This thesis investigates a relatively new method for harvesting wind energy by using flexible piezoelectric polymers with additional sails to increase their ability to harvest wind energy. This paper also introduces a new topology deemed the “stacked buck” that allows for multiple inputs to a system with a single output. Derivations and analysis detail the workings of the “stacked buck” with a laboratory test to show a working model. This paper also reports another experiment done in a wind tunnel to analyze the capability of the piezoelectric polymers as sources to the “stacked buck” topology with measurements of the power output. The results of this thesis demonstrate that because the design is very modular, it is possible to scale the proposed wind energy harvesting system for small power applications.

This thesis describes the design of a rectenna that is capable of operating in 5G. 5G’s availability will create the opportunity to harvest energy everywhere in the network’s coverage. This thesis investigates a Rectenna device with a new proposed topology in order to eliminate coupling between input and output lines and increase the rectification efficiency. Moreover, it is designed to charge a rechargeable battery of 3V, 1mA, with a 4.8mm diameter. The current design describes using one antenna for energy harvesting; this could be expanded to use an antenna array, which would increase the input power. This would lead to higher output currents, leading to the ability to efficiently charge a wide variety of batteries. Because of its small size, the rectenna could be used for the remote charging of an implantable sensor battery or for other applications where miniaturization is a design consideration.

Thermoelectric (TE) module integration into a notebook computer is experimentally investigated in this thesis for its energy harvesting opportunities. A detailed Finite Element (FE) model was constructed first for thermal simulations. The model outputs were then correlated with the thermal validation results of the selected system. In parallel, a commercial TE micro-module was experimentally characterized to quantify maximum power generation opportunity from the combined system and component data set. Next, suitable &ldquo / warm spots&rdquo / were identified within the mobile computer to extract TE power with minimum or no notable impact to system performance, as measured by thermal changes in the system, in order to avoid unacceptable performance degradation. The prediction was validated by integrating a TE micro-module to the mobile system under test. Measured TE power generation power density in the carefully selected vicinity of the heat pipe was around 1.26 mW/cm3 with high CPU load. The generated power scales down with lower CPU activity and scales up in proportion to the utilized opportunistic space within the system. The technical feasibility of TE energy harvesting in mobile computers was hence experimentally shown for the first time in this thesis.

This thesis presents a low power DC-DC converter suitable for harvesting energy from high impedance thermoelectric generators (TEGs) for the use in body powered electronics. The chip has been fabricated in a 130nm CMOS technology. To meet the power demands of body powered networks, a novel dual-path architecture capable of efficiently harvesting power at levels below 5 μW has been developed. To control the converter, a low power control loop has been developed. The control loop features a low-power clock and a pulse counting system that is capable of matching the converter impedance with high impedance TEGs. The system consumes less than 900nW of quiescent power and maintains an efficiency of 68% for a load of 5 μW. / Graduation date: 2013

This dissertation presents the concept of a small, low-cost, self-powered smart wireless sensor that can be used for monitoring current, temperature and voltage on a variety of utility assets. Novel energy harvesting approaches are proposed that enable the sensor to operate without batteries and to have an expected life of 20-30 years. The sensor measures current flowing in an asset using an open ferromagnetic core, unlike a CT which uses a closed core, which makes the proposed sensor small in size, and low-cost. Further, it allows the sensor to operate in conjunction with different assets having different geometries, such as bus-bars, cables, disconnect switches, overhead conductors, transformers, and shunt capacitors, and function even when kept in the vicinity of an asset. Two novel current sensing algorithms have been developed that help the sensor to autonomously calibrate and make the sensor immune from far-fields and cross-talk. The current sensing algorithms have been implemented and tested in the lab at up to 1000 A. This research also presents a novel self-calibrating low-cost voltage sensing technique. The major purpose of voltage sensing is detection of sags, swells and loss-ofpower on the asset; therefore, the constraint on error in measurement is relaxed. The technique has been tested through several simulation studies. A voltage sensor prototype has been developed and tested on a high voltage bus at up to 35 kV. Finally, a study of sensor operation under faults, such as lightning strikes, and large short circuit currents has been presented. These studies are conducted using simulations and actual experiments. Based on the results of the experiments, a robust protection circuit for the sensor is proposed. Issues related to corona and external electrical noise on the communication network are also discussed and experimentally tested. Further, optimal design of the energy harvester and a novel design of package for the sensor that prevents the circuitry from external electrical noise without attenuation of power signals for the energy harvester are also proposed.

No description available.

In the present thesis, I have proposed methodology of two stages Dickson charge pump, which is capable of harvesting energy at 2.45 GHz RF signal to power any low powered device. Presented design uses a simple and inexpensive circuit consisting of four microstrip patch antennas, some zero-bias Schottky diodes, Wilkinson power divider and a few passive components. Circuit was fabricated on a 60 mils RO4350B substrate (=3.66), with 1.4 mils copper conductor. Demonstration showed the charge pump provides a good performance, as it drives the low powered devices with as low as 10dBm input power at 1m away from the energy source. Thesis paper will present design techniques illustrated with data obtained on prototype circuits. The objective is to wirelessly gather energy from one RF source and convert it into usable DC power that is further applied to a set of low power electronic devices. Radio Frequency Identification (RFID) tag system could also be improved using this method. RF-to-DC conversion is accomplished by designing and characterizing an element commonly known as a Rectenna, which consists of an antenna and an associated rectification circuitry. The rectenna is fully characterized in this dissertation and is used for charging low powered devices.

Las tendencias en la tecnología actual permiten la reducción tanto en tamaño como en potencia consumida de los sistemas digitales complejos. Esta disminución en el tamaño y el consumo da lugar al concepto de dispositivos portátiles que se integren en la vida pertenencias personales y cotidianas como ropa, relojes, gafas, etc. La fuente de alimentación es un factor limitante en la movilidad de los dispositivos portátiles que se ve reducida por la duración de la batería. Además, debido a los costos y difícil accesibilidad, la sustitución o recarga de las baterías a menudo no es viable para los dispositivos portátiles integrados en ropa inteligente. Los dispositivos vestibles están distribuidos en las pertenencias personales y, por tanto, la recolección de energía del usuario es una alternativa para su alimentación. Dispositivos vestibles pueden crear, al igual que los sensores de una red de sensores inalámbricos (WSN), una red de área corporal. El principal objetivo de esta tesis es el estudio de generadores piezoeléctricos, inductivos y termoeléctricos que recolectan energía del cuerpo humano de forma pasiva. El principio físico de un transductor es el mismo independientemente de si la fuente proviene del entorno o del cuerpo humano. Sin embargo, las limitaciones relacionadas con la baja tensión, corriente y niveles de frecuencia conllevan nuevos requerimientos que no están presentes en el caso de la utilización de las fuentes que ofrece el entorno y que suponen el principal desafío de esta tesis. El tipo de energía entrada y transductor a utilizar forman un tándem donde la elección de uno impone el otro. Es importante que las mediciones se realicen diferentes partes del cuerpo humano, mientras se realizan diferentes actividades físicas para localizar las posiciones y las actividades que producen más energía. El acoplamiento mecánico entre transductor y cuerpo humano depende de la ubicación del transductor y la actividad que se realiza. Un diseño específico, teniendo esto en cuenta puede aumentar más de un 200% la eficiencia del transductor como se ha demostrado con láminas piezoeléctricas situadas en plantillas de zapatos. Se han realizado mediciones de aceleraciones en diferentes partes del cuerpo y diferentes actividades para cuantificar la cantidad de energía disponible en actividades cotidianas. Se ha realizado una simulación a nivel de sistema, modelando los elementos de un sistema de energía autoalimentado. El transductor se ha modelado usando las ecuaciones físicas que lo describen con el objetivo de incluir la parte mecánica del sistema. Se han utilizado modelos eléctricos y de comportamiento para el resto de los componentes. De esta manera, el proceso de diseño de la aplicación en su conjunto (incluyendo la carga y un elemento de almacenamiento de energía cuando es necesario) se simplifica a la hora de lograr los requisitos planteados. Obviamente, la carga debe ser un dispositivo de bajo consumo como por ejemplo un transmisor RF. En este caso, es preferible alimentar la carga de forma discontinua, sin una batería, como se deduce de los resultados obtenidos mediante simulación. Sin embargo, la evolución de los transmisores RF de baja potencia puede cambiar esta conclusión en función sobre todo de la evolución del consumo de energía en stand-by y el tiempo de configuración para la operación de transmisión. Se ha deducido a partir del análisis de los generadores inductivos que el análisis en el dominio temporal permite calcular algunas magnitudes que no están disponibles en el dominio frecuencial. Por ejemplo, la potencia máxima se puede calcular en el dominio frecuencial, pero para aplicaciones de recolección de energía es más interesante saber el valor de la energía recuperada durante un cierto tiempo o la potencia media ya que la potencia generada por las actividades humanas pueden ser muy discontinua. Se ha demostrado que los transductores recolectores de energía son capaces de suministrar alimentación a dispositivos electrónicos de baja potencia, como quedó demostrado con un transmisor RF alimentado por una termogenerador que emplea el gradiente de temperatura existente entre el cuerpo humano y el entorno (3-5 K) y que es capaz de realizar medidas y transmitirlas una vez cada segundo / The trends in technology allow the decrease in both size and power consumption of complex digital systems. This decrease in size and power gives rise to the concept of wearable devices which are integrated in everyday personal belongings like clothes, watch, glasses, et cetera. Power supply is a limiting factor in the mobility of the wearable device which gets restricted to the lifetime of the battery. Furthermore, due to the costs and inaccessible locations, the replacement or recharging of batteries is often not feasible for wearable devices integrated in smart clothes. Wearable devices are devices distributed in personal belongings and thus, an alternative for powering them is to harvest energy from the user. Therefore, the energy can be harvested, distributed and supplied over the human body. Wearable devices can create, like the sensors of a Wireless Sensor Network (WSN), a Body Area Network. A study of piezoelectric, inductive and thermoelectric generators that harvest passive human power is the main objective of this thesis. The physical principle of an energy harvesting generator is obviously the same no matter whether it is employed with an environmental or human body source. Nevertheless, the limitations related to low voltage, current and frequency levels obtained from human body sources bring new requirements to the energy harvesting topic that were not present in the case of the environment sources. This analysis is the motivation for this thesis. The type of input energy and transducer form a tandem since the election of one imposes the other. It is important that measurements are done in different parts of the human body while doing different physical activities to locate which positions and activities produce more energy. The mechanical coupling between the transducer and the human body depends on the location of the transducer and the activity that is done. A specific design taking this into account can increase more than a 200% the efficiency of the transducer as has been demonstrated with piezoelectric films located in the insoles of shoes. Acceleration measurements have been performed in different body locations and different physical activities, in order to quantify the amount of available energy associated with usual human movements. A system-level simulation has been implemented modeling the elements of an energy self-powered system. Physical equations have been used for the transducer in order to include the mechanical part of the system and electrical and behavioral models for the rest of the components. In this way, the process of the design of the complete application (including the load and an energy storage element when it is necessary) is simplified to achieve the expected requirements. Obviously, the load must be a low power consumption device as for example a RF transmitter. In this case, it is preferable to operate it in a discontinuous way without a battery as it is deduced from simulation results obtained. However, the evolution in low power transmission modules can change this conclusion depending mostly on the evolution of the power consumption in stand-by mode and the configuration time in transmission operation. It has been deduced from the analysis of inductive generators that time-domain analysis allows to calculate some magnitudes that are not available in frequency domain. For example, the maximum power can be calculated in frequency domain, but for energy harvesting applications it is more interesting to know the value of the recovered energy during a certain time, or the average power since the power generated by human activities can be highly discontinuous. It has been demonstrated that energy harvesting transducers are able to supply power to present-day low power electronic devices as was demonstrated with a RF transmitter powered by a thermogenerator that employs the temperature gradient between human body and the environment (3-5 K) and that it is able to sense and transmit data once every second.

<p>Within the past decade, advances in small-scale electronics have reduced power consumption requirements such that mechanisms for harnessing ambient kinetic energy for self-sustenance are a viable technology. Such devices, known as energy harvesters, may enable self-sustaining wireless sensor networks for applications ranging from Tsunami warning detection to environmental monitoring to cost-effective structural health diagnostics in bridges and buildings. In particular, flexible electroelastic materials such as lead-zirconate-titanate (PZT) are sought after in designing such devices due to their superior efficiency in transforming mechanical energy into the electrical domain in comparison to induction methods. To date, however, material and dynamic nonlinearities within the most popular type of energy harvester, an electroelastically laminated cantilever beam, has received minimal attention in the literature despite being readily observed in laboratory experiments. </p><p>In the first part of this dissertation, an experimentally validated first-principles based modeling framework for quantitatively characterizing the intrinsic nonlinearities and moderately large amplitude response of a cantilevered electroelastic generator is developed. Nonlinear parameter identification is facilitated by an analytic solution for the generator's dynamic response alongside experimental data. The model is shown to accurately describe amplitude dependent frequency responses in both the mechanical and electrical domains and implications concerning the conventional approach to resonant generator design are discussed. Higher order elasticity and nonlinear damping are found to be critical for correctly modeling the harvester response while inclusion of a proof mass is shown to invigorate nonlinearities a much lower driving amplitudes in comparison to electroelastic harvesters without a tuning mass.</p><p>The second part of the dissertation concerns dynamical systems design to purposefully engage nonlinear phenomena in the mechanical domain. In particular, two devices, one exploiting hysteretic nonlinearities and the second featuring homoclinic bifurcation are investigated. Both devices exploit nonlinear magnet interactions with piezoelectric cantilever beams and a first principles modeling approach is applied throughout. The first device is designed such that both softening and hardening nonlinear resonance curves produces a broader response in comparison to the linear equivalent oscillator. The second device makes use of a supercritical pitchfork bifurcation wrought by nonlinear magnetic repelling forces to achieve a bistable electroelastic dynamical system. This system is also analytically modeled, numerically simulated, and experimentally realized to demonstrate enhanced capabilities and new challenges. In addition, a bifurcation parameter within the design is examined as a either a fixed or adaptable tuning mechanism for enhanced sensitivity to ambient excitation. Analytical methodologies to include the method of Harmonic Balance and Melnikov Theory are shown to provide superior insight into the complex dynamics of the bistable system in response to deterministic and stochastic excitation.</p> / Dissertation

In this study, a cylindrical near-field electrospining (CNFES) process will be used to fabricate permanent piezoelectricity of polyvinylidene fluoride (PVDF) piezoelectric fibers, and a piezoelectric fiber harvesting device with parallel electrode was fabricated to capture ambient energy. First, the PVDF powder was mixed in acetone solution uniformly and the dimethyl sulfoxide (DMSO) was mixed with fluorosurfactant to prepare PVDF macromolecular solution. The PVDF macromolecular solution was filled in a metals needle injector and contacted a high power supply, after the PVDF drops in the needle was subjected to high electric field, the drops became a Taylor cone and overcame surface tension of the solution itself, extremely fine PVDF fiber was formed and jetted out. The fibers were collected numerous and quickly by homemade cylindrical collector and the diameter of fiber could be controlled easily by adjusting the rotating speed of the cylinder and the electric field. From the observation of XRD (X-ray diffraction), it reveals a high diffraction peak at 2£c=20.7¢X of piezoelectric crystal £]-phase structure by adjusting PVDF concentrations and DC voltage. By providing 7Hz shake and 0.23% strain, the piezoelectric fiber harvesting device with parallel electrode could generate 76mV; by providing 7Hz shake and 0.14% strain, the device could generate 1.1nA.