Power systems on modern commercial transportation systems are moving to more electric based equipment, thus improving the reliability of the overall system. Electrical equipment on such systems will include some loads that require very high power for short periods of time, on the order of a few seconds, especially during acceleration and deceleration. The current approach to solving this problem is sizing the electrical grid for peak power, rather than the average. A method to efficiently store and discharge the pulsed power is necessary to eliminate the cost and weight of oversized generation equipment to support the pulsed power needs of these applications. Highspeed Flywheel Energy Storage Systems (FESS) are effectively capable of filling the niche of short duration, high cycle life applications where batteries and ultra capacitors are not usable. In order to have an efficient high-speed FESS, performing three important steps towards the design of the overall system are extremely vital. These steps are modeling, analysis and control of the FESS that are thoroughly investigated in this dissertation. This dissertation establishes a comprehensive analysis of a high-speed FESS in steady state and transient operations. To do so, an accurate model for the complete FESS is derived. State space averaging approach is used to develop DC and small-signal AC models of the system. These models effectively simplify analysis of the FESS and give a strong physical intuition to the complete system. In addition, they result in saving time and money by avoiding time consuming simulations performed by expensive packages, such as Simulink, PSIM, etc. In the next step, two important factors affecting operation of the Permanent Magnet Synchronous Machine (PMSM) implemented in the high-speed FESS are investigated in detail and outline a proper control strategy to achieve the required performance by the system. Next, a novel design algorithm developed by S.P. Bhattacharyya is used to design the control system. The algorithm has been implemented to a motor drive system, for the first time, in this work. Development of the complete set of the current- and speed-loop proportional-integral controller gains stabilizing the system is the result of this implementation. In the last part of the dissertation, based on the information and data achieved from the analysis and simulations, two parts of the FESS, inverter/rectifier and external inductor, are designed and the former one is manufactured. To verify the validity and feasibility of the proposed controller, several simulations and experimental results on a laboratory prototype are presented.

Utilizing flywheels to store and reuse energy from regenerative braking on locomotives is a new technology being developed in the Vibration Control and Electromechanics Lab at Texas A&M. This thesis focuses on the motion analysis of a locomotive mounted energy storage flywheel system for a variety of support motion inputs. Two input cases, sinusoidal floor input and ramp input, are analyzed in different sections. Simulation results and methods of ensuring the operating success of the flywheel system are provided at the end of each section. Section 1 introduces the problem and method being used to study the vibration under different circumstances. Section 2 analyzes the response of the flywheel system to sinusoidal floor input given by Ahmadian and Venezia 2000. Natural frequency and transmissibility of the system are utilized to explain the simulation results carried out in the frequency domain. It is found that the motion differences between flywheels(rotors) and magnetic bearings(stators) are guaranteed to be small. Section 3 emulates the locomotive traversing a bump with 1:150 slope. Simulation shows that catcher(backup) bearings are needed to limit the vibration of rotors through a bump. It is also found that gyroscopic effect causes problems in vibration isolation. Section 4 explores de-levitation method and installation of gimbals as possible remedies to this problem. Finally, a summary of simulation results from different input cases is made.

Thermal energy storage systems, precisely latent thermal energy storage (LTES), are systems capable of recovering and storing thermal energy from waste processes, including hot exhaust gases out of combustion engines, or even renewable sources of energy like solar energy. LTES rely on phase change materials (PCMs) to store a significant amount of thermal energy in a relatively small volume. With limited volume and at almost constant temperature, they are capable of storing a large amount of thermal energy, mainly latent energy. Studies of LTES systems have focused primarily on system and process optimization including transient behavior as well as field performance. A major drawback in the development of the use of PCM in LTES has been the low thermal conductivity characteristic of most PCMs. Thus, there is a need to enhance heat transfer using reliable techniques, with the goal of reducing the charging and discharging times of PCM in LTES systems. Some approaches that have been studied in the past include use of finned tubes, insertion of metal matrix into PCM, and microencapsulation of PCM. The performance of TES configurations in forced convection have been characterized using Reynolds numbers (Re), and Stefan numbers (Ste) of the heat transfer fluid (HTF) for different enhancement techniques. The goal of this study is to experimentally investigate the effectiveness of corrugated PCM panels with high surface-to-volume ratio in forced convection as a function of HTF mass flow rate, charging temperature, and flow direction through a corrugated TES unit. The PCM (octadecane) has been segmented using sealed corrugated panels containing several channels immersed in the HTF stream. With this approach, the author expects that the charging and discharging times will be substantially reduced due to the high surface-to-volume ratio of the PCM panel for heat transfer. Of the three conditions examined, the HTF direction influenced the charging and discharging times the most with significant reductions in these times observed when the HTF flow direction through the TES was upwards. Buoyancy effects, observed at high Stefan numbers, were important during the charging (melting) process and greatly influenced the temperature profiles along each channel. Results indicate that the devised TES is more effective than some other TES systems in the literature.

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The world’s increased energy storage demand, as well as the environmental concerns related to the combustion of fossil fuels, has triggered a transition to intermittent renewable energy sources as well as to electrical and hybrid vehicles. Current day rechargeable batteries are, due to the invention and development of lithium ion batteries, technologically well positioned to answer to some of these demands. Conventional batteries, however, utilize inorganic materials of limited supply that require large amounts of energy during refining and processing. The materials also add a significant cost to the final product, making the rechargeable batteries less attractive for large scale applications. During the last decade, significant efforts have been made to find suitable organic matter based electrode materials that can replace the inorganic materials. One class of organic materials that can be used for electrical energy storage, or be included as components in organic matter based energy storage systems, is conducting polymers. The aim of this thesis was to investigate the possibilities and limitations of using the conducting polymer polypyrrole in energy storage applications. The polymer was synthesized onto cellulose extracted from the Cladophora sp. algae, and the result was a flexible composite material. Symmetrical energy storage devices constructed with the composite material were shown to exhibit a pseudocapacitive behavior. The resistance in the cells was investigated and was found to scale linearly with the separator thickness. Cells could be cycled for 4,000 cycles without significant capacitance loss and cells that were overcharged to 1.8 V cell potential, were found to be protected by a resistive potential drop. Devices were constructed as proof-of-concept and were used to power a remote control and a digital thermometer. The self-discharge in polypyrrole was studied extensively. It was found that oxygen was responsible for the oxidation of the reduced electrode, while the positive electrode self-discharged due to a faradaic reaction. Through spectroscopy and the temperature dependence of the self-discharge, it was suggested that the self-discharge of oxidized polypyrrole is linked to the degradation at high potentials, commonly referred to as overoxidation.

Cellulose is the most abundant biopolymer in the world and the main component of paper. Modern society requires electronic devices to be more flexible and environmental friendly, which makes cellulose as a good candidate for the next generation of green electronics. However, lots of researches employed “paper-like” petroleum-based polymers to fabricate electronics rather than using real cellulose paper. Cellulose, as a representative of environmental friendly materials, caught into people's attention because of its sustainable nature, ease of functionality, flexibility and tunable surface properties, etc. There are some general challenges about using cellulose for electronics, such as its non-conductivity, porosity and roughness, but these features can be taken advantages of on certain occasions. This thesis focuses on the study of cellulose-based electronic devices by chemical or physical modification of microfibrillated cellulose (MFC). Particularly, three electronic devices were fabricated, including ionic diodes, electric double layer supercapacitors, pseudocapacitors. In addition, a rational design of dye-sensitized solar cell was investigated, although it was not directly cellulose-based, it led the way to the next generation of cellulose-based solar cells. The extraordinary physical and chemical properties of MFC were successfully leveled in those devices, in addition, inspiring and effective fabrication methods were proposed and carried out to solve the major problems faced by paper-based electronics, such as conductivity, flexibility, packaging and designs.

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 (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 291-297). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 47-49). Also available via the Internet.