Thesis (Ph. D.)--Physics, Georgia Institute of Technology, 2008. / Committee Chair: James Gole; Committee Member: Ahmet Erbil; Committee Member: Alexei Marchenkov; Committee Member: Meilin Liu; Committee Member: Peter Hesketh.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 93-95). Also available in electronic version.

Thesis (M.S. in Engineering Acoustics)--Naval Postgraduate School, December 1990. / Thesis Advisor(s): Atchley, Anthony A. ; Hofler, Thomas J. "December 1990." Description based on title screen as viewed on March 31, 2010. DTIC Descriptor(s): Heat Transfer, Coupling (Interaction), Peak Values, Ratios, Temperature, Thermodynamics, Edges, Isolation, Sensitivity, Regions, Short Range (Time), Profiles, Plates, Internal, Acoustic Arrays, Pressure, Drives, Leading Edges, Mean, Amplitude, Sound Pressure, Stacking, Thermopiles. DTIC Identifier(s): Heat Pumps, Energy Conversion, Energy Storage, Heat Transfer, Thermoacoustic Couples, Theses Author(s) subject terms: Acoustics, Thermoacoustics, Thermoacoustic Heat Transport. Includes bibliographical references (p. 34). Also available in print.

Currently, renewable energy sources are the main driver for future electricity generation. This trend is growing faster in the developed countries in order to reduce the green house effect and also in response to the limited supply of oil, gas and coal which are currently the major sources for electric generation. For example, the main renewable energy sources are from wind energy and solar energy but these energies are only available to those countries that are exposed to these resources. In this thesis an alternative energy source is investigated where it can be generated from the moving objects or in form of kinetic energy. The idea is to convert the kinetic energy during landing aircraft into electrical energy which it can also be stored and transferred to the existing electrical network. To convert this kinetic energy to electrical energy, the linear generator (LG) and uncontrolled rectifier have been used for energy conversion. The LG have been modelled in 3-phase model or in dq model and combined with the diode rectifier that is used to generate the dc signal outputs. Due to the uncontrolled rectifier the electrical outputs will have decaying amplitude along the landing time. This condition also happen to the LG outputs such as the force and the power output. In order to control these outputs the cascaded buck-boost converter has been used. This converter is responsible to control the output current at the rectifier and also the LG output power during landing to more controllable power output. Here, the H∞ current control strategy has been used as it offers a very good performance for current tracking and to increase the robustness of the controller. During landing, huge power is produced at the beginning and when the landing time is increased, the generated input power from LG is reduced to zero. Due to this, the energy storage that consists of ultracapacitor, bidirectional converter and boost converter are used in order to store and to release the energy depends on the input power source and load grid power. The voltage proportional-integral (PI) control strategy has been used for both the converters. The last part is to transfer the energy from the source and at the ultracapacitor to the load by using the inverter as the processing device. The power controller and current controller are used at the inverter in order to control the power ?ow between the inverter and the grid. This is when the reference power is determined by the load power in order to generate the reference currents by using the voltage oriented controller (VOC), while the H∞ current controller is used to regulate the inverter currents in order to inject the suitable amount of current that refer to the load power. Finally, a complete energy recovery system for landing aircraft with the grid connection have been put together to make the whole system to be as a new renewable energy source for the future electricity generation.

Nos travaux s’inscrivent dans le contexte global de la transition énergétique et de l’émergence des micro-réseaux, et de leur capacité, à terme, d’intégrer la production distribuée d’énergie tout en assurant la stabilité et la qualité du service. Parmi les technologies émergentes, les procédés Power-To-Gaz et en particulier le Power-to-Methane que nous étudions ici (production de CH4 à partir de l’électricité, en passant par H2 et CO2) ont l’avantage : d’absorber le surplus de production électrique, de récupérer et valoriser les émissions de CO2, et d’offrir des capacités de stockage importantes et de longue durée.Notre problématique porte sur la modélisation et la simulation d’un système PtM avec comme objectif d’assurer la continuité d’alimentation en CH4, ainsi que la sécurité du système en fonctionnement.Dans un premier temps nous effectuons le choix de technologies adaptées afin de déterminer la structure d’un système PtM avant de dimensionner ce système. Nous nous appuyons sur la modélisation REM (Représentation Energétique Macroscopique) pour intégrer les comportements physiques des équipements du système en régime stationnaire, mais également en régime transitoire, en prenant en compte des phases comme : le démarrage, le préchauffage…, et ainsi simuler le fonctionnement de ce système.Dans un second temps, nous développons une stratégie de gestion d’énergie multiniveaux afin de garantir le bon fonctionnement des équipements et du système dans sa globalité. Nous choisissons de la mettre en œuvre à travers la proposition d’un système multi-agents (SMA) et nous modélisons chacun des agents. Nous implémentons partiellement ce SMA et nous le simulons en connexion avec le modèle REM du système PtM pour montrer la faisabilité de notre approche. / Our work is concerned with energy transition and the emergence of micro-grids and their ability to integrate distributed power generation while at the same time ensure stability and service quality. Among the emerging technologies, the Power to Gas process and in particular the Power to Methane process which we are addressing here (production of CH4 from electricity, via H2 and CO2), have the advantage of absorbing surplus of electricity production, recovering CO2 emissions, as well as offering significant and long-term storage capacity.Our concern was in relation to the modeling and simulation of a PtM system with the objective of ensuring the continuity of CH4 supply and ensuring the safety of the system in operation.First, we chose the appropriate technologies to determine the structure of a PtM system before sizing this system. We utilised the REM modeling (Energetic Macroscopic Representation) to integrate the physical behaviors of the equipment of the system in a steady state, and in a transient state, taking into account phases like starting, preheating…, and ultimately the simulation of the operation system.In the second phase, we developed a multilevel energy management strategy to ensure the proper working order of each piece of equipment and of the global system. We chose to implement it through a multi-agent system (MAS) and we modeled each one of the agents. We partially implemented the MAS and simulated it with the REM model of the PtM system to show the feasibility of our approach.

A reversible solid oxide fuel cell (RSOFC) system could buffer intermittent electrical generation, e.g. wind, wave power by storing electrical energy as hydrogen and heat. RSOFC were fabricated by thermoplastic extrusion of (La₀.₈Sr₀.₂)₀.₉₅MnO[subscript(3−δ)] (LSM) ceramic support tubes, which were microstructurally stable with 55% porosity at 1350°C. A composite oxygen electrode of LSM-YSZ was applied, providing a homogeneous substrate for a 20 μm - 30 μm thick YSZ electrolyte. A dip-coated 8YSZ slurry, and a painted commercial 3YSZ ink gave sintered densities of 90% and nearly 100% at 1350°C, respectively. A porous NiO/YSZ fuel electrode was also painted on. A Ag/Cu reactive air braze was unsuccessful at forming a void-free joint between the RSOFC and a 316 stainless steel gas delivery tube, as the braze did not penetrate the oxidation layer on the steel. Two alumina-based ceramic cements failed to fully seal the cell to an alumina gas delivery tube, due to thermal expansion coefficient mismatches and porosity after curing. Therefore, the maximum open circuit voltage (OCV) obtained during RSOFC testing was 0.8 V at 440°C. LSM-YSZ symmetrical cell performance measurements with oxygen pressure showed a diffusion polarisation, which was assigned to dissociative adsorption and surface diffusion of oxygen species. A collaborative RSOFC system software model showed ohmic and activation losses dominated the RSOFC, and diffusion losses were insignificant. Pressurisation from 1 to 70 bar increased the RSOFC Nernst voltage by 11% at 900°C, and reduced the entropy of the gases, reducing heat production and increasing electrical efficiency. A 500 kg Sn/Cu phase change heat store prevented the system overheating. Over a 16 h discharge-charge RSOFC cycle in the range 5 mol.% - 95 mol.% hydrogen in steam, at 20.4 A per cell or 3250 A m⁻², the electrical energy storage efficiency was 64.4%.