the inside. A three-cell-stack has been assembled by connecting the cone-shaped SOFC units in electrical series via metallic interconnects and seals. The open circuit voltage (OCV) of the three-cell-stack was 2.9V and the maximum power was over 0.9W at 800{degree sign}C with humidified hydrogen as fuel and the ambient air as oxidant. Analysis of the impedance spectrum suggests that there is still potential to raise the stack output via improving the electrode performance.
Fabrication and Characterization of Stacked SOFCs Using Rapid Fabrication Technique
Authors: Arihara Kayo , Fujishiro Yoshinobu , Awano Masanobu
Published: May 2007

SOFCs technology is important for developing high efficient energy conversion system. The application fields of SOFC system are possible to improve by among the module design, electrochemical properties and manufacturing speed and cost. In addition, compact modules with small SOFCs are interest for mobile power modules in future. For the purpose of developing ceramic manufacturing process of SOFCs, we are carrying out development of rapid-prototyping-like fabrication techniques using computer manipulation of micro-nozzle and ceramic pastes. Gd-doped CeO2 (GDC) based micro cells (<1.0mm) and the stacked modules have been developed with direct assemble techniques. The products and characterization of the prepared GDC-SOFC cells are shown.
Two-cell Stack Test of Honeycomb SOFCs with Air Preheating Channels
Authors: Shimizu Satoshi , Wang Zhenwei , Kobuna Shunsuke , Yamazaki Yohtaro
Published: May 2007

We report a two-cell stack test of honeycomb SOFCs with air preheating channels. The honeycomb was made of 3YSZ with 3×3 channels. The size of each channel was 5×5 mm and the thickness of channel walls was 1 mm. Electrode materials were Ni(60 wt%)/8YSZ and La0.7Sr0.3MnO3. The OCV of 2.19 V was obtained at 800 ºC. Ag plates were used for the gas sealing and the interconnection between the honeycomb unit cells. The high value of OCV and the stable current during the experiment indicates a good gas sealing and small leak currents. After the measurement, the stack was cooled to room temperature, and held for 10 days, then it was heated again to 800 ºC. A small amount of OCV reduction was observed, however, no reduction was observed in the maximum power density. This successful test indicates that the interconnection using Ag plates is promising for honeycomb SOFC stacks.
An Aging Study of Solid Oxide Fuel Cells for Intermediate Temperature Operation
Authors: Reitz Thomas L. , Xiao Haiming , Rottmayer Michael , Seibert Anthony
Published: May 2007

The longevity performance of a tape cast solid oxide fuel cell using a LSM-based cathode was studied for 500 hours at various power densities. Polarization experiments indicated an enhancement in performance during the long term polarization. Electrochemical Impedance Spectroscopy (EIS) experiments were used to deconvolute the component impedances in the cell. The EIS data indicated that the vast majority of cell activation was associated with a single semi-circular feature which occurred in the low frequency region. Additional experiments were performed to attempt to assign specific electrode processes to corresponding semicircular features in the EIS spectra. These data suggest that steady polarization of the cell results in a gradual increase in cell performance which can be attributed to a ripening of the LSM-based cathode.