Wireless Sensor Networks (WSNs) has become increasingly important in the Oil and Gas industry. Despite the various advantages WSN has compared to the wired counter parts, it also faces some critical challenges in the oil fields; one of them is the power supply. The periodic replacement of batteries for the WSN in the downhole environments has been economically inconvenient and the enormous cost induced by the maintenance has turned people's attention to the energy harvesting technology, hoping for a more sustainable solution. Power supply is only half of the problem. To retrieve the data recorded by the various sensors in the downhole environments, a reliable way of wireless communication is required. A new approach utilizing acoustic communication was proposed. This thesis presents an Archimedean Screw Turbine (AST) based energy harvester that takes advantage of the abundant flow energy in the upper stream section of the oil production cycle, especially in the water injection wells and oil extraction wells, with the goal of providing power supply to Wireless Sensor Networks (WSNs) and underwater acoustic modems deployed in the various locations in the downhole environments. Parametric study on the number of blades, screw length, screw pitch, and rotational speed was conducted through CFD analysis using Ansys Fluent in order to determine the optimal geometry and operating conditions. The relationship between power generation and AST geometries, such as AST length and AST pitch, were discovered and the optimal rotational speed was revealed to be solely dependent on the screw pitch. Experiments were conducted in the lab environment with various flow rates and various external resistive loads to verify and determine the maximum power generation of the designed harvester. FEA analysis was conducted using the Acoustic and Structural Interaction Module of COMSOL MULTIPHYSICS to determine the attenuation characteristics of acoustic waves propagating in the water-filled pipes buried in soil. Experiments with and without the harvester integrated in the pipe system were conducted in lab environment using a pair of under water acoustic modems to determine the acoustic communication capability. The impact of the integrated harvester on the acoustic communication was tested. Combining energy harvesting technology and underwater acoustic communication together, this system can potentially achieve real-time monitoring and communication in the oil downhole environment. / Master of Science / Oil and Gas industry has been the primary energy source provider for our society for hundreds of years. As this industry evolves with new technologies, it also faces new challenges. One of the main challenges is the power supply problem in the oil field because of the limited lifespan of traditional batteries used in the oil production process. This study present a novel energy harvesting device that can replace the traditional batteries. By taking advantage of the constant fluid flow in various wells at oil field, the device can provide power for electronic devices, including but not limited to wireless sensors, communication modules, at the oil extraction sites, without needing additional power supply. This novel energy harvesting device can also be integrated with communication modules that uses acoustic wave to achieve wireless acoustic communication between underground and the surface. In this study, the harvester design, optimization, tests, and integration with acoustic modems were presented. With the help of such energy harvesting device, Oil and Gas industry will be one step closer to achieving true wireless, and real-time monitoring and communication. This will not only reduce maintenance cost but also greatly improve the production efficiency.

As power demand across communities increases, focus has been given to the maintenance of power lines against harsh environments such as wind-induced vibration (WIV). Currently, Inspection robots are used for maintenance efforts while fixed tuned mass dampers (FTMDs) are used to prevent structural damages. However, both solutions are facing many challenges. Inspection robots are limited by their size and considerable power demand, while FTMDs are narrowband and unable to adapt to changing wind characteristics, and thus are unable to reposition themselves at the antinodes of the vibrating loop. In view of these shortcomings, we propose a mobile damping robot (MDR) that integrates inspection robots' mobility and FTMDs WIV vibration control to help maintain power lines. In this effort, we model the conductor and the MDR by using Hamilton's principle and we consider the two-way nonlinear interaction between the MDR and the cable. The MDR is driven by a Proportional-Derivative controller to the optimal vibration location (i.e, antinodes) as the wind characteristics vary. The numerical simulations suggest that the MDR outperforms FTMDs for vibration mitigation. Furthermore, the key parameters that influence the performance of the MDR are identified through a parametric study. The findings could set up a platform to design a prototype and experimentally evaluate the performance of the MDR. / Master of Science / Power lines are civil structures that span more than 160000 miles across the United States. They help electrify businesses, factories and homes. However, power lines are subject to harsh environments with strong winds, which can cause Aeolian vibration. Vibration in this context corresponds to the oscillation of power lines in response to the wind. Aeolian vibration can cause significant structural damages that impact public safety and result in a significant economic loss. Today, different solutions have been explored to limit the damages to these key structures. For example, the lines are commonly inspected by foot patrol, helicopters, or inspection robots. These inspection techniques are labor intensive and expensive. Furthermore, Stockbridge dampers, mechanical vibration devices, can be used to reduce the vibration of the power line. However, Stockbridge dampers can get stuck at location called nodes, where they have zero efficiency. To tackle this issue, we propose a mobile damping robot that can re-adjust itself to points of maximum vibration to maximize vibration reduction. In this thesis, we explore the potential of this proposed solution and draw some conclusions of the numerical simulations.

This work addresses issues in energy harvesting that have plagued the potential use of harvesting through the piezoelectric effect at the MEMS scale. Effective energy harvesting devices typically consist of a cantilever beam substrate coated with a thin layer of piezoceramic material and fixed with a tip mass tuned to resonant at the dominant frequency of the ambient vibration. The fundamental natural frequency of a beam increases as its length decreases, so that at the MEMS scale the resonance condition occurs orders of magnitude higher than ambient vibration frequencies rendering the harvester ineffective. Here we study two new geometries for MEMS scale cantilever harvesters. The zigzag and spiral geometries have low fundamental frequencies which can be tuned to the ambient vibrations. The second issue in energy harvesting is the frequency sensitivity of the linear vibration harvesters. A nonlinear hybrid energy harvester is presented that has a wide frequency bandwidth and large power output. Finally, linear and nonlinear energy harvesting devices are designed for powering the cardiovascular pacemakers using the vibrations in the chest area induced by the heartbeats. The mechanical and electromechanical vibrations of the zigzag structure are analytically modeled, verified with Rayleigh's method, and validated with experiments. An analytical model of coupled bending torsional vibrations of spiral structure is presented. A novel approximation method is developed for analyzing the electromechanical vibrations of energy harvesting devices. The unified approximation method is effective for linear, nonlinear mono-stable, and nonlinear bi-stable energy harvesting. It can also be utilized for piezoelectric, electromagnetic or hybrid energy harvesters. The approximation method accurately approximates the effect of energy harvesting on vibrations of energy harvester with changes in damping ratio and excitation frequency. Experimental investigations are performed to verify the analytical model of the nonlinear hybrid energy harvester. A detailed experimental parametric study of the nonlinear hybrid design is also performed. Linear and nonlinear energy harvesting devices have been designed that can generate sufficient amounts of power from the heartbeat induced vibrations. The nonlinear devices are effective over a wide range of heart rate. / Ph. D.

In the past two decades, the miniaturization of highly functional electronic devices has yielded the present condition where such devices are light enough, have a long enough battery life, are robust enough, and even stylish enough to be utilized for extended periods of time. Such devices can monitor activity and various bodily vital signs, and/or provide assistive actions. Due to the interrelationship between persons and assistive electronic devices, it is examined whether the actions (human motion) themselves can be used to power the electronic devices assisting those very actions. Such functionality results in a synergistic win-win interaction, rare in energy systems where trade-offs are pervasive. These interactions are studied in the context of the three types of solution spaces in implantable (inside the body), wearable (on the body), and peripheral (outside the body) devices. Specifically, it is studied whether heartbeats can power the pacemakers regulating the heartbeat; whether walking can power the portable communication equipment guiding the path; and whether movement within a smart building can power the occupancy measurement in automatic occupancy-drive lighting and climate control systems making the building habitable yet energy efficient. Novel energy harvesting solutions are developed for each category, with the impetus of harvesting sufficient energy to perform the desired function without encumbering the body. / Ph. D.

As wearable technology and wireless sensor nodes become more and more ubiquitous, the batteries required to power them have become more and more unappealing as they limit lifetime and scalability. Energy harvesting from body heat provides a solution to these limitations. Energy can be harvested from body heat using thermoelectric generators, or TEGs. TEGs provide a continuous, scalable, solid-state energy source ideal for wearable and wireless electronics and sensors. Unfortunately, current TEG technology produces low power (< 1 mW) at a very low voltage (20-90 mV) and require the load to be matched to the TEG internal resistance for maximum power transfer to occur. This thesis research proposes a power management integrated circuit (PMIC) that steps up ultralow voltages generated by TEGs to a regulated 3 V, while matching the internal resistance. The proposed boost converter aims to harvest energy from body heat as efficiently and flexibly as possible by providing a regulated 3 V output that can be used by a variable load. A comparator-based burst mode operation affords the converter a high conversion ratio at high efficiency, while fractional open circuit voltage maximum power point tracking ensures that the controller can be used with a variety of TEGs and TEG setups. This control allows the converter to boost input voltages as low as 50 mV, while matching a range of TEG internal source resistances in one stage. The controller was implemented in 0.25 µm CMOS and taped out in February 2016. Since these fabricated chips will not be completed and delivered until May 2016, functionality has only been verified through simulation. Simulation results are promising and indicate that the peak overall efficiency is 81% and peak low voltage, low power efficiency is 73%. These results demonstrate the the proposed converter can achieve overall efficiencies comparable to current literature and low power efficiencies better than similar wide range converters in literature. / Master of Science

The rapid advancement in complimentary metal-oxide-semiconductor (CMOS) electronics has led to a reduction in the sizes of wireless sensor networks (WSN) and a subsequent decrease in their power requirements. To meet these power requirements for long time of operation, energy harvesters have been developed at the micro scale which can convert vibration energy into electrical energy. Recent studies have shown that for mechanical-to-electrical conversion at the mm-scale (or micro scale), piezoelectric mechanism provides the best output power density at low frequencies as compared to the other possible mechanisms for vibration energy harvesting (VEH). However, piezoelectric-based VEH presents a fundamental challenge at the micro scale since the resonance frequency of the structure increases as the dimension decreases. Electromagnetic induction is another voltage generation mechanism that has been utilized for VEH. However, the electromagnetic induction based VEH is limited by the magnet and coil size and the decrease in power density at the micro scale. Hybrid energy harvesting is a novel concept that allows for increased power response and increased optimization of the generated voltage. The work in this field is currently limited due to integration challenges at small dimensions. An effective design for low frequency piezoelectric VEH is presented in this work. A unique cantilever design called arc-based cantilever (ABC) is presented which exhibits low natural frequencies as compared to traditional cantilevers. A general out-of-plane vibration model for ABCs was developed that incorporated the effects of bending, torsion, transverse shear deformation and rotary inertia. Different configurations of micro ABCs were investigated through analytical modeling and validation experiments. ABC structures were fabricated for dual-phase energy harvesting from vibrations and magnetic fields. Next, a levitation-induced electromagnetic VEH concept based on double-repulsion configuration in the moving magnet composite was studied. Computational modeling clearly illustrated the advantages of the double-repulsion configuration over the single-repulsion and no-repulsion configurations. Based on the modeling results, an AA battery-sized harvester with the double-repulsion configuration was fabricated, experimentally characterized and demonstrated to charge a cell phone. The scaling analysis of electromagnetic energy harvesters was conducted to understand the performance across different length scales. A micro electromagnetic harvester was developed that exhibited softening nonlinear spring behavior, thus leading to the finding of nonlinear inflection in magnetically-levitated electromagnetic harvesters. The nonlinear inflection theory was developed to show its causal parameters. Lastly, a coupled harvester is presented that combines the piezoelectric and electromagnetic voltage mechanisms. The advantages of each mechanism were shown to positively contribute to the performance of hybrid harvester. The cantilever provided low stiffness, low frequency, and pure bending, while the magnetic system provided nonlinearity, broadband response, and increased strain (and thus voltage). / Ph. D.

Renewable energy is a critical component in combating climate change. Ocean wave energy is a source of renewable energy that can be harvested using Wave Energy Converters (WECs). One such WEC is the floating Oscillating Water Column (OWC), which has been successfully field tested and warrants further exploration. This research implements a publicly accessible code in MatLab and SimuLink to simulate the dynamics of a floating OWC in the time domain. This code, known as the Floating OWC Iterative Time Series Solver (FlOWCITSS), uses the pressure distribution model paired with state space realization to capture the internal water column dynamics of the WEC and estimate pneumatic power generation. Published experimental results of floating moored structures are then used to validate FlOWCITSS. While FlOWCITSS seemed to capture the period and general nature of the heave, surge, and internal water column dynamics, the magnitude of the response sometimes had errors ranging from 1.5% −37%. This error could be caused by the modeling techniques used, or it could be due to uncertainties in the experiments. The presence of smaller error values shows potential for FlOWCITSS to achieve consistently higher fidelity results as the code undergoes further developments. To demonstrate the use of FlOWCITSS, geometry variations of a Backward Bent Duct Buoy (BBDB) are explored for a wave environment and mooring configuration. The reference model from Sandia National Labs, RM6, performed significantly better than a BBDB with an altered stern geometry for a 3 second wave period, indicating that stern geometry can have a significant impact on pneumatic power performance. / Master of Science / Renewable energy is a critical component in combating climate change. Ocean wave energy is a source of renewable energy that can be converted into electricity using Wave Energy Converters (WECs). One such WEC is the floating Oscillating Water Column (OWC), which has been successfully field tested and warrants further exploration. Floating OWCs are partially submerged floating structures that have an internal chamber which water oscillates in. The motions of the water displace air inside this chamber, causing the air to be forced through a high speed turbine, which generates electricity. This research develops a publicly accessible code using MatLab and SimuLink to evaluate the motions and power generation capabilities of floating OWCs. This code is then validated against physical experiments to verify its effectiveness in predicting the device's motions. This publicly accessible code, known as the Floating OWC Iterative Time Series Solver (FlOWCITSS), showed error ranging from 1.5 % - 37% for the most important motions that are relevant to energy harvesting and power generation. These errors could be caused by the numerical models used, or uncertainties in experimental data. The presence of smaller error values shows potential for FlOWCITSS to achieve consistently higher fidelity results as the code undergoes further developments. To demonstrate the use of FlOWCITSS, geometry variations of floating OWCs are explored.

Currently, in the railroad industry, the lack of electrical sources in freight cars is a problem that has yet to find practical solutions. Although the locomotive generates electricity to power the traction motors and all the equipment required to operate the train, the electrical power cannot, in a practical manner, be carried out along the length of the train, leaving freight cars unpowered. While this has not been a major issue in the past, there is a strong interest in equipping modern cars with a myriad of devices intended to improve safety, operational efficiency, or health monitoring, using devices such as GPS, active RFID tags, and accelerometers. The implementation of such devices, however, is hindered by the unavailability of electricity. Although ideas such as Timken's generator roller bearing or solar panels exist, the railroads have been slow in adopting them for different reasons, including cost, difficulty of implementation, or limited capabilities. The focus of this research is on the development of vibration-based electromechanical energy harvesting systems that would provide electrical power in a freight car. With size and shape similar to conventional shock absorbers, these devices are designed to be placed in parallel with the suspension elements, possibly inside the coil spring, thereby maximizing unutilized space. When the train is in motion, the suspension will accommodate the imperfections of the track, and its relative velocity is used as the input for the harvester, which converts the mechanical energy to useful electrical energy. Beyond developing energy harvesters for freight railcar primary suspensions, this study explores track wayside and miniature systems that can be deployed for applications other than railcars. The trackside systems can be used in places where electrical energy is not readily available, but where, however, there is a need for it. The miniature systems are useful for applications such as bicycle energy. Beyond the design and development of the harvesters, an extensive amount of laboratory testing was conducted to evaluate both the amount of electrical power that can be obtained and the reliability of the components when subjected to repeated vibration cycles. Laboratory tests, totaling more than two million cycles, proved that all the components of the harvester can satisfactorily survive the conditions to which they are subjected in the field. The test results also indicate that the harvesters are capable of generating up to 50 Watts at 22 Vrms, using a 10-Ohm resistor with sine wave inputs, and over 30 Watts at peak with replicated suspension displacements, making them suitable to directly power onboard instruments or to trickle charge a battery. / Ph. D.

MEMS devices are finding application in diverse fields that include energy harvesting, microelectronics and sensors. In energy harvesting, MEMS scale devices are employed due to its efficiencies of scale. The miniaturization of energy harvesters permit them to be integrated as the power supply for sensors often in the same package and also extends their use to remote and extreme ambient applications. Unlike inductive harvesting, piezoelectric and magnetoelectric devices lend easily to MEMS scaling. The processing of such Piezo-MEMS devices often requires special fabrication, characterization and testing techniques. Our research work has focused on the development of the various technologies for a) the better characterization of the constituent materials that make up these devices, b) the conceptualization and structural design of unique MEMS energy harvesters and finally c) the development of the unit operations (many novel) for fabrication and the mechanical and electrical testing of these devices. In this research work, we have pioneered some new approaches to the characterization of thin films utilized in Piezo-MEMS devices: (1) Temperature-Time Transformation (TTT) diagrams are used to document texture evolution during thermal treatment of ceramics. Multinomial and multivariate regression techniques were utilized to create the predictor models for TTT data of Pb(Zr0.60Ti0.40 O3) sol-gel thin films. (2) We correlated the composition (measured using Energy Dispersive X-ray analysis (EDX) and Electron Probe Micro Analysis (EPMA)) of Pb(Zr0.52Ti0.48 O3) RF sputtered thin films to its optical dispersion properties measured using Variable Angle Spectroscopic Ellipsometry (VASE). Wemple-DiDomenico, Jackson-Amer, Tauc and Urbach optical dispersion factors and Lorentz Lorenz polarizability relationships were combined to realize a model for predicting the elemental content of any thin film system. (3) We developed in house capability for strain analysis of magnetostrictive thin films using laser Doppler Vibrometry (LDV). We determined a methodology to convert the displacements measurements of AC magnetic field induced vibrations of thin film samples into magnetostriction values. (4) Finally, we report the novel use of a thermo-optic technique, Time Domain Thermoreflectance (TDTR) in the study of Pb(Zr,Ti)O3 (PZT) thin film texturing. Time Domain Thermoreflectance (TDTR) has been proved to be capable of measuring thermal properties of atomic layers and interfaces. Therefore, we utilized TDTR to analyze and model the heat transport at the nano scale and correlate with different PZT crystalline orientations. To harvest energy at the low frequency (<100Hz) of ambient vibrations, MEMS energy harvesters require special structures. Extensive research has led us to the development of Circular Zigzag structure that permits inertial mass free attainment of such low frequencies. In addition to Si micromachining, we have fabricated such structures using a new Micro water jet micromachining of thin piezo sheets, unimorphs and bimorphs. For low frequency magnetic energy harvesting, we also fabricated the first magnetoelectric macro fiber composite. This device also employs a novel low temperature metallic bonding technique to fuse the magnetostrictive layer to the piezoelectric layers. A special low viscosity epoxy enabled the joining of the flexible circuit to the magnetoelectric fibers. Lastly, we developed a nondimensional tunable Piezo harvester, called PiezoCap, which decouples the energy harvesting component of the device from the resonant vibration component. We do so by using magnets loaded on piezo harvester strips, thereby making them piezomagnetoelastic and vary the spacing between 2 magnet+piezoelectric pairs to eliminate dimensionality and permit active tunability of the harvester's resonant frequency. / Ph. D.

Although the locomotive of a train is energized, in general, other railcars are not. This prevents commercial rail companies from installing sensor equipment on the railcars. Thus, several different solutions have been proposed to provide energy for commercial railcars. One such solution is a vibration-based energy harvester which can be mounted in the suspension coils of the railcar. The harvester translates the linear motion of the suspension vibration into rotational motion to turn a 3-phase AC generator. When subjected to real-world suspension displacements, the harvester is capable of generating peak energy levels in excess of 70 W, although the average energy harvested is much lower, around 1 W. A battery pack can be used to store the useful energy harvested. However, a power conditioning circuit is required to convert the 3-phase AC energy from the harvester into DC for the battery pack. The power converter should be capable of extracting maximum power from the energy harvester as well as acting as a battery manager. Experimental results with the energy harvester conclude that maximum power can be extracted if the harvester is loaded with 2 . In order to maintain a constant input impedance, the duty cycle of the power converter must be fixed. Conversely, output regulation requires the duty cycle to change dynamically. Consequently, there is a tradeoff between extracting maximum power and prolonging the battery life cycle. The proposed converter design aims to achieve both maximum power transfer and battery protection by automatically switching between control modes. The proposed converter design uses an inverting buck-boost converter operating in discontinuous conduction mode to maintain a constant input impedance through a fixed duty cycle. This constant input impedance mode is used to extract maximum power from the harvester when the battery is not close to fully charged. When the battery is near fully charged, extracting maximum power is not as important and the duty cycle can be controlled to regulate the output. Specifically, one-cycle control is used to regulate the output by monitoring the input voltage and adjusting the duty cycle accordingly. Finally, the converter is designed to shut down once the battery has been fully charged to prevent overcharging. The result is a power converter that extracts maximum power from the energy harvester for as long as possible before battery protection techniques are implemented. Previous related studies are discussed, tradeoffs in converter design are explained in detail, and an experimental prototype is used to confirm operation of the proposed control scheme. / Master of Science