bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Two-phase Flow Condition in Gas Channel and GDL on Cell Performance of Polymer Electrolyte Fuel Cell
Authors: Inoue Gen , Yoshimoto Takashi , Kawano Tomotaka , Matsukuma Yosuke , Minemoto Masaki
Published: May 2007

The output performance of polymer electrolyte fuel cell is affected by water droplets. In order to examine the two-phase flow condition in gas channels and the influence on output performance, local differential pressure in cathode gas channels and cell voltage were simultaneously measured, and the influence of local liquid water distribution on cell voltage was examined on various operating conditions. As a result, it was found that the voltage drop and stability was affected by droplets in channels, and these phenomena were different by the place where there was a droplet. Furthermore, the movement and the flow pattern of liquid water in gas channels were examined by experimental results and relative humidity distribution calculated by a numerical analysis. As a result, it was possible to estimate the two-phase flow pattern by apparent relative humidity including liquid phase.
Impact of Cold Start and Hot Stop on the Performance and Durability of a Proton Exchange Membrane (PEM) Fuel Cell
Authors: Du Bin , Pollard Richard , Ramani Manikand , Graney Paul , Elter John F.
Published: May 2007

Rapid fuel cell performance degradation was observed after just 30 cold start/hot stop cycles. Relative humidity (RH) was found to be the primary operating parameter associated with the rapid voltage decay during this thermal cycling. It was found that repeated thermal cycling could affect the RH inside a fuel cell and, consequently, alter the water activity of membrane/ionomer. We propose an extension of the generally accepted reverse-current carbon corrosion mechanism to account for the RH effects. The rapid voltage decay was linked to a RH- dependent cathode carbon corrosion process which was attributed to a lag in the ionomer/membrane hydration state during the thermal cycling. It has been demonstrated that one can reduce the carbon corrosion rate by avoiding the combination of cold starts and hot stops. Recommended strategies for mitigation are discussed in the context of the corrosion mechanism.
Investigation on Vehicular PEMFC Power Modules
Authors: Hou Ming , Hou Zhongjun , Yan Xiqiang , Jiang Yuyu , Ming Pingwen , Yi Baolian
Published: May 2007

Proton Exchange Membrane Fuel Cell (PEMFC) is one of the potential alternative power sources for transportation application due to its high energy efficiency, environmental friendliness and fossil independence. Vehicular PEMFC activities have been done in DICP and Sunrise Power for many years and achieved great progress. In this paper, a typical PEMFC module is presented; and its structure and main components are introduced. The PEMFC performances in the test station and FC system are elucidated. The PEMFC module with high fuel utilization and high safety can be used in a wide pressure range. The rated power outputs are respectively 50 kW at the pressure of less than 0.5 bar (g) and 80 kW at 2 bar (g). The modes of connection and array of the stacks in FC modules can be changeable to meet well the limited space demands in vehicles.
Fuel Cell Hardware-in-Loop for PEM Fuel Cell Systems
Authors: Moore Robert M. , Randolf Guenter , Virji Maheboob B. , Hauer Karl-Heinz
Published: May 2007

Hardware-in-Loop (HiL) methodology is well established in the automotive industry, where the hardware element is typically a controller and the HiL technique is applied to develop and debug control algorithms for automotive drive systems. In contrast, this paper is focused on the use of a new HiL methodology (Fuel Cell HiL) for experimental fuel cell evaluation. In this methodology a fuel cell is experimentally evaluated within the context of a fuel cell system design, an application (e.g., a fuel cell vehicle), and for a typical use pattern (e.g., a standard drive cycle).
Engineered Metallic Strip For Fuel Cell Applications
Authors: Chen L , Lynch Peter F. , Kaiser Joseph G.
Published: May 2007

Investigations and developments of metallic materials for fuel cell components have been very active recently. This paper reviews how several materials technologies have been applied in feasibility studies for potential viable solutions in the development and manufacturing of PEMFC bipolar plates, SOFC interconnects as well as stack sealing materials.
Advanced SOFC Interconnect Development at PNNL
Authors: Yang Zhenguo Gary , Xia Guan-Guang , Stevenson Jeff W.
Published: May 2007

PNNL has been conducting research on metallic interconnects and their interfaces with electrodes for high performance, low cost planar SOFC stacks. This work, which is focused on both materials development and mechanistic understanding, presently has three primary areas of emphasis: 1) surface modification of candidate alloys for improved surface stability and scale electrical conductivity, (2) improving the understanding of interactions between alloy interconnects and electrodes and development of electrical contact layers, and (3) investigating and understanding the oxidation behavior and degradation of bare and coated high temperature oxidation- resistant alloys under interconnect dual atmosphere exposure conditions. This paper summarizes and provides an update on our recent development efforts in that area.
Study of the Oxidation of a Ferritic Stainless Steel Coated with La0.8Sr0.2MnO3 by Pulse Laser Deposition for Application in Solid Oxide Fuel Cells
Authors: Xie Jianhui , Yoo Yeong , Davidson Isobel
Published: May 2007

The effectiveness in reducing the corrosion of a ferritic (430) stainless steel at moderate and high temperatures by coating it with a thin, dense layer of La0.8Sr0.2MnO3 was investigated. The thin coating of La0.8Sr0.2MnO3 was found to be effective in reducing the growth of oxide scales on the 430 stainless steel. More importantly, the coated steel samples were found to have significantly lower area specific resistances after oxidation treatments than similarly treated uncoated steel samples. The activation energies of the coated steel samples were significantly lower than those of the oxidized bare steel samples for all treatment conditions studied. SEM and X-ray diffraction analyses provided further confirmation that the thin La0.8Sr0.2MnO3 coating is effective in reducing the growth of oxide scale on the surface of the heat treated steel. This study indicates that, cheap and commercially available 430 ferritic stainless steel, with the protection of a thin, dense coating of La0.8Sr0.2MnO3, may be considered as a potential candidate for usage as the interconnect material in solid oxide fuel cells.
Development of SOFC Stack Using Low-Cost and Low-ASR Ceramic Interconnects
Authors: Liu Zhien , Ohrn Ted , Kneidel Kurt
Published: May 2007

The multi-layer ceramic (MLC) interconnect is fabricated using multiple layers of YSZ tape, with each layer containing conductive vias to provide for electrical current flow through the interconnect. Fuel and air supply to cells is accomplished through the use of flow passages in the layers. MLC interconnect using low-cost conductive materials as vias was developed. All ceramic SOFC stacks utilizing electrolyte- supported cells and MLC interconnect with low-cost vias were built and tested, low-ASR and long term stable performance of which was demonstrated. pO2 simulation in low-cost vias was performed under different fuel utilization, and confirmed that low-cost conductive via materials have low ASR in normal SOFC stack operation conditions.
Deposition of Thin Films For Solid Oxide Fuel Cell Components
Authors: Nasrallah Magdi M.
Published: May 2007

Pulse laser deposition technique (PLD) was used to investigate the optimum deposition conditions for thin multilayer components of solid oxide fuel cells (SOFC). Parameters including deposition atmosphere, laser energy, frequency, and substrate temperature were investigated in order to identify the best deposition conditions. The deposited layers include thin films of Yttria stabilized Zirconia (YSZ) electrolyte, Samaria doped Ceria (CSO) buffer, and various cathode compositions of the general formula (La1-xSrx)[(Fe,Ga)1-y (Co,Mg,Cu,Cr,Ni)y]O3, the layers were simultaneously deposited on silicon wafers. The cathode composition of choice is (La1- xSrx)(Fe1-yCoy)O3, (LSCF). The microstructure, uniformity, density, and morphology of the deposited layers were investigated using field emission scanning electron microscopy, EDAX analysis, and optical microscopy. Attempts were also made to investigate the nature of the interface between the deposited layers as a function of temperature. Multiple depositions were carried out at laser frequency between 4-38 Hz, base pressure of 10-6 atm, 10-2 mbar oxygen partial pressure, and a substrate temperature between room temperature and 4000C. The depositions were carried out in the form of concentric layers on the silicon wafers, with the electrolyte at the bottom followed by the buffer layer then the cathode. The diameter of the deposited layers where sequentially decreased from 3, to 1 inch to allow characterization of each layer separately in the trilayer configuration.
Influence of Electrode Porosity and Potential of the Oxygen Reduction Kinetics on the Intermediate Temperature SOFCs Cathodes
Authors: Lust Enn , Möller Priit , Nurk Gunnar , Kivi Indrek , Kallip Silvar
Published: May 2007

Electrochemical characteristics of various half-cells, based on samaria and gadolinia doped ceria electrolytes and nano-micro-mesoporous La0.6Sr0.4CoO3-δ, Pr0.6Sr0.4CoO3-δ, Gd0.6Sr0.4CoO3-δ, 70 wt% La0.6Sr0.4CoO3-δ + 30 wt% Ce0.8Gd0.2O1.925 and 70 wt% La0.6Sr0.4Co0.8Fe0.2O3-δ + 30 wt% Ce0.8Gd0.2O1.925 cathodes, have been obtained by electrochemical impedance, cyclic voltammetry and chronoamperometry methods. The seeming activation energy Eact depends on the chemical composition of half-cell, specific surface area and pore size distribution inside the cathode. Eact decreases with increasing negative potential. More pronounced dependence of Eact on potential has been established for mixed cathodes. The transfer coefficient for the oxygen reduction reaction αc > 0.5 dependent on the half-cell studied has been obtained. Analysis of Nyquist and Bode plots indicates the complicated adsorptsion/absorption and mass transfer processes inside the porous material. Dependence of the ratio of limiting steps on cathode porosity and chemical composition as well as on the electrode potential and temperature applied was established.
Effect of Initial Reduction Temperature on Redox Properties of IT-SOFC
Authors: Liu Bin , Zhang Yun , Cheng Mojie
Published: May 2007

The redox properties of anode supported cells with Ni-YSZ anodes initially reduced at different temperatures were investigated through monitoring the changes of ohmic resistance and open circuit voltage of anode supported cells by using electrochemical impedance spectroscopy (EIS) technique. The results show higher temperature reduction can reduce the reoxidation rate and relieve the damage to electrolyte film. The different nickel particle size distribution, as a result of different temperature reduction, should be responsible for the different redox properties.
Performance Characteristics of an Integrated 50We Portable JP8 SOFC - Reformer System
Authors: Cheekatamarla Praveen K. , Finnerty Caine M. , Du Yanhai , Lu Yixin , Robinson Charles L. , DeWald Paul G. , Andrews Stanely
Published: May 2007

NanoDynamics Energy Incorporated is developing a family of compact, integrated, partial oxidation reformer (POX) - SOFC systems suitable for methane, propane, diesel and JP8 fuels. The development program aims to bring to the market highly efficient, clean, and cost competitive fuel cell systems with outputs above 50We for portable power generation applications. The partial oxidation reformer was combined with a SOFC stack and a system test for the integrated process chain was performed. The necessary start up strategies and balance-of- plant (BoP) components including fuel and air supply, exhaust gas heat recovery, back-up power, power electronics and control system have been identified. The performance of the system is evaluated for different operating conditions. The results from these studies will be presented in this paper. Finally, the performance characteristics of the POX-SOFC unit have been compared to that of a steam reforming-SOFC system.
Liquid Tin Anode Solid Oxide Fuel Cell for Direct Carbonaceous Fuel Conversion
Authors: Tao Thomas , Bateman Linda , Bentley Jeff , Slaney Michael
Published: May 2007

The Liquid Tin Anode Solid Oxide Fuel Cell (LTA-SOFC) is a modified version of SOFC that allows the direct oxidation of carbonaceous fuels. The LTA-SOFC uses many conventional SOFC components but differs from conventional SOFC because its anode is liquid tin allowing directly oxidization of fuel without fuel reforming or other fuel processing. In addition, the anode stores energy, allowing the cell to deliver power in case fuel flow has been interrupted. As a result, the LTA-SOFC requires less components resulting in simpler and more efficient system. This paper describes the basic LTA-SOFC cell architecture and cell/stack test results using carbonaceous fuels such as JP-8, natural gas, coal, bio-mass and plastic feedstock.
Analysis of Percent On-Cell Reformation of Methane in SOFC Stacks and the Effects on Thermal, Electrical, and Mechanical Performance
Authors: Recknagle Kurtis P. , Koeppel Brian , Sun Xin , Khaleel Moe , Yokuda Satoru , Singh Prabhakar
Published: May 2007

Numerical simulations were performed to determine the effect that varying the percent on-cell steam-methane reformation would have on the thermal, electrical, and mechanical performance of generic, planar solid oxide fuel cell stacks. The study was performed using three-dimensional model geometries for cross-, co-, and counter-flow configuration stacks of 10x10- and 20x20-cm cell sizes. The analysis predicted the stress and temperature difference would be minimized for the 10x10-cm counter- and cross-flow stacks when 40 to 50% of the reformation reaction occurred on the anode. Gross electrical power density was virtually unaffected by the reforming. The co-flow stack benefited most from the on-cell reforming and had the lowest anode stresses of the 20x20-cm stacks. The analyses also suggest that airflows associated with 15% air util
Development of Intermediate Temperature Solid Oxide Fuel Cell Modules and Systems
Authors: Nishi Junya , Kano Jiro , Nishiwaki Futoshi , Inagaki Toru , Yamasaki Satoru , Shibata Makoto , Hosoi Kei
Published: May 2007

The Kansai Electric Power Company, Inc. and Mitsubishi Materials Corporation started a joint research project for developing intermediate temperature solid oxide fuel cells in 2001. High performance disk-type cells with lanthanum gallate- based electrolyte and a seal-less cell-stack design enable high efficiency operation at temperatures below 800{degree sign}C. The 4th generation 1 kW-class module with internal manifolds was developed and the electrical efficiency of 54%HHV-DC was achieved in 2005. In the first durability test of the 4th generation 1 kW-class module carried out for 4,200 hours in 2006, the voltage degradation rate was about 0.5%/1,000hours. In parallel, the development of 10 kW-class module and CHP system has been in progress since 2004. 10 kW-class module test was carried out and the efficiency of 50%HHV at electric power output of 12.6 kW-DC was achieved in 2006. The field test of 10kW-class CHP system will be carried out in FY2007.
Analysis of Transient Response Characteristics for Small Solid Oxide Fuel Cell (SOFC) Systems
Authors: Shimada Takanobu , Kato Tohru , Momma Akihiko , Tanaka Yohei , Takano Kiyonami , Nagata Susumu
Published: May 2007

The steady-state performance and transient response of the 1kW- class SOFC system was analyzed using the numerical model, since frequent load changes are often required. Based on the analysis, if the weight density of the catalyst is 100 g/m3 in the cell, the conversion rate of CH4 is about 80% even when the temperature of the reformer is 550{degree sign}C. DC output of the system is 1262 W (54% (HHV)) at the rating when fuel utilization is 75%. In this case, the SOFC system can be operated thermal self-sufficiently at partial loads. Moreover the system maintains the same efficiency as the rating even if the fuel is decreased to 50% of the rating. The damping time constant of temperature for load change does depend on the flow rate of inlet gas to the system. The transient period of the SOFC system is influenced by the cell resistance dependence on the temperature.
Employment of Computer Simulations in SOFC Development
Authors: Yakabe Hisataka
Published: May 2007

Computer simulations were employed in SOFC development. In special, computational fluid dynamics were used to evaluate heat balance in a SOFC module unit, to analyze cell performance, and to predict reformer performance. In this paper, some examples for the simulations were presented.
Application of Infrared Thermal Imaging to Map Stress Distributions in a Solid Oxide Fuel Cell
Authors: Clague Ralph , Aguiar Patricia , Brett Dan J. , Marquis Andrew J. , Schottl Stephan , Simpson Rob , Brandon Nigel P.
Published: May 2007

The application of infrared thermal imaging to the study of solid oxide fuel cell components with applied thermal gradients is demonstrated. Thermal imaging of a technologically relevant SOFC sample was carried out while a temperature gradient was induced by heating the sample in a furnace and blowing cold nitrogen at its centre. Subsequently the stress field in the sample was determined by a novel method of converting the thermal image into nodal temperatures for a finite element analysis. Asymmetry in the temperature distribution across the samples was marked, whereas previous versions of the thermal gradient experiment had assumed axisymmetry.
Experimental Analysis of the Polarization Effects at Variable Local Temperature and Fuel Consumption in a 100 kWe SOFC Stack
Authors: Santarelli Massimo , Leone Pierluigi , Gariglio Marcello , Calì Michele , Spinelli Paolo , Orsello Gianmichele , De Benedictis Ferrante
Published: May 2007

The polarization behavior of a 100 kWe size solid oxide fuel cell generator was investigated, with two imposed values of setup temperature and fuel consumption. The generator is the SOFC CHP-100 Siemens Power Corporation (SPC), which is at present operating at the SPC subsidiary TurboCare in Torino (Italy). In the work some cell sectors, of different pedigree and position, are compared in terms of the main polarization effects at different temperature and fuel consumption. The polarization behavior is related to the fuel consumption sensitivity of each sector and this shows how the fuel distribution affects the polarization behavior. A deeper analysis is shown by performing a parameter estimation, allowing an analysis of the local anode activation effects with variable temperature and fuel consumption: the estimated anode exchange current densities are strictly related to the local fuel consumption sensitivity of every sector. Finally, the multi-pedigree of the stack arrangement is discussed.
Model and Simulation of a SOFC CHP Plant Fuelled with Hydrogen
Authors: Leone Pierluigi , Santarelli Massimo , Calì Michele
Published: May 2007

In this paper the characteristics and problems of a SOFC CHP system is investigated in the hypothesis of hydrogen feeding. The possibility of SOFC systems fed by hydrogen is not deeply investigated: the main advantage of SOFC is the possibility to be fed by different fuels, while hydrogen has to be produced. Nevertheless, in case of a context with possibility of producing hydrogen at low cost by means of renewable sources (e.g. hydroelectricity), it could be of interest to investigate a SOFC system fed with hydrogen fuel due to a better system performance and environmental benefits. A model is proposed describing the operation of an air-cooled SOFC system: results are discussed pointing out the thermal management and its effect on the electrical performance of system. It is shown that the design of a high temperature cathode recirculation system allows one to overcome the thermal management while obtaining higher electrical performances.
Cost Reduction Through Thermal Management Improvements in Large Scale Carbonate Fuel Cells
Authors: Venkataraman Ramakrishnan , Farooque Mohammad , Ma Zhiwen
Published: May 2007

Cell area and power density are critical parameters that affect the cost of a fuel cell. Fuel cell stacks generate heat in addition to electricity and reaction products. In large area fuel cell stacks, internal cell temperatures and power density are determined by the effectiveness of heat removal. Fuel Cell Energy (FCE) has developed carbonate fuel cell power plants based on its Direct Fuel CellÔ (DFC) technology, which uses endothermic methane steam reforming for hydrogen generation and heat removal internally in the stack. Controlling internal reforming is an important part of thermal management. FCE has developed a three-dimensional stack simulation model that captures all the essential physics and predicts temperature, flow and compositional variations of different gas streams in the fuel cell stack. This model has been used to optimize thermal management resulting in a 20% reduction in stack thermal gradient and a 20% increase in power output.
Need Of Codes and Standards For User Friendly Hydrogen Refueling
Authors: Mahajan Shantanu V. , Shwchun John
Published: May 2007

Hydrogen is the most promising energy carrier to replace the fossil fuels. Hydrogen is very clean form of energy. The fuel cell technology is in embryonic stage and most of the future development of hydrogen economy will depend on hydrogen refueling infrastructure. Hydrogen is new form of energy and lack of codes and standards is a major barrier for the infrastructural development. This paper focuses on procedures and precautions to be standardized so as to have safe, user friendly operations and the ongoing efforts to strengthen the hydrogen infrastructure
Greenhouse Gas Analysis for Hydrogen Fuel Cell Vehicles
Authors: Unnasch Stefan
Published: May 2007

Hydrogen can be produced from many feedstocks with different production and delivery pathways. Production options include conversion from a variety of feedstocks and energy sources. Delivery modes for vehicle fueling include compressed gas in tube trailers and pipelines, liquefied hydrogen in trucks, or on-site production. Alternative carrier options such as chemical hydrides are also being investigated. The energy inputs and greenhouse gas emissions (GHG) were analyzed for different production pathways for hydrogen fuel cell vehicles (FCVs) and comparable gasoline fueled vehicles. The results for on-site reforming of natural gas, central plant natural gas reforming, petroleum coke gasification, central plant biomass pyrolysis, and on-site electrolysis using a mix of natural gas based and renewable power are presented in this paper. Well to wheel energy inputs and GHG emissions were determined from primary energy inputs to the fuel cycle using analysis tools developed by TIAX, which account for the contribution of energy from natural gas, biomass, petroleum, and electric power.
Development of Low Calorie Gas Assisted Solid Oxide Electrolysis Cells
Authors: Kato Tohru , Nguyen Lan T. , Honda Takeo , Tanaka Yohei , Shimada Takanobu , Amano Masatsugu , Negishi Akira , Kato Ken , Nozaki Ken , Iimura Yoko
Published: May 2007

For producing pure hydrogen with high efficiency and low cost, Solid oxide electrolysis cells (SOECs) assisted by low calorie gas were proposed. To use low coat metal as electrodes and an interconnector, tubular SOECs operated at 700~800oC were tried fabricated. The thickness of the electrolyte in the SOEC reduce to approximately 10 μm by using Slurry coating technique and electrolytic performance of the fabricated cells was measured. As a result of this experiment, the hydrogen production rate of a testing cell whose effective electrode area was 18.8 cm2 achieved 56 sccm at 800oC under practical operating condition. Further, the way of improving cell performance was discussed.
Hydrogen Production from Bio-Ethanol on Rh Based Catalysts
Authors: Palmeri Natale , Cavallaro Stefano , Chiodo Vitaliano , Freni Salvatore , Frusteri Francesco
Published: May 2007

The influence of metal precursor on the catalytic behaviour of Rh/MgO catalysts in the steam reforming of ethanol was investigated. High dispersed catalysts were obtained in the case of use an inorganic precursor like Rh-nitrate. Catalytic tests performed at molten carbonate fuel cell (MCFC) operative conditions (TR = 923 K) clearly shown that reaction under study is a structure sensitive reaction since the turnover frequency (TOF) significantly increases as the Rh mean particle size increases too. Catalysts prepared by using Rh- acethyl-acetonate as precursor shown a higher stability since they are in general less affected by coke formation. Thermodynamic consideration made on the basis of the outlet composition of reaction stream, allowed to calculate the experimental equilibrium constant (Kexp) for i) methane steam reforming (MSR) , ii) water gas shift (WGS), iii) methane pyrolisys and iv) Bouduard reactions.
Catalysis of Nuvera's On-Board Fuel Processor for Fuel Cell Vehicles
Authors: Shi Yanlong , van Plet John , Khan Rafey , Ruffo Michael , Zhao Jianli L. , Bowers Brian , Cross James
Published: May 2007

Nuvera's state-of-the-art on-board fuel processor is a very compact system with catalyst and heat exchanger volume of 80 liters, with a maximum power input of 215 kWth, and with hydrogen efficiencies capabilities above 77%. For our fuel processor we use four distinct reaction zones, ATR-HTS-LTS- PrOx. The entire fuel processor, with balance of plant controls components, can be packaged in a volume of 150-liter designed to fit in the floor of a vehicle.The on-board fuel processor design is quite flexible; it can operate on a number of fuels including gasoline, diesel, ethanol, methanol and gas fuels, and the fuel processor can be either scaled up or scaled down for other applications, for example, APU systems. Also, the on- board fuel processors were integrated successfully with Nuvera's automotive PEM fuel cell stacks. A fuel processor start-up time of less than 4 minutes was achieved to the target value for the fuel cell.
MEMS Based Micro-reformer: Performance with Catalyst Packing and Catalyst Coating
Authors: Kundu Arunabha , Jang J. H. , Lee H.R , Gil J.H. , Jung C.R. , Cha H.Y. , Miesse C.M. , Ku B. , Kim S.H. , Oh Y.S. , Chae K.S.
Published: May 2007

MEMS (micro-electro-mechanical system) fabrication technology was used to reduce the size of reformer and steam reforming catalyst was coated on the wall of micro-channels by a novel process. The comparison of performance with the packing the catalyst inside the micro-channels was also carried out. For that purpose, a process for packing catalyst inside micro- channels was developed. Serpentine type of micro-channels was used for both cases. Different issues for packing and coating inside the micro-channels like stability of the coating and durability of the system were examined.
Operational Requirements for a Multi-fuel Processor that Generates Hydrogen from Bio- and Petroleum-Based Fuels for Both SOFC and PEM Fuel Cells.
Authors: Irving Patricia M. , Pickles Jeffrey S.
Published: May 2007

Hydrogen production from processing a wide range of renewable and petroleum-based liquid fuels has been demonstrated for the generation of portable or auxiliary power by a fuel cell. The reforming process was enhanced and cost decreased through use of InnovaTek's proprietary catalysts in a micro-channel reformer. Very high throughput and efficient conversion in an inherently safe, compact, and scalable reactor is achieved using this technology. Multiple fuel types and multiple reforming processes are possible using the same catalysts and reactor hardware. The InnovaGen® reformer may be integrated with PEM or SOFC fuel cells or used for stand-alone hydrogen production.
Evaluation of Integrated Fuel Processor for Residential PEMFCs Cogeneration System
Authors: Seo Yutaek , Seo Dong Joo , Roh Hyun-Seog , Jeong Jin Hyeok , Yoon Wang Lai
Published: May 2007

Natural gas fuel processor has been developed for 1 kW class residential PEMFCs system. Unit processes and auxiliary units are integrated into packaged hardware, which shows thermal efficiency of 78% as a HHV basis with methane conversion of 92% at rated load. After confirming the performance at rated load, partial load operations are carried out by investigating the composition of product gas and thermal efficiencies at discrete load levels. The start up time is about an hour for CO concentration in product gas below 10 ppm. Dynamic response of fuel processor with load fluctuation is investigated to establish the load change strategy. In the following paper, operation results of fuel processor as well as fuel processor failure analysis are presented to evaluate the developed fuel processor.
Optimal Design of a 1-kWe Thermal Plasma Reformer
Authors: Wang C. S. , Chang Y.C. , Hong S.S. , Lee H.B. , Tsai Huan-Liang , Kuo N.S. , Chang K. I. , Kuo C.H.
Published: May 2007

Hydrogen is an energy source for a fuel cell power generation system. It can be continuously produced if sustainable and renewable fuels (such as alcohols, vegetable oils, and used cooking oils) are used. Thermal plasma hydrogen reformer (H2- Reformer), which has fuel-flexible and high volume production capabilities, is a critical key component for production of hydrogen as energy use. We have developed such a 1-kWe H2- Reformer that effectively reforms different types of renewable energy sources and water. Technically it is basically a steam reforming of hydrocarbons using thermal plasma. No catalysts are used in the reformation. The reformation is very effective for heavy hydrocarbon fuels.
Development of a Modular Fuel Cell Generator: Description of 4kW Modular Unit
Authors: Pugazhendhi Perumal , Loutfy Kevin , Loutfy Raouf O.
Published: May 2007

Diesel generators are already a major source of air pollution in the United States and they are growing in numbers and in total installed capacity every year. Now is an ideal time for regulators and industry to pursue strategies to advance the fuel cell which is a clean and economic alternative to the diesel generator. More specifically, PEM fuel cells are commonly considered the most promising fuel cell technology in that they combine high power density and specific power with fast start up, fast response, and environmental friendliness. Fuel cells need hydrogen gas as their fuel but that can be generated by reformation or electrolysis and stored in compressed gas cylinders at reasonable densities. At MER, we have designed, built and tested a compact 4kW fuel cell modular unit as a part of a 72 kW fuel cell generator. The viability, flexibility, redundancy, reliability and cost-effectiveness of the modular concept are demonstrated in this paper.
A Fuel Cell Hybrid Powertrain Development
Authors: Sapienza Cristoforo , Andaloro Laura , Matera Fabio , Dispenza Giorgio , Cretì Pasquale , Ferraro Marco , Antonucci Vincenzo
Published: May 2007

CNR-ITAE is involved in two projects related to hybrid fuel cell vehicles. The aim is to develop fuel cell - battery hybrid powertrains to be used in vehicles designed for some niche markets such as electric buses and lightweight electric vehicles. There have been tested a traction battery pack, a Nuvera fuel cell power module (Powerflow) and the combination of a parallel fuel cell - battery hybrid system. In this configuration the fuel cell power module is used as main power source for the powertrain, also providing battery charge when needed. The battery has the role to provide peak power during the starts of the vehicle. The hybrid powertrain has shown a fast response to even extreme and impulsive loads and a wider range compared to a battery vehicle without compromising the weight limitations on the vehicles.
Biogas Purifying for Application of MCFC
Authors: Lee Jong Gyu , Jun J.H , Kim T.H. , Ahn B.S , Park K.H , Choi D.S. , Park J.Y.
Published: May 2007

Biogas could be produced in wastewater treatment plants with an anaerobic digestion process. The ADG contains normally CH4, CO2 and various impurities such as sulfur compounds and siloxanes. Using the ADG as a fuel, molten carbonate fuel cells (MCFC) have the potential to provide significant environmental and economic benefits. However, such impurities would be harmful to fuel cells. In this work, a purification process for the ADG was designed and installed in order to utilize the gas as a fuel for MCFC. Operational results from the field test with a 250kW-class MCFC power plant were presented in this paper.
Development of Hydrogen Generators for Residential Power Supply using PEMFC
Authors: Mathiak Jens , Kalk Thorsten , Pasdag Oliver , Heinzel Angelika
Published: May 2007

ZBT can look back on 10 years of history in successful development of hydrogen generators for residential power supply using PEM fuel cells. ZBT has always focused on efficient steam reforming and heat integration. All hydrogen generators contain a steam reformer, a shift unit, a CO-purification unit, evaporator, heat exchanger and burner. The core technology is protected by international patents (1). Especially the requirements obtained from industrial partners were used to optimise the hydrogen generator to meet the demands of residential applications. Sometimes not all of these demands can be fulfilled and compromises are necessary. For example high efficiency requires heat integration which leads to high complexity of the system, higher volume/weight and finally elevated production costs or short start-up time requires a radical temperature gradient which has a negative impact on life time (2). All these correlations have to be discussed between product management and development to identify reasonable compromises.
Control Strategy of a Fuel Cell/Ultra Capacitor Hybrid System
Authors: Hwang Jenn-Jiang
Published: May 2007

This paper studies a hybrid power system for transportation applications, i.e., fuel cell/ultracapacitor hybrid powertrain. First, the characteristics of fuel cell and ultracapacitor as power sources are summarized. Then the configurations of the hybrid fuel cell powertrains are presented. Finally, example hybrid powertrains are designed and simulated using Simplorer. The simulation results indicate that ultracapacitors can effectively assist the fuel cell to meet the vehicle power demands and help achieve a better performance and a higher fuel economy.
PEM Fuel Cell Controls for Stationary Applications
Authors: Zhou Zhi J. , Parks John , Elter John F.
Published: May 2007

Direct material cost (DMC) and system reliability have been the two most critical limiting factors in proton exchange membrane (PEM) fuel cell commercialization for portable, stationary, and mobile applications. One way to reduce DMC, increase reliability, and improve manufacturability and serviceability for faster commercial adaptation, is to have a highly integrated system with minimum number of parts (e.g. actuators and sensors) while still being able to maintain high system performance, stability, reliability, and durability. Although this design philosophy is very effective in reducing cost, it creates significant challenges in controls and system integration in order not to compromise system performance. This paper reviews the current controls and system challenges, progresses, and outlook of Plug Power PEM fuel cell systems for stationary applications.
Polarization Based Statistical Approach to Fuel Cell Vehicle Diagnostics
Authors: Milačić Miloš , Davies Kevin
Published: May 2007

In this paper we present a method for dynamic acquisition and analysis of a 3-D polarization surface of a fuel cell stack that requires no service procedure or special handling and can be facilitated in situ during regular daily operation. This method is based on statistical processing of information acquired during regular driving. By continuously mapping fuel cell operating parameters against their statistically computed limits, the monitoring device can set an alert if the performance of the fuel cell falls out of normal operating confidence intervals. The method is presently implemented as stand alone device. In the future development, with this method refined and its demonstrated reliability, the functionality can be transferred to an automotive electronic control unit (ECU).
Direct Hydrogen 5.0 kW PEM Fuel Cell System Supplying an Uninterruptible Power Supply
Authors: Ferraro Marco , Sergi Francesco , Cretì Pasquale , Brunaccini Giovanni , Andaloro Laura , Antonucci Vincenzo
Published: May 2007

Hydrogen systems appear as strong contenders to replace batteries in the emergency backup or uninterrupted power supply (UPS) markets. Cost-effective alternatives able to face traditional technologies (such as lead acid batteries and engine-generator sets) that have demonstrated good reliability, flexibility and durability are currently examined by telecommunication wireless operators. In this study is reported a feasibility study for an Uninterruptible Power Supply (UPS) system based on 5 KW class PEM Fuel Cell Power Module in order to compare this solution with a conventional UPS battery based system. A commercialized Power Module was tested to analyze operational performance, time response with variable load, cold start, consumption, efficiency, quality of power.
Development of a Solid-State Methanol Fuel Classified as Non-Dangerous Goods for Direct Methanol Fuel Cells (DMFC)
Authors: Mori Koichi , Yagi Minoru , Obuse Hiroshi , Nozue Mituru , Satou Shigeaki
Published: May 2007

A Solid-State Methanol fuel with improved safety and portability has been developed by applying clathrate compound technology to liquid methanol for Direct Methanol Fuel Cells (DMFC).
Modeling and Simulating of an Energetic Complex System Constituted by a Photovoltaic Array, a Wind Turbine, an Electrolyzer and Fuel Cells
Authors: Poggi Philippe , Muselli Marc , Cristofari Christian , Darras Christophe , Serre-Combe Pierre , Le Naour François
Published: May 2007

This paper models an hybrid system for providing a typical electrical load for a family. The system consists of a photovoltaic (PV) array, a wind turbine (WT), and a fuel cell. The fuel cell produces complementary power and is able to satisfy the load. An electrolyzer, using PV or WT energy not consumed by the load, produces hydrogen for the fuel cell. At the beginning of operation, the hydrogen stock is sufficient to satisfy a given number of days of autonomous operation. The data used are the typical hourly load, the hourly solar radiation in the plane of the PV array, and a local meteorological station estimate of the hourly wind speed averaged over 18 years. The objective was to optimize the system, in terms of power for each component.
Identification and Characterization of Three Near-Term Direct Hydrogen PEM Fuel Cell Markets
Authors: Mahadevan Kathya , Stone Harry , Judd Kathleen , Paul Darrell
Published: May 2007

Thirty-six pre-automotive market segments were examined to determine the market opportunity for direct hydrogen polymer electrolyte membrane fuel cells (H-PEMFC) to 2015. Potential near-term opportunities to 2008 for H-PEMFC identified include public sector emergency response, forklifts in high throughput distribution centers, and baggage tractors at airports. The telecommunications market was not analyzed because it already is a developing market for H-PEMFC. Results of the lifecycle cost analyses show that H-PEMFC offer value over existing technologies for backup power applications for emergency response radio sites when run-times of 1-3 days are required and in harsh environments which can shorten the life of batteries. For longer run-times, hydrogen fuel cost and tank rental significantly impact the competitiveness of H-PEMFC for radio sites. H-PEMFC-powered forklifts in high-productivity environments represent a promising early opportunity. However, the value of H-PEMFC-powered forklifts compared to existing alternatives is reduced for applications with lower hours of operation and declining labor rates. Improvements in hydrogen cost and fuel cell life have the greatest impact on reducing the annual cost of owning and operating a H-PEMFC-powered pallet truck. H- PEMFC-powered baggage tractors in airports are more expensive than battery-powered baggage tractors on a lifecycle cost basis. Decreasing the cost of hydrogen, increasing fuel cell life, and lowering capital cost will have the greatest impact on lowering the annual cost of owning and operating a H-PEMFC- powered baggage tractor.
Effects of cardiopulmonary bypass surgery on coronary flow in children assessed with transthoracic Doppler echocardiography
Authors: Aburawi Elhadi H. , Berg Ansgar , Liuba Petru , Pesonen Erkki
Published: May 2007

Perturbation of coronary blood flow (CF) is an important contributor to myocardium-related complications. The study was primarily designed to assess the impact of cardiopulmonary bypass (CPB) surgery on CF by aid of transthoracic Doppler echocardiography. Changes in CF after off-pump coarctation surgery were also studied. All ultrasounds were performed before and 5 ± 1 days after surgery. Eighteen children underwent CPB surgery of ventricular left-to-right shunts at the mean age of 6 mo, while off-pump surgery (aortic coarctectomy) was undertaken at the mean age of 10 days in 12 children. After CPB surgery, both left anterior descending coronary artery mean diameter and basal CF increased from 1.7 ± 0.3 to 2.1 ± 0.4 mm ( P = 0.001) and 27 ± 10 to 47 ± 15 ml/min ( P = 0.0001), respectively. These two coronary variables decreased after off-pump coarctectomy: left anterior descending coronary artery mean diameter from 1.8 ± 0.1 to 1.7 ± 0.1 mm ( P = 0.06), and CF from 44 ± 12 to 25 ± 8 ml/min ( P = 0.001). The findings are in keeping with the hypothesis that the previously reported impairment of coronary flow reserve after CPB surgery could be due to increase in basal coronary flow after CPB. Off-pump coarctectomy seems to have little impact on CF, as the postsurgical decline in flow in these patients seems to relate to the reduction in cardiac pressure afterload.
Local ascorbate administration augments NO- and non-NO-dependent reflex cutaneous vasodilation in hypertensive humans
Authors: Holowatz Lacy A. , Kenney W. Larry
Published: May 2007

Full expression of reflex cutaneous vasodilation (VD) is dependent on nitric oxide (NO) and is attenuated with essential hypertension. Decreased NO-dependent VD may be due to 1) increased oxidant stress and/or 2) decreased l-arginine availability through upregulated arginase activity, potentially leading to increased superoxide production through uncoupled NO synthase (NOS). The purpose of this study was to determine the effect of antioxidant supplementation (alone and combined with arginase inhibition) on attenuated NO-dependent reflex cutaneous VD in hypertensive subjects. Nine unmedicated hypertensive [HT; mean arterial pressure (MAP) = 112 ± 1 mmHg] and nine age-matched normotensive (NT; MAP = 81 ± 10 mmHg) men and women were instrumented with four intradermal microdialysis (MD) fibers: control (Ringer), NOS inhibited (NOS-I; 10 mM NG-nitro-l-arginine), l-ascorbate supplemented (Asc; 10 mM l-ascorbate), and Asc + arginase inhibited [Asc+A-I; 10 mM l-ascorbate + 5 mM ( S)-(2-boronoethyl)-l-cysteine-HCl + 5 mM Nω-hydroxy- nor-l-arginine]. Oral temperature was increased by 0.8°C via a water-perfused suit. NG-nitro-l-arginine was then ultimately perfused through all MD sites to quantify the change in VD due to NO. Red blood cell flux was measured by laser-Doppler flowmetry over each skin MD site, and cutaneous vascular conductance (CVC) was calculated (CVC = flux/MAP) and normalized to maximal CVC (%CVCmax; 28 mM sodium nitroprusside + local heating to 43°C). During the plateau in skin blood flow (ΔTor = 0.8°C), cutaneous VD was attenuated in HT skin (NT: 42 ± 4, HT: 35 ± 3 %CVCmax; P < 0.05). Asc and Asc+A-I augmented cutaneous VD in HT (Asc: 57 ± 5, Asc+A-I: 53 ± 6 %CVCmax; P < 0.05 vs. control) but not in NT. %CVCmax after NOS-I in the Asc- and Asc+A-I-treated sites was increased in HT (Asc: 41 ± 4, Asc+A-I: 40 ± 4, control: 29 ± 4; P < 0.05). Compared with the control site, the change in %CVCmax within each site after NOS-I was greater in HT (Asc: −19 ± 4, Asc+A-I: −17 ± 4, control: −9 ± 2; P < 0.05) than in NT. Antioxidant supplementation alone or combined with arginase inhibition augments attenuated reflex cutaneous VD in hypertensive skin through NO- and non-NO-dependent mechanisms.
Complex airway behavior and paradoxical responses to bronchoprovocation
Authors: Winkler Tilo , Venegas Jose G.
Published: May 2007

Heterogeneity of airway constriction and regional ventilation in asthma are commonly studied under the paradigm that each airway's response is independent from other airways. However, some paradoxical effects and contradictions in recent experimental and theoretical findings suggest that considering interactions among serial and parallel airways may be necessary. To examine airway behavior in a bronchial tree with 12 generations, we used an integrative model of bronchoconstriction, including for each airway the effects of pressure, tethering forces, and smooth muscle forces modulated by tidal stretching during breathing. We introduced a relative smooth muscle activation factor (Tr) to simulate increasing and decreasing levels of activation. At low levels of Tr, the model exhibited uniform ventilation and homogeneous airway narrowing. But as Tr reached a critical level, the airway behavior suddenly changed to a dual response with a combination of constriction and dilation. Ventilation decreased dramatically in a group of terminal units but increased in the rest. A local increase of Tr in a single central airway resulted in full closure, while no central airway closed under global elevation of Tr. Lung volume affected the response to both local and global stimulation. Compared with imaging data for local and global stimuli, as well as for the time course of airway lumen caliber during bronchoconstriction recovery, the model predictions were similar. The results illustrate the relevance of dynamic interactions among serial and parallel pathways in airway interdependence, which may be critical for the understanding of pathological conditions in asthma.
Short-term variability of airway caliber—a marker of asthma?
Authors: Diba Chantale , Salome Cheryl M. , Reddel Helen K. , Thorpe C. William , Toelle Brett , King Gregory G.
Published: May 2007

Variability in airway caliber is a characteristic feature of asthma. Previous studies reported that the variability in respiratory system impedance (Zrs), measured by the forced oscillation technique during several minutes of tidal breathing, is increased in asthma and may be a marker of inherent instability of the airways. The aims of this study were to determine if short-term variability in impedance correlates with peak expiratory flow (PEF) variability or airway hyperresponsiveness (AHR). The SD of log-transformed impedance (lnZrsSD) was measured as a marker of short-term variability and compared with the diurnal variability of PEF over 2 wk in 28 asthmatic and 7 nonasthmatic subjects and with AHR to histamine in a cohort of 17 asthmatic and 82 nonasthmatic subjects. In addition, lnZrsSD was measured in eight nonasthmatic subjects before and after methacholine challenge in the upright and supine positions. There were no significant differences in lnZrsSD between asthmatic and nonasthmatic subjects ( P = 0.68). Furthermore, in asthmatic subjects, lnZrsSD did not correlate with diurnal variability of PEF ( rs= −0.12 P = 0.54) or with AHR to histamine ( r = 0.10, P = 0.71). Neither methacholine challenge nor supine posture caused any significant change in lnZrsSD. We conclude that our findings do not support previous reports about the utility of short-term variability of impedance. Our findings suggest that, using standard methods for forced oscillometry, impedance variability does not provide clinically useful information about the severity of asthma.