SOFC Development Research Articles

Innovative, Laser-Based Process for Development and Manufacturing of SOFCs

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Development of Tubular SOFC at TOTO

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Failure Analysis as an Essential Component of an SOFC Development Program

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Status of National Project for SOFC Development in Japan

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4412 数値計算による円筒横縞形SOFCの出力向上(J11-2 SOFC,J11 小型・分散エネルギー技術)

Performance of SOFC takes influence from chemical reaction, electrical resistance and gas diffusion polarization. The tubular type SOFC has gas distribution in an axis direction. The electrode and electrolyte inside includes electric current density distribution. Therefore, theory of two dimensions transportation phenomenon is necessary for a performance simulation. In this study, the numerical analysis of SOFC performance was carried out. The analysis result accorded with the operation data well and realized a design of high performance SOFC. Mitsubishi Heavy Industries (MHI) has been commissioned to a new national project "Development of SOFC-Gas Turbine Combined Cycle System with Tubular Type Cell" and "Study and Development of high performance SOFC" by New Energy and Industrial Technology Development Organization (NEDO). This study contents are parts of the latter project.

Performance of LSCF cathodes in cell tests

SOFC development at Forschungszentrum Jülich is aiming at high power density and high durability to achieve cost reduction in manufacturing and installation. For higher power density, the work on materials development has been focused on improving the cathode performance using perovskites based on (La,Sr)(Co,Fe)O 3− δ (LSCF). Materials screening and preliminary investigations were carried out with 5 cm × 5 cm cells. SOFCs with La 0.58Sr 0.4Fe 0.8Co 0.2O 3 cathodes have successfully been developed giving reproducibly a power output of 1.2 W cm −2 at 800 °C and 0.7 V with hydrogen as fuel gas. Long-term cell tests lasting up to 3000 h revealed a degradation of the cells between 0.5 and 1.5%/1000 h of operation. This loss in performance is higher than for conventional cathodes based on (La,Sr)MnO 3 (LSM) and under further investigation to find the reason for the performance losses.

Electrical and sintering behaviour of Y 2Zr 2O 7 (YZ) pyrochlore based materials: the influence of bismuth

Solid oxide fuel cell can convert fuels rich in H 2 into electrical energy directly without pollution by electrochemical reaction with oxygen. The efficiency of energy conversion and durability of performance mainly depend on the oxide ion conducting solid electrolyte activity. The global experience gained all these years in the SOFC development has prompted for a change from the state of the art functional electrolyte material, yttria stabilized zirconia (YSZ) having a conductivity of 0.1 S cm −1 at 1000 °C to a new material, which exhibits equivalent conductivity values in the intermediate temperature range (600–700 °C). In this work, Y 2Zr 20 7 (YZ), an ionic conducting stable pyrochlore based oxide prepared by glycine nitrate combustion route is systematically characterised. Both circular and rectangular pellets were fabricated by uniaxial compression followed by annealing at different temperatures. The functional properties such as porosity, percentage thermal shrinkage in volume and percentage densification of the sintered pellets are compiled. Bismuth oxide is found to be an effective sintering aid in general. So the effect of bismuth oxide addition on YZ was investigated through sintering studies, XRD, TGA/DTA, SEM and conductivity measurements. The results obtained on YZ with and without bismuth oxide addition are discussed with respect to the requirement of an electrolyte for ITSOFC application.

Status and Recent Progress in SOFC Development at Haldor Topsøe A/S and Risø

The SOFC technology under development at Haldor Topsoe A/S and Riso National Laboratory is based on an integrated approach ranging from manufacturing of planar anode-supported cells and compact stacks to analysis of total systems. The standard cells are thin and robust with dimensions of 12 x 12 cm 2 and cell stacks are based on internal manifolding. Production of cells is being up-scaled continuously. The durability of the standard stack design with standard cells has been tested for more than 13000 hours including nine full thermal cycles with an overall voltage degradation rate of about 1% per 1000 hours. Recently, the degradation rate has been significantly reduced by introduction of improved stack component materials. 75-cell stacks in the 1+ kW power range have been tested successfully, so far for several hundred hours. Stacks have been delivered in a pre-reduced state to partners and tested successfully in test systems with natural gas as fuel. The consortium of Haldor Topsoe A/S and Riso has an extended program to develop the SOFC technology all the way to a marketable product. Stack and system modelling including cost optimisation analysis is used to develop 5 kW stack modules for operation in the temperature range 700-850°C. To ensure the emergence of cost-competitive solutions, a special effort is focused on manufacturing and testing of larger anode-supported cells. The SOFC program comprises development of next generation cells and multi stack modules for operation at lower temperature with increased durability and mechanical robustness. Development of cells with porous metallic support and new electrode materials is in progress in order to ensure long-term competitiveness.

Development of Planar SOFC Stacks for CHP

The SOFC technology under development at DOTS is based on an integrated approach ranging from the manufacturing of planar electrolyte supported cells and compact stacks to the integration in total systems. The cells are thin, mechanically stable and show an excellent redox stability under operation conditions. The prototype production of cells in cooperation with Kerafol is being up-scaled continuously. The main issues in the stack development are polarization losses, durability and cost. Up to 60-cell stacks in the power range 300-1000 W were tested successfully. The tests with hydrogen/steam and methane/hydrogen/steam as fuel showed no difference in the power output at a fuel utilization more than 45%. The compact stacks have been tested for thousand hours without degradation. The SOFC development at IKTS focuses on the reliable technology for cell and stack prototype production.

Development of Tubular SOFC at TOTO

Stacks and modules of the TOTO tubular SOFCs were evaluated using Japanese town gas (13A). The tubular cell is fabricated by the TOTO wet process. A stack, which consisted of 2x6 cells, generated 0.34 kW at 0.2 A/cm 2 and a power generation efficiency of 57%-LHV in DC output. A small module, which consisted of 5 stacks, generated 1.5 kW at 0.2 A/cm 2 and 55%-LHV. A thermally self-sustaining module, which consisted of 20 stacks, generated 6.5 kW at 0.2 A/ cm 2 and 48%-LHV. The desulfurized town gas was supplied to the modules after being partially steam reformed. In the test of the thermally self-sustaining module, the thermal energy of the exhaust gas was used for steam reforming through an integrated heat exchanging steam reformer in which a commercial steam reforming catalyst was embedded.

The Development of Several 100 kW-Class Tubular Type Solid Oxide Fuel Cell System (SOFIT)

Electric Power Development Co., Ltd. (JPOWER) started SOFC development in collaboration with Mitsubishi Heavy Industries, Ltd. in 1991. When development of a pressurized SOFC 10 kW module was completed, radical improvement of the modular structure was performed, aiming for further improvement in reliability and lower cost. It has been checked that there is no technical problem in the new structure of SOFC module. We plan to examine several prototype 100 kW-class atmospheric SOFC co-generation systems (SOFIT) from 2006 to verify the SOFC system using the new structure module, and the reliability of more than 10,000 hours operation at JPOWER's Chigasaki laboratory.

Sol–gel synthesis and characterization of Co-doped LSGM perovskites

One of the major requirements for the development and commercialization of low-cost SOFCs is the reduction in the operating temperature. One of the methods to reach this aim is the use of solid electrolytes which exhibit superior ionic conductivity at intermediate temperatures (IT, T < 800 °C). Among these ionic conductors, doped LaGaO 3 materials show high oxide ionic conductivity in the 600–800 °C range. These perovskites are usually prepared by time- and energy-consuming solid state reaction. In this paper, La 0.8Sr 0.2Ga 0.8Mg 0.2O 2.8 (LSGM) and La 0.8Sr 0.20Ga 0.8Mg 0.2− x Co x O 3− δ (LSGMC) powders containing different amounts of Co ( x = 0.05, 0.085 and 0.10) were prepared from precursors synthesised by citrate sol–gel method. The precursors were calcined at 1000 °C (10 h) and dense high-purity pellets were obtained by pressing (300 MPa) and sintering in air at 1475 °C (5, 10 and 20 h). Sintered pellets of LSGM and LSGMC contained very small amounts (<1%) of SrLaGa 3O 7 and SrLaGaO 4, respectively, as detected by X-ray diffraction (XRD) and by the combined use of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The data clearly showed the feasibility of sol–gel methods to produce Co-doped LSGM perovskite type oxides.

Development of MOLB Type SOFC

Development of MOLB Type SOFC

Status of National Project for SOFC Development in Japan

Solid oxide fuel cell development at NEDO, which was initiated in 1989, entered a third phase in 2001. During this phase, the development of thermally self-supporting modules and elemental studies to extend technology for SOFC adaptability are to be carried out. The development of cogeneration system and combined cycle system is to be carried out from 2004 to 2007. An overview of the R&D on SOFCs being accomplished by NEDO is presented herein.

Failure Analysis as an Essential Component of an SOFC Development Program

Post-test analysis provides the stack and materials development teams with valuable feedback after each test. Prototype systems, stacks and single cells are taken apart following a standard procedure to capture all relevant information. Those observations lead to a root cause analysis of the failure of either stack or single cell. Hence a loop is created, linking every activity of the program from research and development, pilot plant production, testing and back to research and development. Failure analysis tools Failure Modes and Effect Analysis (FMEA) and Fault Tree Analysis (FTA) provide support for root cause analysis. The analysis itself is performed by a standard set of autopsy procedures, scanning electron microscopy (SEM) and possibly x-ray diffraction (XRD). A collection of information is then grouped and trends are noted and related to the performance of cell, stack or prototype systems. Learning and recommendations are recorded and implemented. Failure analysis is the activity that closes the loop of the development program cycle.

Roles of Ceria in SOFC Electrode Reactions

AbstractFor Abstract see ChemInform Abstract in Full Text.

Development of Anode-Supported SOFC with Metallic Interconnectors

High stability against thermal cycles was achieved in a SOFC stack with metallic interconnects and anode-supported cells at a reduced operating temperature of 1023 K. The basic structual design of a cell stack that is capable of mitigating thermal stresses and is mechanically robust, even under fast startup and shutdown cycles, has been completed. The degradation rate was found to be less than 1% per cycle in thermal cycle tests of single- and three-cell stacks from room temperature to 1023 K at a heating rate of 200 K/h. Even in a thermal cycle test of a 10-cell stack, no cells were cracked. Simulation of thermal stresses between room temperature and 1023 K confirms the experimental results. By simple surface modification treatment of metallic components, a stable stack operation was achieved, with a degradation rate of less than 5% per 1000 h.

Development of Thin-Film SOFC for Stationary and Mobile Application by Using Plasma Deposition Technology

At the German Aerospace Center (DLR) in Stuttgart, a concept for planar SOFC using a metallic substrate support and thin-film layers, which are deposited by plasma spray processes (spray concept), has been developed. This concept enables the fabrication of the entire membrane-electrode assembly in a single consecutive spray process without any sintering steps or other thermal post-treatment after spraying, thus promising fast and cost-effective cell fabrication. Based on this concept adequate stack designs and stack technologies for the assembly of stacks have been developed for both stationary and mobile applications. The nature of the cell supporting substrate has a significant influence on the electrochemical performance of plasma sprayed cells; hence substrate development is a key issue. This paper describes the current status of development of the DLR spray concept including the stack designs, scale-up aspects of the fabrication technology, recent developments with substrates and the electrochemical characterization of single cells and short-stacks for both stationary and mobile application.

Development of MOLB Type SOFC

Development of MOLB Type SOFC

Status of National Project for SOFC Development in Japan

Solid oxide fuel cell development at NEDO, which was initiated in FY1989, entered a third phase in PY2001. During this phase, the development of thermally self-supporting modules and elemental studies to extend technology for SOFC adaptability are to be carried out. An overview of the SOFC R&D being accomplished by NEDO and the status of projects other than the NEDO project are presented herein.