bluuebunny/crossref_metadata_2025 huggingface dataset:
Projected Cost, Energy Use, and Emissions of Hydrogen Technologies for Fuel Cell Vehicles
Authors: Ruth Mark F. , Diakov Victor , Laffen Melissa J. , Timbario Thomas A.
Published: December 2010

Each combination of technologies necessary to produce, deliver, and distribute hydrogen for transportation use has a corresponding levelized cost, energy requirement, and greenhouse gas emission profile depending upon the technologies’ efficiencies and costs. Understanding the technical status, potential, and tradeoffs is necessary to properly allocate research and development (R&D) funding. In this paper, levelized delivered hydrogen costs, pathway energy use, and well-to-wheels (WTW) energy use and emissions are reported for multiple hydrogen production, delivery, and distribution pathways. Technologies analyzed include both central and distributed reforming of natural gas and electrolysis of water, and central hydrogen production from biomass and coal. Delivery options analyzed include trucks carrying liquid hydrogen and pipelines carrying gaseous hydrogen. Projected costs, energy use, and emissions for current technologies (technology that has been developed to at least the bench-scale, extrapolated to commercial-scale) are reported. Results compare favorably with those for gasoline, diesel, and E85 used in current internal combustion engine (ICE) vehicles, gasoline hybrid electric vehicles (HEVs), and flexible fuel vehicles. Sensitivities of pathway cost, pathway energy use, WTW energy use, and WTW emissions to important primary parameters were examined as an aid in understanding the benefits of various options. Sensitivity studies on production process energy efficiency, total production process capital investment, feed stock cost, production facility operating capacity, electricity grid mix, hydrogen vehicle market penetration, distance from the hydrogen production facility to city gate, and other parameters are reported. The Hydrogen Macro-System Model (MSM) was used for this analysis. The MSM estimates the cost, energy use, and emissions trade offs of various hydrogen production, delivery, and distribution pathways under consideration. The MSM links the H2A Production Model, the Hydrogen Delivery Scenario Analysis Model (HDSAM), and the Greenhouse Gas, Regulated Emission, and Energy for Transportation (GREET) Model. The MSM utilizes the capabilities of each component model and ensures the use of consistent parameters between the models to enable analysis of full hydrogen production, delivery, and distribution pathways. To better understand spatial aspects of hydrogen pathways, the MSM is linked to the Hydrogen Demand and Resource Analysis Tool (HyDRA). The MSM is available to the public and enables users to analyze the pathways and complete sensitivity analyses.
Start/Stop Induced Carbon Corrosion in Polymer Electrolyte Fuel Cells
Authors: Linse Nicolas , Scherer Gu¨nther G. , Wokaun Alexander , Gubler Lorenz
Published: December 2010

The effect of different operating parameters on carbon corrosion in polymer electrolyte fuel cells was investigated by applying single triangular potential pulses to cells operated in H2/N2 mode. Corrosion rates were determined by integration of the resulting CO2 concentration peaks in the cathode exhaust gas. A significant effect of the lower voltage limit was observed which was attributed to a partial inhibition of the platinum catalyzed corrosion pathway through the formation of a stable oxide layer on the platinum surface. Humidity variation experiments showed a linear correlation between carbon corrosion rate and water vapor partial pressure. However, corrosion rate strongly decreased at low relative humidity, showing that both absolute and relative water content influence corrosion. Since the distinction between the influence of absolute and relative water content is not clear yet, interpretation of temperature effects is difficult. In case of fully humidified gases, corrosion rates showed an exponential-like increase with increasing temperature. In order to assess the relevance for real start-up and shut-down processes, carbon corrosion rates were compared to degradation data obtained in application oriented start/stop cycling experiments, which were carried out by alternating purging of the anode compartment with hydrogen and air. Generally, fuel cell performance loss rates are in good agreement with corrosion rates determined in potential pulse experiments. Due to the high complexity of real start-up and shut-down processes, however, potential pulse experiments can not provide an accurate prediction of start/stop induced degradation behavior.
Design Optimization of Integrated Coal Gasification Solid Oxide Fuel Cell Systems
Authors: Ghezel-Ayagh Hossein , Walzak James , Jolly Stephen , Patel Dilip , Stauffer David
Published: December 2010

Integrated Gasification Fuel Cell (IGFC) power plants incorporating solid oxide fuel cells (SOFCs) are attractive alternatives to traditional pulverized coal-fired and Integrated Gasification Combined Cycle (IGCC) power plants. IGFC systems are projected to achieve electrical generation efficiencies greater than 50% based on high heating value of coal, while separating at least 90% of the carbon dioxide emissions for capture and environmentally secure storage. A comprehensive IGFC system design and optimization study is presented based on recent SOFC performance testing and technology advancements. Details of the system power island cost break-down are also presented, indicating the cost-competitiveness of IGFC systems relative to other coal-fueled power generation technologies. Comparisons of the projected IGFC system efficiency and water consumption are made to pulverized coal-fired and IGCC power plants.
Effective Sulfur Control for Fuel Cells: FCE Experience
Authors: Daly Joseph M. , Farooque Mohammad
Published: December 2010

Most of the fuel cell systems are designed to operate on commonly available gaseous hydrocarbon fuels such as natural gas, propane and anaerobic digester gas. These fuels contain a myriad of sulfur compounds, some present as contaminants from the source and others added as odorant for notification of a gas leak. Sulfur is a known poison for the fuel cell anodes and reforming catalysts. Therefore, the sulfur compounds present in the fuel are required to be removed prior to entering the fuel cell system. FuelCell Energy has developed an ambient-temperature sulfur removal system with high sulfur capacity for fuel cell applications. The attractive features of the design are simplicity, small size, and long life resulting in a low-cost and compact sulfur control solution. The system has been proven on natural gas, liquefied natural gas, propane and ADG. The FCE system performance with different types of fuels (NG, LNG, and propane) will be discussed in this paper.
Free Vibration Analysis of a PEMFC Using the Finite Element Method
Authors: Ahmed Hasnet E. U. , Zu Jean W. , Bazylak Aimy
Published: December 2010

In this study, a free vibration analysis of a polymer electrolyte membrane fuel cell (PEMFC) is performed by modelling the PEMFC as a composite plate structure. The membrane, gas diffusion electrodes, and bi-polar plates are modelled as composite material plies. Energy equations are derived based on the Mindlin plate theory, and natural frequencies and mode shapes of the PEMFC are calculated using finite element modelling. A parametric study is conducted to investigate how the natural frequency varies as a function of thickness, Young’s modulus, and density for each component layer. It is observed that increasing the thickness of the bi-polar plates has the most significant effect on the lowest natural frequency, with a 25% increase in thickness resulting in an 11% increase in the natural frequency. The mode shapes of the PEMFC provide insight into the maximum displacement exhibited as well as the stresses experienced by the material under various vibration conditions.
Elementary Reaction Models for CO Electrochemical Oxidation on an Ni/YSZ Patterned Anode
Authors: Shi Yixiang , Lee Won Yong , Ghoniem Ahmed F.
Published: December 2010

Analysis of recent experimental impedance spectra and polarization curves of nickel/yttria-stabilized zirconia (Ni/YSZ) patterned anode of a solid oxide fuel cell (SOFC) are used to determine the limiting steps in CO electrochemical oxidation kinetics. A comprehensive 1D model is proposed for the prediction of the steady-state polarization curve of a patterned anode SOFC. The model incorporates gas species adsorption/desorption with surface diffusion and one of two possible charge transfer reaction steps: O charge transfer reaction [O2−(YSZ)+(Ni)+↔(YSZ)+O(Ni)+2e−], or CO charge transfer reaction [O2−(YSZ)+CO(Ni)↔(YSZ)+CO2(Ni)+2e−]. We show that the mechanism incorporating charge transfer between adsorbed CO and oxygen vacancy is able to better predict the experimental data. We estimate some of the model parameters, such as the exchange current density and charge transfer coefficient by fitting the simulation of the polarization curves to the experimental data.
Automated Fuel Cell Stack Assembly: Lessons in Design-for-Manufacture
Authors: Laskowski Christina , Gallagher Ryan , Winn Andrew , Derby Stephen
Published: December 2010

Within the next decade, proton-exchange membrane (PEM) fuel cell technology will need to progress from low-volume to high-volume production. The second of two fully-functional fuel cell stack assembly robotic stations is being developed to meet the requirements for this transition; meanwhile, a fuel cell stack is being modified to ease the challenges of automated assembly. This document outlines the most recent iteration of the robotic fuel cell assembly station, challenges encountered, stack design features which impair automation efforts, stack modifications and their impact on assembly success, and a methodology for designing successful stacks in tomorrow’s automated assembly plants. Numerous design aspects of the stack, intended for manual assembly, proved challenging for robotic assembly: in particular, those pertaining to component tolerances, stack compliance, fasteners, environmental requirements, overall stack alignment, MEA handling, and part alignment verification. Each of these challenges was addressed during the refinement of the second robotic station, in many cases via modification of the stack. Nonetheless, each of these factors represents a continuing liability, both in cost and time, to rapid, accurate, reliable stack assembly. Methodology for incorporating these critical design-for-manufacture considerations into future stack designs is therefore addressed as well. As the stack assembly workcell continues to improve, research will focus upon further stack redesign specifically to optimize fuel cell manufacturing throughput.
Thermal Sealing of Membrane Electrode Assemblies for High-Temperature PEM Fuel Cells
Authors: Share Dylan , Krishnan Lakshmi , Walczyk Dan , Lesperence David , Puffer Raymond
Published: December 2010

The main challenges of low temperature (80–120°C) Nafion-based PEM technology are (1) low cathode performance due to slow kinetics of the oxygen reduction reaction (2) high material costs (3) considerable system design and operation for water management (4) low tolerance to impurities in fuel stream and (5) low quality heat resulting in low overall system efficiency. Furthermore, Nafion membranes achieve maximum conductivity only when hydrated, limiting their operation to <100 C. Operating the fuel cell >100 C is desirable to overcome the aforementioned limitations. Though several high temperature membranes for PEMFC have been developed, polybenzimidazole (PBI) membranes with high Phosphoric acid content (>90%) developed by BASF Fuel cell are currently seeing commercial interest. The most vital step in MEA manufacturing is the sealing of the membrane in between the electrode-substrate assembly to form a five-layer architecture. Currently, MEA sealing is done by a thermal seal process. This paper examines the effect of thermal sealing process parameters, namely (1) sealing temperature (2) percent compression (3) sealing time and (4) manufacturer-specified post-processing after sealing on the fuel cell performance. A design of experiments was developed with these input process parameters and the polarization behavior during single cell operation, as well as internal cell resistance, were analyzed as performance parameters. ANOVA analysis revealed the statistically significant input factors for the thermal sealing process, which are essential for the rapid and high-quality manufacturing of membrane electrode assemblies for high temperature fuel cells. Furthermore, a multiphysics model has been developed to allow for further refinement of the MEA sealing process.
Development of Dynamic Simulation Model of Fuel Cell for Air Independent Propulsion System
Authors: Yu Sangseok , Lee Sang Min , Lee Young Duk , Ahn Kook Young , Ji Hyunjin
Published: December 2010

Conventional air independent system is very difficult to meet the required efficiency target with high performance when it is used for submarine. The fuel cell system with liquid oxygen is applied to the air independent propulsion of submarine which can promise wider tactical range than conventional system. In this study, a dynamic simulation model is developed to evaluate the performance of the fuel cell air independent propulsion system (FCAIP). The simulation model is a cascading fuel cell stack model which can precisely predict the performance of very unique stack design architecture suggested by Siemens AG. The dynamic stack model is used for the evaluation of thermal management of fuel cell system under load follow-up.
Cold Pressing of Membrane Electrode Assemblies for High-Temperature PEM Fuel Cells
Authors: Share Dylan , Krishnan Lakshmi , Lesperence David , Walczyk Daniel , Puffer Raymond
Published: December 2010

With the current economic and environmental situation, the development of affordable and clean energy sources is receiving much attention. One leading area of promise is PEM fuel cells. Presently, manufacture of high temperature Polybenzimidizole (PBI) based PEM Membrane Electrode Assemblies (MEAs) is usually performed by sealing in a thermal press. A typical sealing process requires heated tooling to press electrode-subgasket assemblies into a sol-gel PBI membrane. MEAs designed for transportation purposes have a large active area that requires expensive heated tooling, which in turn requires significant power to operate. A previous Design of Experiments (DoE) and analysis revealed that sealing temperature is a statistically insignificant sealing parameter with respect to MEA performance. To further investigate the effects of sealing temperature on MEA performance in hopes of reducing manufacturing costs, an additional DoE was performed in which MEAs were manufactured with the tooling at room temperature. This paper examines the effect of thermal sealing process parameters, namely: (1) sealing temperature; (2) percent compression, and; (3) seal time on the fuel cell performance. MEAs were manufactured using three different thickness membranes with these input process parameters. Polarization behavior during single cell operation, internal cell resistance and catalyst utilization were analyzed as performance parameters. This data is compared to MEAs made with traditional heated tooling. The analysis reveals the insignificance of sealing temperature on the initial performance of the MEA.
A New High Voltage Impedance Spectrometer for the Diagnostic of Fuel Cell Stacks
Authors: Wasterlain Se´bastien , Harel Fabien , Candusso Denis , Hissel Daniel , Franc¸ois Xavier
Published: December 2010

This paper presents a novel architecture of an impedance spectrometer dedicated to the characterization and diagnostic of large Fuel Cell (FC) stacks operated in galvanostatic mode. The validation tests are first performed on a single Proton Exchange Membrane Fuel Cell (PEMFC). Then, experiments are carried out on a twenty-cell PEMFC stack delivering more significant power levels. The proposed impedancemeter allows spectrum measurements on cells located in the middle of the stack, where common mode potentials are usually too high for commercial devices. Moreover, the impedances of different individual cells in the stack are acquired with a synchronous measurement reference (global stack impedance). This capability allows distinguishing any singular cell behavior or drift effect of operational parameters (e.g. stack temperature and polarization current).
Numerical and Experimental Study on Behaviors of Physical Properties of Molten Carbonate Fuel Cell (MCFC) Stack Components
Authors: Lee Seung Ryoon , Kim Joon Ho , Park Jong Hoon , Kang Dong Woo , Chang In Gab , Lee Tae Won
Published: December 2010

Estimation of the mechanical strength of the stack components is important to get performance reliability, because when a specific pressure is applied to this stack at specific temperature, some of components have very weak mechanical strength at a given temperature. Properties of the stack components are measured using experimental and numerical method. Structural behavior of the stack can then be estimated during stack operation. The stack of Internal Reforming MCFC consists of various components, which are mainly composed of the anode, cathode, matrix, carbonate electrolyte, biopolar plate, etc. Mechanical properties of anode, cathode and matrix are necessary to simulate structural behavior of the stack during operation. Mechanical properties of each component in unit cell can be measured by comparing experimental with numerical results on compression. It can be possible to simulate structure behavior of the whole stack during operation based on this data. Numerical results on compression can be done using ABAQUS program which can compute strain-stress analysis. After comparing experimental with numerical results on compression of unit cell, mechanical properties of unit cell are obtained. The unit cell is then simplified to a one block of mesh which has mechanical properties of unit cell based on data. Finally the whole stack is modeled by stacking blocks as mentioned above. Thus, the structural behavior of the whole stack during operation can be computed efficiently.
Electrochemical Characterization and Mechanisms of Solid Oxide Fuel Cells by Electrochemical Impedance Spectroscopy Under Different Applied Voltages
Authors: Sun Li , DiGiuseppe Gianfranco
Published: December 2010

In this paper, the behavior of an anode-supported solid oxide fuel cell is studied by using voltage-current density measurement and electrochemical impedance spectroscopy. The cell total polarization obtained from electrochemical impedance spectroscopy results is shown to be consistent with the area-specific resistance calculated from the voltage-current density curve. An electrolyte-supported solid oxide fuel cell is then used to build an equivalent electrical circuit model using reference electrodes and electrochemical impedance spectroscopy. A four-constant phase element model is proposed to analyze the anode-supported solid oxide fuel cell. The model is used to evaluate an anode-supported solid oxide fuel cell under different cell voltages. The individual resistances are also studied as a function of applied voltage, and their physical meaning is explained in terms of reaction mechanisms occurring at the cathode and anode. It is shown that some of the obtained resistances are independent of diffusion while others have both a charge transfer and diffusion component.
Effect of Co-Doped GDC Buffer Layer on the Power Density of Solid Oxide Fuel Cell (SOFC)
Authors: Song Jung-Hoon , Park Young-Min , Bae Hong-Youl , Ahn Jinsoo , Seong Byeong-Geun , Kim Do-Hyeong , Jun Joong-Hwan
Published: December 2010

It is usually accepted that the doped ceria buffer layer is needed between the conventional yttria-stabilized zirconia (YSZ) electrolytes and the Fe and Co containing cathode materials such as (La,Sr)(Co,Fe)O3-δ (LSCF) to improve the cell performance and to prevent unwanted chemical reactions between them. In this study, the effect of the sintering temperature, cobalt doping amount, and the starting powders of GDC (Gadolinium Doped Ceria) layer were investigated. The cell testing result indicated that it would be desirable to decide the sintering temperature of the GDC layer less than 1250°C to minimize the effect of the solid solutions based on (Zr, Ce)O2. Furthermore, 5 days operations of the button cell with cobalt doped GDC layer showed the increased ohmic and polarization resistance, indicating the cobalt segregation from the GDC layer during the long term operation.
Development of a PEM Fuel Cell Electrode Coating Testbed
Authors: Hoffman Casey J. , Walczyk Daniel F.
Published: December 2010

Two of the largest barriers to PEMFC commercialization are the materials costs for individual components, especially platinum catalyst, and the fact that few large-scale manufacturing capabilities currently exist. This paper focuses on the development of a testbed which will be used for evaluating coating technologies for use in the manufacture of polymer electrolyte membrane (PEM) fuel cell electrodes. More specifically, the focus is on diffusion electrode architecture, in which the catalyst layer is applied to a gas diffusion layer (GDL) rather than on the membrane. These electrodes are used for both low- and high-temperature PEM fuel cells. A flexible web coating testbed has been designed and built to allow for testing of different gas diffusion electrode (GDE) and GDL deposition methods. This testbed, which is approximately two meters in length, includes a variety of both coating and drying capabilities as well as additional space for quality measurement and control system testing. Testbed capabilities and planned experimentation is discussed in detail. In the future, various non-contact deposition methods for the microlayer and catalyst inks will be investigated (e.g., direct spray, ultrasonic spray) to determine those that will provide higher throughput and repeatability through increased process control capability, while improving electrode performance.
Development of kW Class Planar Type SOFC Stacks and a 5kW Class Cogeneration System
Authors: Lee Taehee , Choi Jin Hyeok , Choi Mi-hwa , Yoo Young-Sung
Published: December 2010

Korea Electric Power Research Institute (KEPRI) has studied anode-supported planar type SOFCs and cogeneration systems. The cell was composed of NiO-YSZ/YSZ/LSCF and the fabrication process of 10 × 10 cm2 and 15 × 15 cm2 cells was established. KEPRI successfully manufactured and operated a 1 kW class SOFC cogeneration system in 2008. The 1 kW stack was made of 48 cells with 10 × 10 cm2 area and ferritic stainless steel interconnectors. The 1 kW system showed about 1.3 kWDC power with hydrogen and 1.2 kWDC with a city gas under self-sustained operating condition. The system also recuperated heat of about 1.1 kW by making hot water. A 5 kW SOFC system consisted of a hot box part and a cold BOP part for the effective thermal management. The hot box part included 2 sub-module stacks, a fuel reformer, a catalytic combustor and heat exchangers. A sub-module stack was designed to comprise 65 cells with 15 × 15 cm2 area and ferritic stainless steel interconnectors. The system was manufactured and tested using short stacks.
Study on Catalytic Reactions in Solid Oxide Fuel Cells With Comparison to Gas Phase Reactions in Internal Combustion Engines
Authors: Fridriksson Helgi S. , Sunde´n Bengt , Yuan Jinliang , Andersson Martin
Published: December 2010

Solid oxide fuel cells (SOFCs) have the attractive feature to be able to make use of hydrocarbon fuels in their operation by reforming the fuel into pure hydrogen, either internally or externally. This can open up for a smoother transition from the existing hydro-carbon economy toward a more renewable hydrogen economy. Since both SOFCs and internal combustion (IC) engines can make use of hydrocarbon fuels, it is of interest to examine the major differences in their utilization of the hydrocarbons and investigate how this type of fuel contributes to the power output of the respective systems. Thereby, various advantages and disadvantages of their reactions are raised. It was shown that even though there are fundamental differences between SOFCs and IC engines, both types face similar problems in their designs. These problems mostly include material design and operation management, but even problems related to the chemical reactions, e.g., carbon deposition for SOFCs and pollutant formation for IC engines.
High Temperature Mechanical Properties of Ni-YSZ Cermets for SOFC Anode
Authors: Iguchi Fumitada , Kitahara Hiromichi , Yugami Hiroo
Published: December 2010

The mechanical properties of Ni-YSZ cermets at high temperature in reduction atmosphere were evaluated by the four points bending method. We studied the influences of reduction and thermal cycles, i.e. a cycle from R.T. to 800°C, to flexural strength and Young’s modulus. The flexural strength of Ni-YSZ at room temperature was lower than that of NiO-YSZ by about 10 to 20% mainly caused by the increment of porosity. But, the flexural strength of Ni-YSZ at 800°C was drastically decreased by an half of that at R.T. In addition, the stress–strain diagram of Ni-YSZ at 800°C indicated that it showed weak ductility. The maximum observed strain was over 0.5% at 30MPa. On the contrary, NiO-YSZ showed only brittlely at 800°C. The difference was caused by Ni metal in the Ni-YSZ cermets. Therefore, it was expected that Ni-YSZ is easily deformed in operation, though residual stress between an anode and an electrolyte was low. The influence of thermal cycles to flexural strength and Young’s modulus was not observed clearly. At the same time, the differences of microstructure were not observed. Therefore, it was concluded that the cycle does not change mechanical properties significantly.
Visualization of GDL Deformation by Freezing of Water Using X-Ray Radiography
Authors: Kim Jongrok , Je Junho , Kaviany Massoud , Son Sang Young , Kim Moo Hwan
Published: December 2010

During operation of Polymer Electrolyte Membrane Fuel Cells (PEMFCs), electro-chemical reactions generate water, which exists as a liquid because of the PEFMC’s low operating temperature. The water remains in the PEFMC after it is turned off. During the winter this water can freeze; associated increase in its volume deforms the gas diffusion layer (GDL). The deformed GDL reduces the cell’s power output and durability. In this investigation, X-ray microscopy was used demonstrate that water freezing changed the geometry of GDL by water freezing.
Performance Enhancement in Proton-Exchange Membrane Fuel Cell for Cathode Pulsating Flow
Authors: Kim Yun Ho , Han Hun Sik , Kim Seo Young , Rhee Gwang Hoon
Published: December 2010

The effect of cathode flow pulsation on the performance enhancement of a 10-cell proton-exchange membrane fuel cell is investigated. We perform the experiment using two pulsation devices. One pulsation device, i.e., acoustic woofer, generates a pulsating flow, which is added to a unidirectional flow supplied from a compressed air tank. The other pulsation device is a crankshaft system that produces a pure oscillatory flow without mean flow. In the case of cathode pulsating flow with mean flow, the fuel cell power output and the limiting current density dramatically increase as pulsating frequency increases at given pulsating amplitude, while the fuel cell efficiency slightly decreases. This result is contributed that the pulsating flow enhances the dispersion inside the cathode channels, and then improving the oxygen and temperature distributions. This performance enhancement by cathode pulsating flow is more distinct at low cathode mean flow rates. In the case of cathode pulsating flow without mean flow, the fuel cell stack is operated despite cathode mean flow is absent. The limiting current density is extended as the pulsating frequency and swept distance (amplitude) increase. When the pulsating frequency and swept distance are 2.38Hz and 13.65mm respectively, the fuel cell performance is equal to that the cathode mean flow rate is 1.29 lpm. Also, the case of pulsating flow is more stable at the concentration loss region than the case of non-pulsating flow for the same performance conditions.
Mass Transport Analysis in a Pulsating Cathode Flow of PEM Fuel Cell
Authors: Han Hun Sik , Kim Yun Ho , Kim Seo Young , Hyun Jae Min
Published: December 2010

A theoretical and experimental study is performed for the mass transfer enhancement by a cathode flow pulsation in a fuel cell. The cathode flow pulsation is considered to reduce the stoichiometry of air. Emphasis is given to explicit role of the cathode flow pulsation on the mass transfer enhancement over the electrode surface. A simple 2D mass transport model for a pulsating cathode flow is developed to investigate the effect of cathode flow pulsation on the oxygen concentration distribution over the cathode channel length in the mass transfer limit situation. Comprehensive analytic solutions disclose the improved concentration distribution by the flow pulsation, which increases mass transfer from the cathode channel to the catalyst layer. Enhancement of mass transport is more pronounced at lower Reynolds numbers. The performance enhancement by flow pulsation is shown to be consistent with the experiment of a 10-cell proton exchange membrane fuel cell stack. The effects of the pulsating frequency on the fuel cell performance are examined at a fixed pulsating velocity amplitude. The experimental results obtained show that both the maximum power density and limiting current density are substantially enhanced when the pulsating component is added to cathode mainstream flow.
Anode Supported SOFC With GDC Barrier Layer Deposited by Aerosol Deposition Method
Authors: Seong Byeong-Geun , Song Jung-Hoon , Park Young-Min , Bae Hong-Youl , Ahn Jin-Soo , Kim Do-Hyeong , Jun Joong-Hwan , Choi Jong-Jin , Park Dong-Soo
Published: December 2010

In this study, a thin (less than 1 micrometer) interlayer of gadolinia doped ceria (GDC) was applied by aerosol deposition (AD) process between YSZ electrolyte and LSCF-GDC composite cathode. The GDC interlayer was co-fired with the cathode without an additional heat treatment step. Performance of the cells with the GDC layer was evaluated with small button type cells. The results show that the GDC layer was dense enough to successfully prevent the formation of SrZrO3 layer after cathode heat treatments under 1100°C. Electrochemical performance of the cells largely depended on the sintering temperatures. Maximum power densities were 1.0 ± 0.1 W/cm2 at 750°C after sintering at the temperatures between 1000°C and 1060°C. Through SEM and TEM study, solid solution layer at the interface of GDC layer and YSZ layer was found in the specimen after sintering at 1000°C and SrZrO3 layers on both sides of the GDC layer after heat treatment at 1100°C. These layers contributed to the poor performance of the cells sintered at over 1080°C. Therefore, the temperatures for cathode sintering have to be precisely controlled to get the best performance. AD process requires week vacuum and takes only couple minutes to finish deposition. This presentation also shows scaling up the ADM process to 320 mm × 220 mm planar cells for dozens kW stack application at the Research Institute of Industrial Science and Technology (RIST) in Korea. Long term operation tests for the large cells are now on process.
Progress in Understanding Silica Transport Process and Effects in Solid Oxide Fuel Cell Performance
Authors: Zafred Paolo R. , Sofie Stephen W. , Gentile Paul S.
Published: December 2010

One of the enabling technologies required for commercialization of high efficiency solid oxide fuel cell (SOFC) stacks is the development of low cost ceramic refractories capable of withstanding the harsh environment during start-up and steady state operation. Although low density, high purity fibrous alumina materials have been used for more than two decades in manufacturing of SOFC stack components, their low mechanical strength and high cost have precluded their use in the next generation pre-commercial generator modules. A current trend in SOFC stack design is to use high strength, low purity mullite bonded, cast ceramics which can be produced in large volume at a relatively low cost. Sufficient strength is required to provide structural support of the stack and its upper internals in addition to withstanding the severe thermal gradients in both steady state and transient conditions. To reduce costs while achieving suitable mechanical strength, thermal shock, and creep resistance, certain levels of silica and other impurities are present in the refractory ceramic. Silica, however, has been established to poison SOFC anodes thus degrading cell performance and stack life. Therefore, silica transport within the stack has become a dominant issue in SOFC generator design. As a result, an important design requirement for the stack ceramic materials is to develop a fundamental understanding of the silicon species transport process based on refractory composition and gas atmosphere in effort to minimize silicon species volatilization through the porous material. The vaporization behavior of the Al-Si-O system has been investigated in numerous studies and verified experimentally. It is well known that when aluminum silicate components are exposed to a reducing atmosphere, the partial pressure of oxygen is low, therefore this causes formation of volatile SiO(g). This SiO(g) gaseous phase is transported by the fuel stream to the anode/electrolyte interface and electrochemically oxidizes back into SiO2 over the triple phase boundaries (TPB) by the oxygen transported via the fuel cell. This re-deposition process of SiO2, known also as Si poisoning, blocks the reaction of fuel oxidation as it takes over the reactive sites, leading to noticeable degradation in cell performance. In this paper, the status of research on formation of volatile silicon species in aluminosilicate SOFC insulation materials is examined. The formation of volatile SiO(g), SiO(OH)(g), and SiO(OH)2(g) are indicated to facilitate silicon transport in anode fuel streams. Silica deposition is shown to degrade fuel cell anode performance utilizing a novel SOFC silicon poisoning test setup, and silica deposition is only observed on YSZ in the electrochemically active regions of the cell.
The Effect of Electric Double Layers on Ionic Conductivity in the Agglomerates of PEM Fuel Cell Anodes
Authors: Zenyuk Iryna , Litster Shawn
Published: December 2010

We present a theoretical analysis of ionic transport inside the catalyst particle agglomerates that form the electrodes of proton exchange membrane (PEM) fuel cells. The electrodes continue to be the subject of intense research and development because they are still the largest cost and source of performance degradation in PEM fuel cells. The advancement of electrodes requires proper understanding of the electrode structure and the relevant transport processes. However, the details of the electrode microstructure and the micro-scale and nano-scale transport mechanisms are still not well understood. A common hypothesis, supported by recent coarse-grained molecular dynamics simulations, is that the primary pores (the pores inside the agglomerates) are void space and not filled with Nafion electrolyte. Instead, it has been postulated that the primary pores are saturated with liquid water during operation. Here, we report on the effect of the electric double layers (EDLs), which form at the interface between the water and the carbon catalyst supports, on the ionic transport within the agglomerates. The multi-scale model addresses phenomena at two length scales: (1) the nano-scale EDL thickness and (2) the microscale agglomerate radius. We model the EDL using the Gouy-Chapman-Stern model, which provides a pore average conductivity for the spherical conduction-reaction model of the agglomerate. We use a spherical agglomerate model to calculate an effectiveness factor for the electrochemical reactions. Here we present the application of the model to the anode, where the low activation overpotential allows linearizations and convenient analytical solutions. A key finding of this work is the important role the EDLs have in establishing the effectiveness of the platinum catalyst utilization. In addition, we resolve the dependence of the agglomerate effectiveness factor on the activation overpotential and agglomerate radius. We observe a significant nonmonotonic dependence of the catalyst effectiveness factor on the overpotential and dramatic improvement in effectiveness of catalyst utilization with smaller agglomerates.
Recycling Sodium Metaborate to Sodium Borohydride Using Wind-Solar Energy System for Direct Borohydride Fuel Cell
Authors: Ved Ankeeth Suresh , Miley G. H. , Seetaraman T. S.
Published: December 2010

One of the major issues with DBFC is availability of Sodium borohydride and economics of converting sodium metaborate, product of reactions in DBFC, to sodium borohydide. Work has been done by L Kong et all [1] to convert Sodium metaborate to sodium borohydride using magnesium hydride. The work presented here discusses various other possibilities to recycle NaBO2 and how it could be coupled with existing wind and solar energy systems to make it economically viable. A little variation form Brown Schlesinger process [2], commonly used to produce sodium borohydide is proposed and with discussion on possible renewable energy system are presented below. a] Steam reforming of methane : Solar energy can be utilized to convert water into steam. Also possibilities of using geothermal energy where available cannot be ruled out. b] Using sea water to get sodium metal: Electrolysis of seawater enables us to have this process on board on offshore wind mills. Also presence of other salts in sea like calcium chloride favor electrolysis. c] Hydrolysis of NaBO2 to make boric acid: This is the deviation from the exiting Brown Schlesinger and thermoeconomics is under investigation. d] Boric acid reacts with methanol to give trimethylborate. e] Sodium metal in presence of hydrogen from steam reforming react to give sodium hydride. f] Sodium hydride and trimethylboate react to give sodium borohydide and sodium methoxide which decomposes into methanol and NaOH. Another method that would be included in this study is using NaBO2 to produce borohallide (BX3) which in presence of LiAlH4 would give B2H6 which with sodium carbonate (from sodium metaborate and methane or carbon dioxide) would give sodium hydroxide. This is under study and hence not much data is available right now. From the cost study it is seen that for the first mentioned process the initial cost associated is high and exact amount is still under debate. Advantage of utilizing renewable source is that the renewable energy can be converted into efficient source of energy for mobile applications.
Reference Based Fuel Cell Stack Simulator
Authors: Lindahl Peter A. , Shaw Steven R.
Published: December 2010

This paper presents a test system which uses the current and voltage relationship of a single fuel cell or small scale stack as a reference for reproducing the electrical terminals of a full stack. The voltage of the reference cell is measured and amplified by the simulator to the voltage level that would be generated by a large scale fuel cell stack. This scaled voltage can be applied to a realistic load for studying stack / load interactions, stack electro-chemical performance characteristics and cell durability. This reference simulator system provides an alternative in stack / load studies to costly and cumbersome power level fuel cell stacks while providing more realistic results than model-based stack simulators. The simulator system was tested using a single InDEC Solid Oxide Fuel Cell (SOFC) scaled to simulate a 21 cell stack. Data from these tests are included and show good steady-state and dynamic accuracy.
Preparation and Characterization of Nanocomposite Calcium Doped Ceria Electrolyte With Alkali Carbonates (NK-CDC) for SOFC
Authors: Abbas Ghazanfar , Raza Rizwan , Chaudhry Muhammad Ashraf , Zhu Bin
Published: December 2010

The entire world’s challenge is to find out the renewable energy sources due to rapid depletion of fossil fuels because of their high consumption. Solid Oxide Fuel Cells (SOFCs) are believed to be the best alternative source which converts chemical energy into electricity without combustion. Nanostructured study is required to develop highly ionic conductive electrolyte for SOFCs. In this work, the calcium doped ceria (Ce0.8Ca0.2O1.9) coated with 20% molar ratio of two alkali carbonates (CDC-M: MCO3, where M = Na and K) electrolyte was prepared by co-precipitation method in this study. Ni based electrode was used to fabricate the cell by dry pressing technique. The crystal structure and surface morphology was characterized by X-Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM). The particle size was calculated in the range of 10–20nm by Scherrer’s formula and compared with SEM and TEM results. The ionic conductivity was measured by using AC Electrochemical Impedance Spectroscopy (EIS) method. The activation energy was also evaluated. The performance of the cell was measured 0.567W/cm2 at temperature 550°C with hydrogen as a fuel.
Novel Dynamic Quasi-3-Dimensional High Temperature Fuel Cell Model With Internal Manifolding
Authors: McLarty Dustin , Samuelsen Scott , Brouwer Jack
Published: December 2010

High temperature fuel cells have demonstrated potential for a wide array of energy applications while meeting future efficiency and emission targets. Earlier works captured either steady state performance of stacks or transient behavior of single cells. This work develops a model that can simulate and spatially resolve transient temperature, pressure and species distributions for a simulated fuel cell stack in a computationally efficient manner. The novel model accounts for internal manifolding of fuel and oxidant streams and predicts two dimensional fields associated with the dynamic operation of a single high temperature fuel cell. The MatLab-Simulink® model calculates dynamic performance for both solid oxide and molten carbonate fuel cells that utilize both direct and indirect internal reforming. This paper presents dynamic response characteristics to perturbations in power, fuel utilization and composition, and investigates control strategies that minimize PEN temperature variations and fluctuations during the transient responses. Air flow and inlet temperature controls are sufficient to control average PEN temperature, but internal heat transfer dynamics substantially change the spatial temperature distribution dynamics at different operational power densities.
Hybrid Fuel Cell Gas Turbine System Design and Optimization for SOFC
Authors: McLarty Dustin , Samuelsen Scott , Brouwer Jack
Published: December 2010

Fuel Cell–Gas Turbine (FC-GT) hybrid technology portends a significant breakthrough in electrical generation. Hybrid systems reach unprecedented high efficiencies, above 70% LHV in some instances, with little to no pollution, and great scalability. This work investigates two high temperature fuel cell types with potential for hybrid application ranging from distributed generation to central plant scales; sub MW to 100MW. A new library of dynamic model components was developed and used to conceptualize and test several hybrid cycle configurations. This paper outlines a methodology for optimal scaling of balance of plant components used in any particular hybrid system configuration to meet specified design conditions. The optimization strategy is constrained to meet component performance limitations and incorporates dynamic testing and controllability analysis. This study investigates seven different design parameters and confirms that systems requiring less cathode recirculation and producing a greater portion of the total power in the fuel cell achieve higher efficiencies. Design choices that develop operation of the fuel cell at higher voltages increase efficiency, often at the cost of lower power density and greater stack size and cost. This work finds existing SOFC technology can be integrated with existing gas turbine and steam turbine technology in a hybrid system approaching 75% fuel to electricity conversion efficiency in optimized FC-GT hybrid configurations.
Regeneration of Pt Electrode Activity in H3PO4/PBI Doped PEMFC Membrane Following CO Poisoning
Authors: Ubong Etim U. , Phillips Diana , Gieseke Matt
Published: December 2010

An investigation has been made on a high temperature polybenzimidazole (PBI) proton exchange membrane doped with phosphoric acid. Two and five percent concentrations of CO in the hydrogen were evaluated to determine the effect of high CO concentrations on the performance of the PBI membrane under conditions that are representative of reformed fuels. A 3 × 3 matrix of fuel composition, temperature and air stoichiometry was studied at two pressures: one atmosphere and one bar gage. A controlled experiment using hydrogen of 99.997% purity was used as a baseline fuel before and after the exposure to higher CO concentrations. A comparison between the pure hydrogen runs and those where CO was also present in the fuel showed a significant reduction in cell performance. Subsequent runs with pure hydrogen restored the cell performance. The mechanism that led to the cell recovery with pure hydrogen will be discussed.
Modeling and Simulations of PEMFCs Operating With Periodically Purged Dead-Ended Anode Channels
Authors: Siegel Jason B. , Stefanopoulou Anna G. , Yesilyurt Serhat
Published: December 2010

PEMFC operation with dead-ended anode has inherent transient behavior: the cell operates between purge cycles that replenish fuel and discharge accumulated gases, such as nitrogen and water vapor, and liquid water. During the operation when the anode exit is shut, gases that cross-over from the cathode accumulate and stratify in the anode channels above the liquid water when the gravity is acting in the flow direction. In this work, we present a transient two-dimensional along the channel model and simulations of the PEMFC operating with a dead-ended anode. The transport of gas species in flow channels and gas diffusion layers is modeled by Maxwell-Stefan equations. Flow in the channels is modeled by laminarized Navier-Stokes equations, where the inertial terms are dropped from the force balance, but the buoyancy effect due to the variation of the composition of gas mixture is included at the anode side. Flow in the gas diffusion layers is modeled by Darcy’s Law. Permeation of nitrogen in the membrane is considered since it can accumulate in the anode as opposed to instant reaction of oxygen (hydrogen) at the anode (cathode) catalyst layer(s). The membrane is considered as a resistance (interface) to transport of water vapor and nitrogen. Ohm’s Law is used to model the transport of charged particles, i.e. electrons in the electrodes and flow plates and protons in the membrane. A finite-element representation of the governing equations in the 2D PEMFC geometry is solved using a commercial multiphysics software, COMSOL. The imposed boundary conditions are chosen to match the experimental conditions. According to model results the reversible voltage degradation between purge cycles is mostly caused by nitrogen accumulation in the anode that leads to partial fuel starvation in the cell.