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1
Mehta, Ankur 1983. "A microfabricated solid oxide fuel cell." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27050.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references (p. 83-85).
With the ever-increasing ubiquity of mobile consumer electronic devices comes the rising demand for portable electric power. Current battery technology gives a very modest energy return per weight or volume. Hydrocarbons have a significantly higher energy density, and so fuel conversion systems only need to have several percent efficiency to match and surpass the specific energy of conventional batteries. Thus, there is a strong market for successful portable fuel powered electric generators. The goal of this thesis is to investigate the design of one such device, a two-chamber microfabricated solid oxide fuel cell (SOFC). This device produces electric current through the electrochemical oxidation of fuel through an ionic conductor. Oxide ions permeate across a ceramic electrolyte membrane to react with the fuel, driving electrons back around through the load. The focus of this work is to analyze the behavior of these membranes to prevent failure as the device is heated to its operating temperature near 800K. Experiments and analysis of free-standing electrolyte membranes indicate that failure is unavoidable over the required temperature range, and so supported structures are investigated. The results of experiments with a perforated nitride supported membrane presented herein indicate the need for a more thorough understanding of the thin film stresses responsible for membrane failure, as well as careful support structures to accommodate these. Designs for future devices are presented to improve stability and move closer to a final complete portable power system.
by Ankur Mehta.
S.B.
M.Eng.
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Pramuanjaroenkij, Anchasa. "Mathematical Analysis of Planar Solid Oxide Fuel Cells." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/234.
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The mathematical analysis has been developed by using finite volume method, experimental data from literatures, and solving numerically to predict solid oxide fuel cell performances with different operating conditions and different material properties. The in-house program presents flow fields, temperature distributions, and performance predictions of typical solid oxide fuel cells operating at different temperatures, 1000 C, 800 C, 600 C, and 500 C, and different electrolyte materials, Yttria-Stabilized zirconia (YSZ) and Gadolinia-doped ceria (CGO). From performance predictions show that the performance of an anode-supported planar SOFC is better than that of an electrolyte-supported planar SOFC for the same material used, same electrode electrochemical considerations, and same operating conditions. The anode-supported solid oxide fuel cells can be used to give the high power density in the higher current density range than the electrolyte-supported solid oxide fuel cells. Even though the electrolyte-supported solid oxide fuel cells give the lower power density and can operate in the lower current density range but they can be used as a small power generator which is portable and provide low power. Furthermore, it is shown that the effect of the electrolyte materials plays important roles to the performance predictions. This should be noted that performance comparisons are obtained by using the same electrode materials. The YSZ-electrolyte solid oxide fuel cells in this work show higher performance than the CGO-electrolyte solid oxide fuel cells when SOFCs operate above 756 C. On the other hand, when CGO based SOFCs operate under 756 C, they shows higher performance than YSZ based SOFCs because the conductivity values of CGO are higher than that of YSZ temperatures lower than 756 C. Since the CGO conductivity in this work is high and the effects of different electrode materials, they can be implied that conductivity values of electrolyte and electrode materials have to be improved.
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Nelson, George Joseph. "Solid Oxide Cell Constriction Resistance Effects." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10563.
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Solid oxide cells are best known in the energy sector as novel power generation devices through solid oxide fuel cells (SOFCs), which enable the direct conversion of chemical energy to electrical energy and result in high efficiency power generation. However, solid oxide electrolysis cells (SOECs) are receiving increased attention as a hydrogen production technology through high temperature electrolysis applications. The development of higher fidelity methods for modeling transport phenomena within solid oxide cells is necessary for the advancement of these key technologies. The proposed thesis analyzes the increased transport path lengths caused by constriction resistance effects in prevalent solid oxide cell designs. Such effects are so named because they arise from reductions in active transport area.
Constriction resistance effects of SOFC geometry on continuum level mass and electronic transport through SOFC anodes are simulated. These effects are explored via analytic solutions of the Laplace equation with model verification achieved by computational methods such as finite element analysis (FEA). Parametric studies of cell geometry and fuel stream composition are performed based upon the models developed. These studies reveal a competition of losses present between mass and electronic transport losses and demonstrate the benefits of smaller SOFC unit cell geometry. Furthermore, the models developed for SOFC transport phenomena are applied toward the analysis of SOECs. The resulting parametric studies demonstrate that geometric configurations that demonstrate enhanced performance within SOFC operation also demonstrate enhanced performance within SOEC operation.
Secondarily, the electrochemical degradation of SOFCs is explored with respect to delamination cracking phenomena about and within the critical electrolyte-anode interface. For thin electrolytes, constriction resistance effects may lead to the loss of electro-active area at both anode-electrolyte and cathode-electrolyte interfaces. This effect (referred to as masking) results in regions of unutilized electrolyte cross-sectional area, which can be a critical performance hindrance. Again analytic and computational means are employed in analyzing such degradation issues.
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Baba, Nor Bahiyah. "Novel processing of solid oxide fuel cell." Thesis, Edinburgh Napier University, 2011. http://researchrepository.napier.ac.uk/Output/4271.
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ABSTRACT Solid oxide fuel cells (SOFCs) are of major interest in fuel cell development due to their high energy conversion efficiency, wide range of fuels and environmental friendliness. One important obstacle for their industrial development is their processing difficulties. These difficulties have recently been addressed by employing a novel technique namely electroless nickel - yttria-stabilised zirconia (YSZ) co-deposition which eliminates multi-layer processing and high temperature sintering. The novel work carried out in this research programme investigates the effects of different processing parameters on the co-deposited anodes for SOFCs. In particular, YSZ particle size, electroless bath agitation method, electroless bath pH and substrate surface condition are investigated. These variables were investigated for their effect on (i) the ceramic to metal ratio – important in terms of matching the coefficient of thermal expansion of the anode and substrate, as well as providing electronic conductivity, and (ii) the porosity content in the deposited layers – required for fuel and exit gas penetration through the anode. The experimental work was based on a full factorial Design of Experiment (DoE) approach and consisted of three phases – namely, designing, running and analysing. A 16 run 24 full factorial DoE with five replications was constructed with YSZ particle sizes of 2 and 10 µm; bath agitation of air bubbling and mechanical stirring; bath pH of 4.9 and 5.4; and substrate surface treatment of hydrofluoric acid etching and mechanical blasting. A total of 80 samples were analysed for nickel content by energy dispersive X-ray analysis and porosity content by Archimedes buoyancy measurement. The DoE was analysed by the ANOVA statistical tool in Minitab 15 software. The co-deposition conditions that produced anodes with (i) the lowest volume percentage of nickel and (ii) the highest level of porosity were determined. Linear regression models for both nickel to YSZ content and porosity responses were built to estimate the correlation between experimental and predicted data. The coefficient of determination, R2 for nickel to YSZ content indicated a reasonable correlation between experimental and predicted values while the regression model for porosity response was less reliable. One anode containing 50 vol.% nickel recorded an electronic conductivity at 400oC in air that is comparable to the published data. Another series of tests at higher temperatures (up to 800oC) in air and nitrogen resulted in encouraging electronic conductivities being recorded.
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Ghosh, Ujjal. "One dimensional modeling of planar solid oxide fuel cell." Ohio : Ohio University, 2005. http://www.ohiolink.edu/etd/view.cgi?ohiou1177438858.
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Stutz, Michael Jun. "Hydrocarbon fuel processing of micro solid oxide fuel cell systems." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17455.
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Pornprasertsuk, Rojana. "Ionic conductivity studies of solid oxide fuel cell electrolytes and theoretical modeling of an entire solid oxide fuel cell /." May be available electronically:, 2007. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Ford, James Christopher. "Thermodynamic optimization of a planar solid oxide fuel cell." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45843.
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Solid oxide fuel cells (SOFCs) are high temperature (600C-1000C) composite metallic/ceramic-cermet electrochemical devices. There is a need to effectively manage the heat transfer through the cell to mitigate material failure induced by thermal stresses while yet preserving performance. The present dissertation offers a novel thermodynamic optimization approach that utilizes dimensionless geometric parameters to design a SOFC. Through entropy generation minimization, the architecture of a planar SOFC has been redesigned to optimally balance thermal gradients and cell performance. Cell performance has been defined using the 2nd law metric of exergetic efficiency. One constrained optimization problem was solved. The optimization sought to maximize exergetic efficiency through minimizing total entropy production while constraining thermal gradients. Optimal designs were produced that had exergetic efficiency exceeding 92% while maximum thermal gradients were between 219 C/m and 1249 C/m. As the architecture was modified, the magnitude of sources of entropy generation changed. Ultimately, it was shown that the architecture of a SOFC can be modified through thermodynamic optimization to maximize performance while limiting thermal gradients. The present dissertation highlights a new design methodology and provides insights on the connection between thermal gradients, performance, sources of entropy generation, and cell architecture.
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Kapoor, Abhishek Surinder. "Microwave Sintering of Solid Oxide Fuel Cell Materials." NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-05092008-144010/.
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The influence of sintering temperature and hold time on the microstructure of of a microwave sintered LSM-YSZ (lanthanum strontium manganate - yttria stabilized zirconia) cathode has been studied. For experimental purposes, a microwave furnace was designed and fabricated with a closed loop temperature feedback control system. A type R thermocouple was used to provide accurate temperature readings inside the microwave cavity. An Allen Bradley Micrologix PLC was used to control the system. This furnace was used as a test bed for experiments involving the rapid sintering of solid oxide fuel cell (SOFC) materials. The SOFC specimens were made by depositing LSM-YSZ cathode material onto YSZ-8 electrolyte buttons. The specimens were sintered for a variety of temperatures and hold times. The microstructure obtained through microwave sintering showed equal or better pore size distribution as compared to those obtained through conventional sintering. The sintered structure was found to be less dense and to contain smaller pores as the sintering temperature was reduced to 1100ËC or lower. Rapid sintering of SOFC materials has potential advantages in terms of SOFC performance and offers potential energy savings when compared with conventional sintering. This research has demonstrated the feasibility of rapid sintering of porous SOFC materials. The next step is to optimize the microwave sintering schedule with respect to the electrical performance and the long term stability of the SOFC.
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Lin, Roger J. 1974. "Evaluation of micro solid oxide fuel cell technology." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/7977.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2003.Includes bibliographical references (leaves 67-70).
Micro solid oxide fuel cells are one type of fuel cell being researched for use in portable electronic devices or applications requiring portable power. This emerging technology combines fuel cell technology with microfabrication technology to achieve a micro sized fuel cell on a small silicon die. The potential exists for outperforming standard battery technology by an order of magnitude. A review of micro solid oxide fuel cell technology and its main technical challenges is done. Critical evaluation of the energy density of the micro solid oxide fuel cell based on assumptions of efficiency and packaging is made. Discussion of possible use models of micro solid oxide fuel cells and outside factors affecting their adoption by both military and consumer markets is given. A survey of intellectual property related to the field is performed, along with a summary of companies active in the area. A rough cost model for production and brief commercialization outlook is presented.
by Roger J. Lin.
M.Eng.
11
Rhazaoui, Khalil. "Solid oxide fuel cell microstructure and performance modeling." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/23301.
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The fundamental operation of Solid Oxide Fuel Cells (SOFCs) relies on the liberation of electrons at reaction sites within porous electrodes. These reaction sites, or triple-phase boundary (TPB) points, must be percolated to allow for reactants and products to flow to and from these sites. Due to the fact that electrochemical reactions in composite electrodes are dependent on the presence of TPB sites, a direct link exists between SOFC electrode microstructures and electrochemical performance. Recently, the development of advanced tomography and imaging techniques has allowed for this link to be better understood and quantified. This thesis presents the development of a novel effective conductivity model (ResNet) for 3D composite, anisotropic microstructures in the context of Ni-YSZ electrode characterization. The ResNet model is first used to derive the effective conductivity of simple structures, conductivities of which can be found in the literature. Good agreement was found in this initial study. The model is then used to compute the effective conductivities of more complex synthetic microstructures, comparing model outputs to those given by COMSOL Multiphysics, a commercial modeling platform. It was found that for a sufficiently high resolution, both models converge to the same results. Varying the discretization resolution allowed for an optimum discretization resolution to be determined, based on the mean particle size used for fabrication. The introduction of Volume Elements into the ResNet model is then presented, and the optimum aggregation resolution is extracted from a set of simulations. This allowed for the analysis of a real SOFC anode microstructure to be carried out, and underlined the importance of selecting a microstructure sample of a size that can be considered representative of the entire electrode. After a series of simulations on synthetically generated microstructures, several microstructural parameters are varied to carry out a sensitivity analysis on the effective conductivities and current densities of the microstructures. This analysis yielded an optimum ratio of 7 particles per structure length for microstructure size representativeness. Using the parameters derived from the studies presented in this thesis, the effective conductivities of two experimental Ni/10ScSZ anodes are extracted using the ResNet model and compared to their experimentally determined values. Excellent agreement was obtained, validating the ResNet model and associated work. In a final instance, it was shown that using the ResNet model in the electronic phase in conjunction with the VOF model developed by Golbert et al. does not yield a noticeable difference in current density output when compared to results obtained without using the ResNet. When applied to the ionic phase however, using the ResNet model in conjunction with the VOF model is found to predict as much as 50% lower computed area current densities than when the volume fraction average model is used.
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Othman, Mohd Hafiz Dzarfan Bin. "High performance micro-tubular solid oxide fuel cell." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9572.
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The development of micro-tubular solid oxide fuel cells (SOFCs) has received more and more attention recently due to a number of advantages of this configuration, such as high volumetric power output and rapid start-up/shut-down. Previously, the fabrication of micro-tubular SOFC was achieved through multiple-step processes, which involves at least one sintering in each step, making the cell fabrication time consuming and costly. For a more economical fabrication of micro-tubular SOFC with more reliability and flexibility in quality control, an advanced dry-jet wet extrusion technique, i.e. a phase inversion-based co-extrusion process, followed by co-sintering and reduction processes has been developed and systematically investigated in this thesis. At the beginning of the study, a dual-layer hollow fibre which consists of a ceriumgadolinium oxide (CGO) electrolyte outer layer of approximately 80 μm supported by an asymmetric nickel (Ni)-CGO anode inner layer, is successfully fabricated using this technique. The resultant cell of the corresponding dual-layer hollow fibre produces the maximum power density of 0.34-0.68 W cm-2 at 550-600 oC. Improvement on the structure of the dual-layer hollow fibres is performed by reducing the electrolyte layer thickness to as thin as 10 μm and the maximum power density of the corresponding cell increases to about 1.11 W cm-2 at 600 oC. However, the value of power density is still slightly lower than what have been previously reported in the literature. One of the major reasons for such lower power output is the less effective porosity in the anode layer of hollow fibres. Therefore, the optimisation on anode porosity of the dual-layer HF is carried out and resulting in the outstanding power output of about 2.32 W cm-2 at 600 oC. This result indeed highlights the advantage of co-extrusion/co-sintering as a fabrication technique in developing high quality micro-tubular SOFC.
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Bae, Joong-Myeon. "Properties of selected oxide cathodes for solid oxide fuel cell." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244213.
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Oh, Raymond H. "Processing of a Hybrid Solid Oxide Fuel Cell Platform." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10429.
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Solid oxide fuel cell platforms consisting of alternating cellular layers of yttria-stabilized zirconia electrolyte and Fe-Ni metallic interconnects (Fe45Ni, Fe47.5Ni, Fe50Ni) were produced through the co-extrusion of two particulate pastes. Subsequent thermal treatment in a hydrogen atmosphere was used to reduce iron and nickel oxides and co-sinter the entire structure. Issues surrounding this process include the constrained sintering of the layers and the evolution of residual stress between the dense, fired layers.
Sintering curves for individual components of the layers were measured by dilatometry to ascertain each materials impact on overall sintering mismatch. X-ray diffraction, scanning electron microscopy and weight loss were utilized to examine phase evolution within the Fe-Ni alloys during reduction. YSZ powders densified above ~1050C and shrinkage was rapid above the sintering temperature. Shrinkage of the interconnect occurred in two stages: reduction and the initial stages of sintering concluded around ~600C, plateauing shortly and continuing at ~900C as pore removal and grain growth ensued simultaneously. Constrained sintering resulted in the formation of remnant porosity within the interconnect layers.
Interconnect compositions were chosen in efforts to minimize disparities in thermal expansion with the electrolyte. Residual strains on the surfaces of the layers were measured by x-ray diffraction. Corresponding stresses were calculated using the sin2y method. Grain growth within the interconnect prohibited random planes to be measured so stress measurements were confined to the ceramic layers.
Various material properties such as thermal expansion were collected and employed in a modified finite element model to estimate residual stresses in the platform. A method for determining a crucial parameter, the zero stress temperature was outlined and incorporated. Modeled values were found to agree well with XRD values, providing indirect confirmation of the zero stress temperature calculations. Discrepancies were attributed to microcracks found within the layer that arose due to residual stress values surpassing the tensile strength of the zirconia.
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Ford, James Christopher. "An Enhanced Transient Solid Oxide Fuel Cell Performance Model." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14052.
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In order to facilitate the application of solid oxide fuel cells, in conjunction with reduced research and development costs, there is a need for accurate performance models to aid scientists and engineers in component and process design. To this end, an enhanced transient performance model has been developed. The present thesis enhances transient modeling and simulation via characterization of two important transient phenomena. They are bimodal stimuli (i.e., simultaneous changes in reactant supply and load demand) electrical transients, inclusive of the simulation of electrolysis, and the electrochemical light off phenomenon. One key result of the electrochemical light off simulations was that the realization that electrochemical parameters such as cell potential may be used as dynamic control variables during transitional heating of the cell. Reflective of the state-of-the-art in controls and dynamic simulation development, the modeling efforts are completed in the MATLAB computing environment. There is then a tangible software development that accompanies the modeling and simulation exercises and transient insights resolved.
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Lewis, Gene Stacey. "Low temperature sintering of solid oxide fuel cell electrolytes." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402178.
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Wright, Emma Victoria. "Investigation of a novel solid oxide fuel cell interconnect." Thesis, Keele University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265019.
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Pike, Thomas William. "Development and processing of solid oxide fuel cell materials." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5861/.
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The work presented within this thesis focuses on the synthesis, characterisation and processing of novel materials for use within solid oxide fuel cells. A range of perovskite materials, previously shown to have potential for solid oxide fuel cell applications, were selected for further studies. These included LaMnO\(_3\), SrFeO\(_{3-δ}\) and Sr\(_{0.8}\)Ti\(_{0.6}\)Nb\(_{0.4}\)O\(_{3-δ}\). These materials were doped with various dopants, including cations such as V\(^{5+}\) and Ti\(^{4+}\) and also SiO\(_4\)\(^{4-}\) oxyanions. Once doped, the materials were analysed by X-ray powder diffraction and underwent testing to ascertain their suitability for use as solid oxide fuel cell electrodes. This included identifying structural stability in anode conditions alongside thermal expansion studies. Overall, improvements over undoped samples were noted, especially for Sr\(_{0.8}\)Ti\(_{0.6}\)Nb\(_{0.4}\)O\(_{3-δ}\) samples doped with V\(^{5+}\) and SrFeO\(_{3-δ}\) samples doped with SiO\(_4\)\(^{4-}\), although LaMnO\(_3\) doped with Ti\(^{4+}\) proved less successful. Production methods for the formation of microtubular solid oxide fuel cells were also investigated. Powder processing for paste formation was examined, for subsequent use in extrusion. The extrusion process was also investigated, alongside debinding and sintering studies. The development of a reliable and repeatable process for cell production proved difficult, especially on a smaller scale necessary to facilitate the testing of novel materials.
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Joulaee, Nasim. "Thermo-mechanical damage analysis in solid oxide fuel cell." Université Louis Pasteur (Strasbourg) (1971-2008), 2007. http://www.theses.fr/2007STR13202.
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Bozeman, Joe Frank III. "SULFUR-TOLERANT CATALYST FOR THE SOLID OXIDE FUEL CELL." Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1276835949.
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Baderuddin, Feroze Khan. "Microextrusion 3D-Printing of Solid Oxide Fuel Cell Components." Youngstown State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1484573220607538.
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Lowrie, Fiona Louise. "Mechanical properties of a solid oxide fuel cell electrolyte." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/8664.
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Tseronis, Konstantinos. "Modelling and Design of Solid Oxide Fuel Cell Systems." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511906.
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Mebane, David Spencer. "Discrete Numerical Simulations of Solid Oxide Fuel Cell Electrodes: Developing New Tools for Fundamental Investigation." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19864.
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Thesis (Ph.D)--Materials Science and Engineering, Georgia Institute of Technology, 2008.Committee Chair: Meilin Liu; Committee Co-Chair: Yingjie Liu; Committee Member: David McDowell; Committee Member: Ian Ferguson; Committee Member: Tom Fuller.
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Mirzababaei, Jelvehnaz. "Solid Oxide Fuel Cells with Methane and Fe/Ti Oxide Fuels." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1415461807.
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Compson, Charles E. "Design, Fabrication and Characterization of Novel Planar Solid Oxide Fuel Cells." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14477.
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Planar solid oxide fuel cells (SOFCs) were designed, fabricated and characterized in order to develop a (1) cost-effective method for fabrication of thin electrolyte layers, (2) hermetic sealing and (3) stable interconnects. Electrophoretic deposition (EPD) was discovered to be an excellent method for fabricating dense electrolyte layers of about 5m thick on porous non-conducting substrates. The EPD process was thoroughly studied from proof-of-concept to statistical reproducibility, deposition mechanism, modeling and process optimization. Deposition on non-conducting substrates was found to follow many of the same fundamental trends as that on conductive substrates except for the voltage efficiency and detailed charge transfer mechanism. Eventually, the process was optimized such that an SOFC was fabricated that achieved 1.1W/cm2 at 850C. Further, a novel sealless planar SOFC was designed that incorporates a hermetic interface between the electrolyte and interconnect similar to tubular and honeycomb designs. The hermetic interface successfully acted as a blocking electrode under DC polarization, indicating its potential to act as a sealant. Leakage rates across the interface were 0.027sccm at 750c, similar to polycrystalline mica seals. Through a process of tape casting and lamination, a two-cell stack without sealant was fabricated and achieved a power density of 75mW/cm2 at 750C. Finally, the degradation rate of silver and silver-based interconnects was studied under static and dual-atmosphere conditions. Corrosion of silver grain boundaries along with sublimation losses results in the formation of large pores, resulting in up to 30 of anode oxidation after 8hrs testing at 750c. Further stability studies indicated that silver-based interconnects would be better suited for applications at operating temperatures less than 650C.
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Zalar, Frank M. "Model and theoretical simulation of solid oxide fuel cells." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1189691948.
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Fisher, James C. "A novel fuel cell anode catalyst, perovskite LSCF compared in a fuel cell anode and tubular reactor testing /." Akron, OH : University of Akron, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1152215855.
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Thesis (M.S.)--University of Akron, Dept. of Chemical Engineering, 2006."December, 2006." Title from electronic thesis title page (viewed 12/31/2008) Advisor, Steven S. C. Chuang; Faculty Readers, George Chase, Lu-Kwang Ju ; Department Chair, Lu-Kwang Ju; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Tesfai, Alem T. "Solid oxide fuel cells SOFCRoll single cell and stack design and development." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/4505.
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This study has focused on the implementation of a stack system for a novel design of solid oxide fuel cell (SOFCRoll). The issues affecting the commercialization of SOFCs are mainly based on durability and cost. The new design offers a number of advantages over the existing designs; it seeks to retain the specific advantages of both the tubular (high unit strength, no sealing problems) and planar arrangements (high power density). This design also aims to achieve low manufacturing cost by utilizing a cheap, easily scalable production technique: tape casting, together with co-firing all components, in one single step. In this study aspects of the design and operation of SOFCRoll stacks were studied particularly those affecting the single cell test reproducibility such as pre test quality control and scale up issues such as bundle and stack gas distribution. Initially the performance of single cells was characterized and the variation of their power output with temperature was observed. The maximum power, 0.7W at 800°C was achieved with a high silver content. The OCV and total resistance of this cell were 0.93V, 0.30Ω respectively. A standard pre-test quality control and current collection technique was introduced. At 800°C reproducible performance of 0.5W power obtained, average OCV was 0.935V and average series and polarization resistances of 0.18Ω and 0.19Ω was achieved respectively. Once single cell reproducibility was achieved, the design and operation of a 5 cell SOFCRoll bundle was investigated. A FLUENT CFD model was used to optimize the gas distribution in the five cell manifold design. The value of the model as a design tool was demonstrated by the comparison of 3 different gas manifold designs. The final manifold design M3 achieved 2.5W which is consistent with the 0.5W per a cell target. This manifold was then used as the basis for the development of a 25 cell stack which was built and tested. The 25 cell stack testing results were down to 0.35W per a cell. The performance drop highlighted the problem of fuel cell manufacturing reproducibility and also the importance of introducing reproducible manufacturing tequniques. That been the case for single cell manufacturing reproducibility issue, the fundamental concern for performance drop remains a design issue. To optimize the SOFCRoll design and to assist with the development program a single-cell CFD model was developed using FLUENT. The model was validated by comparison with data from experimental measurements for the single cell. The model work was used to predict the geometrical effect of the SOFCRoll tubular and the spiral gas channel configuration and current collector configuration. Results indicate the outlet gas flow velocity is higher around the spiral, near the gas inlet (the gas interring the cell preferentially flows around the spiral) therefore, velocity decrease as the gas moves along the cell. The lowest outlet velocity is registered opposite to the gas inlet, thus creating non-uniform gas distribution. The current density distribution is not uniform and is affected primarily by reactant flow distributions along the cell and possible current collection issues particularly around the spiral part of the cell.
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Bessette, Norman F. II. "A mathematical model of a tubular solid oxide fuel cell." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/19260.
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Bulut, Basar. "Second Law Analysis Of Solid Oxide Fuel Cells." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1219161/index.pdf.
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In this thesis, fuel cell systems are analysed thermodynamically and electrochemically. Thermodynamic relations are applied in order to determine the change of first law and second law efficiencies of the cells, and using the electrochemical relations, the irreversibilities occuring inside the cell are investigated. Following this general analysis, two simple solid oxide fuel cell systems are examined. The first system consists of a solid oxide unit cell with external reformer. The second law efficiency calculations for the unit cell are carried out at 1273 K and 1073 K, 1 atm and 5 atm, and by assuming different conversion ratios for methane, hydrogen, and oxygen in order to investigate the effects of temperature, pressure and conversion ratios on the second law efficiency. The irreversibilities inside the cell are also calculated and graphed in order to examine their effects on the actual cell voltage and power density of the cell. Following the analysis of a solid oxide unit cell, a simple fuel cell system is modeled. Exergy balance is applied at every node and component of the system. First law and second law efficiencies, and exergy loss of the system are calculated.
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Tang, Ling. "MODIFICATION OF SOLID OXIDE FUEL CELL ANODES WITH CERIUM OXIDE COATINGS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1244252739.
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Torres-Caceres, Jonathan. "Manufacturing of Single Solid Oxide Fuel Cells." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5875.
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Solid oxide fuel cells (SOFCs) are devices that convert chemical energy into electrical energy and have the potential to become a reliable renewable energy source that can be used on a large scale. SOFCs have 3 main components; the electrolyte, the anode, and the cathode. Typically, SOFCs work by reducing oxygen at the cathode into O2- ions which are then transported via the electrolyte to the anode to combine with a fuel such as hydrogen to produce electricity. Research into better materials and manufacturing methods is necessary to reduce costs and improve efficiency to make the technology commercially viable. The goal of the research is to optimize and simplify the production of single SOFCs using high performance ceramics. This includes the use of 8mol% Y2O3-ZrO2 (YSZ) and 10mol% Sc2O3-1mol%CeO2-ZrO2 (SCSZ) layered electrolytes which purport higher conductivity than traditional pure YSZ electrolytes. Prior to printing the electrodes onto the electrolyte, the cathode side of the electrolyte was coated with 20mol% Gd2O3-CeO2 (GDC). The GDC coating prevents the formation of a nonconductive La2Zr2O7 pyrochlore layer, which forms due to the interdiffusion of the YSZ electrolyte ceramic and the (La0.6Sr0.4)0.995Fe0.8Co0.2O3 (LSCF) cathode ceramic during sintering. The GDC layer was deposited by spin coating a suspension of 10wt% GDC in ethanol onto the electrolyte. Variation of parameters such as time, speed, and ramp rate were tested. Deposition of the electrodes onto the electrolyte surface was done by screen printing. Ink was produced using a three roll mill from a mixture of ceramic electrode powder, terpineol, and a pore former. The pore former was selected based on its ability to form a uniform well-connected pore matrix within the anode samples that were pressed and sintered. Ink development involved the production of different ratios of powder-to-terpineol inks to vary the viscosity. The different inks were used to print electrodes onto the electrolytes to gauge print quality and consistency. Cells were produced with varying numbers of layers of prints to achieve a desirable thickness. Finally, the densification behaviors of the major materials used to produce the single cells were studied to determine the temperatures at which each component needs to be sintered to achieve the desired density and to determine the order of electrode application, so as to avoid over-densification of the electrodes. Complete cells were tested at the National Energy Technology Laboratory in Morgantown, WV. Cells were tested in a custom-built test stand under constant voltage at 800°C with 3% humidified hydrogen as the fuel. Both voltage-current response and impedance spectroscopy tests were conducted after initial startup and after 20 hours of operation. Impedance tests were performed at open circuit voltage and under varying loads in order to analyze the sources of resistance within the cell. A general increase in impedance was found after the 20h operation. Scanning electron micrographs of the cell microstructures found delamination and other defects which reduce performance. Suggestions for eradicating these issues and improving performance have been made.M.S.M.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering; Mechanical Systems
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Bessette, Norman F. II. "Modeling and simulation for solid oxide fuel cell power system." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17824.
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Rogier, Eric Nicolas. "Simulating Heat Recovery of a Solid Oxide Fuel Cell using EES." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2258.
Full textAbstract:
Solid Oxide Fuel Cells (SOFC) as the heat source for a heat engine power cycle can greatly increase the overall efficiency. The maximum efficiency is limited in at least the following ways. All thermal heat engine power cycles are limited by the Carnot efficiency which is a function of the hot and cold reservoirs the cycle operates between. Another irreversibility that limits the maximum efficiency of a fossil fuel cycle is the combustion reaction. In a boiler or combustion chamber, the chemical reaction of combustion happens spontaneously, meaning that the reaction happens without being used to generate power. A fuel cell decreases this irreversibility because it generates work as the combustion reaction happens. A SOFC can do this without an expensive catalyst due to the higher operating temperature. The power generated by the fuel cell can be added to the power generated by the thermal power cycle operating from the exhaust of the SOFC. The total work generated would be more than the system would have generated from just the heat engine resulting in a higher overall efficiency for the cycle. A SOFC and a recovery power cycle was simulated in Engineering Equation Solver (EES) to solve for ideal operating conditions. The fuel cell and gas turbine system had a net power output of 136 MW and had an efficiency of 60.84%, assuming the fuel cell had an 85% fuel utilization.
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Gentile, Paul Steven. "Investigation of aluminosilicate refractory for solid oxide fuel cell applications." Diss., Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/gentile/GentileP1210.pdf.
Full textAbstract:
Stationary solid oxide fuel cells (SOFCs) have been demonstrated to provide clean and reliable electricity through electro-chemical conversion of various fuel sources (CH₄ and other light hydrocarbons). To become a competitive conversion technology the costs of SOFCs must be reduced to less than $400/kW. Aluminosilicate represents a potential low cost alternative to high purity alumina for SOFC refractory applications. The objectives of this investigation are to: (1) study changes of aluminosilicate chemistry and morphology under SOFC conditions, (2) identify volatile silicon species released by aluminosilicates, (3) identify the mechanisms of aluminosilicate vapor deposition on SOFC materials, and (4) determine the effects of aluminosilicate vapors on SOFC electrochemical performance. It is shown thermodynamically and empirically that low cost aluminosilicate refractory remains chemically and thermally unstable under SOFC operating conditions between 800°C and 1000°C. Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) of the aluminosilicate bulk and surface identified increased concentrations of silicon at the surface after exposure to SOFC gases at 1000°C for 100 hours. The presence of water vapor accelerated surface diffusion of silicon, creating a more uniform distribution. Thermodynamic equilibrium modeling showed aluminosilicate remains stable in dry air, but the introduction of water vapor indicative of actual SOFC gas streams creates low temperature (<1000°C) silicon instability due to the release of Si(OH)₄ and SiO(OH)₂. Thermal gravimetric analysis and transpiration studies identified a discrete drop in the rate of silicon volatility before reaching steady state conditions after 100-200 hours. Electron microscopy observed the preferential deposition of vapors released from aluminosilicate on yttria stabilized zirconia (YSZ) over nickel. The adsorbent consisted of alumina rich clusters enclosed in an amorphous siliceous layer. Silicon penetrated the YSZ along grain boundaries, isolating grains in an insulating glassy phase. XPS did not detect spectra shifts or peak broadening associated with formation of new Si-Zr-Y-O phases. SOFC electrochemical performance testing at 800-1000°C attributed rapid degradation (0.1% per hour) of cells exposed to aluminosilicate vapors in the fuel stream predominately to ohmic polarization. EDS identified silicon concentrations above impurity levels at the electrolyte/active anode interface.
'Co-authored by Paolo R. Zafred, Stephen W. Sofie, Camas F. Key, and Richard J. Smith.'
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Church, Benjamin Cortright. "Fabrication and Characterization of Solid Oxide Fuel Cell Interconnect Alloys." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4829.
Full textAbstract:
Metal alloy honeycomb structures were fabricated using a paste extrusion technique and characterized for potential application as interconnects in solid oxide fuel cells. Thermal expansion characteristics of Fe-Cr, Fe-Ni, Ni-Cr, Fe-Ni-Cr, and similar alloys containing an oxide dispersion were determined and compared with the thermal expansion behavior of yttria-stabilized zirconia (YSZ). A method was developed to calculate thermal expansion mismatch between two materials under a variety of heating and cooling conditions. It was shown that Fe 20 wt% Cr and Fe 47.5 wt% Ni alloys have low expansion mismatch with YSZ under a wide range of heating and cooling conditions. Oxidation experiments showed that Fe-Cr alloys have superior oxidation resistance in air at 700℃compared with Fe-Ni-Cr alloys with similar chromium contents. The inclusion of oxide dispersions (Y₂O₃ and CaO) into an alloy honeycomb was shown to improve oxidation resistance without affecting thermal expansion behavior. The honeycomb extrusion process provides a method by which experimental alloys can be produced and characterized rapidly to develop an alloy suitable for use as an interconnect in a solid oxide fuel cell.
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Green, Christopher K. "Development of Model for Solid Oxide Fuel Cell Compressive Seals." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19696.
Full textAbstract:
Fuel cells represent a promising energy alternative to the traditional combustion of fossil fuels. In particular, solid oxide fuel cells (SOFCs) have been of interest due to their high energy densities and potential for stationary power applications. One of the key obstacles precluding the maturation and commercialization of planar SOFCs has been the absence of a robust sealant. A leakage computational model has been developed and refined in conjunction with leakage experiments and material characterization tests at Oak Ridge National Laboratory to predict leakage in a single interface metal-metal compressive seal assembly as well as multi-interface mica compressive seal assemblies. The composite model is applied as a predictive tool for assessing how certain parameters (i.e., temperature, applied compressive stress, surface finish, and elastic thermo physical properties) affect seal leakage rates.
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Timurkutluk, Bora. "Performance Anaylsis Of An Intermediate Temperature Solid Oxide Fuel Cell." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608816/index.pdf.
Full textAbstract:
An intermediate temperature solid oxide fuel cell (SOFC) is developed and its
performance is investigated experimentally and theoretically. In the experimental
program, a gadolinium doped ceria based membrane electrode group is developed
with the tape casting and screen printing methodology and characterized. An
experimental setup is devised for the performance measurement of SOFCs and the
performance of produced cells is investigated over a range of parameters including
the electrolyte thickness, the sintering temperature, the operation temperature etc.
The experimental setup is then further modified to measure the temperature
distribution in the large SOFC single cells. The effects of operating parameters on
the temperature distribution are investigated and the parameter spaces leading high
efficiency without cracking the ceramic membrane are identified.
In theoretical study a mathematical model is developed to represent the fluid flow,
the heat transfer, the species transport and the electrochemical reaction in
intermediate temperature of solid oxide fuel cells.The differential equations are
solved numerically with a commercial CFD code which employs a control volume
based approach. The temperature distribution and species distribution during theSOFC operation is analyzed. The effects of operation parameters on critical SOFC
characteristics and the performance are numerically investigated over a range of
parameter space.
The experimental and numerical results are compared to validate the mathematical
model. The mathematical model is found to agree reasonable with experimental data.
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Xie, Hua. "TiC based cermets for solid oxide fuel cell interconnect application /." Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1240704831&sid=13&Fmt=2&clientId=1509&RQT=309&VName=PQD.
Full textAbstract:
Thesis (M.S.)--Southern Illinois University Carbondale, 2006."Department of Mechanical Engineering and Energy Processes." Includes bibliographical references (leaves 56-58). Also available online.
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Adamson, Mark T. "Structural and material analysis of the solid oxide fuel cell." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288638.
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Clarke, Richard. "Coatings on stainless steel for solid oxide fuel cell interconnects." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3639.
Full textAbstract:
Enabling inexpensive and ubiquitous steels for use as solid oxide fuel cell interconnects has two major hurdles to overcome. Firstly, corrosion must be limited such that the interconnect can have longevity. Secondly, the evaporation of chromium from the corrosion layer must also be limited such that the fuel cell can have longevity. The evaporation of chromium from chromia, titanium doped chromia, and chromium cobalt spinels was studied and characterized. Spinels lost the least amount of mass during evaporation experiments, and changed the least after experimental conditions were imposed on them that. Chromium titanate samples retained a significant amount of chrome that would have evaporated had the sample been chromium oxide alone. This was due to local changes at the surface with titanium becoming enriched and blocking loss of further chromium. Various methods of depositing titanium doped chromia on the surface of SS430 were investigated. Sol-gel was attempted, but proved problematic. Evaporation of elemental titanium onto SS430 followed by conversion to rutile by heating followed by the evaporation of chromium into the rutile layer was investigated at length. These layers are nanoscale when evaporated and about 10 times thicker after oxidation. Characterization of the resulting Ti layers showed that at low temperatures a thick dense layer of rutile could be observed. At higher oxidation temperatures, the titanium was difficult to find. Evaporation of cobalt onto SS430 created thin films when oxidized. The films were shown to control the evaporation of chromium by production of spinels. These layers were characterized with X-Ray Diffraction and scanning electron microscopy and impedance spectroscopy. They were shown to be quite conductive compared to the titanium coatings.
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Lockett, Matthew. "A study of micro-tubular solid oxide fuel cell stacks." Thesis, University of Birmingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.668330.
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Hagos, Samuel Tesfazghi. "Solid oxide fuel cell design and application of formal methods." Thesis, City University London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394171.
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Corrie, Benjamin. "Synthesis and structural characterisation of solid oxide fuel cell materials." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5993/.
Full textAbstract:
Three general systems, tetrahedrally coordinated oxides, apatite oxides and brownmillerite type Ba\(_2\)Sc\(_2\)O\(_5\) systems have been investigated. Powder diffraction indicated the successful incorporation of aluminium and gallium into Ba\(_2\)GeO\(_4\) which led to an increase in ionic conductivity, with a further increase of an order of magnitude in wet atmospheres due to proton conductivity. Neutron diffraction and TGA studies indicated the successful incorporation of water and flourine in La\(_8\)Sr\(_2\)(Si/Ge)\(_6\)O\(_2\)\(_6\) apatites. The interstitial positions for flourine and water ions were different from each other and for germanium and silicon apatites suggesting that the interstitial positions are composition dependant rather than universal for apatite systems. Neutron diffraction, TGA and AC impedance spectroscopy indicated successful doping of Y/Yb into BaSc\(_0\)\(_.\)\(_6\)\(_5\)\(_-\)\(_x\)Ti\(_0\)\(_.\)\(_3\)O\(_2\)\(_.\)\(_6\)\(_5\) stabilising the oxygen deficient perovskite structure with increased stability of CO\(_2\) and good conductivity. Whilst neutron diffraction of 4K on hydrated BaSc\(_0\)\(_.\)\(_2\)\(_5\)Y\(_0\)\(_.\)\(_4\)\(_5\)Ti\(_0\)\(_.\)\(_3\)O\(_2\)\(_.\)\(_6\)\(_5\) has located the proton positions.
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Ong, Katherine M. (Katherine Mary). "Modeling of solid oxide fuel cell performance with coal gasification." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104226.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references.
Growing concern over greenhouse gas emissions has driven research into clean coal power production alternatives. Novel coal power plant designs that lower CO2 emissions are imperative in the coming decades to mitigate global temperature rise. High-efficiency stationary power systems that integrate coal gasification with solid oxide fuel cells (SOFCs) have been championed by the Department of Energy for the past couple of decades. However, many fundamental questions about this system still need to be addressed by modeling the complex coupling between SOFC's and gasification. More specifically, work is needed to characterize SOFC performance with a range of syngas (H₂+CO) mixtures produced by coal gasification. This thesis used a multiscale modeling approach to analyze SOFC performance with coal syngas at both the systems level and at the surface reaction scale. The first investigation in this thesis couples an equilibrium gasifier model to a detailed ID SOFC model to study the theoretical performance of the coupled system run on steam or carbon dioxide. The results of this study indicate that the system performs substantially better with steam gasification than with CO₂ gasification as a result of the faster electro-oxidation kinetics of H₂ relative to CO. The coupled system is then shown to reach higher current densities and efficiencies when the heat released by the fuel cell is sent to the gasifier instead of a bottoming cycle. 55-60% efficiency is then predicted for the system with heat transfer and steam gasification, making this technology competitive with other advanced system designs and almost twice as efficient as conventional coal-fired power plants. The second study in this thesis investigates SOFC behavior with H₂ and CO (syngas) mixtures that come from coal gasification. SOFC models typically neglect CO electrochemistry in the presence of H₂ and H₂0, assuming that the water-gas-shift reaction proceeds faster than CO electrooxidation. The results of this study show, however, that CO electro-oxidation cannot be neglected in syngas mixtures, particularly at high current densities for high CO-content syigas. First the simulations demonstrate that incoming CO is not all shifted to form H₂ by reforming reactions before reaching the electrochemical reaction sites. Furthermore, the results of this 'study confirm that direct electro-oxidation of CO contributes non-negligible current relative to H₂ at high anode overpotentials. Together these results show that CO electro-oxidation plays an important role in SOFC performance not only via water-gas-shift reforming, but also via direct electro-oxidation when H₂ is also present. This work suggests that accurate models for both surface reforming and direct electro-oxidation of CO in SOFC anodes must be included in order to capture performance when using coal syngas mixtures. Finally, a multi-step mechanism for the simultaneous electro-oxidation of H₂ and CO in SOFCs is implemented and studied. This mechanism combines a couple of reaction pathways: hydrogen (H) spillover to the electrolyte, and oxygen (O) spillover to hydrogen and CO on the anode. This mechanism is successfully verified in the model against a wide range of experimental data for mixtures of CO/CO₂, H₂/N₂, H₂/H₂0, H₂/CO, and H₂/CO₂ . The simulations show that H spillover is the dominant source of current at low anode activation overpotentials, but also demonstrate that the currents produced by 0 spillover are non-negligible at high overpotentials. Furthermore, it is shown that the current produced by 0 spillover to CO is not limited by the rate of CO adsorption on nickel, which leads CO to contribute more to cell performance at high currents. Together these three modeling studies demonstrate how coal can be efficiently converted to electricity via gasification and the simultaneous electro-oxidation of H₂ and CO in a solid oxide fuel cell.
by Katherine M. Ong.
Ph. D.
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Kosinski, Marcin Robert. "Nanomaterials for solid oxide fuel cell electrolytes and reforming catalysts." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2588.
Full textAbstract:
In this work, a broad range of analytical methods was applied to the study of the following three materials systems: yttria-stabilised zirconia (YSZ), samarium-doped ceria (SDC) and SDC-supported metal catalysts. YSZ and SDC were studied in the light of their application as solid electrolytes in Solid Oxide Fuel Cells. The SDC-supported metal catalysts were evaluated for application in the reforming of methanol. The conductive properties of YSZ pellets derived from powders of different Y contents and particle size ranges were investigated using Impedance Spectroscopy (IS). Comparative studies of the crystallography (by X-ray Powder Diffraction (XRD)), morphology (by Scanning and Transmission Electron Microscopy (SEM, TEM)), chemical composition (by Energy Dispersive X-ray Spectroscopy (EDX) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS)) and sintering behaviour (dilatometry) were employed in the overall assessment of the conductivity results collected. Detailed studies of three SDC compositions were performed on nanopowders prepared by a low temperature method developed in the Baker group. Modifications led to a simple and reliable method for producing high quality materials with crystallites of ~10 nm diameter. The products were confirmed by XRD and TEM to be single-phase materials. Thermogravimetric analysis, dilatometry, specific surface area determination, elemental analysis and IS were carried out on these SDC powders. The relationships between particle size, chemical composition, sintering conditions and conductivity were studied in detail allowing optimum sintering conditions to be identified and ionic migration and defect association enthalpies to be calculated. Finally, the interesting results obtained for the SDC nanopowders were a driving force for the preparation of SDC-supported metal catalysts. These were prepared by three different methods and characterised in terms of crystallographic phase, specific surface area and bulk and surface chemical composition. Isothermal catalytic tests showed that all catalysts had some activity for the reforming of methanol and that some compositions showed both very high conversions and high selectivities to hydrogen. These catalysts are of interest for further study and possibly for commercial application.
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Nwosu, Nkem O. E. "Optimisation of electroless co-deposited solid oxide fuel cell electrodes." Thesis, Edinburgh Napier University, 2013. http://researchrepository.napier.ac.uk/Output/6448.
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Research already carried out on the use of the recently patented electroless nickel ceramic codeposition technique as a method of manufacturing solid oxide fuel cell (SOFC) electrodes has thus far indicated that, while functional electrodes can be manufactured by the technique, for optimum performance of the cell, amplification of the ceramic content of the coatings is still required. By mainly employing external agents such as surface active agents (surfactants) and magnetic fields (in a bid to aid ceramic particle stability), this research focused on the prospect of increasing the ceramic content of cermets co-deposited for use as SOFC electrodes. A total of 137 co-deposited samples were produced from different bath compositions. As a prelude to the study, the interactions between the ceramic powders used (yttria stabilised zirconia (YSZ) / lanthanum strontium manganate (LSM)) and the medium for the deposition process – the electroless nickel solution, were investigated by zeta potentiometry and ultraviolet-visible spectroscopy techniques. The results obtained from the studies led to a variation of a series of fundamental plating factors such as the ceramic bath loading and particle size of the powders. While the former was found to yield the highest ceramic content in the coating at a bath loading of 50 g/l, variation of latter notably produced mixed results. With the introduction of surfactants, it was noted that above the surfactant's (sodium dodecyl sulphate) critical micelle concentration, the incorporation of ceramic particles (YSZ) into the nickel matrix steadily increased to as much as 60 volume %. An inverse relationship was though found to exist between the coating thickness and the surfactant's bath concentration. Uniform coatings were found to be associated with low magnetic field strengths while although increased magnetic field strengths positively resulted in the amplification of particle incorporation into the coating, a lack of cohesion between the coating and the substrate – as indicated by coating flake-off, was observed at such strengths. It is suggested that because the magnetic flux was more dominant than the normally ionic plating mechanism, the particles co-deposited under the influence of a high magnetic field were relatively unstable after the coating process. Since LSM is alkaline in nature this work confirms that future research on the application of electroless nickel ceramic co-deposition as a method of manufacturing SOFC cathodes, be focused on the use of alkaline electroless nickel baths rather than the acidic solutions, which better suite YSZ particles.
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Cooper, Samuel J. "Quantifying the transport properties of solid oxide fuel cell electrodes." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/31600.
Full textAbstract:
The performance of Solid Oxide Fuel Cell (SOFC) electrodes is determined both by their porous microstructure and the intrinsic properties of their component materials. This thesis details the development of two characterisation tools for analysis of mass and charge transport processes in SOFC electrode materials. Firstly, a new approach to isotopic exchange is described, which allows the oxygen self-diffusion (D*) and effective surface exchange (k*) to be measured in ambient atmospheres. This is significant as many similar studies in the literature are limited to investigations in pure, dry oxygen, or other proxy environments, which are not representative of realistic SOFC operating conditions. A finite difference simulation was created to generate profiles that were used to extract material parameters from this 'back-exchange' data. The technique was then validated by comparison of the results from two experiments in pure, dry oxygen (both single step and back-exchange), which demonstrated good agreement with values of D* and k* in the literature, for the common SOFC cathode material La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF6428). A third experiment found the surface exchange coefficient to increase by a factor of 5 when exchanged under ambient conditions compared with pure, dry oxygen. Secondly, following an introduction to the tortuosity factor, X-ray tomography was used to 3D image micro-tubular (MT) samples ( c. 1 mm diameter) at three key length-scales. A zirconia based MT-Solid Oxide Electrolyser Cell (SOEC) was imaged at the whole cell level, both before and after 300 hours operation at 750°C . Current collector contact was found to be poor even before operation, but afterwards the paste was seen to agglomerate into metallic silver and no longer span the gap to the current collector wire, which further degraded contact. A ceria based MT-SOFC with a hierarchical microstructure was then imaged at both the micro- and nanoscale. The geometry data was used to determine that the tortuosity factor of this radial system was significantly higher when measured at either length-scale in isolation, than when considered together in a multi length-scale model.
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Guillerm, Antoine-Amaury. "Assessment of a solid oxide fuel cell powering a full electric aircraft subsystem architecture." Thesis, KTH, Flygdynamik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290177.
Full textAbstract:
This paper presents the work from a Master thesisat Bauhaus Luftfahrt (Munich, Germany) about subsystemdesign and analysis for electric commercial aircraft, particularlythe assessment of a Solid Oxide Fuel Cell (SOFC) powering a fullelectric subsystem architecture. The different components of theSOFC system architecture are modelled and assessed with theOpenMDAO framework. They are then assembled together toassess the performance of the whole SOFC system architecture,the main goal being to replace the conventional Auxiliary PowerUnit (APU) on the ground and to provide energy to all thesubsystems (e.g. flight controls, air conditioning, ice and rainprotection among others) of the aircraft during flight andground operations. The mass of the different components of theSOFC system is calculated, and a 2% operational empty massincrease is assumed for subsystem electrification. The resultsshow a kerosene block fuel reduction of 2.1% compared to theconventional baseline aircraft.Denna uppsats presenterar arbetet från ett examensarbete på Bauhaus Luftfahrt (Munchen, Tyskland) om delsystemdesign och analys för elektriska kommersiella flygplan, särskilt bedömningen av en solidoxidbränslecell (SOFC) som driver en fullständig elektrisk delsystemarkitektur. De olika komponenterna i SOFC-systemarkitekturen modelleras och utvärderas med ett Open MDAO-ramverk. Sedan monteras komponenterna ihop för att utvärdera prestandan för hela SOFC systemarkitekturen, där huvudmålet var att ersätta den konventionella hjälpkraftenheten (APU) på marken och att förse alla delsystem med energi (t.ex. flygkontroller, luftkonditionering, is och regnskydd, med mera) av flygplanet under flygning samt markoperationer. Massan för de olika komponenterna i SOFC systemet beräknades, där en ökning av 2% operationell tom massa antogs för delsystemelektrifiering. Resultaten visade en bränslereduktion av fotogenblock på 2,1% jämfört med det konventionella flygplanet.