bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Thin Functional Layers for Anode Supported SOFC by Roll Coating Process
Authors: Büchler Oliver , Bram Martin , Mücke Robert , Buchkremer Hans Peter
Published: September 2009

A new method for the application of functional layers for solid oxide fuel cells was tested. So-called "roll coating" is a promising process for an industrial production of SOFCs, because it allows a high degree of automation. Nickel/yttria-stabilized zirconia (Ni/YSZ), YSZ, YSZ-LSM, and La0.65Sr0.3MnO3-δ (LSM) were used as materials for the anode, anode functional layer, electrolyte, cathode and current collector. The anode substrates were produced by tape casting. The anode and electrolyte were subsequently applied by roll coating on unsintered green tapes as well as presintered substrates. After co-sintering at 1400{degree sign}C for 5h, half-cells with an electrolyte thickness of 10 μm were obtained. Finally, an LSM/YSZ cathode functional layer and an LSM current collector were deposited by screen printing and co-sintered at 1100{degree sign}C for 3 h. The cells had current densities of 1.0 A/cm2 at 800{degree sign}C and 0.7 V, which is lower than the performance of screen-printed Jülich standard cells with the same type of LSM/YSZ cathode. It is expected that the performance of roll-coated cells can be improved by further reducing the thickness of the functional layers. The results show that the anode-supported planar half-cells can be fabricated in a cost-effective way by combining roll coating with subsequent co-firing.
Co-Extrusion / Phase Inversion / Co-Sintering for Fabrication of Hollow Fiber Solid Oxide Fuel Cells
Authors: Droushiotis Nicolas D. , Doraswami Uttam , Othman Mohd , Li Kang , Kelsall Geoff
Published: September 2009

We have used a co-extrusion / phase inversion process, followed by co-sintering and then NiO reduction with hydrogen, to fabricate anode (Ni-CGO) / cerium-gadolinium oxide electrolyte (CGO) dual-layer hollow fibers (HFs) with inner diameters < 1 mm. This is the first time such dual-layer fibers have been produced as components of SOFCs, thereby decreasing the number of fabrication steps compared with single layer extrusion, while ensuring a gas-tight electrolyte layer of controlled thickness (ca. 60-80 μm). A La0.6Sr0.4Fe0.8Co0.2O3 (LSCF)-CGO cathode ca. 100 μm thick was deposited using slurry coating. Preliminary measurements of the performance of the dual-layer microtubular HF-SOFCs were made with hydrogen flowing at 5 cm3 min-1 and air at 40 cm3 min-1, achieving maximum power densities of 420 W m-2, 800 W m-2 and 1000 W m-2 at 450 oC, 550 oC and 580 oC, respectively. A proposed stack design shows how these micro-tubular SOFCs could be connected in parallel to increase currents and in series for scaling up voltages, aiming at the design of practical stacks.
Progress in Metal-Supported SOFCs
Authors: Tucker Michael , Sholklapper Tal , Lau Grace , DeJonghe Lutgard , Visco Steven
Published: September 2009

Metal-supported SOFCs offer considerable cost and robustness advantages over traditional SOFC designs. In particular, the following topics will be addressed: - Advantages of the metal-supported design - Materials choice for electrolyte and metal support - Acceptable operating temperature range - Fabrication methods - Degradation mechanisms, including Cr migration, metal oxidation, anode-support interdiffusion, etc LBNL has demonstrated competitive power density and promising thermal shock and redox cycling tolerance for YSZ-based metal-supported cells. One cell design utilizes infiltrated anode and cathode catalysts coating porous, sintered YSZ electrode backbones. Our early work demonstrated high power density with infiltrated Ni anodes. Maximum power densities of >330mW/cm2 and >1000mW/cm2 were achieved with air and oxygen as oxidant, respectively, at 700{degree sign}C. Ni coarsens rapidly in fuel atmosphere, so we now use more stable oxide-based anode materials. Very promising stability at moderate power density (>200mW/cm2) will be reported, along with an overview of our cell scale-up efforts.
Recent Development Aspects of Metal Supported Thin-Film SOFC
Authors: Franco Thomas , Brandner Marco , Rüttinger Matthias , Kunschert Georg , Venskutonis Andreas , Sigl Lorenz
Published: September 2009

The metal supported solid oxide fuel cell (MSC) technology has attained high interest for the electrical power supply of vehicles by auxiliary power units (APUs) which operate independently from the main engine. Its main advantages compared to other SOFC technologies are higher mechanical stability and better thermal and redox behaviour, which are indispensible for mobile applications. For many years, Plansee has developed and fabricated porous metallic substrates, interconnector plates and protective coatings for various types of SOFCs which are used in mobile as well as in stationary applications. Plansee has recently developed technologies for the production of MSCs in close co-operation with outlines various partners from science and industry. This paper results of this development.
Development of Planar Metal Supported SOFC with Novel Cermet Anode
Authors: Blennow Peter , Hjelm Johan , Klemenso̸ Trine , Persson Aåsa , Brodersen Karen , Srivastava Akhilesh , Frandsen Henrik , Lundberg Mats , Ramousse Severine , Mogensen Mogens
Published: September 2009

Metal-supported solid oxide fuel cells are expected to offer several potential advantages over conventional anode (Ni-YSZ) supported cells, such as increased resistance against mechanical and thermal stresses and a reduction in materials cost. When Ni-YSZ based anodes are used in metal supported SOFC, electrode material from the active anode layer may interdiffuse with the metallic support during sintering. The purpose of this work is to illustrate how the interdiffusion problem can be circumvented by using an alternative anode design based on porous and electronically conducting layers, into which electrocatalytically active materials are infiltrated after sintering. The paper presents the recent results on the electrochemical performance and durability of the novel planar metal-supported SOFC design. The results presented in the paper show that the novel cell and anode design has a promising performance and durability at a broad range of temperatures and is especially suitable for intermediate temperature operation.
Metal-supported Solid Oxide Fuel Cell with Diesel Reformer
Authors: Bae Joongmyeon , Baek Seung-Wook , Jeong Jihoon , Yoon Sangho
Published: September 2009

1 kWe Diesel reforming sub-system was successfully developed and has been operated for 1000 hours without significant degradations. Metal-supported solid oxide fuel cell (SOFC) was also fabricated up to 10x10 cm2 scale avoiding expansive manufacturing process. Our metal-supported SOFC shows several critical and significant milestones to solve the crucial problems of ceramic-supported SOFC such as sealing and mechanical strength. In this paper performance of Diesel reformer with sulfur and low hydrocarbon remover (i.e. post-reformer) is discussed. Fabrication process of metal-supported cell developed by our group is introduced and critical issues to fabricate are discussed.
High Power SOFC Using LSGM Film on NiFe Porous Bi-metal Substrate
Authors: Ju Young-Wan , Eto Hiroyuki , Inagaki Toru , Ishihara Tatsumi
Published: September 2009

Sr and Mg doped LaGaO3 (LSGM) thin film was prepared on NiO-Fe2O3 bi-metal substrate by Pulsed Laser Deposition (PLD) method. Substrate preparation conditions were studied at different sintering temperatures in order to optimize the preparation condition for dense disk with smooth surface. By the thermal reduction, the substrate was changed to a porous Ni-Fe metal substrate. The volumetric shrinkage and porosity of the substrate were also studied at different reduction temperature and the suitable reduction temperature exists at 973 K for porous metal substrate. Stoichiometric composition of LSGM film was successfully prepared by optimal deposition parameter and target composition. Structure of the deposited film was changed from amorphous to crystalline perovskite structure during the annealing at 1073 K for 2 h. Sm0.5Sr0.5CoO3 was prepared as cathode by slurry coating method. The maximum power density (MPD) was achieved a value of 1.6 and 0.9 W/cm2 at 973 and 873 K, respectively, on porous Ni-Fe metal substrate. Even at 673 K, MPD of 0.1 W/cm2 was achieved.
Ceria Film Supported on Ni-Fe Metal Film
Authors: Lee Younki , Choi Gyeong Man
Published: September 2009

An acceptor-doped ceria film supported on Ni-Fe metal film was successfully fabricated. A Ni-Fe metal film (10~20mm) was fabricated by screen printing of NiO-Fe2O3 paste on a Si substrate and subsequent reduction. Gd-doped ceria electrolyte was RF-sputtered on the Ni-Fe film and annealed at 500oC, 30mTorr of oxygen atmosphere. Despite the heat cycle from room temperature to 500oC, no cracks and pores were observed in the electrolyte film.
Fabrication of Cerium Oxide based SOFC having a Porous Stainless Steel Support
Authors: Oishi Naoki , Yoo Yeong
Published: September 2009

Porous stainless steel supported solid oxide fuel cells having nickel - ceria cermet anode, ceria electrolyte and lanthanum strontium iron cobalt perovskite cathode were fabricated by using inexpensive technologies of spraying, pressing and firing. A ceria cell fabricated on a porous support was found to show long-term stability over 1000 hours at 600 {degree sign}C under different current densities with open circuit voltage being 0.84 V over testing. It was shown that gas permeability in porous support had a great influence on fuel cell characteristics, and that cathode polarization accounted for half of internal resistance in a porous stainless steel supported cell.
Degradation Studies on Tubular Metal Supported SOFC
Authors: Rodriguez-Martinez Lide M. , Otaegi Laida , Alvarez Mario , Rivas Mikel , Gomez Nuria , Zabala Aingeru , Arizmendiarrieta Nagore , Antepara Inigo , Urriolabeitia Abel , Olave Mireia , Villarreal Igor , Laresgoiti Ander
Published: September 2009

The stability of tubular metal supported SOFC has been studied as a function of current load, thermal cycles and interconnect-sealing concepts. Long term testing under applied current at 800ºC have been performed over 1000 hours on standard cells. Thermal cycles have been proven intensely (250 cycles) during over 700 hours. Major cause for degradation has been identified in terms of the anode interconnect-sealing design, which involves specific handling and machining of tubes and generation of initial submicron cracks. Cell microstructure seems stable after 1000 hours testing at 300 mA/cm2 and 800ºC.
IDEAL-Cell, a High Temperature Innovative Dual mEmbrAne Fuel-Cell
Authors: Thorel Alain S. , Chesnaud Anthony , Viviani Massimo , Barbucci Antonio , Presto Sabrina , Piccardo Paolo , Ilhan Zeynep , Vladikova Daria E. , Stoynov Zdravko
Published: September 2009

IDEAL-Cell is a new concept of a high temperature fuel cell operating in the range 600-700 {degree sign}C. It is based on the junction between the anode part of a PCFC and the cathode part of a SOFC through a mixed H+ and O2- conducting porous ceramic membrane. This concept, extensively described in the present paper, aims at avoiding all the severe pitfalls connected with the presence of water at the electrodes in both SOFC and PCFC concepts. Spark Plasma Sintering samples were designed specifically for proving the IDEAL-Cell concept. The first electrochemical results obtained at 600 {degree sign}C under hydrogen on millimeter thick samples show that IDEAL-Cell behaves like a high temperature fuel cell.
Compatibility and Reactivity between Materials in an Innovative Dual Membrane Fuel-Cell (IDEAL-Cell) Design
Authors: Caboche Gilles , Hochepied Jean-François , Piccardo Paolo , Przybylski Kazimierz , Ruckdäschel Robert , Ardigo Maria-Rosa , Fatome Emilie , Chevalier Sébastien , Perron Aurélien , Combemale Lionel , Palard Mickaël , Prazuch Janusz , Brylewski Tomasz
Published: September 2009

The IDEAL-Cell project aims at developing an innovative and competitive concept for fuel cell operating between 600-700 {degree sign}C. It is based on the junction between a PCFC anode/electrolyte part and a SOFC electrolyte/cathode, through a mixed porous ceramic membrane. Cathode materials are: La0.60Sr0.40CoO3-d (LSCF40) or La0.60Sr0.40Co0.20Fe0.80O3-d (LSCF48); electrolyte materials are: Ce0.85Y0.15O2-d (YDC15) and BaCe0.85Y0.15O3-d (BCY15). Ni-BCY15 cermet is the anode material. The central membrane is made of BCY15-YDC15 mixture. Good compatibility was observed at electrode/electrolyte cathode interface after long term ageing (20h/1100{degree sign}C following by 500h/700{degree sign}C) and no new phase was detected. Concerning the dual membrane BCY15-YDC15, a good adhesion was obtained between these two electrolyte materials. Finally, reactivity between LSCF40/48 and Crofer 22 APU (selected as first generation interconnect material) was studied in oxidizing atmosphere (1h/1000{degree sign}C following by 200h/700{degree sign}C). SrCrO4 formation was observed due to the diffusion of Cr and reaction with Sr from the cathode material.
Development of a Lower Temperature SOFC
Authors: Wachsman Eric D.
Published: September 2009

A major impediment to commercialization of solid oxide fuel cell (SOFC) technology has been high operating temperature. Higher conductivity, and thus lower temperature, oxide electrolytes have existed for some time (ranging from gallates and ceria to bismuth oxide based materials). However, each of these materials has it's own specific issues. Moreover, transitioning from a zirconia electrolyte to one of these alternate electrolytes requires development of an entirely new cell material set. Over the last 20 years we have focused on using the most conductive, and hence lowest temperature, electrolytes. To overcome inherent instability in reducing environments we developed a bilayer bismuth-oxide/ceria electrolyte. To overcome reactivity with more conventional cathode materials we developed a bismuth-ruthenate/bismuth-oxide composite cathode. Finally, these materials were integrated into an anode supported cell resulting in power densities of ~2 W/cm2 at 650{degree sign}C. The materials issues, how they were addressed, and the ultimate performance achieved are discussed.
Proton Conducting IT-SOFC Utilizing Internally Steam Reformed Alcohol Fuels
Authors: Azimova Maria , McIntosh Steven
Published: September 2009

Cobalt doping on to the B-site of barium cerate zirconate proton conducting oxides is an effective route to lowering required sinter temperatures while maintaining reasonable proton conductivity. BaCe0.48Zr0.4Yb0.1Co0.02O3-δ was found to be stable under SOFC conditions and was thus utilized as the electrolyte in anode supported SOFC. A dual layer tape casting process that enables flexible anode and cathode composition was used to fabricate the cells. These were operated with humidified hydrogen and internally reformed methanol fuel. I-V curves and impedance spectroscopy indicate that further optimization of the electrode composition and structure is required.
Performance of Protonic Ceramic Fuel Cell based on Yb-doped BaZrO3 Electrolyte
Authors: Park Jong-Sung , Lee Jong-Ho , Lee Hae-Weon , Kim Byung-Kook
Published: September 2009

The anode supported fuel cells based on the proton conducting Yb-doped BaZrO3 were fabricated by the dry pressing and sintering at 1300oC. The proton conducting Yb-doped BaZrO3 with the addition of ZnO as a sintering aid were used as electrolyte and the cermet composed of Ni and Ba(Zr0.84Yb0.15Cu0.01)O3-δ were used for the porous anode substrate. The thickness of the electrolyte layer was about 60 μm and the maximum power density of the fuel cells was 51 mW/cm2 at 600oC.
Determination of Global/local Fuel Utilization via Variation of Fuel Utilization
Authors: Reinert Andreas , Strohbach Thomas
Published: September 2009

Knowledge of the actual fuel utilization of a fuel cell stack is very important for characterizing the performance of a fuel cell stack. The actual fuel utilization in many cases does not equal the set fuel utilization defined by the electrical current and the fuel gas flow rate due to possible leakages or an inhomogeneous fuel gas distribution to the fuel cell stack layers. This manuscript describes a method for determining the actual fuel utilization of a fuel cell stack or a fuel cell layer by recording the cell voltages at different fuel utilizations.
Numerical Modeling and Performance Study of a SOFC Button Cell
Authors: Barzi Yaser M. , Raoufi Arman , Lari Hamid , Rezaee Masoud
Published: September 2009

In this study, the computational fluid dynamics is used to predict and evaluate performance of an anode supported SOFC button cell. The elelectrical and electrochemical processes are simulated coupled with heat and mass transfer model. To account for the ohmic losses and joule heating of the current that passes through the cell body, a descrized network ciruit is adopted. The model predictes the cell output voltage, the local EMF and the state varibles pressure, temperature and species concentrations. The local electrical patameters are calculated based on the local pressure, temperature and concentration of the species. The numerical results are compared with the experimental data and good agreement is observed. The SOFC operation are simulated at different input fuel flow rates and humidification. The results show how the input fuel mass flow rate affects the button cell SOFC performence. Also influences of the anode thichness on cell performance are investigated.
Near-Infrared Imaging of SOFCs with Methane and Propane Fuels
Authors: Pomfret Michael B. , Steinhurst Daniel A. , Kidwell David A. , Owrutsky Jeffrey C.
Published: September 2009

A Si-CCD camera-based imaging system is used in-situ to study the effects of hydrocarbon fuels on Ni/YSZ solid oxide fuel cell anode temperatures. Methane and propane are used as fuels. Temperature variations are investigated to explore how carbon deposition varies with fuel, and how deposition and electrochemical oxidation of carbon affect the anode. The temperature change that results from carbon growth during CH4 flow is -2.3 ºC. The temperature change due to the oxidation of carbon deposits from CH4 is +2.0 ºC. Similar experiments with C3H8 produced temperature shifts of -3.4 ºC and +2.4 ºC during fuel flow and electrochemical oxidation, respectively. The temperature drops more quickly when C3H8 is used instead of CH4. As deposits are electrochemically oxidized, the maximum temperature occurs ~2 minutes earlier in the CH4 case. The time profiles indicate that more carbon is present in C3H8 cells.
Electrochemical Properties of Electrode-Supported La0.75Sr0.25Ga0.8Mg0.16 Fe0.04 O3-d Solid Oxide Fuel Cells
Authors: Yu Ji Haeng , Woo Sang Kuk
Published: September 2009

Thick-film La00.75Sr0.25Ga0.8Mg0.16 Fe0.04 O3-d (LSGMF) cells either on NiO-YSZ anode or La0.7Sr0.3Ga0.6Fe0.4O3 (LSGF) cathode substrates were made by spin coating. La-doped CeO2 (LDC) layer was inserted between NiO-YSZ and LSGMF to prevent the reaction during co-firing. As for LSGF-cathode supported cell, no interlayer was necessary because the components of cathode were same to those of LSGMF except for Mg. LSGMF slurry was deposited homogeneously on the porous supports by spin-coating. The current-voltage characteristics of anode- and cathode-supported LSGMF cells were investigated at the temperatures between 700-900{degree sign}C.
Solid Oxide Fuel Cells with Atomic Layer Deposited Platinum Catalyst
Authors: Chao Cheng-Chieh , Prinz Fritz B.
Published: September 2009

Platinum can serve as a catalyst for enhancing the kinetics of hydrogen oxidation reactions (HOR) and oxygen reduction reactions (ORR) in fuel cell operations. In a previous study, we fabricated a solid oxide fuel cell (SOFC) with an atomic layer deposited (ALD) yttria-stabilized zirconia (YSZ) electrolyte and sputtered porous platinum electrodes. To improve the bonding between the electrolyte and the electrodes, we deposited a one-nanometer platinum layer in situ on top of the electrolyte. An 80% improvement in maximum power density was observed at 450 åC due to the reduction of activation losses.
Fabrication and Performance of Ni-Fe Metal-supported SOFC using Gd-doped Ceria Electrolyte
Authors: Kang Young Jin , Choi Gyeong Man
Published: September 2009

Metal-supported solid oxide fuel cells (SOFCs) have the advantage of the thermal shock resistance and higher mechanical strength compared with anode-supported SOFCs. In this study, Ni-Fe metal was used as supporting metal. The supporting metal was initially prepared in oxide form of NiO-Fe2O3, and co-sintered with Gd-doped ceria electrolyte at 1350ºC for 3h in air and later reduced to Ni-Fe metal. Two different cells were prepared and compared to see the effect of the thickness of the electrolyte and the role of the electrode on the performance of the cell.
High Efficiency Reversible Solid Oxide Microtubular Fuel Cells
Authors: Laguna-Bercero Miguel A. , Campana Roberto , Larrea Angel , Kilner John , Orera Victor M.
Published: September 2009

In this paper we present a highly efficient reversible microtubular cell in both modes of operation. These devices can produce hydrogen from electricity and steam (Solid Oxide Electrolyser, SOE), and then use the stored hydrogen to generate electricity and heat (Solid Oxide Fuel Cell, SOFC), acting as a storage device for electrical energy. Evaluation of the performance of the cell in electrolysis mode as a function of the steam concentration supplied to the cathode is discussed. Superior performance was obtained at 950 ºC for electrolysis operation. At 1.5V, we have obtained a current density of -2.95 A/cm2 using 70% H2O/ 15%H2 / 15%N2 as a fuel, with a total internal resistance of 0.26 ohm.cm2. The production of hydrogen in the electrolyser was also tested by mass spectrometry, confirming the high current efficiency for the steam electrolysis. These microtubular cells are very efficient and totally reversible, and especially in SOE mode where their performance is very promising for high temperature electrolysis applications.
Thin Film Electrolyte Micro-SOFC: Fabrication and Performance Improvement through Thin Film Electrolyte and Nano-Structure Electrodes
Authors: Noh Ho-Sung , Lee Heon , Lee Jong-Ho , Lee Hae-Weon , Son Ji-Won
Published: September 2009

The performance improvement, especially at a lower operating temperature regime, by employing thin film and nano-structure electrodes for miniaturized SOFCs is investigated. The anode-supported unit cells with thin ({less than or equal to} 1 um) YSZ electrolytes were fabricated by using pulsed laser deposition (PLD). Performance of the cell was characterized at temperatures lower than 600 oC. We obtained OCV > 1V with less than 1 um-thick thin electrolytes, which implied the thin electrolyte was fairly dense and gas tight. The thin film electrolyte cells exhibited much improved cell performance than that of the anode-supported SOFC cell with a thick (~10 um) YSZ electrolyte at the low operating temperature regime (350-550 oC). The effects of the nano-structured electrodes and thin film electrolytes on the cell performance are investigated.
Long Term Performance Stability of Micro-Tubular SOFCs Operating in the Intermediate Temperature Regime
Authors: Galloway Kevin V. , Sammes Nigel M.
Published: September 2009

Decreasing the operating temperature of SOFCs can reduce degradation of cell and stack materials and can reduce the cost of these materials as well through the use of metallic materials. These qualities have motivated the development of micro-tubular SOFCs for operation in the intermediate temperature range between 450{degree sign}C and 550{degree sign}C. The micro-tubular SOFC investigated is anode supported, consisting of a NiO and Gd0.2Ce0.8O2-x (GDC) cermet anode, thin GDC electrolyte, and a La0.6Sr0.4Co0.2Fe0.8O3-y (LSCF) and GDC composite cathode. The long term performance and IV performance from individual 1.8 mm diameter, 1.2 cm length micro-tubular SOFCs is investigated in the intermediate temperature range.
Geometric Effects of Triple Phase Boundary in Solid Oxide Fuel Cells
Authors: Kim Young Beom , Chao Cheng-Chieh , Gür Turgut M. , Prinz Fritz B.
Published: September 2009

This paper describes the fabrication and testing of a model electrode to study geometric effects at well-defined triple phase boundaries (TPB) in solid oxide fuel cells (SOFC), using silica particle masking and Langmuir-Blodgett deposition. Electrochemical behavior of dense platinum cathodes that were patterned into close-packed circular openings of 300-400 nm in diameter through which the underlying yttria-stabilized zirconia (YSZ) electrolyte was exposed to the gas environment were studied at 450oC. These nano-structured cathodes exhibited better structural integrity and thermal stability at operating temperatures than their porous sputtered Pt counterparts. 100μm-thick 8% polycrystalline YSZ was used as the electrolyte in these tests. It was shown that cathode impedances obtained from EIS Nyquist spectra as well as the maximum power densities scaled almost linearly with TPB density, i.e., higher TPB density resulted in better fuel cell performance.
Guidelines for Thin Film Usage and Microfabrication for Solid Oxide Fuel Cell Application
Authors: Bieberle-Hutter Anja , Evans Anna , Galinski Henning , Rupp Jennifer L. , Ryll Thomas , Scherrer Barbara , Toelke Rene , Gauckler Ludwig J.
Published: September 2009

Guidelines for thin film microfabrication and use in micro-solid oxide fuel cells (micro-SOFC) are given and discussed. Microstructures and microfabrication of metal oxide thin films, the selection of substrate materials, and feature size - property relation will be under main focus and illustrated with recent results from micro-SOFC research. These considerations will help to use silicon technology for the fabrication of micro-SOFC components.
Performance of 30W-class SOFC Module using Anode Supported Micro Tubular Cells
Authors: Otake Takanori , Okada Fumio , Mizutani Yasunobu , Funahashi Yoshihiro
Published: September 2009

The 30W-class SOFC module using 54 anode supported micro tubular cells were successfully fabricated. The performance of the module was high even at low ambient temperatures. This module could start up within an hour. After several rapid start-up operation tests, no degradation was observed.
Fabrication and Characterization of La0.6Sr0.4CoO3-δ/ Ce0.9Gd0.1O2-δ Composites as Current Collecting Materials for Microtubular SOFCs
Authors: Yin Jingtian , Murata Kenji , Misono Teruhiko , Fukui Takehisa
Published: September 2009

The highly porous LSC/GDC composites were fabricated and characterized as a potential air side current collecting material for micro-tubular SOFCs. The results revealed that the properties of the composites were strongly affected by the composition, particle size ratio of starting powders, microstructure and porosity. The composite specimen with 35 vol. % GDC and an open porosity of 73% gave an electrical conductivity of 174 S/cm at 600 ºC, which is 1.8 times as large as that of the LSCF with a porosity of 61%, and a thermal expansion coefficient of 12.6×10-6 K-1 in the temperature range from room temperature to 600 ºC, which is very close to the value of the LSCF cathode. The superior combined property suggests the possibility that they serve as air side current collectors in the micro-tubular SOFCs.
Atomic Layer Deposition of Ceria-based Thin Films as Interlayer for Solid Oxide Fuel Cells
Authors: Fan Zeng , Prinz Fritz B.
Published: September 2009

Traditional YSZ electrolyte membranes benefit from stability and acceptable ionic conductivity at elevated temperatures (above 500{degree sign}C). However, at operating temperatures below 500{degree sign}C, the charge transfer reaction at the cathode/ electrolyte interface becomes very slow and causes significant cathode activation overpotential. Ceria based thin films, like Yttria doped Ceria and Gadolinia doped Ceria, possess higher oxide ion diffusivities and can be potentially used as interlayer between cathode and YSZ electrolyte in order to facilitate the charge transfer kinetics at lower temperatures. In this work, we have focused on growing high quality YDC thin films by atomic layer deposition method and optimizing the growing parameters. Thin films were characterized by X-Ray Diffraction and X-ray Photoelectron Spectroscopy techniques. Prototyping work is being conducted on fuel cells with YDC as interlayer by ALD. The performance of SOFCs with YDC surface coatings on the cathode will be reported.
Effect of Cathode Porosity on the Performances of Cathode Supported Honeycomb SOFCs
Authors: Shimizu Sota , Yamaguchi Toshiaki , Fujishiro Yoshinobu , Awano Masanobu
Published: September 2009

Solid oxide fuel cells (SOFCs) are environmentally friendly and have good energy efficiency. Currently, many researchers have studied reduction of the operating temperatures, saving space and increasing speed of the start-up/shut-down of SOFCs for applications, such as a compact portable power supply. Reduction of SOFC operating temperatures would lead to a decrease in material degradation, and decrease cost by allowing use of metallic materials. We have been developing a novel high performance SOFC supported by a cathode-honeycomb monolith. In this study, the fabrication technique of porous cathode supported honeycomb SOFCs was investigated and the effects of cathode porosity on the SOFC performance were investigated using a practical electrochemical evaluation. Open circuit voltages and performances were affected by cathode porosity, especially those measured in air as cathode atmosphere has large differences.
Development of Tubular Solid Oxide Electrolysis Cells for Hydrogen Production
Authors: Kato Tohru , Sakaki Nobutaka , Negishi Akira , Honda Takeo , Nguyen Lan , Tanaka Yohei , Momma Akihiko , Kato Ken , Iimura Youko
Published: September 2009

Tubular SOECs with operating temperature reduced to 700~800oC are developed. To improve cell performance at low temperatures, Sc2O3 stabilized ZrO2 is chosen as the electrolyte material and thickness of the electrolyte layer is tried to be controlled to about 10 μm. Test electrolysis cells are fabricated by using slurry coating method. Dependence of cell performance on operating conditions is measured. Further, AC impedance method is applied to the cells to estimate interfacial overvoltage. From the experiment, it is clarified that the hydrogen production rate at 750oC goes up to 3.6 sccm/cm2 at the thermoneutral voltage. This value is more than 2 times of that of the commercial alkaline electrolysers.
Solid Oxide Fuel Cell Fuelled by Biofuels
Authors: Milewski Jaroslaw , Lewandowski Janusz
Published: September 2009

An analysis of various biofuels as fuels for Solid Oxide Fuel Cells (SOFC) is presented. The results are compared with Natural Gas (NG) as a reference fuel. The biofuels are characterized by both lower efficiency and lower fuel utilization factors in comparison with NG. The presented results are based on a 0D mathematical model in design point calculation. The governing equations of the model are presented.
SOFC Running on Biogas: Identification and Experimental Validation of "Safe" Operating Conditions
Authors: Girona Kelly , Laurencin Jérôme , Petitjean Marie , Fouletier Jacques , Lefebvre-Joud Florence
Published: September 2009

This work concerns the feasibility of SOFC operation directly on biogas and more specifically, the optimization of biogas internal dry reforming conditions. A special attention is paid to the carbon deposition risk. For such a purpose simulation tools have been developed, based on thermodynamic and electrochemical modelling, in order to determine the risk of carbon formation within the anode during operation. Safe operation conditions in terms of temperature, fuel composition and cell polarization have been established and validated experimentally. In conditions where carbon deposition is expected, performance degradation upon operation has been followed over more than hundred hours on complete cells (Cermet Ni-8YSZ//8YSZ//LSM) by electrochemical impedance spectroscopy. The carbon deposited has been characterized by scanning electron microscopy with particular attention given to its morphology and distribution.
Generation of Electricity from Bio-wastes Using Solid Oxide Fuel Cell
Authors: Shiratori Yusuke , Ijichi Takeo , Oshima Toshihiro , Sasaki Kazunari
Published: September 2009

Direct feeding of biogas to SOFC, which is derived from municipal bio-wastes, has been tested in this research. Because biogas composition is strongly affected by the kind of organic wastes and the operational conditions of methane fermentation, it has been monitored for 100 days using gas chromatograph in order to reveal the fluctuation of biogas composition and its influence on the SOFC performance. CH4/CO2 ratio in the raw biogas was in the range of 1.4-1.9 and had a tendency to decrease when the cattle dung slurry was fed into the reactor. Using anode-supported button cell, stable operation of direct-biogas SOFC was achieved at 800 oC. Cell voltage above 0.8 V was recorded over 350 h at 200 mA cm-2
A Performance Analysis of a Solid Oxide Fuel Cell - Micro Gas Turbine Hybrid System Using Biogas
Authors: Komatsu Yosuke , Kimijima Shinji , Szmyd Janusz S.
Published: September 2009

This paper presents a performance analysis for a Solid Oxide Fuel Cell (SOFC) - Micro Gas Turbine (MGT) hybrid power system using biogas. It was assumed that the supplied biogas consisted of CH4 and CO2; the performance was predicted comprehensively while the concentrations of the both components were varied. The concentration of CH4 in biogas was varied from 100 [%] to 20[%]. The obtained results figured the system performance degradation with decreasing CH4 concentration. It also suggested designing the cell active area to fulfil the requirements for an electrical capacity of 220 [kW]. It was found that lager cell active area was required while the CH4 concentration diluted. The results are promising for the future use of biogas in SOFC-MGT hybrid systems.
Ethanol in simple SOFC Systems
Authors: Breite Manuela , Jahn Matthias , Pfeifer Thomas , Stelter M. , Bernard J.
Published: September 2009

Ethanol is well suited as an energy carrier for fuel cells as it has a high energy density; it is non toxic and simple to transport and store. If used in SOFCs, one major task is to produce synthesis gas from it with a high percentage of H2 and CO. Dry partial oxidation (POX) is the simplest reforming principle for SOFCs. Thermodynamic calculations showed that simple SOFC setups should be possible with an ethanol POX reformer. Thermodynamic equilibria of ethanol partial oxidation were calculated with respect to coke formation. It has been shown that with air ratios above λ = 0.28 and 96 Vol% ethanol / 4 Vol% water sooting does not occur for temperatures above 700{degree sign}C. Currently, the most important task is to identify effective catalysts for the partial oxidation of ethanol. Experiments with low cost base metals like nickel on aluminium oxide showed great promise for ethanol conversion.
Ethanol Fuelled SOFC with ZnO Addition in the Anode
Authors: De Florio Daniel Z. , Tabuti Francisco N. , Fonseca Fabio C. , Muccillo Reginaldo
Published: September 2009

The solid oxide fuel cell (SOFC) has attracted a great deal of attention due to its high efficiency and variety of usable fuels like hydrocarbon or alcohols. In this work, aiming at the use of carbon-containing fuels in SOFC, ZnO was added to the SOFC anode ceramic-metal composite yttria-stabilized zirconia/nickel (YSZ/Ni) in a wide range of relative compositions. Apparent density measurements confirmed that ZnO is a sintering aid for YSZ matrix. X-ray diffraction revealed the presence of YSZ, Ni, ZnO and NiO phases in all samples. The impedance analysis show that the higher is the ZnO concentration, until 50% vol., lower is the electrical resistance of the samples. The single cells preliminary experiments suggest the higher efficiency of ethanol fuelled SOFCs with YSZ/Ni/ZnO anode. Further experiments using doped-ceria instead of YSZ will be accomplished to enhance the SOFC performance at temperatures as low as 500 {degree sign}C.
Direct Methanol Solid Oxide Fuel Cell
Authors: Kuliyev Sadig A. , Aksongur Sila , Mat Mahmut D. , Ibrahimoğlu Beycan , Kozlu Mustafa D.
Published: September 2009

In this study, performance of membrane electrode assembly (MEA) was studied with hydrogen and methanol/water vapor fed directly to the anode. MEA was prepared by using scandia-stablized zirconia (SSZ) electrolyte and NiO-SSZ and Sr-doped lanthanum ferrite (LSF) as anode and cathode material. A three dimensional model of solid oxide fuel cell (SOFC) has been developed and is used to predict the temperature, fuel concentration distribution across the cell. On the other hand we designed special experimental set up for testing MEA performance. The influence of different operation parameters (temperature, fuel concentration, fuel-air flow rate...) to the MEA performance was examined. The results show the maximum power generation from MEA when fed with methanol and hydrogen. The maximum power output of 1.6 W/cm² was obtained at 750oC with pure hydrogen. When methanol was directly used as fuel the maximum power output was 1.2 W/cm² at same temperature.
Utilization Modes for Solid Carbon Conversion in Fuel Cells
Authors: Gür Turgut M.
Published: September 2009

The search for technological breakthroughs in carbon conversion involved various fuel cell arrangements to attain the best possible delivery mode for the solid fuel or the oxidant to the electrochemical reaction site. This paper summarizes different approaches from the mechanistic point of view of engaging the solid fuel and oxygen in order to achieve efficient oxidation of carbon. Also, the operating principle and experimental results are presented for a fluidized bed direct carbon fuel cell (FB-DCFC) integrated with a Boudouard type dry gasifier. Power densities up to 175 mW/cm2 were demonstrated at 850oC for conversion of activated carbon in this fuel cell arrangement, which corresponds to more than 4 W of sustained power generated by the FB-DCFC. A CO "shuttle" mechanism is proposed to explain the operation and behavior of FB-DCFC in CO2 as well as in inert gas environments.
A Novel Direct Carbon Solid Oxide Fuel Cell
Authors: Tang Yubao , Liu Jiang , Sui Jing
Published: September 2009

A direct carbon solid oxide fuel cell (DC-SOFC) was assembled and tested. The cell was a tubular SOFC-like structure, using YSZ as electrolyte, silver paste as anode and cathode, and graphite as fuel. At the testing temperature 800{degree sign}C, the open circuit voltage of the cell was 0.85V and the maximum power reached 47mW with the active cell area of 5.08 cm2. In the lifetime measurement, the cell current was maintained at 71mA. After running 3h, the cell voltage dropped from 0.62V to 0.22V and the discharge value calculated was 771C.
Liquid Tin Anode SOFC For Direct Fuel Conversion - Impact of Coal and JP-8 Impurities
Authors: Tao Thomas , McPhee William , Koslowske Mark , Bentley Jeff , Slaney Mike , Bateman Linda
Published: September 2009

The Liquid Tin Anode solid oxide fuel cell (LTA-SOFC) has a demonstrated capability for direct fuel conversion using virtually any carbonaceous fuel. Two most notable applications under development are direct logistic fuel JP-8 conversion and direct coal (and biomass) conversion. For example a Gen 3.1 cell using logistic fuel only without fuel processing or reforming, has demonstrated specific power of 170 mW/cm2, at least 30 full thermal cycles and less than 7 minutes start up. Direct logistic fuel or coal conversion without fuel reforming/gasification/purification may also bring contaminants or impurities without fuel value in direct contact with fuel cell components. The tin anode is a fluid and a non-structural cell component so it is tolerant of many impurities. However fuel contaminants dissolved in molten tin could have a critical impact on cell components such as the electrolyte that are in direct contact with the molten tin anode. Certain fuel (V, Mo, etc.) impurities had shown causing damage to fuel cell if they were in direct contact with cell components such as electrolyte. This paper will examine liquid tin (molten tin bath) as a potential media to attenuate/reduce/eliminate harmful coal contaminants, providing a mitigation strategy for reducing a key technical risk factor of direct coal conversion using a fuel cell.
Three-dimensional Modeling of Anode-supported Planar SOFC with Direct Internal Reforming
Authors: Qu Zuopeng , Aravind PV , Ye Huaiyu , Dekker Nico , Woudstra Nico , Verkooijen Adrian
Published: September 2009

This paper presents a three-dimensional model of an anode-supported planar SOFC with corrugated bipolar plates serving as gas channels and current collector above the active area of the cell, based on the direct internal reforming reaction of methane and the electrochemical reaction of hydrogen. A co-flow system with gas mixture of methane, water vapor and a small amount of hydrogen as anode gas and air as cathode gas fed at an inlet temperature of 973K was modeled at a single cell unit level. A simple equation for the cell resistance with measured values for the quasi ohmic resistance is used for the calculation of the current density. The modeling results show the current density distribution and temperature profiles in the cell and gas concentrations profiles along the length of the cell channel. Furthermore, the temperature gradient inside the cell was investigated.
Physically Based Model-Predictive Control for SOFC Stacks and Systems
Authors: Vincent Tyrone , Sanandaji Borhan , Colclasure Andrew , Zhu Huayang , Kee Robert J.
Published: September 2009

This paper discusses model-predictive controllers (MPC) that can incorporate physical knowledge of fuel-cell behavior into real-time multiple-input-multiple-output (MIMO) process-control strategies. The controller development begins with a high-fidelity, transient, physical model that represents the physical and chemical processes responsible for fuel-cell function. However, because such large nonlinear models cannot be solved in real time as part of the con-troller logic, linear reduced-order state-space models are required. The model reduction is accomplished via a process called system identification. The controller is designed to interpret sensors in the context of the reduced-order model and determine optimal actua-tion sequences that cause the system to follow a desired output tra-jectory. The process is demonstrated for a tubular SOFC stack that could be used for auxiliary-power unit (APU) applications.
Three-phase Boundary Length Evaluation in Modeled Sintered Composite Solid Oxide Fuel Cell Electrodes
Authors: Metcalfe Craig , Kesler Olivera , Rivard Tony , Gitzhofer François , Abatzoglou Nicolas
Published: September 2009

A numerical methodology for evaluating the three-phase boundary length in sintered composite electrode layers is developed. Three dimensional models of sintered composite electrodes are generated for which the mean particle diameter, composition, and total porosity may be specified as input parameters. Tomographic methods are used to reconstruct the modeled electrode and the percolation for each phase is evaluated. The connected three-phase boundary length is calculated for a range of electrode designs.
Design and Optimisation of SOFC System Components using a Trio Approach: Measurements, Design of Experiments, and 3D Computational Fluid Dynamics
Authors: Peksen Murat , Peters Roland , Blum Ludger , Stolten Detlef
Published: September 2009

In this present paper, a comprehensive trio approach has been proposed to aid in the optimisation of the pre-reforming process, and to develop a new pre-reformer design. Measurements, design of experiments (DOE), and computational fluid dynamics (CFD) have been employed to determine the effects of several design and material parameters on the pre-reformer performance in detail. The optimisation procedure considers geometrical modifications, material alternatives and the feasibility of the end product simultaneously, in order to achieve efficient reforming rates by reduced component weight.
SOFC Modeling Considering Internal Reforming by a Global Kinetics Approach
Authors: Andersson Martin , Yuan Jinliang , Sundén Bengt
Published: September 2009

Fuel cells (FCs) are promising for future energy systems, since they are energy efficient and fuel can be produced locally. When hydrogen is used as fuel, there are no emissions of greenhouse gases. In this study a two dimensional CFD (COMSOL Multiphysics) is employed to study the effect from porous material surface area ratio on reforming reaction rates and gas species distributions for an anode-supported solid oxide fuel cell (SOFC). FCs can be considered as multifunctional energy devises, combining (electro-) chemical reactions, heat exchange, gas- and ionic transport. All these functions are strongly integrated, making modeling an important tool to understand the couplings between mass-, heat-, momentum transport and chemical reactions. Steam reforming takes place at the nickel material surfaces in the anode and water-gas shift reaction occurs where fuel gas is present. Benefit from the internal reforming is that the energy conversion efficiency will be higher, compared to the case of pure hydrogen as fuel.
3D Electrode Microstructure Reconstruction and Modelling
Authors: Rüger Bernd , Joos Jochen , Weber André , Carraro Thomas , Ivers-Tiffée Ellen
Published: September 2009

Polarization losses within the electrodes are determined both by material composition and microstructure. Analyzing and modelling of electrode-microstructure can help to understand and improve electrodes. In this initial study the use of a dual-beam focused ion beam/scanning electron microscope (FIB/SEM) for the reconstruction of a high performance LSCF-cathode will be illustrated. Opportunities that arise from this technology for microstructure modelling and possible sources of error will be discussed. From the obtained reconstruction data the calculation of microstructural parameters like surface area, volume/porosity fraction or tortuosity is possible. Such parameters can be used to calculate cathode performance via microstructure models found in literature [1-4]. However, it would be desirable to use the reconstructed microstructure directly in a model in order to investigate the interaction of microstructure and performance more accurately. A three-dimensional (3D) finite element method (FEM) model [5] is presented that allows the analysis and prediction of cathode performance. The model has already been validated, and we will show how to overcome simplifications concerning the microstructure by an extension of the model enabling a direct use of 3D FIB/SEM-data.
Numerical Simulation of Reactive Transport Phenomena in the Hexis SOFC-System
Authors: Safa Yasser , Hocker Thomas
Published: September 2009

An advanced computational reactive flow code has been implemented into Mathematica® to analyze (electro-) chemical conversions and various transport phenomena in the Hexis® SOFC-stack. The finite element approximation is applied for the space discretization of the continuity equations. The convection dominant cases are stabilized by the SUPG (Streamline Upwind Petrov Galerkin) method. The fluid flow in the interconnect channels is derived analytically with accurate representation of the slip velocity on the porous electrode surfaces. The mathematical system is linearized by means of a pseudo-time step discretization via a semi-implicit scheme. This stable iterative procedure is applied to an evolutionary problem and it converges unconditionally to the steady solution. Due to the low aspect ratio of the thickness to the cross-section of the cell, a one-dimensional model of the cell is coupled with the flow inside the gas channels. This approach reduces the computing time by retaining the main geometric details.