Demands for zero greenhouse-gas emission vehicles have sharpened with today’s increased focus on global warming. Hydrogen storage is a key technology for the implementation of hydrogen powered vehicles. Metal hydrides can claim higher energy densities than alternative hydrogen storage materials, but a remaining challenge is to find a metal hydride which satisfies all current demands on practical usability. Several metals store large amounts of hydrogen by forming a metal hydride, e.g., Mg, Ti and Al. The main problems are the weight of the material and the reaction energy between the metal and hydrogen. Magnesium has a high storage capacity (7.6 wt.% hydrogen) in forming MgH2; this is a slow reaction, but can be accelerated either by minimizing the diffusion length within the hydride or by changing the diffusion properties. Light-metal hydrides have been studied in this thesis with the goal of finding new hydrogen storage compounds and of gaining a better understanding of the parameters which determine their storage properties. Various magnesium-containing compounds have been investigated. These systems represent different ways to address the problems which arise in exploiting magnesium based materials. The compounds were synthesized in sealed tantalum tubes, and investigated by in situ synchrotron radiation X-ray powder diffraction, neutron powder diffraction, isothermal measurements, thermal desorption spectroscopy and electron microscopy. It is demonstrated that hydrogen storage properties can be improved by alloying magnesium with yttrium or scandium. Mg-Y-compounds decompose in hydrogen to form MgH2 nano-structures. Hydrogen desorption kinetics are improved compared to pure MgH2. The influence of adding a third element, gallium or zinc has also been studied; it is shown that gallium improves hydrogen desorption from YH2. ScAl1-xMgx is presented here for the first time as a hydrogen storage material. It absorbs hydrogen by forming ScH2 and Al(Mg) in a fully reversible reaction. It is shown that the hydrogen desorption temperature of ScH2 is reduced by more than 400 °C by alloying with aluminium and magnesium.

Key dynamic processes at nano-scale, such as graphene hydrogenation and fluorination, and carbon nanotube (CNT) growth, cannot be observed in situ in real time. Nevertheless, such processes can be studied through complementary computational methods. This work simulates three important catalytic processes representing the growth of graphitic structures and functionalized graphene. The spillover phenomenon, which has been considered promising for efficient hydrogen storage, includes transfer of H from a metal catalyst to a graphitic receptor, to finally form a graphane island. Although, the spillover is energetically unfavorable to occur on pristine graphene, catalyst saturation provides a way for hydrogen adsorption on the receptor. Ab initio calculations show that the H chemical potential can be increased to a spillover favorable range. Unlike in graphane, upon graphene fluorination different stoichiometric phases form without a nucleation barrier, with the complete CF phase being thermodynamically most stable. After fluorination, graphene electronic properties are transformed from metallic to semiconducting. First-principles and tight-binding methods are used to investigate the patterning of nanoroads and quantum dots on these phases, combining metallic and semiconducting properties on the same sheet. In catalyzed CNT growth the metallic catalyst plays a fundamental role in cap nucleation. Such a mechanism cannot be seen in experiment, nor can it be simulated by first-principles due to its time-scale, yet it can be simulated through molecular dynamics. Tuning the metal-C interaction controls the condition for growth or encapsulation: Surface carbon-diffusion limits the growth below 600 K, and at higher temperatures they depend on cap lift-off. Such tuning can be done through catalyst alloying, as shown through ab initio simulations for Ni-Fe and Cu-Fe bimetallic catalysts. Catalyst shape also plays an important role in CNT growth. The minimization of the Ni surface energy defines the equilibrium crystal shape. Catalyst reshaping is analyzed through C adsorption by first-principles and reactive force fields. The Wulff-construction suggests a significant reduction of the surface energy anisotropy upon C adsorption, based on which a continuum phenomenological model that considers catalyst reshaping in CNT nucleation is formulated. This thesis explains the growth of graphitic structures and functionalized graphene at nano-scale through computational simulations.

Energy storage technology is needed for the storage of surplus baseload generation and the storage of intermittent wind power, because it can increase the flexibility of power grid operations. Underground storage of hydrogen with natural gas (UHNG) is proposed as a new energy storage technology, to be considered for utility-scale energy storage applications. UHNG is a composite technology: using electrolyzers to convert electrical energy to chemical energy in the form of hydrogen. The latter is then injected along with natural gas into existing gas distribution and storage facilities. The energy stored as hydrogen is recovered as needed; as hydrogen for industrial and transportation applications, as electricity to serve power demand, or as hydrogen-enriched natural gas to serve gas demand. The storage of electrical energy in gaseous form is also termed “Power to Gas”. Such large scale electrical energy storage is desirable to baseload generators operators, renewable energy-based generator operators, independent system operators, and natural gas distribution utilities. Due to the low density of hydrogen, the hydrogen-natural gas mixture thus formed has lower volumetric energy content than conventional natural gas. But, compared to the combustion of conventional natural gas, to provide the same amount of energy, the hydrogen-enriched mixture emits less carbon dioxide. This thesis investigates the dynamic behaviour, financial and environmental performance of UHNG through scenario-based simulation. A proposed energy hub embodying the UHNG principle, located in Southwestern Ontario, is modeled in the MATLAB/Simulink environment. Then, the performance of UHNG for four different scenarios are assessed: injection of hydrogen for long term energy storage, surplus baseload generation load shifting, wind power integration and supplying large hydrogen demand. For each scenario, the configuration of the energy hub, its scale of operation and operating strategy are selected to match the application involved. All four scenarios are compared to the base case scenario, which simulates the operations of a conventional underground gas storage facility. For all scenarios in which hydrogen production and storage is not prioritized, the concentration of hydrogen in the storage reservoir is shown to remain lower than 7% for the first three years of operation. The simulation results also suggest that, of the five scenarios, hydrogen injection followed by recovery of hydrogen-enriched natural gas is the most likely energy recovery pathway in the near future. For this particular scenario, it was also found that it is not profitable to sell the hydrogen-enriched natural gas at the same price as regular natural gas. For the range of scenarios evaluated, a list of benchmark parameters has been established for the UHNG technology. With a roundtrip efficiency of 39%, rated capacity ranging from 25,000 MWh to 582,000 MWh and rated power from 1 to 100 MW, UHNG is an energy storage technology suitable for large storage capacity, low to medium power rating storage applications.

Remote communities, characterized by no connection to the main power grid, traditionally get their power from diesel generators. Long geographical distances and lack of suitable roads make the fuel transportation difficult and costly, increasing the final cost of electricity. A microgrid using renewable energy as the main source can serve as a viable solution for this problem with considerable economical and environmental benefits. The focus of this research is to develop a microgrid for a remote community in northern Ontario (Canada) that combines wind, as a renewable source of energy, and a hydrogen-based energy storage system, with the goal of meeting the demand, while minimizing the cost of energy and adverse effect on the environment. The existing diesel generators remain in the system, but their use is minimized. The microgrid system studied in this research uses a wind turbine to generate electricity, an electrolyser to absorb the excess power from the wind source, a hydrogen tank to store the hydrogen generated by the electrolyser, a fuel cell to supply the demand when the wind resource is not adequate, and a diesel generator as a backup power. Two scenarios for unit-sizing are defined and their pros. and cons. are discussed. The economic evaluation of scenarios is performed and a cost function for the system is defined. The optimization problem thus formulated is solved by solvers in GAMS. The inputs are wind profile of the area, load profile of the community, existing sources of energy in the area, operating voltage of the grid, and sale price of electricity in the area. The outputs are the size of the fuel cell and electrolyser units that should be used in the microgrid, the capital and running costs of each system, the payback period of the system, and cost of generated electricity. Following this, the best option for the microgrid structure and component sizes for the target community is determined. Finally, a MATLAB-based dynamic simulation platform for the system under study with similar load/wind profile and sizing obtained in optimization problem is developed and the dynamic behaviour of microgrid at different cases is studied.

A study was carried out on the selection of processing condition that would yield Mg-Ti with most favourable hydrogenation properties. Processing routes under consideration were / mechanical milling under inert atmosphere, reactive milling i.e. milling under hydrogen atmosphere, ECAP (equal channel angular pressing) and thermal plasma synthesis. Structure resulting from each of these processing routes was characterized with respect to size reduction, coherently diffracting volume and the distribution of Ti catalyst. Mechanical milling yielded a particulate structure made up of large Mg agglomerates with embedded Ti fragments with a uniform distribution. Mg agglomerates have sizes larger than 100 &micro / m which arises as a result of a balance between cold welding process and ductile fracture. Repeated folding of Mg particles entraps Ti fragments inside the Mg agglomerates resulting in a very uniform distribution. Coherently diffracting volumes measured by X-ray Rietveld analysis have small sizes ca. 26 nm which implies that the agglomerates typically comprise 1011 crystallites. Mechanical milling under hydrogen, i.e. reactive milling, led to drastic reduction in particle size. Mg and Ti convert to MgH2 and TiH2 which are milled efficiently due to their brittleness resulting in particle sizes of sub-micron range. Hydrogenation experiments carried out on Mg-10 vol % Ti milled under argon yields enthalpy and entropy values of -76.74 kJ/mol-H2 and -138.64 J/K.mol-H2 for absorption and 66.54 kJ/mol H2 and 120.12 J/K.mol H2 for desorption, respectively. For 1 bar of hydrogen pressure, this corresponds to a hydrogen release temperature of 280 &deg / C. This value is not far off the lowest desorption temperature reported for powder processed Mg based alloys. ECAP processing is a bulk process where the powders, consolidated in the first pass, have limited contact with atmosphere. This process which can be repeated many times lead to structural evolution similar to that of milling, but for efficient mixing of phases it was necessary to employ multi-pass deformation. An advantage of ECAP deformation is strain hardening of the consolidated powders which has improved milling ability. Based on this, a new route was proposed for the processing of ductile hydrogen storage alloys. This involves several passes of ECAP deformation carried out in open atmosphere and a final milling operation of short duration under inert atmosphere. The plasma processing yields Mg particles of extremely small size. Evaporation of Mg-Ti powder mixture and the subsequent condensation process yield Mg particles which are less than 100 nm. Ti particles, under the current experimental condition used, have irregular size distribution but some could be quite small, i.e. in the order of a few tens of nanometers. Of the four processing routes, it was concluded that both reactive milling and thermal plasma processing are well suited for the production of hydrogen storage alloys. Reactive milling yield particles in submicron range and plasma processing seems to be capable of yielding nanosize Mg particles which, potentially, could be decorated with even smaller Ti particles.

Die vorliegende Promotion beinhaltet die Untersuchung von irregulären Kohlenstoff-Nanostrukturen, die mittels Hochenergie-Kugelmahlen hergestellt wurden. Die wissenschaftliche Herausforderung besteht darin, die strukturelle Vielfalt dieser Nanostrukturen experimentell zu erfassen, zu klassifizieren und bezüglich ausgewählter Eigenschaften zu bewerten, sowie mit den Herstellungsparametern in Zusammenhang zu bringen. Die Pulver konnten nach den Mahlungen hinsichtlich ihrer Struktur in zwei grundsätzliche Typen eingeteilt werden: (I) ein Nanopulver, das aus graphitischen Stapelpaketen besteht, welche in eine amorphe Matrix eingebettet sind, (II) ein vollständig amorphisiertes Pulver. Die Strukturanalyse in Bezug auf die Mahlbedingungen (Mahlatmosphäre, Mahltemperatur) zeigt, dass die Dauer der Nanostrukturierung sowie die Anzahl und Größe von graphitischen Stapelpaketen gezielt beeinflusst werden kann. Außerdem konnten Hinweise gefunden werden, die darauf hindeuten, dass Mahlen bei tiefen Temperaturen oder unter Wasserstoffatmosphäre die Agglomeration der Nanopartikel verringern kann. Das Kugelmahlen ermöglicht es ebenfalls, die spezifische Oberfläche des Graphitpulvers von 5,5 m2/g auf 725 m2/g innerhalb von fünf Mahlstunden zu erhöhen. Der Anteil der Verunreinigungen (Fe) liegt dabei nicht höher als 0,05 wt%. Es ist jedoch zu beachten, dass sämtliche Eigenschaften stark von den verschiedenen Mahlparametern (Mahltemperatur, Mahlmaterial) abhängen. Die für Adsorptionsuntersuchungen optimalen Eigenschaften (große spezifische Oberfläche, erhöhte Reaktivität, geringe Verunreinigungen) werden schon nach kurzer Mahldauer erreicht. Wiederholungsmahlungen und Wiederholungsmessungen verschiedener Eigenschaften (spezifische Oberfläche, Verbrennungstemperatur) machen deutlich, dass die Ergebnisse reproduzierbar sind, und dass keine Alterungserscheinungen während der Lagerung unter Argonatmosphäre im Zeitraum von einem Jahr auftreten. Die Wasserstoffspeicherung an nanostrukturierten Kohlenstoffpulvern konnte nachgewiesen werden. Die maximalen Speicherkapazitäten für Temperaturen nahe 77 K lagen bei 1,5 wt%. Für niedrigere Temperaturen Tist = 35 K zeigten sich höhere Speicherkapazitäten von bis zu 5 wt%. Die Korrelation der ermittelten Speicherkapazitäten mit den theoretisch erreichbaren Werten in Bezug auf die Oberfläche der Proben zeigt, dass im Experiment deutlich höhere Werte erhalten werden. Dies lässt den Schluss zu, dass neben der Speicherung an der Oberfläche der Pulver ein weiterer Speichermechanismus innerhalb der Mikroporen der Proben stattfindet.

The modular nature of metal−organic materials allows for tuning their properties to meet a specific application through careful design of the molecular precursors, i.e. information encoding at the molecular level. Research in this area is highly interdisciplinary where synthetic organic chemistry, in silico modeling, and various analytical techniques merge together to afford better understanding of the basic science involved and eventually to result in enhanced control over the properties of targeted materials.

We investigated thin film samples of Mg2NiH4 with two intentions. First of all, we wanted to ascertain if the same nanomaterial (Mg2NiH4) prepared by magnetron sputtering and ball milling can exhibit different hydrogen storage properties and to see possible advantages/disadvantages of employing of magnetron sputtering for synthesis of nanometerials for hydrogenstorage. Furthermore, we wanted to see if thin film samples of Mg2NiH4 could be used in a switchable mirror or window device by utilizing the high to low temperature transition at about 510 K. In powder samples, this transition, between a monoclinic conducting low temperature phase to an FCC non-conducting high temperature phase, have been demonstrated in a mechanical reversible conductor–insulator transition [Blomqvist and Nor��us, J. Appl. Phys 91(2002)5141]. The new thin film Mg2NiH4 samples were produced by reacting hydrogen with magnetron sputtered Mg2Ni films on quartz glass or CaF2 substrates. But we could not obtain the monoclinic low temperature phase upon cooling the samples. Instead a cubic phase, related but not identical to the cubic high temperature phase, was formed at temperatures both below and above 510 K. TEM pictures revealed the new cubic phase in the films to have the same cell parameter as the FCC high temperature phase. But the symmetry was lower with similar streaking patterns as observed for the monoclinic low temperature phase. IR-spectroscopy indicated an identical vibrational frequency for... [to full text] / Tiriamojo darbo metu magnetroniniu garinimu suformuotos Mg-Ni dangos, kurios hidrintos esant aukštai temperatūrai ir vandenilio slėgiui. Hidrintos dangos ištirtos įvairiais analizės metodais, siekiant nustatyti magnetronio garinimo būdu suformuotos medžiagos (magnio nikelio hidrido) skirtumus nuo rutulinio trynimo metodu gautos analogiškos medžiagos. Darbe išanalizuoti duomenys ir pateiktas aiškinamasis modelis, kuris atskleidžia plonų dangų ypatybes, dėl kurių dangose pilnai neįvyksta dangos relaksacijos procesai. Nustatyta, kad dėl tų pačių priežasčių, dangų panaudojimo „įjungiamiesiems veidrodžiams“ galimybės yra ribotos.

Energy storage technology is needed for the storage of surplus baseload generation and the storage of intermittent wind power, because it can increase the flexibility of power grid operations. Underground storage of hydrogen with natural gas (UHNG) is proposed as a new energy storage technology, to be considered for utility-scale energy storage applications. UHNG is a composite technology: using electrolyzers to convert electrical energy to chemical energy in the form of hydrogen. The latter is then injected along with natural gas into existing gas distribution and storage facilities. The energy stored as hydrogen is recovered as needed; as hydrogen for industrial and transportation applications, as electricity to serve power demand, or as hydrogen-enriched natural gas to serve gas demand. The storage of electrical energy in gaseous form is also termed “Power to Gas”. Such large scale electrical energy storage is desirable to baseload generators operators, renewable energy-based generator operators, independent system operators, and natural gas distribution utilities. Due to the low density of hydrogen, the hydrogen-natural gas mixture thus formed has lower volumetric energy content than conventional natural gas. But, compared to the combustion of conventional natural gas, to provide the same amount of energy, the hydrogen-enriched mixture emits less carbon dioxide. This thesis investigates the dynamic behaviour, financial and environmental performance of UHNG through scenario-based simulation. A proposed energy hub embodying the UHNG principle, located in Southwestern Ontario, is modeled in the MATLAB/Simulink environment. Then, the performance of UHNG for four different scenarios are assessed: injection of hydrogen for long term energy storage, surplus baseload generation load shifting, wind power integration and supplying large hydrogen demand. For each scenario, the configuration of the energy hub, its scale of operation and operating strategy are selected to match the application involved. All four scenarios are compared to the base case scenario, which simulates the operations of a conventional underground gas storage facility. For all scenarios in which hydrogen production and storage is not prioritized, the concentration of hydrogen in the storage reservoir is shown to remain lower than 7% for the first three years of operation. The simulation results also suggest that, of the five scenarios, hydrogen injection followed by recovery of hydrogen-enriched natural gas is the most likely energy recovery pathway in the near future. For this particular scenario, it was also found that it is not profitable to sell the hydrogen-enriched natural gas at the same price as regular natural gas. For the range of scenarios evaluated, a list of benchmark parameters has been established for the UHNG technology. With a roundtrip efficiency of 39%, rated capacity ranging from 25,000 MWh to 582,000 MWh and rated power from 1 to 100 MW, UHNG is an energy storage technology suitable for large storage capacity, low to medium power rating storage applications.

In the current context of rapidly depleting petroleum resources and growing environmental concerns, it is important to develop materials to harvest and store energy from renewable and sustainable sources. Hydrogen has the potential to be an alternative energy source, since it has higher energy content than petroleum. However, since hydrogen has very low volumetric energy density, hence it is important to design nano porous materials which can efficiently store large volumes of hydrogen gas by adsorption. In this regard carbon nanotube and Metal Organic Framework (MOFs) based materials are worth studying. Ionic liquids (IL) are potential electrolytes that can improve energy storage capacity and safety in Li ion batteries. Therefore it is important to understand IL's thermodynamic and transport properties, especially when it is in contact with electrode surface and mixed with Li salt, as happens in the battery application. This dissertation presents computation and simulation based studies on: 1. Hydrogen storage in carbon nanotube scaffold. 2. Mechanical property and stability of various nanoporous Metal Organic Frameworks. 3. Thermodynamic and transport properties of [BMIM][BF4] ionic liquid in bulk, in Li Salt mixture, on graphite surface and under nanoconfinement. In the first study, we report the effects of carbon nanotube diameter, tube chirality, tube spacer distance, tube functionalization and presence of Li on hydrogen sorption capacity and thermodynamics at different temperature and pressure. In the second one, we observe high pressure induced structural transformation of 6 isoreticular MOFs: IRMOF-1. IRMOF-3, IRMOF-6, IRMOF-8, IRMOF-10 and IRMOF-14, explore the deformation mechanism and effect of Hydrogen inside crystal lattice. In the third study, we observe the equilibrium thermodynamic and transport properties of [BMIM][BF4] ionic liquid. The temperature dependence of ion diffusion, conductivity, dielectric constant, dipole relaxation time and viscosity have been observed and found similar behavior to those of supercooled liquid. The ion diffusion on graphite surfaces and under nanoconfinement was found to be higher compared to those in bulk.