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Estudo de rotas de síntese e processamento cerâmico do compósito NiO-YSZ para aplicação como anodo em células a combustível do tipo óxido sólido; Study of synthesis routes and processing of NiO-YSZ ceramic composite for use as anode in solid oxide fuel cell (SOFC)

Yoshito, Walter Kenji
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 17/03/2011 PT
Relevância na Pesquisa
109.40479%
Este estudo visa a definição de condições de síntese e processamento cerâmico que possibilitem a obtenção do componente anódico com características adequadas para a operação de uma SOFC (Solid Oxide Fuel Cell), ou seja, boa distribuição microestrutural do NiO na matriz de YSZ e porosidade cerca de 30% após redução de NiO. As rotas de síntese selecionadas englobaram a coprecipitação em meio amoniacal, mistura mecânica dos pós e combustão a partir de sais de nitrato. As técnicas de caracterização de pós empregadas incluíram a difração de raios X, microscopia eletrônica de varredura, microscopia eletrônica de transmissão, difração a laser, adsorção gasosa (BET) e picnometria de hélio. Os resultados obtidos indicaram que empregando-se a técnica de coprecipitação, a perda de Ni2+, na forma de complexo [Ni(NH3)n]2+, pode ser minimizada pelo controle do pH em 9,3, mantendo-se a concentração de Ni2+ na solução inicial em 0,1M. No método de mistura mecânica a melhor condição de dispersão dos pós, sem a sedimentação diferencial, foi obtida para valores de potencial zeta em pH 8,0, fixando-se a concentração de dispersante em 0,8% em massa. Na síntese por combustão observou-se que para composições pobres em combustível...

Caracterização de vidros niobofosfatos para aplicação em selagem em célula a combústivel de óxido sólido; Characterization of niobophosphate glasses for solid oxide fuel cell (SOFC) sealing

Rogério, Ademilson
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 16/03/2010 PT
Relevância na Pesquisa
119.633545%
Células a combustível de óxido sólido são sistemas capazes de gerar energia elétrica por meio da oxidação de moléculas hidrogenadas. Normalmente os sistemas planares e tubulares, são compostos por quatro constituintes bem definidos: cátodo, ânodo, eletrólito e selante. Este último componente é o foco do presente estudo, sendo que suas principais características são estabilidade química na temperatura de operação da célula, isolamento elétrico e coeficiente de expansão térmica compatível com os outros constituintes, além da viscosidade elevada e resistência química em atmosferas oxidantes e redutoras. Devido à geometria planar e de multicamadas da célula se optou por usar como selante vidros niobofosfatos. A selagem foi realizada a partir de dispersão de pó de vidro em álcool etílico, gerando uma solução viscosa que foi aplicada sobre o substrato. Posteriormente realizou se um tratamento térmico para a consolidação do selamento. Os vidros estudados foram denominados de Nb30, Nb37, Nb40 e Nb44, de acordo com o teor nominal de óxido de nióbio utilizado na composição. O objetivo desse trabalho foi caracterizar, a partir de precursores os selantes a base de vidros niobofosfatos para aplicar em células a combustível de óxido sólido do tipo planar. Foram feitos caracterizações dos pós dos vidros e de pastilhas cristalizadas para determinar os coeficientes de expansão térmica (CET)...

Fabricação e testes de células a combustível de óxido sólido a etanol direto usando camada catalítica; Solid oxide fuel cells fabrication and operation running direct ethanol using a catalytic layer

Nobrega, Shayenne Diniz da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 07/03/2013 PT
Relevância na Pesquisa
109.70391%
Células a combustível de óxido sólido suportadas no eletrólito de zircônia estabilizada com ítria (YSZ) foram fabricadas usando a técnica do recobrimento por rotação (spin-coating) para deposição de catodos de manganita de lantânio dopada com estrôncio (LSM) e anodos compósitos de níquel e YSZ (Ni-YSZ). Parâmetros microestruturais dos eletrodos, tais como espessura, tamanho médio de partículas e temperatura de sinterização foram otimizados, visando reduzir a resistência de polarização da célula e melhorar o seu desempenho. Estes estudos serviram de base para a fabricação de células com camada catalítica para uso com etanol direto. Sobre o anodo Ni-YSZ da célula foi depositada uma camada catalítica de céria dopada com gadolínia (CGO) com 0,1% em peso de irídio (Ir-CGO). A camada catalítica visa reformar o etanol antes do seu contato com o anodo Ni-YSZ, evitando o depósito de carbono na superfície do Ni que inviabiliza o uso de combustíveis primários contendo carbono nestas células a combustível. Inicialmente, a célula a combustível foi testada com etanol e as melhores condições de operação foram determinadas. Em seguida, as células unitárias foram testadas com etanol sem adição de água por períodos de tempo de até 390 horas. As células a combustível a etanol direto com camada catalítica operam no modo de reforma interna gradual...

Study of a hybrid solid oxide fuel cell: Energetic analysis and sankey diagram

Luz-Silveira, José; De Souza, Antonio Carlos Caetano; Gallo, Giulliano Batelochi
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 657-664
ENG
Relevância na Pesquisa
119.67323%
In this paper a hybrid solid oxide fuel cell (SOFC) system is analyzed. This system applies a combined cycle utilizing gas turbine associated to a SOFC for rational decentralized energy production. Initially the relative concepts about the fuel cell are presented, followed by some chemical and technical informations such as the change of Gibbs free energy in isothermal fuel oxidation (or combustion) directly into electricity. This represents a very high fraction of the lower heating value (LHV) of a hydrocarbon fuel. In the next step a methodology for the study of SOFC associated with a gas turbine system is developed, considering the electricity and steam production for a hospital, as regard to the Brazilian conditions. This methodology is applied to energetic analysis. Natural gas is considered as a fuel. In conclusion, it is shown by a Sankey Diagram that the hybrid SOFC system may be an excellent opportunity to strengthen the decentralized energy production in Brazil. It is necessary to consider that the cogeneration in this version also is a sensible alternative from the technical point of view, demanding special methods of design, equipment selection and mainly of the contractual deals associated to electricity and fuel supply.

Thermodynamic simulation of biomass gas steam reforming for a solid oxide fuel cell (SOFC) system

Sordi,A.; Silva,E. P. da; M. Neto,A. J.; Lopes,D. G.; Pinto,C. S.; Araújo,P. D.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2009 EN
Relevância na Pesquisa
109.40982%
This paper presents a methodology to simulate a small-scale fuel cell system for power generation using biomass gas as fuel. The methodology encompasses the thermodynamic and electrochemical aspects of a solid oxide fuel cell (SOFC), as well as solves the problem of chemical equilibrium in complex systems. In this case the complex system is the internal reforming of biomass gas to produce hydrogen. The fuel cell input variables are: operational voltage, cell power output, composition of the biomass gas reforming, thermodynamic efficiency, electrochemical efficiency, practical efficiency, the First and Second law efficiencies for the whole system. The chemical compositions, molar flows and temperatures are presented to each point of the system as well as the exergetic efficiency. For a molar water/carbon ratio of 2, the thermodynamic simulation of the biomass gas reforming indicates the maximum hydrogen production at a temperature of 1070 K, which can vary as a function of the biomass gas composition. The comparison with the efficiency of simple gas turbine cycle and regenerative gas turbine cycle shows the superiority of SOFC for the considered electrical power range.

Metallic materials in solid oxide fuel cells

Quadakkers,Willem Joseph; Pirón-Abellán,Javier; Shemet,Vladimir
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2004 EN
Relevância na Pesquisa
119.48396%
Fe-Cr alloys with variations in chromium content and additions of different elements were studied for potential application in intermediate temperature Solid Oxide Fuel Cell (SOFC). Recently, a new type of FeCrMn(Ti/La) based ferritic steels has been developed to be used as construction material for SOFC interconnects. In the present paper, the long term oxidation resistance of this class of steels in both air and simulated anode gas will be discussed and compared with the behaviour of a number of commercial available ferritic steels. Besides, in-situ studies were carried out to characterize the high temperature conductivity of the oxide scales formed under these conditions. Main emphasis will be put on the growth and adherence of the oxide scales formed during exposure, their contact resistance at service temperature as well as their interaction with various perovskite type contact materials. Additionally, parameters and protection methods in respect to the volatilization of chromia based oxide scales will be illustrated.

Ultra-thin solid oxide fuel cells: materials and devices

Kerman, Kian
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
EN_US
Relevância na Pesquisa
120.10461%
Solid oxide fuel cells are electrochemical energy conversion devices utilizing solid electrolytes transporting O2- that typically operate in the 800 - 1000 °C temperature range due to the large activation barrier for ionic transport. Reducing electrolyte thickness or increasing ionic conductivity can enable lower temperature operation for both stationary and portable applications. This thesis is focused on the fabrication of free standing ultrathin (<100 nm) oxide membranes of prototypical O2- conducting electrolytes, namely Y2O3-doped ZrO2 and Gd2O3-doped CeO2. Fabrication of such membranes requires an understanding of thin plate mechanics coupled with controllable thin film deposition processes. Integration of free standing membranes into proof-of-concept fuel cell devices necessitates ideal electrode assemblies as well as creative processing schemes to experimentally test devices in a high temperature dual environment chamber. We present a simple elastic model to determine stable buckling configurations for free standing oxide membranes. This guides the experimental methodology for Y2O3-doped ZrO2 film processing, which enables tunable internal stress in the films. Using these criteria, we fabricate robust Y2O3-doped ZrO2 membranes on Si and composite polymeric substrates by semiconductor and micro-machining processes...

Computational Fluid Dynamics Modelling of Solid Oxide Fuel Cell Stacks

Nishida, Robert Takeo
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
129.61188%
Two computational fluid dynamics models are developed to predict the performance of a solid oxide fuel cell stack, a detailed and a simplified model. In the detailed model, the three dimensional momentum, heat, and species transport equations are coupled with electrochemistry. In the simplified model, the diffusion terms in the transport equations are selectively replaced by rate terms within the core region of the stack. This allows much coarser meshes to be employed at a fraction of the computational cost. Following the mathematical description of the problem, results for single-cell and multi-cell stacks are presented. Comparisons of local current density, temperature, and cell voltage indicate that good agreement is obtained between the detailed and simplified models, verifying the latter as a practical option in stack design. Then, the simplified model is used to determine the effects of utilization on the electrochemical performance and temperature distributions of a 10 cell stack. The results are presented in terms of fluid flow, pressure, species mass fraction, temperature, voltage and current density distributions. The effects of species and flow distributions on electrochemical performance and temperature are then analyzed for a 100 cell stack. The discussion highlights the importance of manifold design on performance and thermal management of large stacks.; Thesis (Master...

The Development of a Coupled Physics and Kinetics Model to Computationally Predict the Powder to Power Performance of Solid Oxide Fuel Cell Anode Microstructures

Gaweł, Duncan Albert Wojciech
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
119.44711%
A numerical model was developed to evaluate the performance of detailed solid oxide fuel cell (SOFC) anode microstructures obtained from experimental reconstruction techniques or generated from synthetic computational techniques. The model is also capable of identifying the linear triple phase boundary (TPB) reaction sites and evaluating the effective transport within the detailed structures, allowing a comparison between the structural properties and performance to be conducted. To simulate the cell performance, a novel numerical coupling technique was developed in OpenFOAM and validated. The computational grid type and mesh properties were also evaluated to establish appropriate mesh resolutions to employ when studying the performance. The performance of a baseline synthetic electrode structure was evaluated using the model and under the applied conditions it was observed that the ionic potential had the largest influence over the performance. The model was used in conjunction with a computational synthetic electrode manufacturing algorithm to conduct a numerical powder to power parametric study investigating the effects of the manufacturing properties on the performance. An improvement in the overall performance was observed in structures which maximized the number of reaction sites and had well established transport networks in the ion phase. From the manufacturing parameters studied a performance increase was observed in structures with low porosity and ionic solid volume fractions near the percolation threshold...

NUMERICAL PREDICTION OF EFFECTIVE ELASTIC PROPERTIES AND EFFECTIVE THERMAL EXPANSION COEFFICIENT FOR POROUS YSZ MICROSTRUCTURES IN SOLID OXIDE FUEL CELLS

Shakrawar, Sangeeta
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
120.24305%
Solid oxide fuel cells represent a potentially important application for ceramic materials. There are, however, some significant issues which can affect the reliability and durability of the cell. Mechanical failure owing to stress is one of the critical factors which can affect the stability and working life of the fuel cell stacks. These stresses generate in Solid Oxide Fuel Cells (SOFCs) owing to mechanical forces and change in temperature during fabrication, assembly and operating conditions. There can be chances of cell delamination and micro-cracks in cell electrodes if these stresses are too high. The elastic properties and thermal expansion coefficient play a vital role to improve cell stability and performance. These properties depend on the types of materials and geometries of the composites. In this research, a numerical framework to predict the effective elastic properties and the effective thermal expansion coefficient for porous Yttria-Stabilized Zirconia (YSZ) electrode microstructures in a Solid Oxide Fuel Cell is presented. The electrodes of Solid Oxide Fuel Cells are discretized as porous microstructures that are formed by randomly distributed and overlapping spheres with particle size distributions that match those of actual ceramic powder. Three-dimensional (3D) microstructures of YSZ-pore are formed with a porosity ranging from 25% to 40%. The technique involves the construction of the YSZ-pores microstructures based on measurable starting parameters and subsequent numerical prediction of effective elastic properties and effective thermal expansion coefficient. Three domain sizes are considered for the generation of YSZ-pore microstructures. The method of prediction of effective Young’s modulus (Eeff)...

An Experimental and Modelling Study of Oxygen Reduction in Porous LSM/YSZ Solid Oxide Fuel Cell Cathodes

Kenney, BENJAMIN
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
109.39611%
Solid oxide fuel cells (SOFCs) are electrochemical devices that can convert a variety of fuels directly into electricity. Their commercialization requires efficient operation of its components. The sluggish kinetics for the oxygen reduction reaction (ORR) at the SOFC cathode contributes to the loss in the fuel cell efficiency. In this work, the ORR was investigated for the strontium-doped lanthanum manganite cathode (LSM) and yttria-stabilized zirconia electrolyte (YSZ) system. A combined mathematical modelling and experimental framework was developed to estimate, for the first time, the kinetics of the elementary processes of the ORR for porous LSM cathodes. The kinetics of each process was then analyzed to identify the contribution to the cathode resistance. The steady state and impedance response for polarized and unpolarized LSM cathodes was collected over a temperature range between 750C and 850C and two different oxygen partial pressure (pO2) ranges: (i) between 0.0001atm and 0.001atm, where LSM is considered to be stoichiometric with respect to oxygen and (ii) between 0.01atm and 0.21atm, where LSM is considered to be superstoichiometric with respect to oxygen. A mathematical model was developed to analyze both the steady state and impedance data. Two pathways for the ORR were considered: one where oxygen is transported in the gas phase and one where oxygen is transported along the surface of the LSM cathode. Rate constants...

NUMERICAL MODELING OF THE EFFECT OF SULFUR POISONING ON THE PERFORMANCE OF THE POROUS ANODE SOLID OXIDE FUEL CELL

Manafi Rasi, Negar
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
129.67619%
A numerical model to capture the effect of H2S impurities on the Solid Oxide Fuel Cell (SOFC) performance with Ni-based porous anode is developed. H2S impurities can adversely affect the fuel cell performance, due to the sulfur poisoning of the Ni catalyst of the SOFC anode. The novelty of this work is the derivation of a Butler-Volmer type kinetic formulation that captures the effect of sulfur poisoning on the H2 electro-oxidation reaction in the Ni-YSZ anode of SOFC. The novel kinetic model is then incorporated into a 2-dimensional porous anode model with gas-phase species transport, charged species transport and anode electrochemistry. The result is a performance model that can predict the effect of H2S impurity on the polarization curves of the SOFC by taking into account the transport phenomena in addition to the electrochemistry formulations. Two types of kinetic models named as “coverage dependent kinetic model” and “coverage independent kinetic model”, differing in the coverage dependency of energy of H2 and H2S adsorption reactions are developed and incorporated in the 2D porous anode model. Loss in performance is predicted by both kinetic models and 2D performance models. Both kinetic models predictions show an increase in the current density loss with an increase in H2S concentration. 2D performance models predictions with both coverage dependent and coverage independent models show an increasing trend in both the loss in the cell voltage and increase in the cell resistance upon the increase of the inlet H2S content of the fuel. The 2D performance model with coverage-dependent kinetics predicts lower loss in the cell performance than the 2D performance model with coverage-independent kinetics. By comparing the performance model predictions with the experimental results...

NUMERICAL AND EXPERIMENTAL CHARACTERISATION OF CONVECTIVE TRANSPORT IN SOLID OXIDE FUEL CELLS

Resch, Emmanuel
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 2979040 bytes; application/pdf
EN; EN
Relevância na Pesquisa
119.40627%
In this work, numerical and experimental methods are used to characterise the effects of convective transport in an anode-supported tubular solid oxide fuel cell (SOFC). To that end, a computational fluid dynamics (CFD) model is developed to compare a full transport model to one that assumes convection is negligible. Between these two approaches, the variations of mass, temperature, and electrochemical performance are compared. Preliminary findings show that convection serves to reduce the penetration of hydrogen into the anode, and becomes more important as the thickness of the anode increases. The importance of the permeability of SOFC electrodes on the characterization of convection is also investigated. Experiments performed on Ni-YSZ anodes reveal that permeability is a function of the cell operating conditions, and increases with increasing Knudsen number. An empirical Klinkenberg relation is validated and proposed to more accurately represent the permeability of electrodes in a CFD model. This is a departure from an assumption of constant permeability that is often seen in the literature. It is found that a varying permeability has significant effects on pressure variation in the cell, although according to the electrochemical model developed in this work...

Examination of the Pore Space of a Solid Oxide Fuel Cell Electrode: A Computational Approach

Blore, Drew
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
129.44711%
A numerical model of a solid oxide fuel cell electrode is presented. Using an already established algorithm for dropping spheres as a base, alterations are made to the algorithm to increase the realism of the model. Two changes are analyzed in detail: the ability to drop pore former particles, and the use of pre-agglomerated solid particles. These changes are characterized by their impact on mean pore size, tortuosity, and effective diffusivity. As pore former volume fraction is increased, so too are mean pore size and tortuosity. A higher mean pore size has a beneficial effect on effective diffusivity due to Knudsen effects, while a higher tortuosity has a detrimental effect on effective diffusivity. The impact of mean pore size and tortuosity on diffusivity generally balances and if the impact of porosity is ignored, pore former volume fraction does not greatly affect effective diffusivity. As pore former particle size is increased, mean pore size and tortuosity also increase. Similarly to before, the effects of mean pore size and tortuosity balance. However, effective diffusivity is shown to decrease slightly with an increasing pore former particle size, suggesting a change in tortuosity has greater impact on diffusivity than a change in mean pore size. For a domain constructed with pre-agglomerated particles...

Ethanol and glycerin processor systems coupled to solid oxide fuel cells (SOFC). Optimal operation and heat exchangers network synthesis.

Oliva, Diego Gabriel; Francesconi, Javier Andres; Mussati, Miguel Ceferino; Aguirre, Pio Antonio
Fonte: Pergamon-elsevier Science Ltd Publicador: Pergamon-elsevier Science Ltd
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
Relevância na Pesquisa
119.39611%
This paper is aimed at presenting a methodology for the simultaneous synthesis of solid oxide fuel cell (SOFC) based systems and their associated heat exchangers network (HEN). The optimization model is formulated as a mixed integer nonlinear mathematical programming (MINLP) problem. The optimization goal is to maximize the overall net efficiency of the integrated system. Ethanol and glycerin are studied as fuels fed to the SOFC system as they constitute two renewable and sustainable sources of energy. As main results, net global efficiency values of 69.35% and 66.97% were computed for ethanol and glycerin, respectively. For both cases, the computed optimal operation pressure, the SOFC operation temperature and the fed water/fuel molar ratio values were 2 atm, 1073 K and 3, respectively.; Fil: Oliva, Diego Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológio - CONICET - Santa Fe. Instituto de Desarrollo y Diseño (i); Argentina;; Fil: Francesconi, Javier Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológio - CONICET - Santa Fe. Instituto de Desarrollo y Diseño (i); Argentina;; Fil: Mussati, Miguel Ceferino. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológio - CONICET - Santa Fe. Instituto de Desarrollo y Diseño (i); Argentina;; Fil: Aguirre...

Robust control strategies for hybrid solid oxide fuel cell systems

Allag, Tahar
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Relevância na Pesquisa
120.11953%
Solid Oxide Fuel Cell (SOFC) systems are electrochemical energy conversion devices characterized by the use of solid oxide as the electrolyte. They operate at high temperatures (between 800± ¡ 1000±C). Mitigating fuel starvation and improving load-following capability of SOFCs are conflicting control objectives. In this thesis, this issue is addressed using a hybrid SOFC ultra-capacitor configuration. The fuel cell is controlled by incorporating a steady-state property of fuel utilization into an input-shaping framework. Two comprehensive control strategies are developed. The first is a Lyapunov-based nonlinear control and the second is a standard H-infinity robust control. Both strategies additionally control the state of charge (SOC) of the ultra-capacitor that provides transient power compensation. A hardware-in-the-loop test-stand is developed where the proposed control strategies are verified. An investigation to improve the hybrid fuel cell system by incorporating a lithium-ion battery as an additional power source is conducted. Combining both battery and ultra-capacitor with a fuel cell is potentially a winning combination especially for high power applications. A novel SOC estimation method for lithium-ion battery is investigated. Based on the combined ultra-capacitor battery hybrid system...

Assessment of bio-fuel options for solid oxide fuel cell applications

Lin, Jiefeng
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Dissertação
EN_US
Relevância na Pesquisa
120.26907%
Rising concerns of inadequate petroleum supply, volatile crude oil price, and adverse environmental impacts from using fossil fuels have spurred the United States to promote bio-fuel domestic production and develop advanced energy systems such as fuel cells. The present dissertation analyzed the bio-fuel applications in a solid oxide fuel cell-based auxiliary power unit from environmental, economic, and technological perspectives. Life cycle assessment integrated with thermodynamics was applied to evaluate the environmental impacts (e.g., greenhouse gas emission, fossil energy consumption) of producing bio-fuels from waste biomass. Landfill gas from municipal solid wastes and biodiesel from waste cooking oil are both suggested as the promising bio-fuel options. A nonlinear optimization model was developed with a multi-objective optimization technique to analyze the economic aspect of biodiesel-ethanol-diesel ternary blends used in transportation sectors and capture the dynamic variables affecting bio-fuel productions and applications (e.g., market disturbances, bio-fuel tax credit, policy changes, fuel specification, and technological innovation). A single-tube catalytic reformer with rhodium/ceria-zirconia catalyst was used for autothermal reformation of various heavy hydrocarbon fuels (e.g....

Robust adaptive control for a hybrid solid oxide fuel cell system

Snyder, Steven
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
109.72019%
Solid oxide fuel cells (SOFCs) are electrochemical energy conversion devices. They offer a number of advantages beyond those of most other fuel cells due to their high operating temperature (800-1000 ° C), such as internal reforming, heat as a byproduct, and faster reaction kinetics without precious metal catalysts. Mitigating fuel starvation and improving load-following capabilities of SOFC systems are conflicting control objectives. However, this can be resolved by the hybridization of the system with an energy storage device, such as an ultra-capacitor. In this thesis, a steady-state property of the SOFC is combined with an input-shaping method in order to address the issue of fuel starvation. Simultaneously, an overall adaptive system control strategy is employed to manage the energy sharing between the elements as well as to maintain state-of-charge of the energy storage device. The adaptive control method is robust to errors in the fuel cell's fuel supply system and guarantees that the fuel cell current and ultra-capacitor state-of-charge approach their target values and remain uniformly, ultimately bounded about these target values. Parameter saturation is employed to guarantee boundedness of the parameters. The controller is validated through hardware-in-the-loop experiments as well as computer simulations.

Modeling and simulation of JP-8 fuel based hybrid solid oxide fuel cell system

Nishtala, Kalyan
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
109.95763%
Solid Oxide Fuel Cells (SOFC) are solid state energy conversion devices that operate at high temperatures (800 to 1000 ±C). Their inherent advantage of fuel flexibility, tolerance to impurities, faster chemical kinetics with non precious catalyst materials and capability of supporting bottoming cycle components make them an attractive proposition for energy generation in comparison to other fuel cell technologies. To assist the advancement of this technology, this work develops dynamic, computer-based, mathematical models of an Auto-thermal reformer (ATR) based SOFC system with Jet Propellant-8 as the fuel to the ATR. Limitations in the existing models of SOFC systems lie in handling of complex hydrocarbon mixtures and also in simulating start up conditions. Although experimental data necessary to model these accurately is currently not available, this work puts forth a structured method for model development and management. Hierarchical libraries are developed herein, allowing easy modification of the models on multiple levels for simulation of various SOFC system configurations, which can help in improving accuracy as and when experimental data is accessible. The comprehensive model consists of submodels for individual components...

A Novel approach to engineering structures of a solid oxide fuel cell (SOFC): 3D direct write technology

Khatri-Chhetri, Prasanna
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
119.28535%
This thesis centers on the use of 3D direct write printing processes to produce Solid Oxide Fuel Cell (SOFC) structures having engineered porosity and macro structure. The objective of the work presented here is to be able to locally control porosity in the anode and cathode structure using 3D direct write printing methods. It is well understood that grading the electrodes enhances the SOFC's performance. A hierarchically graded porous electrode structure, varying from smallest pores at the electrode/electrolyte interface to largest pores at electrode/gas interface can be printed via 3D direct write methods. Layers as thin as 15µm have been achieved using this process. The change in the degree of electrode porosity achieved by varying the graphite loading fraction has been experimentally mapped out. The feasibility of changing the composition/porosity within a layer has been demonstrated, which also opens up possibilities for varying chemical composition within a layer/plane. The second contribution of this work centers on the synthesis of a channeled electrode architecture aimed at producing structures with extremely low tortuosity. The proposed direct-write synthesis approach overcomes limitations of alternative approaches by allowing symmetric ribs and channels to be printed that balance out shrinkage stresses. The proposed channel architecture has been demonstrated...