bluuebunny/crossref_metadata_2025 huggingface dataset:
Sulfur removal methods
Authors: Hidalgo‐Vivas A. , Cooper B. H.
Published: December 2010

Hydrogen production processes, e.g., steam reforming and partial oxidation, begin with a pretreatment section where a sulfur removal method is employed to prepare the feedstock. The characteristics of possible reforming fuels, i.e., liquefied natural gas, liquefied petroleum gas, naphtha and diesel are discussed in a refinery context. Sulfur compounds present in crude oil fractions are divided into different classes. Some exhibit a very low reactivity, which makes them more difficult to desulfurize, and which significantly impacts the achievement of ultra‐low sulfur levels. The improved design of efficient hydrodesulfurization processes is based on the understanding of the process chemistry. In the case of a feedstock with low sulfur content, removal of sulfur can be achieved by absorption processes, e.g., absorption on a zinc oxide catalyst bed. In the case of heavier feedstocks or feedstocks with a high sulfur content, a first step consisting of a hydrodesulfurization process becomes necessary. The process conditions, i.e., temperature, pressure, space velocities, catalysts, etc. are determined by the type of feedstock to be treated. The catalysts most generally used for hydrotreatment consist of cobalt and molybdenum oxides or nickel/molybdenum compounds, both supported over alumina. CoMo and NiMo catalysts desulfurize the most refractory compounds through different desulfurization routes, thus the choice of catalyst will be a function of the type of feedstock and process conditions. It is required that the hydrogen sulfide produced by the desulfurization reactions is removed. Options used to remove H
2
S from the system include the use of zinc oxide absorption, amine wash treatment or both.
Membrane reactor concepts
Authors: Wieland S. , Melin T.
Published: December 2010

Fuel cell powered vehicles with on‐board reforming need compact and lightweight components. A membrane reactor that combines hydrogen permeable membranes with a methanol steam reformer promises considerable weight and space savings. Its dense metal membranes produce high‐purity hydrogen over a wide range of pressures and loads. The selective removal of hydrogen yields methanol and CO conversions that are higher than the equilibrium conversion in a conventional reactor. Results with three different metal membranes in a membrane reactor for steam reforming of methanol are presented. A mathematical model accurately describes the measured performance of the membrane reactor and allows predictions for other values of the process parameters.
Autothermal reforming
Authors: Baumann F. , Wieland S. , Himmen M. , Agar D. W.
Published: December 2010

Autothermal reforming (ATR) combines endothermic (viz. steam reforming) with exothermic (viz. partial oxidation) processes. This chapter comments on the differences between the various reforming technologies, their advantages and drawbacks in different application areas and on the use of the terminology ATR as it is used in the literature. The influence of reaction parameters like air stoichiometry, steam content and preheating temperature on the autothermal process is discussed based on simulations and experimental results. An overview of the development of autothermal processes starting in the 1970s up to recent progress in this field is given.
Alternative design possibilities for integrated fuel processors
Authors: Voecks G. E.
Published: December 2010

The majority of fuel processors that have been developed to support proton exchange membrane (PEM) fuel cells have basically been adaptations of largescale commercial processes and designs. This has been largely a result of the combined engineering familiarity of industrial hydrogen production and purification practices, and the evolution of these techniques over the past 30 years as they have developed for the anticipated commercial fuel cell systems' uses. Alternative conversion processes for various fuels, employing technologies not widely practised industrially or designs not previously integrated with fuel cells may offer PEM fuel cell systems certain advantages as they are developed for various applications, including transportation. A review of three different technological approaches that offer unique possibilities are examined for consideration as PEM fuel cell systems continue their development. The technical examples discussed are not intended to be exhaustive but rather chosen to be illustrative of the technology presented.
Well‐to‐wheel efficiencies of different fuel choices
Authors: Höhlein B. , Isenberg G. , Edinger R. , Grube T.
Published: December 2010

In order to assess a future fuel supply, it will be necessary to define and establish energy, emission and cost balances from the primary energy at the source or well up to the final energy carrier (fuel) at the filling station. In addition to vehicles with internal combustion engines, it will be necessary to give consideration to hybrid vehicles, battery‐powered and fuel cell‐powered electric vehicles supplied with fuels produced from both fossil and renewable resources. Overall balances (well‐to‐wheels) including fuel supply (well‐to‐tank) and the use of vehicles (tank‐to‐wheels) in terms of energy, emissions and costs are necessary.
Basic materials corrosion issues
Authors: Shores D. A. , Deluga G. A.
Published: December 2010

The use of corrosion tests that appropriately simulate the environment in the proton exchange membrane fuel cell (PEMFC) is discussed. Caution is advised in the interpretation of electrochemical corrosion tests. Metallic bi‐polar plates typically achieve corrosion resistance by forming passive oxide films, which must be sufficiently conductive to allow high fuel cell current densities. Austenitic stainless steels are obvious candidate alloys. The key issue with regard to corrosion is that the alloy selected should exhibit passive behavior in its local chemical environment and at the electrochemical potentials imposed upon it by the anode or cathode.

Different corrosion tests will yield differing corrosion rates of a given alloy for various reasons: (a), the test measures the corrosion rate at the alloy's natural corrosion potential rather than at an imposed potential; (b), insufficient exposure time was allowed for the alloy to fully develop its passive film; (c), other oxidation or reduction reactions may operate in parallel with the corrosion reactions, which will invalidate the inference of a corrosion rate from a measured net current density.

Therefore, out‐of‐cell corrosion tests should be checked for self‐consistency. Corrosion rates are typically slower in the cathode‐simulating conditions than in anode conditions. Anode‐side corrosion rates are predicted to be higher at low fuel cell power, but cathode‐side corrosion rates are likely to be insensitive to power levels.

A good, commercial grade stainless steel is unlikely to suffer perforation or collapse of the bi‐polar plate within the design lifetime, but other corrosion‐related failure modes may become important. Two of these are an increase in contact resistance and the release of corrosion product cations, which can reduce the conductivity of the membrane. A simple model was used to illustrate how the reduction of membrane conductivity was dependent upon corrosion rate and fuel cell power.
Metal bipolar plates and coatings
Authors: Wind J. , LaCroix A. , Braeuninger S. , Hedrich P. , Heller C. , Schudy M.
Published: December 2010

The use of metals as a material for bipolar plates in proton exchange membrane (PEM) fuel cells offer a number of advantages in comparison with other materials. Several companies and institutes are currently working on the development of such bipolar plates and have patented their results. Whereas in the production of metallic bipolar plates there are no major obstacles, there are still some issues to be solved concerning corrosion and conductivity of these plates in the fuel cell environment. Up to now, the method of solving these issues seems to be to coat the plates with materials which prevent corrosion and growth of oxide layers with a high resistivity. The requirements for these bipolar plates and their current status is outlined in the chapter.
Interdigitated flow field design
Authors: Nguyen T. V. , He W.
Published: December 2010

When interdigitated gas distributors are used in a proton exchange membrane fuel cell (PEMFC), fluids entering the fuel cell are forced to flow through the electrode porous backing layers. This through‐the‐electrode convection increases the transport rates of the reactants and products to and from the catalyst layers, and the shear force of gas flow minimizes electrode flooding by reducing the amount of liquid water that is entrapped in the porous electrodes. To investigate the effects of the gas and liquid water hydrodynamics on the performance of an air cathode of a PEMFC employing an interdigitated gas distributor, a two‐dimensional, two‐phase, multi‐component transport model was developed. The predictive capability of the model was validated against experimental results obtained at multiple operating conditions. The model was also used to investigate the effects of two flow field design parameters on the cathode performance.
Two–phase flow and transport
Authors: Wang C.‐Y.
Published: December 2010

This chapter reviews latest experimental and modeling efforts towards developing a basic understanding of two‐phase flow physics in proton exchange membrane fuel cells. Both hydrogen proton exchange membrane fuel cells and proton exchange membrane based direct methanol fuel cells are discussed. As an important example of materials characterization, wetting characteristics of gas diffusion layers are examined and the techniques of measuring contact angle are discussed. Next, a comprehensive physico‐chemical modeling framework of combining electrochemistry with two‐phase transport is presented along with select numerical examples for both hydrogen and direct methanol fuel cells. The current state of the computational efficiency of these comprehensive models is indicated. A critical need for model validation against detailed data of the current distribution is demonstrated, and a new technique of measuring the current distribution using a segmented flow plate and a multi‐channel potentiostat is presented. Finally, areas for future research into two‐phase transport in proton exchange membrane fuel cells and the associated cathode flooding are pointed out.
First principles modeling of sulfonic acid based ionomer membranes
Authors: Paddison S. J.
Published: December 2010

Proton dissociation in the sulfonic acid groups of hydrated Nafion
®
and polyetherketone membranes along with its connection to proton transport within the membrane pores is discussed. Minimum energy conformations for trifluoromethane and
para
‐toluene sulfonic acids with clusters of 1–6 water molecules were obtained using ab initio electronic structure calculations. These calculations revealed the influence of both the structure and strength of the conjugate base (sulfonate anion) on the dissociation and hydration of the acid. Although spontaneous dissociation was observed for both sulfonic acids after the addition of three water molecules, the proton (as a hydronium ion) is less bound for the perfluorinated system than with the aromatic system. This is due to the increased electron stabilization afforded by the electron withdrawing of the CF
3
group. This molecular membrane specific information was used in combination with membrane morphology data to compute proton diffusion coefficients for both Nafion 117 and 65% sulfonated polyetherketone membranes at hydration levels where the number of water molecules per sulfonic acid fixed site were: 6, 13, and 22.5; and 15, 23, and 30, respectively. The agreement with pulsed field gradient NMR diffusion measurements was very good for both membranes across the entire range of membrane hydration, attesting to the substantial predictive capability of the transport model.
Composite perfluorinate membranes
Authors: Nakao M. , Yoshitake M.
Published: December 2010

As typical composite perfluorinated membranes applied to proton exchange membrane fuel cells, two types of membranes with different reinforcements are reviewed, focusing on their preparation methods, mechanical and electrochemical properties.

One is Gore‐select®which is reinforced with a porous polytetrafluoroethylene (PTFE) sheet. The thin membrane is prepared by impregnating a solution of perfluorinated ionomer into a thin PTFE porous sheet. The other is PTFE micro‐fibril reinforced membrane. The thin membrane is prepared by stretching a thicker composite film. Compared with non‐reinforced membranes, the composite membranes have many advantages both in mechanical properties and in electrochemical performance.
Hydrocarbon membranes
Authors: Kreuer K. D.
Published: December 2010

The preparation of sulfonated hydrocarbon based membranes is described and the properties relevant for polymer electrolyte membrane fuel cell applications are discussed in relation to their typical chemical and microstructural features. Especially sulfonated high performance polyarylene membranes combine good durability with high proton conductivity (in the wet state), making them interesting low‐cost alternatives for perfluorosulfonic acid polymer membranes (e.g., Nafion
®
). The sharp decrease in conductivity with decreasing water content as a direct consequence of the inherently lower acidity and nano‐separation is partially compensated by fewer humidification problems as a result of lower electroosmotic drag. The poorer mechanical properties (brittleness in the dry state and increasing softness in the wet state) have been improved by blending and/or crosslinking. An interesting perspective for liquid direct methanol fuel cell applications, which require low methanol cross‐over, is provided by the lower electroosmotic drag of water and methanol observed at moderate temperatures (>60 °C) and low methanol concentrations. But the generally high swelling in water/methanol mixtures especially at higher temperatures is currently preventing hydrocarbon based membranes from being used in direct methanol fuel cells. While proton and water transport are generally related in conventional membranes, pure proton conductivity in low humidity environment at higher temperature may be achieved with heterocycles (e.g., imidazole) as proton solvent in fully polymeric systems.
High–temperature membranes
Authors: Wainright J. S. , Litt M. H. , Savinell R. F.
Published: December 2010

A review is presented of work in the area of polymer electrolyte membranes for fuel cell operation at temperatures exceeding 100 °C. Development of these electrolytes will permit fuel cell operation with greatly increased tolerance to carbon monoxide, and greatly reduced humidification requirements. The focus is on the electrolyte membranes based on basic polymers doped with acids, i.e., phosphoric acid‐doped polybenzimidazole. The key properties of these membranes including conductivity, permeability, and mechanical strength are reviewed, as well as fuel cell performance under various operating conditions.
Membrane/electrode additives for low–humidification operation
Authors: Lin J.‐C. , Kunz H. R. , Fenton J. M.
Published: December 2010

Proton exchange membrane fuel cells are limited in their potential for commercialization, since a high water content is required in the Nafion®ionomer currently used as the electrolyte. Research is currently being performed to reduce this water requirement while still maintaining high ionic conductivity. One approach that shows promise incorporates solid proton conductors such as phosphotungstic acid or zirconium (hydrogen) phosphate into the ionomer. Operating at low water content in the membrane allows cell operation at higher temperatures without cell pressurization. Higher temperature operation improves the performance of the cell, reduces the cost of the fuel cell power plant, and makes the proton exchange membrane fuel cell more attractive for the direct use of methanol as the fuel. This section presents a survey of approaches that have been used and experimental data showing the current status of performance of proton exchange membrane fuel cells operating with low water content.
High dispersion catalysts including novel carbon supports
Authors: Tada T.
Published: December 2010

Pt catalysts and PtRu catalysts supported on conductive carbon black (catalyst loading is from 10 wt% to 60 wt%) are normally used for proton exchange membrane fuel cells, since supported catalysts have higher active surface area than nonsupported catalysts because of uniform dispersion and smaller particles. Also, supported catalysts are more stable concerning catalyst agglomeration than nonsupported catalysts during fuel cell operation. In the case of Pt catalyst, the effect of carbon support on the catalyst's characterization and catalytic activity of the oxygen reduction reaction are investigated. The effect of metal loading on the catalytic activity of the oxygen reduction reaction is also discussed. In the case of PtRu catalyst, the influence of carbon support and metal loading on the catalyst's characterization and the CO tolerance of the catalysts are investigated. The effect of operating conditions and electrode structure on CO tolerance of the PtRu catalyst's anode are also discussed. Moreover, catalyst agglomeration phenomenon of Pt catalyst and degradation of CO tolerance of PtRu catalyst after fuel cell operation are investigated.
Principles ofMEApreparation
Authors: Kocha S. S.
Published: December 2010

A brief history of the evolution of the fuel cell electrode, emphasizing the technological developments that have lead to the contemporary polymer electrolyte membrane electrode assembly (MEA). This is followed by a discussion of the requirements, functions and properties of individual components and processes by which they are fabricated into MEAs. Lastly, basic in situ electrochemical techniques that may be applied as diagnostic tools to understand and advance the performance of MEA technology are reviewed.
Novel catalysts, catalysts support and catalysts coated membrane methods
Authors: Debe M. K.
Published: December 2010

This chapter introduces a new type of catalyst electrode for proton exchange membrane (PEM) fuel cells based on a nanostructured thin film catalyst support system. The nanostructured film consists of a single layer of a dense distribution of oriented crystalline whiskers of an organic pigment material. With areal number densities of 3–5 billion cm
−2
and micrometer scale lengths, using dry processes, the whiskers are grown, coated uniformly with catalysts and transferred to the surface of a PEM to form an electrode. The physical and chemical properties of the nanostructured supports are reviewed first, followed by properties of the catalyst coatings and finally the electrode layer formation. Differences of these characteristics and properties from conventional carbon particle supported dispersed catalysts are widely made. Fuel cell performance examples and comparisons contrasting the mass and area cathode specific activities of the two types of catalyst electrode systems are demonstrated. The differences have implications for how membrane electrode assembly (MEA) are fabricated, ultimate catalyst loadings, system humidification requirements and durability.
Beginning‐of‐lifeMEAperformance — efficiency loss contributions
Authors: Gasteiger H. A. , Gu W. , Makharia R. , Mathias M. F. , Sompalli B.
Published: December 2010

Beginning‐of‐life H2‐fed fuel cell performance of membrane electrode assemblies (MEA) made using state‐of‐the‐art subcomponents (25–50 µm membranes, 47 wt% Pt on carbon, 0.15–0.4 mg cm−2Pt cathode loading, ≤1100 equivalent weight (EW) ionomer/binder) was studied. Performance data were taken using small‐scale (50 cm2) cells and a large‐scale (500 cm2, 22 cell) stack, and voltages were corrected for membrane resistance in order to isolate cathode polarization losses. Based on catalyst and MEA cyclic voltammetry and in‐situ testing with pure O2feed, we observed loading independent O2kinetic control up to 1.8 A cm−2at 80 °C under fully humidified conditions; this indicates negligible effects of cathode layer proton transport limitations with pure O2. With air as the oxidant, we observed O2kinetic control below 0.2 A cm−2and the onset of O2transport resistances at higher current densities. Results with helox (21% O2in helium) as the cathode feed revealed that the O2transport resistances were roughly evenly distributed between gas and solid phases. With incomplete reactant humidification, additional membrane resistance was observed and proton conductivity losses in the cathode layer became significant. Moreover, thin (25 µm) low‐equivalent weight (EW) MEAs outperformed thicker (50 µm) high EW MEAs even after correcting for membrane ohmic losses. This is due to faster water transport of the thinner low EW MEAs resulting in improved retention of cathode layer proton conductivity under dry conditions.
Effect of ionic contaminants
Authors: Okada T.
Published: December 2010

In polymer electrolyte membrane (PEM) fuel cells, the electrolyte membrane is easily contaminated by foreign cations because of a higher affinity of these cations with the sulfonic acid group than that of H
+
. Thereby three modes of degradation in the membrane which affect fuel cell performance are anticipated. The first is a direct effect, and comes from alteration of the membrane bulk properties, e.g., lowering of membrane ionic conductivity, water content, H
+
transference number. This effect is normally not so serious unless the membrane is severely contaminated. The second comes from the altered water flux inside the membrane, owing to the terms of electroosmotic drag and diffusion coefficient of water affected by the presence of contaminant ions. This results in membrane drying and lowering of membrane conductivity. The degradation starts when the contaminant level exceeds 5%. Simulation results concerning the water concentration profile, membrane ohmic resistance and membrane overpotential are presented based on water flux equations derived using experimentally obtained transport parameters. The last effect comes from the degradation of the cathode catalyst due to the presence of contaminant ions at the interface between the platinum catalyst and the ionomer layer. This effect is the most serious as regards the fuel cell performance, because a contaminant level as low as 1% is enough to come into effect. Membrane contamination by foreign cations, especially local contamination at the cathode catalyst layer, deteriorates the fuel cell performance significantly, and needs special caution in fuel cell design.
Reliability issues and voltage degradation
Authors: Fowler M. , Mann R. F. , Amphlett J. C. , Peppley B. A. , Roberge P. R.
Published: December 2010

To date the application of fuel cell systems has focused on operational performance and little attention has been given to the reliability of fuel cells and stacks. This section discusses reliability and system effectiveness as they are related to fuel cell stacks, with a specific focus on proton exchange membrane (PEM) fuel cell stacks. The potential applications of different reliability analysis methodologies to fuel cell stacks is discussed. The potential failure modes and causes of failure experienced in fuel cells stacks are outlined. There are a number of reliability analysis techniques practiced today that would be useful in the further development of fuel cell stacks. This section briefly introduces these techniques and the information and data requirements of each technique. The three basic techniques to be addressed include: failure mode and effects analysis, reliability block diagrams and fault tree analysis. Durability or irreversible degradation of the stack is defined as the ability of a membrane and electrode assembly (MEA) to resist permanent change in performance over time. With respect to fuel cell stacks, the definitions for reliability of the stack include failure modes that can lead to catastrophic failure, as well as performance degradation to below an acceptable level. Stability or reversible degradation are the recoverable phenomena involving voltage or current density decay. The application of reliability terminology for fuel cell stacks is addressed, and different definitions for failure are discussed. Causes of PEM fuel cell failure are likely to be defect propagation, low level contamination, corrosion of the plates leading to increased contact resistance, thermal or hydration cycling leading to mechanical stress, catalyst particle ripening, swelling of polymer materials in the active catalyst layer leading to changes in water removal characteristics, compaction of the gas diffusion layer due to mechanical stresses, degradation of the polymer material and surface chemistry changes in gas diffusion layer.
Air‐supply components
Authors: Pischinger S. , Lang O.
Published: December 2010

The careful layout of air‐supply systems is a key parameter to achieve high overall efficiencies of PEM fuel cell applications. This part of the system determines the humidification concept as well as pressure level and power density, respectively. This chapter describes the basic requirements which must be taken into account during the layout of a PEM fuel cell system. The thermodynamic fundamentals of compressor and expander units are explained and examples of practical units are shown. Furthermore, acoustic aspects are discussed and the influence on the humidification concept is discussed. Finally, a simulation tool is presented which supports the user in the layout of the overall system and represents a hardware‐in‐the‐loop environment. This tool supports component developments under steady‐state and transient boundary conditions so that control algorithms can be developed.
Stack materials and design
Authors: Kordesch K. , Hacker V.
Published: December 2010

Materials, manufacturing processes, commercial products of carbon used for alkaline fuel cells and cell stacks and different designs are reviewed in this chapter. Different methods for water product removal used in terrestrial and in space applications together with electrode production techniques and development aspects of electrode materials for multi‐layer electrodes are discussed.
System design and applications
Authors: Strasser K.
Published: December 2010

Over a period of 20 years, starting from 1967, research and developmental work on alkaline fuel cells was conducted at Siemens with the aim of increasing power density of the cell, improving long‐term behavior, cell function and design, decreasing cost and gather experience by testing laboratory models and prototypes. Based on Raney nickel as the anode catalyst and doped silver as the cathode catalyst, a cell voltage of 0.7 V at a current density of 400 mA cm
−2
can be reached. Cell operating conditions are 80 °C and 2 bar reactant pressures (absolute H
2
and O
2
). The cell is characterized by the dimensions 240 × 245 cm
2
and an active area of 340 cm
2
. Reaction water is removed from the cell by an electrolyte circulation. It is evaporated and condensed in a slit‐like regenerator by removing the waste heat. The fuel cell stack, electrolyte regenerator and electromechanical control unit form a compact module block, which yields power ratios of approximately 10 kg kW
−1
and 8 l kW
−1
, respectively. Modules with 35, 60 and 70 cells and a power output of 1–7 kW have been realized and also power plants consisting of more modules with a power output of 20–100 kW and a voltage of more than 200 V. A 100 kW prototype fuel cell power plant was tested successfully as part of an air independent propulsion system in the U205 submarine of the German Navy from August 1988 to March 1989. But in spite of the positive results the polymer electrolyte fuel cell was preferred because of its better long‐term behavior and higher power density. There is no doubt that the relatively high production cost will limit the application in special areas such as submarines in the short term.
A comparison between the alkaline fuel cell (
AFC
) and the polymer electrolyte membrane (
PEM
) fuel cell
Authors: Kordesch K. , Cifrain M.
Published: December 2010

This comparison discusses the electrode and system design differences between acid fuel cells with an immobilized electrolyte (e.g., contained in a matrix, in a gelled layer or in a membrane) and alkaline systems, mainly using a free flowing electrolyte. The inherent electrochemical and technological advantages and disadvantages are pointed out. The likely reasons for the historically often changed selection of certain fuel cell types for various applications are presented, relating the choices to opportunities and technical circumstances. These choices are by no means final and are still open. However, they depend not so much on technical or electrochemical problems and solutions, but on available materials, manufacturing feasibilities and in particular on the cost of the total system to be used for a specific purpose. A modern example is the planned use of polymer electrolyte membrane (PEM) fuel cells for electric vehicles. These membrane fuel cells are supposed to replace a combustion engine which costs $50–100 kW
−1
power output, but do require at the present time an investment of thousands of dollars per kilowatt. Why did so many proponents chose this system and/or this application? Can other systems do better? This comparison suggests alternatives.
Stack materials and stack design
Authors: Breault R. D.
Published: December 2010

The 35 year history of phosphoric acid fuel cell stack development at United Technologies Corporation is traced through three generations of power plants that culminated in the 200 kW ™PC‐25 fuel cell power plant. The evolution of stack materials and designs for the electrolyte retaining matrix, electrode substrate, electrolyte reservoir plates, separator plates and coolers are described. Electrolyte management issues relating to water management, electrolyte distribution between cell components, freeze prevention, acid evaporation, and acid transfer by electrochemical pumping are reviewed. Corrosion issues relating to separator plates, anode corrosion, edge seal corrosion and operation at low power levels are discussed. Thoughts on potential improvements to reduce the cost and double the life of the phosphoric acid fuel cell stack are presented.
Catalyst studies and coating technologies
Authors: Landsman D. A. , Luczak F. J.
Published: December 2010

An account is given of the development of electrocatalysts for the phosphoric acid (phosphoric acid) fuel cell starting from unsupported platinum black and ending with carbon‐supported platinum alloys. The incentive for this work was the need to reduce the cost of the phosphoric acid fuel cell by reducing the amount of platinum it contained while simultaneously raising its performance. Equally important was the concurrent effort aimed at optimizing the structure of the polytetrafluoroethylene (PTFE)‐bonded, gas‐diffusion electrodes so that the noble metal catalysts were used as effectively as possible. Methods to control the structure of the catalyst layer were devised based on studies of the way in which aqueous dispersions of the supported catalyst and PTFE interact. Procedures used to prepare electrodes in the laboratory were modified and scaled up for production purposes. A novel process for depositing catalyst layers on electrode substrates was developed and several different coating technologies were evaluated for applying PTFE‐bonded, silicon carbide, electrolyte‐retaining matrices to the electrodes. Some operating conditions that can have an adverse affect on the life of the electrodes are considered. Most of the work described here originated in the laboratories and workshops of International Fuel Cells — a unit of United Technologies Corporation — and culminated in the PC25 phosphoric acid fuel cell power plant.
Experience with 200
k
W
PC
25 fuel cell power plant
Authors: King J. M. , McDonald B.
Published: December 2010

The 200 kW PC25 fuel cell power plant has demonstrated the intrinsic characteristics of fuel cells: high electrical and overall efficiency over a wide range of loads, rapid transient response, quiet operation and low emission of controlled pollutants. The power plants are designed to an industry standard and certified by an independent agency. Permitting approval for power plant installation has been achieved with minimal problems.

The standard production power plant has been installed in a wide range of climates, operated on natural gas with compositions delivered in over 100 cities and 19 countries, and connected to many different electrical systems. A number of installations are fueled with waste gas from the anaerobic digestion process in waste water treatment plants. It has been applied to a variety of buildings in a number of electrical and thermal configurations. By the first half of 2002, the more than 200 power plants in the installed fleet had accumulated five million operating hours. Routine maintenance interval while the power plant is operating has reached six months. Individual units have exceeded 40 000 operating hours without overhaul and power plant availability in the high 90s has been demonstrated.

The primary factors limiting broader application of the power plants are high power plant cost and a lack of knowledge of the fuel cell characteristics and benefits.
Stack material and stack design
Authors: Mugikura Y.
Published: December 2010

MCFC power plants have been developed in many countries. The efficiencies of MCFC plants are expected to be higher than those of conventional power plants, such as advanced combined cycle power plants. The MCFC stack is the main element and the key technology in MCFC systems is to achieve both high efficiency and long lifetime. Molten carbonate is used as the electrolyte and is known to be a significantly reactive material. The high reactivity of the molten carbonate provides excellent cell reaction rates but accelerates corrosion of cell components. Suitable stack designs and materials to prevent corrosion of cell components are the main focus of the following chapter. Different materials for the anode, cathode, matrix and separator plate are considered. Performance and lifetime data of stack manufacture are given. Internal and external reforming is compared. Different concepts for gas manifolds and gas flow types are discussed. The status of stack technology is given. Furthermore, optimization of operating conditions as another approach to fulfilling the requirements concerning high efficiency over a long time is discussed.
Low temperature electrolytes and catalysts
Authors: Yamamoto O.
Published: December 2010

Fluoride‐type oxide ion conductors are reviewed in terms of electrical conductivity and oxide ion transport number as the electrolyte in low‐temperature solid oxide fuel cells. In particular, zirconia‐based systems and ceria‐based systems are introduced. Electrode materials with high oxygen reduction catalytic activity at low temperatures are introduced, and also anode materials for the reduction of hydrocarbons at low temperatures are discussed.
MEA
/cell preparation methods:
J
apan/
A
sia
Authors: Suzuki M.
Published: December 2010

Many cell designs and manufacturing technology of membrane and electrode assembly (MEA) have been tried in Japanese solid oxide fuel cell (SOFC) developments. Since the development of SOFC stacks is related very closely with the manufacturing process and cell design, the representative MEA/cell preparation methods are described below as the tubular type and the planer type. In the early 1990s, concerning the tubular cell, it was generally considered that cost reduction was difficult, although the reliability was excellent. At that time, Japanese manufactures started developing the tubular cell by the sintering method in order to reduce cell preparation costs. The difficulty of fabricating tubular cells by the sintering method is that the dense electrolyte and interconnect film must be deposited on the porous substrate. Two kinds of slurry coating methods, dipping and printing, were applied. As of 2002, the low cost tubular cell manufacturing technology is at the 10 kW class module stage. Concerning the planer type, 15 kW modules were manufactured and tested in 2001. In this development, MEAs are fabricated with an embossed self‐supporting yttria‐stabilized zirconia (YSZ) electrolyte, Ni/YSZ anode and a doped LaMnO
3
cathode. The dimpled MEA structure has two advantages for cost reduction. One is the increase of the active surface area and the other is the adaptable flat (ribbless) separators. An anode supported YSZ electrolyte planer cell and a doped LaGaO
3
electrolyte cell are also under development in Japan.
Novel electrolytes operating at 400‐600 °C
Authors: Ishihara T.
Published: December 2010

Some high oxide ion and proton conductors that can be used as electrolytes operating at temperatures less than 600 °C are reviewed. In particular, the oxide ion conductivity of the perovskite oxide of LaGaO3is discussed and applications of the LaGaO3‐based oxide as the electrolyte of solid oxide fuel cells (SOFCs) are introduced. Since the LaGaO3‐based oxide is highly stable over a widerange, the open circuit potential of the fuel cell is close to the theoretical one and a high power density of a few 100 mW cm−2has been achieved at 873 K in spite of the 0.5 mm thick La0.8Sr0.2Ga0.8Mg0.125Co0.085O3(LSGMC) electrolyte. A high power density has also been exhibited in the cell using a larger sized LSGMC electrolyte. LSGMC has a great potential as an electrolyte of fuel cells operating at intermediate temperatures. On the other hand, the CeO2‐based oxide is also promising as an electrolyte of intermediate temperature SOFCs because oxide ion transport number increased with decreasing temperature. A new family of oxide ion conductors with a noncubic structure has recently been reported and the ion conductivity in these oxides is also discussed. On the other hand, proton‐conducting oxides are also studied as electrolytes of intermediate temperature SOFCs and the applications of some perovskite proton‐conducting oxides as electrolytes of intermediate temperature fuel cell are also mentioned.
Alkaline methanol/air power devices
Authors: Koscher G. A. , Kordesch K.
Published: December 2010

Methanol is a promising fuel for power devices like fuel cells because it has a high theoretical capacity per volume and weight, it is relatively easy to handle and it is easy to store. Many investigations into the alkaline methanol fuel cell system were made in the 1960s and 1970s. This chapter provides a brief summary of this research and tries to explain why interest in these systems has declined.
Portable direct methanol fuel cell systems
Authors: Narayanan S. R. , Valdez T. I.
Published: December 2010

The simplicity of the direct electrooxidation of methanol in a polymer electrolyte membrane fuel cell and the technological advances achieved in performance and efficiency in the last 10 years has spurred the development of direct methanol fuel cell (DMFC)‐based portable power systems in the power range of 0.1–150 W. Most of the system demonstrations to date have focused on proving the feasibility of novel stack designs, membrane types, integrated system configurations, and miniaturization concepts. This article includes discussion of the specific power and power density requirements for various portable system applications, the status of stack technology, progress in the implementation of balance‐of‐plant designs, and a summary of the characteristics of various DMFC portable power source demonstrations. Compact monopolar and bipolar designs are demonstrated at various power levels. Integrated systems at the 25–150 W level have demonstrated functionality for multi‐purpose power source applications for the military and commercial area, although these demonstration present substantial scope for weight and volume improvements. Efforts in the power range of 0.1–15 W have focused on size and mass, as these are premium requirements for the small portable consumer electronics market. Recent demonstrations relate to lightweight stack configurations while closed loop systems with water recovery and thermal management are at best in the initial phases of demonstration.
Small‐sizePEMsystems for special applications
Authors: Büchi F. N.
Published: December 2010

The trend towards more mobility in many aspects of life in 21stcentury society creates a need for mobile power sources in situations and areas where no grid power is available. Today mobile power in the medium power range (several 10 W to several kW) is mostly provided by either batteries or IC engine‐driven generators. However competing technologies such as low temperature fuel cells are evolving. This article describes the fuel requirements, advantages, and properties, examples of systems and applications of polymer electrolyte fuel cells for these special applications.
General motors/
OPEL
Fuel cell activities — driving towards a successful future
Authors: Rodrigues A. , Fronk M. , McCormick B.
Published: December 2010

General Motors (GM) is the world's largest automobile maker. Over the years, GM has supported fuel cell activities as an alternative propulsion system to the internal combustion engine. In 1966, GM demonstrated the first driveable fuel cell vehicle. Since then, with continuous research and development and system optimization, various successful fuel cell systems have been demonstrated. GM has progressively made improvements with increases in power densities in both their fuel cell stacks and fuel cell processors, as well as a focus in understanding and developing systems. To aggressively drive fuel cell applications to commercialization, GM has partnered with a conglomerate of companies, each bringing its unique contribution to the commercialization plan. Maintaining several options and understanding both the near‐term and long‐term needs of the market, GM is pursuing hydrogen‐fueled and gasoline‐reformate‐fueled fuel cell systems in both the automotive and nonautomotive application markets.
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‐fuel cell module for an air independent propulsion system in a submarine
Authors: Strasser K.
Published: December 2010

Since the end of the 1960s the German Navy has been looking for an innovative, nonnuclear propulsion technology, which allows significant increase in the submerged mission duration of submarines and simultaneously low heat and low noise signature. One of the technologies that seems to be able to fulfill such requirements is the fuel cell. During the 1980s, by order of a German consortium of different industrial companies headed by the shipyard Howaldtswerke Deutsche Werft AG (HDW) an alkaline fuel cell power plant with a power output of 100 kW, based on a 6 kW FC module of the Siemens alkaline fuel cell technology, was installed on Submarine U1 of the German Navy and was tested by the Navy from August 1988 to March 1989, gathering knowledge and experience from successful tests of this new FC system. In parallel by order of the German Federal Ministry of Defence, Siemens had to develop a 30–50 kW fuel cell module, based on the polymer electrolyte membrane fuel cell (PEMFC) as a power source for an air independent submarine propulsion system. Started at the beginning of the 1980s, the development was finished in 1996. Two FC module prototypes had achieved all the requirements of the customer's specification regarding function, power output, shock, stray field, inclination, electromagnetic compatibility, noise, dimensions, weight and technical safety. By testing the dynamic and static load behavior, the outstanding properties of the FC modules were confirmed. The FC module is being used as part of the FC power plant of an air independent propulsion system on the new German Submarine Class 212 worldwide for the first time. Further developments aim to enlarge the FC module power and voltage (120–200 kW; 208–300 V) to decrease the cost. The PEMFC technology, now available at Siemens, has been further used to investigate different propulsion systems (electric buses; forklift trucks) and power supplies.
Space‐shuttle fuel cell
Authors: Wagner H. A.
Published: December 2010

The space shuttle uses three alkaline fuel cells to satisfy all electrical power requirements from pre‐launch to post‐landing. The space shuttle operates on all three fuel cells in parallel but can operate safely on two fuel cells if there is a problem with one of the fuel cells. The alkaline fuel recombines hydrogen and oxygen gases to form water and create electricity. The product water is provided to the astronauts for use as their drinking water. The current fuel cells operate for up to 2600 h before requiring an overhaul. The long life alkaline fuel cell is being developed to extend the useful life out to 5000 h between overhauls. A secondary goal is to demonstrate the ability to operate the space shuttle on a single fuel cell during entry and landing.
PEMFCfuel cell systems
Authors: Garche J. , Jörissen L.
Published: December 2010

The stationary applications of the proton exchange membrane (PEM) fuel cell are described. The applications are divided into the combined heat and power generation for household energy supply (<10 kWel) and larger units (50–250 kW) for district energy supply, secure energy supply, and premium power supply. However, this chapter focuses on residential applications. The technical aspects of the whole fuel cell system are discussed with emphasis on this application, with its subsystems as the gas processing or the heat and water management system, together with the best operating conditions of the fuel cell and the questions of economy and ecology. The developers of PEM fuel cell systems in North America, Europe, and Japan are stated and the competing technologies based on Carnot processes are also shown. Finally the market expectations for the residential PEM fuel cell systems are discussed.
MCFCfuel cell systems
Authors: Bischoff M. , Farooque M. , Satou S. , Torazza A.
Published: December 2010

Fuel cell systems are able to convert chemical energy directly into electrical energy and, therefore, they are in principle able to achieve much higher electrical efficiencies than conventional thermal systems. Fuel cells also have environmental advantages: they emit negligible amounts of NOx, SOxand particulates although the latter two reflect a need for fuel cells utilizing fuel gas which is nearly sulfur‐ and particulate‐free. The most important characteristic of MCFCs is that they are fed with fuel gas containing hydrogen and carbon monoxide. The obvious method is to supply this fuel gas through thermal reforming of natural gas or through gasification of coal. Therefore, the total MCFC energy conversion system is considerably more than just the stack itself.
SOFCfuel cell systems
Authors: Veyo S. E. , Fukuda S. , Shockling L. A. , Lundberg W. L.
Published: December 2010

Siemens Westinghouse Power Corporation is developing the tubular solid oxide fuel cell and has applied the solid oxide fuel cell (SOFC) in a successfully concluded proof‐of‐concept field test of a grid and district heating system connected atmospheric pressure 100 kWe power system that has operated for over 16 000 h without noticeable performance degradation. A 250 kWe power system of similar design will be introduced commercially in 2004. A hybrid power system consisting of a pressurized SOFC coupled hydraulically to a micro gas turbine has been constructed as a proof‐of‐concept experiment. Although testing has not yet been concluded, the hybrid system has operated showing promising performance. SOFC systems operate with characteristically high electrical efficiency—typically 50% (net a.c./LHV) can be approached with atmospheric pressure systems and 60% with simple pressurized SOFC/micro gas turbine hybrid cycle systems. More complex hybrid cycles are projected to approach 70% efficiency. Basics of the Siemens Westinghouse tubular SOFC technology are discussed and three cycle concepts are reviewed. The status of current and planned technology demonstration projects is also discussed and the results of several recent conceptual design studies that explore the potential of the SOFC for larger capacity power systems are summarized.