Master of Science, University of Toledo, 2023, Electrical Engineering

Massive carbon emissions are to blame for recent global environmental problems such as the greenhouse effect and severe smog. As a result, governments are promoting the growth of low-carbon economies in order to lower carbon emissions while preserving long-term economic prosperity. A promising approach to address climate change issues that also offers grid flexibility, energy security, and the highest return on investment is known as an integrated energy system (IES), which is constructed as nuclear power reactors coupled with renewable energy generation and industrial operations. A secondary benefit to such an ecosystem involves the generation of hydrogen (H2) within the IES, which can be sold to heavy-industry thereby offering an additional revenue stream for the IES, particularly since nuclear power plant operations can be prohibitively expensive. This thesis presents modeling of Solid Oxide Electrolyzer (SOEC), Solid Oxide Fuel Cell (SOFC) and the advanced nuclear reactors; Small Modular Reactors (SMRs) technologies paired with nuclear and renewable energy sources, energy storage systems, and power conversion systems to produce a nuclear renewable integrated energy system (NR-IES). An essential component to this work, in particular, is the modeling of the SMR, the SOEC, and the SOFC, which are used to facilitate H2 production when energy-demand is low, and also to re-convert stored H2 to electrical power when energy-demand is high. Solid oxide cell (SOC) and SMR systems are designed and developed using MATLAB/Simulink. A functional mockup unit (FMU) of the SOC models were developed with the intention of integrating them with a Python-based co-simulation (CS) NR-IES framework. In this research, the energy-dispatching decisions in the NR-IES have been controlled and coordinated using the deep reinforcement learning (DRL) technique framework. According to the modeling results, the use of NR-IES, and specifically the SOEC and SOFC, to facilitate H2 production and s (open full item for complete abstract)

Committee: Raghav Khanna (Committee Chair); Ahmad Javaid (Committee Member); Daniel Georgiev (Committee Member) Subjects: Energy; Engineering

PhD, University of Cincinnati, 2017, Engineering and Applied Science: Materials Science

Microfabricated solid oxide fuel cells (mSOFCs) have recently gained attention as a promising technology, with the potential to offer a low temperature (as low as 300°C), reduced start-up time, and improved energy density for portable power applications. At present, porous Pt is the most common cathode being investigated for mSOFCs. However, there are significant technical challenges for utilizing pure metallic electrodes at the operating temperatures of interest due to their tendency towards Ostwald ripening, as well as no bulk ionic conductivity. Nanocomposite materials (e.g. Pt/YSZ) are a promising alternative approach for providing both microstructural and electrochemical stability to the electrode layer. The overall objective of this research was to explore the processing of nanocomposite metal / metal oxide materials (i.e. Pt/YSZ) for use as a high performance cathode electrode for mSOFCs. The Pt/YSZ nanocomposite cathodes were deposited through a co-sputtering process and found to be stable up to 600°C in air for extended periods of time through an exhaustive materials and electrochemical study. A percolation theory model was utilized to guide the design of the Pt/YSZ composition, allowing for a networked connection of ionic- and electron-conduction through the membrane, leading to an extension of the triple phase boundary (TPB). The Pt/YSZ composite deposition pressure was found to be a key in helping to stabilize the morphology of the film. By increasing the deposition pressure, this led to the formation of intergranular void spacing, or porosity, as well as a reduction of film strain in the post-annealed film. Surface analyses of the composite film demonstrated that the lower film strain led to a minimization of Pt hillock grain coarsening and de-wetting, even after exposure to high temperatures (600°C) for extended periods of time (tested up to 24hrs) in air. Analyses of the Pt/YSZ composite microstructure and composition by TEM confirmed an int (open full item for complete abstract)

Committee: Raj Singh Sc.D. (Committee Chair); Relva Buchanan Sc.D. (Committee Member); Hong Huang Ph.D. (Committee Member); Rodney Roseman Ph.D. (Committee Member) Subjects: Materials Science

Master of Science (MS), Wright State University, 2011, Chemistry

Solid oxide fuel cell (SOFC) technology has attracted great attention due to advantages such as low emissions and high efficiency. In this work, solid oxide fuel cells were fabricated by incorporating functional layers deposited by a novel aerosol jet® printing method. The buffer and cathode layers were printed from gadolinium doped ceria (Ce0.9Gd0.1)O1.95 (CGO) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) inks, respectively. The CGO layer was deposited on the sintered electrolyte and then LSCF was subsequently deposited onto the CGO layer. The polarization curves showed a 19% improvement in current density using LSCF as the cathode instead of LSM. Cathode grain size was shown to change by 85% over the sintering temperatures examined. Lastly, the effect that ethyl cellulose additive had on the resulting cathode was determined. It was discovered that the porosity of the microstructure was not correlated to the additive's molecular weight. The actual causes of the cathode porosity may be the order of polymer branching or the ethoxy content of the ethyl cellulose.

Committee: Eric Fossum PhD (Advisor); David Grossie PhD (Committee Chair); Rachel Aga PhD (Committee Chair) Subjects: Chemistry

Master of Science (MS), Ohio University, 2005, Mechanical Engineering (Engineering)

Using modeling and simulation, the present work offers parametric study for Planar Solid Oxide Fuel Cell (PSOFC) as a function of fuel gas composition. The study comprises of one-dimensional steady and dynamic state modeling of single PSOFC in Aspen Custom Modeler. The simulations are performed at the interface of fuel channel and anode, and the reaction kinetics, the spatial distributions of temperature and specie concentrations inside the PSOFC are calculated. Steady state model estimates the cell performance as function of CO, and the dynamic model estimates the transient performance degradation, due to Area Specific Resistance (ASR) degradation. Additionally, the dynamic model analyzes the sensitivity of cell performance on input variables, and recovery time for the small variations. The analysis shows that temperature, current density, flow-rate, ASR and fuel composition affect the cell performance. At low current densities, the cell performances are comparable, up to 80% CO in the fuel gas.

Committee: David Bayless (Advisor) Subjects: Engineering, Mechanical

Doctor of Philosophy (PhD), Wright State University, 2019, Engineering PhD

Drop on demand (DOD) inkjet printing has been widely investigated for its low cost, noncontact, high throughput, and reproducible process advantages. This dissertation research sought to capitalize on these advantages for use in micro solid oxide fuel cells (micro SOFCs). Understanding the important variables underpinning the inkjet process, including ink formulation, jet kinematics, and process settings was essential. These variables were evaluated for their impact on drop deposition quality, resolution, microstructure, and electrochemical functionality, with the end goal of making submicron to micron scale ceramic features. Initially, the fluid kinematics of single pass printing was investigated using a dilute, solid-solvent, colloidal, ink suspension of of La0.6Sr0.4Fe0.8Co0.2O3 (LSFC) and α-terpineol. Favorable process conditions were identified that attained uniform, well-shaped, circular dots ~ 0.1 μm thick and ~ 80 μm in diameter. Multiple, sequential ink passes were employed to increase feature dimensions on the x/y/z axes. This required additional process constraints to control deposition quality and resolution of micro features including micro-dots (0-D), micro-lines (1-D) and micro-planes (2-D). Using optimal conditions, 0-D dots and 1-D lines with x/y dimensions < 100 μm and z axis dimensions < 1 μm with dense, open or networked microstructures were demonstrated; in addition 2-D planes having smooth surface and continuous intra-planar ceramic coverage with dimensions as small as ~ 100 μm by ~ 100 μm were achieved. Sintering the inkjetted submicron prototypes produced consolidated submicron films that were uniform, smooth and void of defects such as cracks or delamination. Thermal treatments resulted in grain growth from an average crystallite size of ~158 nm to ~ 356 nm. Heat treatments < 800°C were essential to avoid deleterious effects on electrochemical activity. Electrochemical characterizations of prototypes produced tolerable peak power (open full item for complete abstract)

Committee: Hong Huang Ph.D. (Advisor); Sharmila Mukhopadhyay Ph.D. (Committee Member); Jason Deibel Ph.D. (Committee Member); Lei Kerr Ph.D. (Committee Member); Thomas Reitz Ph.D. (Committee Member) Subjects: Engineering; Materials Science

Master of Sciences, Case Western Reserve University, 2017, Materials Science and Engineering

The performance of solid oxide fuel cells (SOFCs) with three different lanthanum strontium manganite (LSM) based cathode compositions were evaluated. All cells were yttria-stabilized zirconia (Zr0.92Y0.08O2-d, 8YSZ) electrolyte-supported button cells, consisting of a nickel oxide – yttria-stabilized zirconia (NiO-8YSZ) anode and a cathode of 8YSZ and LSM. The three LSM compositions differed in the amount of excess Mn: Composition A was (La0.85Sr0.15)0.90MnO3±d (10% excess Mn); Composition B was (La0.80Sr0.20)0.95MnO3±d (5% excess Mn); and Composition C was (La0.80Sr0.20)0.98MnO3±d (2% excess Mn). The cells were tested under conventional and accelerated conditions, where the accelerated conditions were meant to simulate the results of months of long-term testing in just 500 hours (approximately three weeks) of testing by using high operating temperature and current density. Accelerated tests showed lower degradation rates, lower continuous area specific resistance (ASR), and higher power output than conventional tests for all cathode compositions. Continuous measurements of the cells' output voltage versus time, together with periodic electrochemical impedance spectroscopy (EIS) measurements, were used to evaluate the performance of the cells in terms of ASR degradation rates (% ASR rise per kh) and power outputs. The EIS measurements also permitted a partial deconvolution of the cathode ASR from the anode ASR. Cathodes with 10% excess Mn tested under accelerated conditions had the lowest degradation rates, but the highest continuous ASR and lowest power outputs. Cathodes with 2% excess Mn tested under accelerated conditions had the lowest continuous ASR and highest power outputs; thus it was concluded that cells with the lowest amount of excess Mn cathodes performed the best.

Committee: Mark De Guire (Advisor); Arthur Heuer (Committee Member); Roger French (Committee Member) Subjects: Energy; Materials Science

Master of Science, University of Akron, 2016, Polymer Science

Fly ash is the combustion product of coal, which is composed of silicone dioxide, calcium oxide and heavy metal element. Fly ash would impair water quality, air impurity and humane health if it was released to the atmosphere. The disposal of fly ash has been a hot issue among increasing enormous researchers due to the unprecedented health issues and awareness of environmental protection. Adhesive is a kind of material that can bind two separate items and prevent the detachment of them. Among all kinds of adhesive, epoxy adhesive is more appealing since it has excellent chemical and heat resistance, strong mechanical strength and wide range of adaptability. In this research, the epoxy adhesive was used to immobilize the fluffy fly ash, which would prevent the flying of ash particles and the leak of heavy metal in fly ash. The immobilized fly ash has strong mechanical strength, so it can be recycled as landfilling or building material without any leak of heavy metal. The reaction mechanism of the three components of the adhesive and the influence of surfactant to the mixing of adhesive and fly ash were also studied and characterized. Finally, the work that aims to dissolve the epoxy adhesive in water has been discussed in this research. The technic of enhancing the performance of solid oxide fuel cell would also be studied in this thesis.

Committee: Steven Chuang (Advisor) Subjects: Polymer Chemistry

Doctor of Philosophy, The Ohio State University, 2015, Materials Science and Engineering

In this work, thin-film LT-SOFC modules were fabricated by colloidal processing and their per-formance was demonstrated. Nano-particulate colloid syntheses, dip-coating, and rapid thermal processing methods yielded fine-particle membrane microstructures, with high porosity and con-ductivity in the platinum/gadolinium-doped ceria (GDC) composite electrodes and density in the yttria-stabilized zirconia (YSZ) electrolytes.

Committee: Hendrik Verweij (Advisor); Sheikh Akbar (Committee Member); Gerald Frankel (Committee Member) Subjects: Energy; Engineering; Materials Science

Doctor of Philosophy, Case Western Reserve University, 2015, Materials Science and Engineering

Solid oxide fuel cells (SOFCs) have great importance as a more efficient source of electrical power than conventional systems. Nonetheless, there is limited understanding of the processes by which their performance decreases with time, especially during long-term operation (>2 kh). This study sought explanations for performance loss in the microstructural changes that take place in the anodes during operation of periods from 2 to 16 kh. Recently developed three-dimensional (3D) analysis techniques enable the study of aspects of the anode microstructure, such as tortuosity and triple-phase boundary density, that cannot be fully depicted in two-dimensional analyses. The complex multi-phase microstructure of SOFC anodes adds other challenges for applying this technique to study lifetime degradation of SOFCs. The project is divided into four sections: 1) sample preparation and experimentation, including adaptations of standard techniques to the porous microstructures of SOFC anodes; 2) 3D reconstruction and results, including development of original computer codes for the determination of active and inactive triple phase boundary density; 3) microstructural characterization of anodes tested for up to 16 kh at 800 °C, 860°C or 925 °C, including qualitative analysis of chemical composition of the anodes using energy dispersive x-ray spectroscopy (EDS); 4) development of kinetic models of microstructural change in SOFCs during operation, based on the quantitative analysis and calculated microstructure parameters for the tested SOFC anodes, to enable predictions of long-term performance of SOFCs. Application of 3D reconstruction to SOFC anodes provided insight to the anode microstructure. The microstructural parameters such as volume fractions, particle diameter, active/inactive triple phase boundary, tortuosity; were calculated for the as-reduced cell and cells after operations. Ni and pore phase re-distribution to the anode interfaces were observed during cell (open full item for complete abstract)

Committee: Mark De Guire (Committee Chair); Arthur Heuer (Advisor); James McGuffin-Cawley (Committee Member); M. Cenk Cavusoglu (Committee Member) Subjects: Materials Science

Master of Science in Chemistry, Youngstown State University, 2012, Department of Chemistry

The world is facing an energy crisis and there is an immediate need to find a sustainable source of energy. Landfill gas has the potential to be a valuable source since methane is a major constituent. Currently the majority of the landfills either burn away their gas in flares or combust it in mechanical engines to produce electricity. The issue with mechanical engines is that incomplete combustion of gases can lead to pollution of atmosphere and are also highly inefficient. In this research we are studying the effects of landfill gas on SOFC performance. The tests were performed on a button cell and the electrochemical cell used for our voltammetric experiments was called the ProboStatTM. Several different types of anodes were studied to understand the working of the SOFCs, but Ni-YSZ was the main focus. The cathode used was LSM (lanthanum strontium manganite).The anode was supplied with landfill gas and the cathode with air. Landfill gas contains impurities such as organic and inorganic sulfur, halogenated organics and siloxanes. These impurities can cause anode poisoning by passivating the cell. How the presence of hydrogen sulfide affects the working of the cell was studied. Also, the effect of water vapor was studied. SEM and XRD were used to analyze the electrodes. RAE Systems Colorimetric gas detection tubes and gas chromatography coupled with various detection methods were used to analyze landfill gas. Based on the study it can be concluded that landfill gas has to be treated to reduce the sulfide content from 100's of ppm to single digits or less in order to sustain SOFC operation at 750 °C. Alternatively, a background of hydrogen in the pre-treated landfill gas was shown to offer some means of protection against sulfide passivation.

Committee: Clovis Linkous PhD (Advisor); Timothy Wagner PhD (Committee Member); Ruigang Wang PhD (Committee Member) Subjects: Chemistry

Master of Science, University of Toledo, 2010, College of Engineering

Solid oxide fuel cells are highly efficient energy conversion devices which convert fuels electrochemically to electricity with negligible pollution emissions. Anode of solid oxide fuel cell plays an important role in converting hydrogen into hydrogen ions and electrons. Many techniques like plasma spraying, tape casting, screen printing, sintering process etc have been discovered for the fabrication of anode supported solid oxide fuel cells. In order to meet the high demand of energy in present days a new technique is required for increasing the efficiency. Among the various methods, increasing porosity of anode is one. This can be achieved by fabricating the anode by electrodeposition technique, which has been proved as an effective way of increasing porosity. In this work, we demonstrated that nanoporous Ni can be electroplated on a Zr substrate. Electrochemical dealloying of copper from a Ni-Cu alloy wire is carried out first to better understand the effect of voltage and run time on the process. As the potential increases the amount of copper dealloyed in to the solution was also increased. Passivation of nickel occurs as the time increases, allowing the formation of NiO. The preparation of nanoporous nickel films on zirconium by electrochemical deposition of Ni-Cu alloy followed by selective anodic etching of the more noble metal, copper, was studied in an aqueous solution containing Ni and Cu at room temperature. Variable potential electrodeposition produces crystalline or grain Ni-Cu alloys on Zr substrate, in which the Ni content increases as the deposition potential becomes more negative. Cyclic voltammetric data indicates that the anodic dissolution of nickel is retarded by passivation. By taking the advantage of nickel passivation, selective anodic etching of Cu is carried out. Multicyclic electrochemical alloying/dealloying process makes the film rich of nickel and complete dealloying of copper.

Committee: Yong Gan PhD (Advisor); Matthew Franchetti PhD (Committee Member); Calvin Li PhD (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2012, Mechanical Engineering

Solid oxide fuel cells (SOFCs) are electrochemical energy conversion devices capable of producing electrical power with high efficiency and low emissions. SOFCs are characterized by ceramic electrolyte membranes which transport oxide ions in the range of temperatures between 600°C and 1000°C. In order to facilitate efficient, low-range temperature operation the electrolyte is typically made very thin, on the order of 40 µm. SOFCs also employ porous electrodes on either side of the electrolyte which are then placed in contact with current collectors and seals. In the fuel cell environment, with high temperatures, substantial thermal gradients, mechanical loading between layers, as well as the desire to be able to thermally cycle the cell, one of the layers or components must provide mechanical support. It is typical for either the anode or electrolyte to provide the necessary mechanical support. This thesis focuses on an electrolyte that is used for electrolyte-supported SOFC configuration. To address the need for mechanically robust electrolytes, NexTech Materials has developed the FlexCellTM electrolyte. This electrolyte design incorporates 40 µm thick conducting regions in a honeycomb pattern, and surrounding 200 µm thick stability regions. Various experiments on and determinations about this material and design must be made to ensure sufficient mechanical stability during fuel cell operation. Thermal stresses from high temperatures, temporal and spatial temperature gradients, and differential thermal expansion of contacting materials, are critical issues within SOFCs. The critical property related to these issues, coefficient of thermal expansion (CTE), was measured in this work. An apparatus to measure the CTE of the FlexCellTM electrolyte material was designed and implemented. The average CTE of 3 mol% Y2O3-ZrO2 (yttria stabilized zirconia or 3YSZ) was found to increase from 9 µm•m-1•°C-1 between room temperature (RT) and 180°C to nearly 11.5 µm•m-1•°C-1 from R (open full item for complete abstract)

Committee: Dr. Mark E. Walter (Advisor); Dr. Brian D. Harper (Committee Member) Subjects: Materials Science; Mechanical Engineering

Master of Science, The Ohio State University, 2010, Mechanical Engineering

A planar solid oxide fuel cell is characterized by a thin ceramic electrolyte sandwiched between porous electrodes, along with seals and current collectors. To perform as a good oxide ion conductor, the electrolyte needs to be very thin. However, a thin electrolyte is highly prone to damage during production, assembly, and subsequent operation. To be both electrochemically efficient and mechanically robust, NexTech Materials Ltd has developed an innovative electrolyte, the FlexCellTM, for use in electrolyte-supported SOFCs. This electrolyte design has a honeycomb structure that supports thin, “active areas” thus providing good electro-chemical efficiency as well as mechanical robustness. To optimize the FlexCell and understand its mechanical limits, a combination of experiments and finite element modeling are performed. The out-of-plane dimensions are much smaller than the in-plane dimensions, and hence a two-scale approach is required for optimizing the geometrical design of the FlexCell. At the large-scale, the whole electrolytic membrane is modeled with equivalent properties, whereas at the small-scale, the repeating pattern of the honeycomb structure is studied. Nextech's goal to commercially produce ultra large FlexCells of the order of 700 to 1200 cm2 depends largely on its mechanical performance. The aim of this work is to suggest ways to geometrically alter the design so that the mechanical membrane performs well under mechanical and thermal loading. By performing finite element simulations on the large area FlexCell, design parameters which influence its mechanical robustness are identified. Results of this analyses show the areas of high stresses. The stresses can be mapped to the small-scale to study small-scale failure. Since it is not known if optimal geometries scale with membrane size, a more methodical approach is undertaken to ensure that the thin active areas have adequate support in thermally varying environments.

Committee: Mark Walter PhD (Advisor); Sandip Mazumder PhD (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2007, Materials Science and Engineering

Solid oxide fuel cells have been investigated frequently with models predicated on linear electrical circuit elements, ignoring finer details of electrochemical transport. To gain better understanding of the operation of solid oxide fuel cells based on their underlying physics, the most simple system of fundamental equations, consistent with solid oxide fuel cell thermodynamics, has been constructed. The system includes the continuity equation for mass/charge transport, the Poisson equation relating electrostatic potential and charge density, and interface flux expressions reflecting activated state processes. The driving force of all transport processes is the electrochemical potential gradient of mobile species. This potential includes entropic interaction and electrostatic energies. Gas phase mass transport was not considered in this work. The equation system governed calculations simulating various electrical and electro-chemical measurement experiments, specifically: equilibrium open-circuit cell voltage measurement, cell voltage measurement with increasing dc current density, and electrochemical impedance spectroscopy. The 1-D solid oxide fuel cell system investigated is composed of two dense mixed-conducting electrodes and a dense purely ion-conducting electrolyte. Relaxing the system from initial non-equilibrium, the calculated equilibrium cell voltage agreed O(10 −9%) with the theoretical Nernst voltage. Also, non-thermodynamic and non-material parameters did not affect this agreement, validating the thermodynamics of the equation system. The effects of kinetic and geometric variables on the behavior of the investigated system were clearly observed in both dc current density and electrochemical impedance simulations. As the perturbation amplitude was increased, the onset of nonlinear impedance response was seen.

Committee: Henk Verweij (Advisor) Subjects: Engineering, Materials Science

Doctor of Philosophy, The Ohio State University, 2007, Chemical Engineering

Solid oxide fuel cells (SOFCs) show promise for generating clean power from a variety of fuels. The major roadblocks to their implementation are a large cathodic resistance, which causes insufficient power densities and high fabrication costs, and anodic deactivation caused by carbon-based fuels such as coal and biomass-derived gases and their sulfur impurities. The large cathodic resistance is caused by slow oxygen activation kinetics and oxide ion transport of the current manganite-based cathode. At the anode, deactivation occurs through the conventional nickel-based material's poor sulfur tolerance and tendency to form carbon fibers. Thus, the development of catalytically active materials suitable for use as electrodes is needed to help SOFCs realize their full potential. Replacing manganite with reducible transition metals (e.g., cobalt) leads to mixed (electronic and ionic) conductivity and improved performance through the enlargement of the electrochemically active area. However, further improvements are limited because the oxygen reduction kinetics and oxygen-surface interactions are poorly understood. The present work examines the catalytic phenomena of doped-lanthanum ferrites for use as cathode materials in intermediate temperature (500 and 800°C) applications. The kinetics and energetics of the oxygen reduction reaction is related to surface and bulk structural changes that occur as a function of environment and dopant levels. The current research also focuses on understanding deactivation of conventional anode materials in the presence of carbon fuels with sulfur impurities. The results show formation of adsorbed sulfur and surface sulfides even when the bulk phase is stable. The use of this information to modify conventional anode materials is still an active area of research. Characterization is performed by XRD, XPS, and vibrational spectroscopy to complement the oxidation results. Since gasification of biomass takes place in a fluidized bed reactor, (open full item for complete abstract)

Committee: Umit Ozkan (Advisor) Subjects:

Master of Science (MS), Ohio University, 2012, Mechanical Engineering (Engineering and Technology)

Solid Oxide Fuel Cells (SOFC) offer potential for high conversion efficiency, high energy utilization, low emissions and quiet operation. Because of the cost associated with hydrogen storage, coupling an onboard fuel reformer with a SOFC stack is an attractive option for small decentralized and Mobile Electric Power (MEP) generation and as an Auxiliary Power Unit (APU) for motor vehicles. In this study Aspen Plus simulation software is used to develop a 5 kWe APU model using JP-8 as a fuel. JP-8 is selected because of its near ubiquitous use by the U.S. Army and Air Force for ground and air operations. The SOFC platform is selected due to its inherent advantages including: high fuel conversion efficiency, compact design, low noise and emissions. In this study desulfurized JP-8 surrogate fuel is reformed in an onboard autothermal reformer (ATR). The resultant H2 and CO mixture is used as fuel for the SOFC stack. The steam rich anode exhaust is recycled to supply the ATR with thermal energy and steam required to reform the fuel. Such an implementation makes the proposed system lighter and more compact, avoiding the need for an external steam generator and additional heat source for the ATR” (Tanim & Bayless, 2011). Ni-YSZ based tubular and planar SOFC stacks operating at 910 °C and 850 °C, respectively are evaluated as part of the study. ATR performance from 700 °C to 850 °C in the H2O/C ratio range of 0.10-1.0 is investigated. The tubular cell based system (T-SOFC) showed a maximum net AC efficiency of 39.55% at 700 °C reformer temperature and a minimum of 32.60% at 850 °C. The planar cell based system (P-SOFC) demonstrated a maximum and minimum efficiency of 37.10% and 29.20% at 700 °C and 800 °C reformer temperatures, respectively. Sensitivity analyses are conducted evaluating the effect of the fuel utilization factor (Uf) and the current density (j) to determine optimum system operating windows. Finally, the T-SOFC and P-SOFC systems are compared and the results (open full item for complete abstract)

Committee: Jason Trembly PhD (Committee Chair); David Bayless PhD (Committee Co-Chair); Gregory Kremer PhD (Committee Member); JungHun Choi PhD (Committee Member); Hugh Richardson PhD (Committee Member) Subjects: Mechanical Engineering

Master of Science (MS), Ohio University, 2011, Mechanical Engineering (Engineering and Technology)

Electrolyte-supported Solid Oxide Fuel Cells have been proven capable of generating usable electricity when supplied with various fuels, including a synthetic fuel (syngas) generated from gasified coal. Coal, however, contains contaminants, namely phosphine (PH3), that remain in the syngas despite cleanup technologies, which can lead to lowered electrical performance caused by the formation of secondary compounds. This study investigates a strategy of varying the operational voltage to potentially mitigate the formation of secondary compounds, including nickel phosphide (NixPy), thus prolonging the life of the cell. Two operational voltage conditions were investigated, 0.7 volts and 0.6 volts, with four cells per voltage tested. The degradation of the cell was determined using electrical data generated as well as with material analysis. Post-mortem cells were analyzed for the presence of secondary formations with techniques including XRD, SEM/EDX, and XPS. The results indicate that the operational voltage has little effect on the formation of nickel phosphides and the prevailing nickel phosphide specie was Ni2P in both operational voltage conditions.

Committee: David Bayless (Advisor); Gregory Kremer (Committee Member); Carole Womeldorf (Committee Member); Gang Chen (Committee Member) Subjects: Engineering; Mechanical Engineering

Doctor of Philosophy (PhD), Ohio University, 2008, Chemical Engineering (Engineering and Technology)

Lanthanum strontium vanadate (LSV), a perovskite ceramic electrocatalyst suitable for use as a solid oxide fuel cell (SOFC) anode, has shown significant activity toward the selective oxidation of H2S from a fuel stream. With this in mind, the feasibility of a two-stage SOFC reaction process using LSV-based SOFCs as an alternative to H2S sorbents was investigated. A procedure for producing a bilayer LSV anode via an inexpensive screen-printing method was optimized and planar SOFCs utilizing these bilayer LSV anodes were tested under H2, syngas and syngas with H2S environments. Considering LSV/yttria stabilized zirconia (YSZ) bilayer anodes, it was found that the optimum anode thickness of 65 μm at 800°C yields a maximum power density of 5.85 mW/cm2, while at 900°C the optimized anode thickness of 80 μm realizes a maximum power density of 17.96 mW/cm2. Substitution of gadolinium-doped ceria (GDC) for YSZ in the bilayer LSV anode was shown to improve catalytic performance; peak power densities for optimized LSV/GDC-based SOFCs at 800 and 900°C were 16.60 and 34.86 mW/cm2, respectively.It was demonstrated that all tested LSV-based SOFCs showed little to no performance degradation due to catalytic poisoning when utilizing syngas containing H2S as fuel, corroborating previous results. It was also shown that LSV had poor activity toward CO oxidation either directly or as a water-gas shift catalyst over the tested temperature range. A feasibility study of the aforementioned two-stage SOFC reaction process showed that SO2 found in the exhaust from the LSV-based SOFC caused performance degradation to a Ni-based SOFC, though not to the extent caused by an equal amount of H2S; this finding suggests that SOFCs utilizing LSV/YSZ anodes may indeed offer promise as a method for warm-gas remediation of H2S contained in hydrocarbon fuel streams.

Committee: David J. Bayless PhD (Advisor); Michael Prudich PhD (Committee Member); Howard Dewald PhD (Committee Member); Daniel Gulino PhD (Committee Member); Jeffrey Rack PhD (Committee Member) Subjects: Chemical Engineering

Doctor of Philosophy (PhD), Ohio University, 2007, Chemical Engineering (Engineering)

Coal is the United States' most widely used fossil fuel for the production of electric power. Coal's availability and cost dictates that it will be used for many years to come in the United States for power production. As a result of the environmental impact of burning coal for power production more efficient and environmentally benign power production processes using coal are sought. Solid oxide fuel cells (SOFCs) combined with gasification technologies represent a potential methodology to produce electric power using coal in a much more efficient and cleaner manner. It has been shown in the past that trace species contained in coal, such as sulfur, severely degrade the performance of solid oxide fuel cells rendering them useless. Coal derived syngas cleanup technologies have been developed that efficiently remove sulfur to levels that do not cause any performance losses in solid oxide fuel cells. The ability of these systems to clean other trace species contained in syngas is not known nor is the effect of these trace species on the performance of solid oxide fuel cells. This works presents the thermodynamic and diffusion transport simulations that were combined with experimental testing to evaluate the effects of the trace species on the performance of solid oxide fuel cells. The results show that some trace species contained in coal will interact with the SOFC anode. In addition to the transport and thermodynamic simulations that were completed experimental tests were completed investigating the effect of HCl and AsH3 on the performance of SOFCs.

Committee: David Bayless (Advisor) Subjects: Engineering, Chemical

Master of Science (MS), Ohio University, 2005, Chemical Engineering (Engineering)

Planar solid oxide fuel cell (PSOFC) research at Ohio University has shown that the PSOFC may be used to produce electrical energy using gasified Ohio coal. Electrolyte supported PSOFCs with an anode containing nickel, yttria stabilized zirconium, and cerium oxide were operated for over 500 hours. PSOFCs were tested by supplying the fuel cell with a simulated coal syn gas and assessing the performance of the fuel cell by operating it under a load of 14 Amps and measuring the fuel cell's potential and area specific resistance (ASR). PSOFCs used in the research were found to have a potential of 0.74±0.01 Volts under a load of 0.21±0.01 Amps/cm 2 and an ASR increase of 0.10±0.16 percent per 100 hours of operation with out H 2 S and have a potential of 0.66±0.01 Volts under a load of 0.21±0.01 Amps/cm 2 and an ASR increase of 5.4±2.8 percent per 100 hours of operation with 249±9 ppm H 2 S.

Committee: David Bayless (Advisor) Subjects: Engineering, Chemical