Metal membranes play a vital role in hydrogen purification. Defect-free membranes can exhibit effectively infinite selectivity for hydrogen. Membranes must meet multiple objectives, including providing high fluxes, resistance to poisoning, long operational standards, and be cost effective. Alloys offer an alternate route in improving upon membranes based on pure metal such as Pd. Development of new membranes is hampered by the large effort and time required not only to experimentally develop these membranes but also to properly test these materials. We show how first principle calculations combined with coarse-grained modeling can accurately predict H2 fluxes through binary and ternary alloy membranes as a function of alloy composition, temperature and hydrogen pressures. Our methods require no experimental input apart from the knowledge of the bulk crystal structure. Our approach is demonstrated for pure Pd, Pd-rich binary alloys, PdCu binary alloys, and PdCu-based ternary alloys. PdCu alloys have experimentally shown to have potential for resistance to sulfur poisoning. First, we used plane wave Density Functional Theory to study the binding and local motion of hydrogen for the alloys of interest. This data was used in combination with a Cluster Expansion Method along with the Leave-One-Out analysis to generate comprehensive models to predict hydrogen behavior in the interstitial binding sites within the bulk of the alloys of interest. These models not only were required to correctly fit our calculated data, but they were also required to properly predict behaviors for local conditions for which we had not collected information. These models were then used to predict hydrogen solubility and diffusivity at elevated temperatures. Although we are capable of combining first principle theory calculations with coarse grain modeling, we have explored a pre-screening method in order to determine which a particular material are worth performing additional calculations. Our heuristic lattice model is a simplified model involving as few factors as possible. It is by no means intended to predict the exact macroscopic H properties in the bulk of fcc materials, but it is intended as a guide in determining which materials merit additional characterization.

Hydrogen fuel is seen as energy of the future. Hydrogen molecules (H₂) are mostly used in the petrochemical industry and ammonia production. Hydrogen molecules are produced in large majority by steam reforming of hydrocarbons (methane). However, the purification of hydrogen is still a major factor in the cost of producing hydrogen. The range of membranes is large with advantages and drawbacks of each type of membrane. Among those membranes, metal alloy membranes are widely used because of their selectivity, durability, and resistance to poisoning. In the past, it was assumed an alloy once formed would remain in its initial structure while hydrogen gas was permeating through. It has been shown experimentally that the presence of hydrogen in palladium gold metal alloys will change the structure of the alloy from a disordered to an ordered phase. Hydrogen isotherms at different temperatures were used to demonstrate the change in structure. This structural change resulted in an increase in solubility of hydrogen in the membrane. In this work, using NVT-Monte Carlo we calculated the effect of hydrogen on the structure and on the solubility of Pd₉₆Au₄ and Pd₈₅Au₁₅ alloys. The palladium gold alloy was used because it demonstrated high resistance to sulfur poisoning and similar or higher permeability seen in to pure Pd. The methods used do not require any experimental input except for the structure of the bulk crystal. The interstitial binding energies were calculated using a Cluster Expansion model derived previously by Semidey and Kang from plane wave Density Functional Theory. The metal atoms enthalpies of formation were calculated from a truncated version of the Cluster Expansion derived by Sluiter for fcc metal structures. We conclude that hydrogen presence in the metal membrane will change the membrane from a disordered to a Short Range Ordered structure.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2009. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed December 15, 2009) Includes bibliographical references (p. 72-80).

M. Tech. Electrical Engineering. / Hydrogen is in the middle of many discussions as being a good alternative to petrol for the struggle against pollution and global warming. The fact that hydrogen can be found in infinite quantities such as in water or in space makes it a renewable energy. It is the object of much research works in order to be used in replacement of fossil energy such as in hybrid vehicles. However, the main shed of hydrogen is the difficulties to store it. Indeed, being the first element of the periodic table, it is the lightest, spreads a lot and can burn easily. The aim of this project is to achieve the wiring diagram of an electrical bicycle. The use of a hydrogen fuel cell allows feeding the electrical motor of the vehicle. However, due to a matter of low response time of the fuel cell, lithium-ion batteries are also used. Indeed, at the start state for instance, the fuel cell needs some time to warm and reach the nominal temperature of functioning. Lithium-ion batteries allow feeding the electrical motor during the warm up time but also to respond to peak of load. Hybrid motorization represents the future of car industry and tends to be used as a replacement of petrol engine partly responsible of greenhouse gases emissions. Some of those vehicles are already put in place in some big cities all over the world and allow moving rapidly without polluting. This project concerns a hybrid system for an electrical bicycle but the idea is to extend to bigger kind of vehicles.

In order for metal hydride hydrogen storage systems to compete with existing energy storage technology, such as gasoline tanks and batteries, it is important to have fast reaction rates, especially quick refill times. Improving the hydriding rate involves enhancing the heat transfer within the reaction bed. To complement experimental investigations, a two-dimensional transient model has been developed to describe the heat and mass transfer phenomena within a metal hydride bed. The metal hydride model is thermally coupled to a fuel cell through heat transfer relations and utilized to compare different heat transfer enhancements and storage tank configurations. Three cases are simulated: a base case with no heat transfer enhancements, a case with fins attached to the outside of the tank, and a case with an annular tank design. The results demonstrate that the annular metal hydride tank meets the requirements of the fuel cell while providing a robust and compact hydrogen storage system.

In this thesis, we use first-principles calculations to study the structural, electronic, and thermal properties of several complex hydrides. We investigate structural and electronic properties of Na-Li alanates. Although Na alanate can reversibly store H with Ti catalyst, its weight capacity needs to be improved. This can be accomplished by partial replacement of Na with lighter elements. We explore the structures of possible Na-Li alloy alanates, and study their phase stability. We also study the structural and thermal properties of Li/Mg/Li-Mg Amides/Imides. Current experimental results give a disordered model about the structure of Li-Mg Imide, in which the positions of Li and Mg are not specified. In addition the model gives a controversial composition stoichiometry. We try to resolve this controversy by searching for low-energy ordered phases. In the last part, we study the structural, energetic, and electronic properties of the La-Mg-Pd-H system. This quaternary system is another example of hydrogenation-induced metal-nonmetal transition without major reconstruction of metal host structure, and it is also with partial reversible H capacity. Experiment gives partially disordered H occupancy on two Wyckoff positions. Our calculation explains the structural and bonding characteristics observed in experiment.

A novel batch reactor concept is proposed for the catalytic production of hydrogen in distributed and portable applications. In the proposed CHAMP (CO2/H2 Active Membrane Piston) reactor, a batch of hydrocarbon or synthetic fuel is held in the reaction chamber where it reacts to produce hydrogen with simultaneous removal of the hydrogen by permeation through an integrated, selective membrane. These processes proceed to the desired level of completion at which point the reaction chamber is exhausted and a fresh batch of fuel mixture brought in. Unique to the CHAMP reactor is the ability to precisely control the residence time, as well as the ability to compress the reaction chamber dynamically, or mid-cycle, in order to increase the instantaneous hydrogen yield rate. An idealized reactor model demonstrates that the ideal limits of performance (in the absence of transport limitations) exceed those of comparable continuous flow designs. A comprehensive, coupled, transport-kinetics model is used to quantify the effects of mass transport limitations on reactor performance and search the design parameter space for optimal points. Two modes of operation are studied: fixed-volume mode wherein the piston is stationary and constant-pressure mode in which the rate of compression matches the permeation of hydrogen through the membrane. Finally, to validate these numerical models and confirm our understanding of the key operating principles, prototype reactors were built and experimentally characterized.

Hydrogen Assisted Jet Ignition (HAJI) is an advanced ignition process that allows ignition of ultra-lean mixtures in an otherwise standard gasoline fuelled spark ignition engine. Under typical operating conditions, a small amount of H2 (~ 2 % ofthe main fuel energy or roughly the equivalent of 1 g/km of H2) is injected just before ignition in the region of the spark plug. By locating the spark plug in a small prechamber (less than 1 % of the clearance volume) and by employing a H2 rich mixture, the content of the prechamber is plentiful in the active species that form radicals H and OH on decomposition and has a relatively high energy level compared to the lean main chamber contents. Thus, the vigorous jets of chemically active combustion products that issue through orifices, which connect to the main chamber, burn the main charge rapidly and with almost no combustion variability (less than 2% coefficient of variation in IMEP even at λ = 2.5). / The benefits from the low temperature combustion at λ = 2 and leaner are that almost zero NOx is formed and there is an improvement in thermal efficiency. Efficiency improvements are a result of the elimination of dissociation, such as CO2 to CO, which normally occurs at high temperatures, together with reduced throttling losses to maintain the same road power. It is even possible to run the engine in an entirely unthrottled mode, but at λ = 5. / Although only a small amount of H2 is required for the HAJI process, it is difficult to both refuel H2 and store it onboard. In order to overcome these obstacles, the viability of a variety of more convenient fuels was experimentally assessed based on criteria such as combustion stability, lean limit and emission levels. The prechamber fuels tested were liquefied petroleum gas (LPG), natural gas, reformed gasoline and carbon monoxide. Additionally, LPG was employed as the main fuel in conjunction with H2 or LPG in the prechamber. Furthermore, the effects of HAJI operation under sufficient exhaust gas recirculation to allow stoichiometric fuel-air supply, thus permitting three-way catalyst application were also examined. / In addition to experiments, prechamber and main chamber flame propagation modeling was completed to examine the effects of each prechamber fuel on the ignition of the main fuel, which consisted of either LPG or gasoline. The modeling and experimental results offered similar trends, with the modeling results giving insight into the physiochemical process by which main fuel combustion is initiated in the HAJI process. / Both the modeling and experimental results indicate that the level of ignition enhancement provided by HAJI is highly dependent on the generation of chemical species and not solely on the energy content of the prechamber fuel. Although H2 was found to be the most effective fuel, in a study of a very light load condition (70 kPa MAP) especially when running in the ultra-lean region, the alternative fuels were effective at running between λ = 2-2.5 with almost zero NOx formation. These lean limits are about twice the value possible with spark ignition (λ = 1.25) in this engine at similar load conditions. In addition, the LPG results are very encouraging as they offer the possibility of a HAJI like system where a commercially available fuel is used as both the main and prechamber fuel, while providing thermal efficiency improvements over stoichiometric operation and meeting current NOx emission standards.

Thesis (M.S.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references (leaves 84-87).

Thesis (M.S.)--Missouri University of Science and Technology, 2009. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed January 22, 2009) Includes bibliographical references (p. 53-55).