Dissertations / Theses on the topic 'Piezoelectric energy'

Wireless micro-sensors can enjoy popularity in biomedical drug-delivery treatments and tire-pressure monitoring systems because they offer in-situ, real-time, non-intrusive processing capabilities. However, miniaturized platforms severely limit the energy of onboard batteries and shorten the lifespan of electronic systems. Ambient energy is an attractive alternative because the energy from light, heat, radio-frequency (RF) radiation, and motion can potentially be used to continuously replenish an exhaustible reservoir. Of these sources, solar light produces the highest power density, except when supplied from indoor lighting, under which conditions the available power decreases drastically. Harnessing thermal energy is viable, but micro-scale dimensions severely limit temperature gradients, the fundamental mechanism from which thermo piles draw power. Mobile electronic devices today radiate plenty of RF energy, but still, the available power rapidly drops with distance. Harvesting kinetic energy may not compete with solar power, but in contrast to indoor lighting, thermal, and RF sources, moderate and consistent vibration power across a vast range of applications is typical. Although operating conditions ultimately determine which kinetic energy-harvesting method is optimal, piezoelectric transducers are relatively mature and produce comparatively more power than their counterparts such as electrostatic and electromagnetic kinetic energy transducers. The presented research objective is to develop, design, simulate, fabricate, prototype, test, and evaluate CMOS ICs that harvest ambient kinetic energy in periodic and non-periodic vibrations using a small piezoelectric transducer to continually replenish an energy-storage device like a capacitor or a rechargeable battery. Although vibrations in surrounding environment produce abundant energy over time, tiny transducers can harness only limited power from the energy sources, especially when mechanical stimulation is weak. To overcome this challenge, the presented piezoelectric harvesters eliminate the need for a rectifier which necessarily imposes threshold limits and additional losses in the system. More fundamentally, the presented harvesting circuits condition the transducer to convert more electrical energy for a given mechanical input by increasing the electromechanical damping force of the piezoelectric transducer. The overall aim is to acquire more power by widening the input range and improving the efficiency of the IC as well as the transducer. The presented technique in essence augments the energy density of micro-scale electronic systems by scavenging the ambient kinetic energy and extends their operational lifetime. This dissertation reports the findings acquired throughout the investigation. The first chapter introduces the applications and challenges of micro-scale energy harvesting and also reviews the fundamental mechanisms and recent developments of various energy-converting transducers that can harness ambient energy in light, heat, RF radiation, and vibrations. Chapter 2 examines various existing piezoelectric harvesting circuits, which mostly adopt bridge rectifiers as their core. Chapter 3 then introduces a bridge-free piezoelectric harvester circuit that employs a switched-inductor power stage to eliminate the need for a bridge rectifier and its drawbacks. More importantly, the harvester strengthens the electrical damping force of the piezoelectric device and increases the output power of the harvester. The chapter also presents the details of the integrated-circuit (IC) implementation and the experimental results of the prototyped harvester to corroborate and clarify the bridge-free harvester operation. One of the major discoveries from the first harvester prototype is the fact that the harvester circuit can condition the piezoelectric transducer to strengthen its electrical damping force and increase the output power of the harvester. As such, Chapter 4 discusses various energy-investment strategies that increase the electrical damping force of the transducer. The chapter presents, evaluates, and compares several switched-inductor harvester circuits against each other. Based on the investigation in Chapter 4, an energy-investing piezoelectric harvester was designed and experimentally evaluated to confirm the effectiveness of the investing scheme. Chapter 5 explains the details of the IC design and the measurement results of the prototyped energy-investing piezoelectric harvester. Finally, Chapter 6 concludes the dissertation by revisiting the challenges of miniaturized piezoelectric energy harvesters and by summarizing the fundamental contributions of the research. With the same importance as with the achievements of the investigation, the last chapter lists the technological limits that bound the performance of the proposed harvesters and briefly presents perspectives from the other side of the research boundary for future investigations of micro-scale piezoelectric energy harvesting.

Energy harvesting technology has the ability to create autonomous, self-powered electronic systems that do not rely on battery power for their operation. The term energy harvesting describes the process of converting ambient energy surrounding a system into useful electrical energy through the use of a specific material or transducer. A widely studied form of energy harvesting involves the conversion of mechanical vibration energy into electrical energy using piezoelectric materials, which exhibit electromechanical coupling between the electrical and mechanical domains. Typical piezoelectric energy harvesting systems are designed as add-on systems to a host structure located in a vibration rich environment. The added mass and volume of conventional vibration energy harvesting designs can hinder to the operation of the host system. The work presented in this dissertation focuses on advancing piezoelectric energy harvesting concepts through the introduction of multifunctionality in order to alleviate some of the challenges associated with conventional piezoelectric harvesting designs.

The concept of multifunctional piezoelectric self-charging structures is explored throughout this work. The operational principle behind the concept is first described in which piezoelectric layers are directly bonded to thin-film battery layers resulting in a single device capable of simultaneously harvesting and storing electrical energy when excited mechanically. Additionally, it is proposed that self-charging structures be embedded into host structures such that they support structural load during operation. An electromechanical assumed modes model used to predict the coupled electrical and mechanical response of a cantilever self-charging structure subjected to harmonic base excitation is described. Experimental evaluation of a prototype self-charging structure is then performed in order to validate the electromechanical model and to confirm the ability of the device to operate in a self-charging manner. Detailed strength testing is also performed on the prototype device in order to assess its strength properties. Static three-point bend testing as well as dynamic harmonic base excitation testing is performed such that the static bending strength and dynamic strength under vibration excitation is assessed. Three-point bend testing is also performed on a variety of common piezoelectric materials and results of the testing provide a basis for the design of self-charging structures for various applications.

Multifunctional vibration energy harvesting in unmanned aerial vehicles (UAVs) is also investigated as a case study in this dissertation. A flight endurance model recently developed in the literature is applied to model the effects of adding piezoelectric energy harvesting to an electric UAV. A remote control foam glider aircraft is chosen as the test platform for this work and the formulation is used to predict the effects of integrating self-charging structures into the wing spar of the aircraft. An electromechanical model based on the assumed modes method is then developed to predict the electrical and mechanical behavior of a UAV wing spar with embedded piezoelectric and thin-film battery layers. Experimental testing is performed on a representative aluminum wing spar with embedded self-charging structures in order to validate the electromechanical model. Finally, fabrication of a realistic fiberglass wing spar with integrated piezoelectric and thin-film battery layers is described. Experimental testing is performed in the laboratory to evaluate the energy harvesting ability of the spar and to confirm its self-charging operation. Flight testing is also performed where the fiberglass spar is used in the remote control aircraft test platform and the energy harvesting performance of the device is measured during flight.
Ph. D.

Energy harvesting technologies have drawn much attention as an alternative power source of roadway accessories in different scales. Piezoelectric energy harvesting consisting of PZT piezoceramic disks sealed in a protective package is developed in this work to harness the deformation energy of pavement induced by traveling vehicles and generate electrical energy. Six energy harvesters are fabricated and installed at the weigh station on I-81 at Troutville, VA to perform on-site evaluation. The electrical performance of the installed harvesters is evaluated by measuring the output voltage and current generated under real traffic. Instant and average power outputs are calculated from the measured waveforms of output voltage and current. The analysis of the testing results shows that the electrical productivity of the energy harvesters are highly relevant to the axle configuration and magnitude of passing vehicles. The energy transmission efficiency of the energy harvester is also assessed.
Ph. D.

In recent years, vibration-based energy harvesting technologies have gained great importance because of reduced power requirement of small electronic components. External power source and maintenance requirement can be minimized by employment of mechanical vibration energy harvesters. Power sources that harvest energy from the environment have the main advantages of high safety, long shell life and low cost compared to chemical batteries. Electromagnetic, electrostatic and piezoelectric transduction mechanisms are the three main energy harvesting methods. In this thesis, it is aimed to apply the piezoelectric elements technology to develop means for energy storage in munitions launch. The practical problems encountered in the design of piezoelectric energy harvesters are investigated. The applicability of energy harvesting to high power needs are studied. The experience compiled in the study is to be exploited in designing piezoelectric energy harvesters for munitions applications. Piezoelectric energy harvesters for harmonic and mechanical shock loading conditions with different types of piezoelectric materials are designed and tested. The test results are compared with both responses from analytical models generated in MATLAB®
and ORCAD PSPICE®
, and finite element method models generated in ATILA®
. Optimum energy storage methods are considered.

Piezoelectric energy harvesting has been around for almost a decade to generate power from the ambient vibrations. Although the generated power is very small, but there are several ways to increase and enhance the generated power. This project presents different methods of optimizing the output power by changing the structural configuration of the energy harvesters, selection of piezoelectric material and circuit interface of these harvesters. To understand the different steps of the enhancement, the process of energy conversion by piezoelectric material has been first looked at. Different groups of piezoelectric material were studied to see what kind of materials have the ability of increasing the generated power. As mechanical configuration of the energy harvesters has a significant effect on the output voltage, their configuration such as Cantilever beam type, Cymbal type and Circular diaphragms has been described and compared. After the power generated in the piezoelectric crystal , the current is sent to through an interface circuit to get rectified and regulated. This circuit can be modified to increase the power as well. There are several types of circuits that can increase the output voltage significantly. Synchronized Switch Harvesting (SSH) techniques, Synchronous Electric Charge Extraction technique and voltage doubler are such examples. These techniques have been also studied and compared. Because of the outgrowing industry of piezoelectric energy harvesting in Medical field, their function and their progress has also been reviewed.

Piezoelectric nanostructures of ZnO were employed for development of vibration energy harvesters. Columnar nanorod structures of ZnO, incorporated into various heterojunction-based device prototypes, were strained to generate voltage signals. The fabricated devices’ prototypes were based on different top electrodes such as: p-n junction-type Poly(3,4-ethylenedioxythiophene) Polystyrene sulfonate (PEDOT:PSS)/ZnO devices, metal-insulator-semiconductor type Poly(methyl methacrylate) (PMMA)/ZnO devices. Similarly, various bottom electrode materials based prototypes were also assembled: ZnO/indium tin oxide (ITO), ZnO/silver (Ag) and ZnO/zinc (Zn). The overall device design was based on flexible electrodes and substrates, due to which low temperature (below 100 °C) fabrication processes were implemented. Device performance measurement and characterisation techniques were explored and implemented to improve the reliability of results. These techniques included open-circuit voltage and short-circuit current output measurement, resistive load matching and impedance analysis. The analysed performance of energy harvester was assessed in relation to its constituent material properties. The parameters which affect the energy harvester performance were investigated and for this p-n junction-based (PEDOT:PSS/ZnO) devices were used. It was analysed that devices with optimum shunt (Rsh) and series resistance (Rs), which were in the ranges of 0.08 – 0.17 kΩ and 0.5 – 1.65 kΩ respectively, generated the highest peak open-circuit voltage (Voc) and peak power density (PL) of 90 – 225 mV and 36 – 54 μW cm-2. However, the p-n junction-based devices with low shunt resistance (Rsh), ranged between 0.2 – 0.3 kΩ, were considered to be affected with leakage losses, such as short-circuits. Therefore, these devices generated lower Voc and PL in the range of 20 - 60 mV and 2 - 16 μW cm-2. Similarly, the p-n junction-based devices with higher Rs, ranged between 0.3 – 0.6 kΩ, were adversely affected by I2R losses and therefore their generated power density was also dropped to 0.22 - 0.25 μW cm-2. In addition to parasitic resistance losses, the most significant phenomenon investigated in ZnO energy harvesters was, screening of polarisation ii charges in ZnO. The polarisation screening effects were observed to be related to the electrical properties of device components like electrode material type and conductivity of ZnO. Hence, the effect of electrode electrical properties on electric field screening was investigated. In this regard, device electrodes were varied and their effect on energy harvesting efficiency was studied. A comparison based on the performance of bottom electrodes like indium tin oxide (ITO), silver (Ag) and zinc foil on device performance was made. It was observed that due to lower screening effects of ITO, the ITO-based devices generated voltage output which was two orders of magnitude higher than the zinc foil-based devices. Similarly, the screening effects of top electrode materials, like PEDOT:PSS and PMMA, on device output generation were investigated. The PMMA-based devices generated average 135 mV which was higher than average 100 mV generation of PEDOT:PSS-based devices; which indicated that the PMMA-based devices had slower screening rate. On the contrary, the PMMA-based devices’ 7 times higher series resistance than PEDOT:PSS-based devices caused the PL of PMMA-based devices to be 0.4 μW cm-2, which was two orders of magnitude lower than 54 μW cm-2 generated by PEDOT:PSS-based devices. Further to electrode materials study, polarisation screening caused by electrical properties of ZnO was also anaylsed. In this regard, the surface-induced conductivity of ZnO was decreased by using surface coating of copper thiocyanate (CuSCN). The reduction in ZnO conductivity was considered to reduce the screening of polarisation charges. Consequently, the power density of ZnO devices was enhanced from 54 μW cm-2 to 434 μW cm-2.

As we enter the age of the internet of things (IoT), more embedded devices are appearing in our everyday items, such as electrical appliances, watches, mobile phones, and even clothes. These are devices that are able to communicate with one another and collect sensing data about their environment. An emerging area of interest in this field is the wearable devices, such as smart devices for healthcare and wellness implantables. These devices require power and batteries will need to be constantly recharged, adding to the users’ inconvenience. Energy harvesters are devices that are able to harness ambient energy such as movement and convert it into useful electrical energy. As such, energy harvesters are expected to play an important role in powering such devices in order to save space and more importantly to increase the comfort and convenience of the users. This work presents a piezoelectric energy harvester that captures energy from stretchable surfaces such as the human skin, exterior of organs and even garments. The main feature of the harvester is the inclusion of a ribbon structure encased in a flexible elastomer, Ecoflex. This allows the device to stretch to tens of percents, while maintaining strain levels of the piezoelectric material within its mechanical limits, which is required since stretchable surfaces can strain to tens of percent. This device provides an efficient method of converting overall device stretch to bending stress within the piezoelectric material, and can strain both horizontally and vertically. Polyvinylidene fluoride (PVDF) and its copolymer, polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) are the material of choice due to their flexibility and magnitude of piezoelectric coefficients. A thickness of 10-28 μm is chosen for the PVDF film and the total device thickness including the Ecoflex ranges from 1-3 mm. Bimorph structure and alternately-connected electrodes ensure that charge cancellation is minimized. Static and transient finite element modeling are carried out to characterize the devices and obtain trends for design parameters. The trends obtained will allow the user to select device parameters given certain constraints such as film thickness and device effective Young’s modulus. Two fabrication approaches are used to fabricate planar PVDF, PVDF-TrFE films. The first approach involves fabricating the film starting from PVDF-TrFE powder. The powder is dissolved in a solvent and cast using an in-house stainless steel structure onto a wafer that has spincast gelatin. Gelatin acts as a release layer. Aluminum and chromium are sputtered and patterned on the wafer before a second layer of PVDF-TrFE is cast again. A top metal is then patterned and a method to etch the PVDF-TrFE is developed in order to access the bottom metal. Each PVDF-TrFE layer is 10 μm thick. To ensure that the electrodes are flexible, mesh designs are incorporated. Various measurements such as mechanical, ferroelectric and piezoresponse measurements are carried out to verify the performance of the film. The second approach uses commercial PVDF film of 28 μm, with 6 μm of silver ink as the electrodes. These silver ink allows for the metal to stretch to 10% and the mesh design is not needed. Two types of patterning the metal are devised. One method involves using a laser cutter to define the shape of a label, which then acts as a mask. Another lithographic method has been devised in order to accurately define the patterns. This method involves temporarily bonding the film to a wafer and using dry film photoresist. Top and bottom side metal alignment is carried out using backside alignment option of the photolithography tool. With the planar films, a molding method is then developed in order to mold the film into the required ribbon shape. This method involves 3D printing various assembly rigs in order to achieve the desired final shapes. A snap-in locking mechanism has also been devised to enable self-alignment of the film to the mold, which is difficult to achieve on device patterns smaller than 500 μm radius. Ecoflex is used as the elastomer since this material can stretch to 400%. Three device sizes, namely 350, 500 and 750 μm radius devices are fabricated in order to have different devices for comparison with respect to scaling of the design. These devices are able to stretch up to 40%, while still maintaining structural integrity. The 350 μm device is able to generate 292 nW of power for an active volume of 0.387 cm3 when stretched 20%. This energy density is similar to other devices, albeit being able to strain at a much higher overall level. Finally, various extensions of the harvester are explored to provide an overview of the possible future work for the harvester.

Piezoelectric materials have a unique characterization which can absorb energy from the environment and convert it to electrical energy. In this conducted research energy harvesting of the THin layer UNimorph DrivER (THUNDER) were investigated. THUNDER is a curved PZT which bring considerable benefits in compare of flat PZT such as better vibration absorption capacity and higher energy recovery efficiency. Also one of the most important characteristics of THUNDER is its low resonance frequency. Because the maximum power a harvester can achieve is at its resonance frequency. So it has application in low resonance frequency situations. In this work, general constitutive law for piezoelectric materials is reduced because it is assumed THUNDER is thin and modeled as a Euler-Bernoulli beam. To obtain mechanical-electrical coupling equations, Hamilton principle is used. Hamilton principle is using kinetic and potential energy and work due to the external force as its input. As a result, modals and natural frequency of THUNDER are obtained. Then based on boundary condition, natural frequency can be achieved. By using Rayleigh-Ritz approach and in-extensional assumption and assuming excitation is sinusoidal, discretize mechanical-electrical coupling equations can be written. For the experiment part, two modes energy harvesting circuit is used, the first one is full bridge rectifier in low-level excitation and steps down converter in high-level excitation. Also, resistor and battery are used as an external load. Because rectified voltage is equal battery voltage, so the model needs to be adjusted by putting a step-down converter in the circuit to adjust Voltage and get the maximum power from the model. In the case of the resistor as an external load, the maximum power will achieve near resonance frequency and also by increasing the amplitude of resistors, more power can be achieved by the circuit. Also, step down converter is used in two modes, continuous conduction mode(CCM) and Discontinuous conduction mode(DCM). Power harvesting in this two mode also compared.

Vibration-based energy harvesting has been investigated by several researchers over the last decade. The ultimate goal in this research field is to power small electronic components (such as wireless sensors) by using the vibration energy available in their environment. Among the basic transduction mechanisms that can be used for vibration-to-electricity conversion, piezoelectric transduction has received the most attention in the literature. Piezoelectric materials are preferred in energy harvesting due to their large power densities and ease of application. Typically, piezoelectric energy harvesters are cantilevered structures with piezoceramic layers that generate alternating voltage output due to base excitation. This work presents distributed-parameter electromechanical models that can accurately predict the coupled dynamics of piezoelectric energy harvesters. First the issues in the existing models are addressed and the lumped-parameter electromechanical formulation is corrected by introducing a dimensionless correction factor derived from the electromechanically uncoupled distributed-parameter solution. Then the electromechanically coupled closed-form analytical solution is obtained based on the thin-beam theory since piezoelectric energy harvesters are typically thin structures. The multi-mode electromechanical frequency response expressions obtained from the analytical solution are reduced to single-mode expressions for modal vibrations. The analytical solutions for the electromechanically coupled voltage response and vibration response are validated experimentally for various cases. The single-mode analytical equations are then used for deriving closed-form relations for parameter identification and optimization. Asymptotic analyses of the electromechanical frequency response functions are given along with expressions for the short-circuit and the open-circuit resonance frequencies. A simple experimental technique is presented to identify the optimum load resistance using only a single resistor and an open-circuit voltage measurement. A case study is given to compare the power generation performances of commonly used monolithic piezoceramics and novel single crystals with a focus on the effects of plane-stress material constants and mechanical damping. The effects of strain nodes and electrode configuration on piezoelectric energy harvesting are discussed theoretically and demonstrated experimentally. An approximate electromechanical solution using the assumed-modes method is presented and it can be used for modeling of asymmetric and moderately thick energy harvester configurations. Finally, a piezo-magneto-elastic energy harvester is introduced as a non-conventional broadband energy harvester.
Ph. D.

Motion-driven energy harvesters can replace batteries in low power wireless sensors, however selection of the optimal type of transducer for a given situation is difficult as the performance of the complete system must be taken into account in the optimisation. In this thesis, a complete piezoelectric energy harvester system model including a piezoelectric transducer, a power conditioning circuit, and a battery, is presented allowing for the first time a complete optimisation of such a system to be performed. Combined with previous work on modelling an electrostatic energy harvesting system, a comparison of the two transduction methods was performed. The results at 100 Hz indicate that for small MEMS devices at low accelerations, electrostatic harvesting systems outperform piezoelectric but the opposite is true as the size and acceleration increases. Thus the transducer type which achieves the best power density in an energy harvesting system for a given size, acceleration and operating frequency can be chosen. For resonant vibrational energy harvesting, piezoelectric transducers have received a lot of attention due to their MEMS manufacturing compatibility with research focused on the transduction method but less attention has been paid to the output power electronics. Detailed design considerations for a piezoelectric harvester interface circuit, known as single-supply pre-biasing (SSPB), are developed which experimentally demonstrate the circuit outperforming the next best known interface's theoretical limit. A new mode of operation for the SSPB circuit is developed which improves the power generation performance when the piezoelectric material properties have degraded. A solution for tracking the maximum power point as the excitation changes is also presented.

La récupération d'énergie par élément piézoélectrique est une technique prometteuse pour les futurs systèmes électroniques nomades autoalimentés. L'objet de ce travail est d’analyser des approches simples et agiles d’optimisation de la puissance produite par un générateur piézoélectrique. D'abord le problème de l’optimisation de l’impédance de charge d’un générateur piézoélectrique sismique est posé. Une analyse du schéma équivalent global de ce générateur a été menée sur la base du schéma de Mason. Il est démontré que la puissance extraite avec une charge complexe adaptée puisse être constante quelle que soit la fréquence et que de plus elle est égale à la puissance extraite avec la charge résistive adaptée du même système sans pertes. Il est montré toutefois que la sensibilité de cette adaptation à la valeur de la réactance de la charge la rend difficilement réaliste pour une application pratique. Une autre solution pour améliorer l’énergie extraite est de considérer un réseau de générateurs positionnés en différents endroits d’une structure. Des simulations sont proposées dans une configuration de récupération d’énergie de type directe sur une plaque encastrée. Les générateurs piézoélectriques, associés à la technique SSHI, ont été reliés selon différentes configurations. Les résultats attestent que l’énergie produite ne dépend pas de façon critique de la manière dont sont connectés les éléments. Toutefois l’utilisation d’un seul circuit SSHI pour l’ensemble du réseau dégrade l’énergie extraite du fait des interactions entre les trop nombreuses commutations. Enfin une nouvelle approche non-linéaire est étudiée qui permet l’optimisation de l’énergie extraite tout en gardant une grande simplicité et des possibilités d’auto alimentation. Cette technique appelée S3H pour « Synchronized Serial Switch Harvesting » n’utilise pas d’inductance et consiste en un simple interrupteur en série avec l’élément piézoélectrique. La puissance récupérée est le double de celle extraite par les méthodes conventionnelles et reste totalement invariante sur une large gamme de résistances de charge
Piezoelectric energy harvesting is a promising technique for battery-less miniature electronic devices. The object of this work is to evaluate simple and robust approaches to optimize the extracted power. First, a lightweight equivalent circuit derived from the Mason equivalent circuit is proposed. It’s a comprehensive circuit, which is suitable for piezoelectric seismic energy harvester investigation and power optimization. The optimal charge impedance for both the resistive load and complex load are given and analyzed. When complex load type can be implemented, the power output is constant at any excitation frequency with constant acceleration excitation. This power output is exactly the maximum power that can be extracted with matched resistive load without losses. However, this wide bandwidth optimization is not practical due to the high sensitivity the reactive component mismatch. Another approach to improve power extraction is the capability to implement a network of piezoelectric generators harvesting on various frequency nodes and different locations on a host structure. Simulations are conducted in the case of direct harvesting on a planar structure excited by a force pulse. These distributed harvesters, equipped with nonlinear technique SSHI (Synchronized Switching Harvesting on Inductor) devices, were connected in parallel, series, independently and other complex forms. The comparison results showed that the energy output didn’t depend on the storage capacitor connection method. However, only one set of SSHI circuit for a whole distributed harvesters system degrades the energy scavenging capability due to switching conflict. Finally a novel non-linear approach is proposed to allow optimization of the extracted energy while keeping simplicity and standalone capability. This circuit named S3H for “ Synchronized Serial Switch Harvesting” does not rely on any inductor and is constructed with a simple switch. The power harvested is more than twice the conventional technique one on a wide band of resistive load

The piezoelectric energy harvester has become a new powering option for some low-power electronic devices such as MEMS (Micro Electrical Mechanical System) sensors. Piezoelectric materials can collect the ambient vibrations energy and convert it to electrical energy. This thesis is intended to demonstrate the behavior of a piezoelectric energy harvester system at elevated temperature from room temperature up to 82°C, and compares the system’s performance using different piezoelectric materials. The systems are structured with a Lead Magnesium Niobate-Lead Titanate (PMN-PT) single crystal patch bonded to an aluminum cantilever beam, Lead Indium Niobate-Lead Magnesium Niobate-Lead Titanate (PIN-PMN-PT) single crystal patch bonded to an aluminum cantilever beam and a bimorph cantilever beam which is made of Lead Zirconate Titanate (PZT). The results of this experimental study show the effects of the temperature on the operation frequency and output power of the piezoelectric energy harvesting system. The harvested electrical energy has been stored in storage circuits including a battery. Then, the stored energy has been used to power up the other part of the system, a wireless resonator force sensor, which uses frequency conversion techniques to convert the sensor’s ultrasonic signal to a microwave signal in order to transmit the signal wirelessly.

This research investigates vibration energy harvesting by modelling several piezoelectric-based structures. The usage of piezoelectric transduction under input vibration environments can be profitable for obtaining electrical energy for powering smart wireless sensor devices for health condition monitoring of rotating machines, structures and defence communication technology. The piezoelectric transduction shows strong prospect in the application of power harvesting because it can be applied at the microelectromechanical system design level in compact configuration with high sensitivity with respect to low input mechanical vibration. In this research work, the important aspects of the continuum thermopiezoelectric system associated with the laws of thermodynamics, Maxwell relations and Legendre transformations have been developed to explore the macroscopic thermopiezoelectric potential equations, the thermopiezoelectric equations of state and energy function forms. The application of the continuum thermopiezoelectric behaviour can be used to further formulate novel analytical methods of the electromechanical cantilevered piezoelectric bimorph beams with the tip mass using the weak and strong forms resulting from Hamiltonian’s principle.The constitutive electromechanical dynamic equations of the piezoelectric bimorph beam under one or two input base excitations can be used to derive the equations of the coupled electromechanical dynamic response of transverse-longitudinal form (CEDRTL), the coupled electromechanical dynamic response of longitudinal form (CEDRL) and the coupled electromechanical dynamic response of transverse form (CEDRT). The derivation of the constitutive electromechanical dynamic equations using the weak form of Hamiltonian’s principle can be further derived using the Ritz method associated with orthonomality whereas the closed form or distributed parameter reduced from strong form of Hamiltonian’s principle, can be further formulated using the convergent eigenfunction series with orthonormality. Laplace transformation can be used to give the solution in terms of the multi-mode transfer functions and multi-mode frequency response functions of dynamic displacement, velocity, electric voltage, current, power and optimal power. Moreover, the broadband multi-electromechanical bimorph beam with multi-resonance can also be explored showing the single- and multi-mode transfer functions and frequency response functions. A parametric case study of the piezoelectric bimorph beam with the tip mass and transverse input excitation is discussed to validate the weak and closed forms of the CEDRTL, under series and parallel connections, using the multi-mode frequency response functions with variable load resistance.A further case study of a broadband multi-electromechanical piezoelectric bimorph beam is also discussed using the weak form of the CEDRT to give the frequency response functions under variable load resistance. Finally, the piezoelectric bimorph beams with and without tip masses under transverse base input excitation are also comprehensively discussed using the weak forms of the CEDRTL and CEDRT models and compared with experimental results for variable load resistance. A piezoelectric bimorph beam with tip mass is investigated to show the close agreement between the CEDRTL model and experimental results using the polar amplitudes from the combined action of simultaneous longitudinal and transverse base input excitation.

Con la presente tesi viene esaminato un metodo per modificare la frequenza di risonanza di trasduttori piezoelettrici mediante applicazione di carichi elettrici esterni. L'elaborato inizia con la presentazione dei cristalli utilizzati nel lavoro di tesi, concentrandosi sul processo di fabbricazione di un bimorph cantilever impiegato come convertitore elettromeccanico di energia, la cui frequenza di risonanza è modellizzata analiticamente mediante la legge di Newton e il modello di Euler-Bernoulli. Su tale struttura vengono condotte misure mediante shaker elettrodinamico e analizzatore d'impedenza, ai fini di giusticare il modello analitico presentato. Con lo scopo di sincronizzare la frequenza di risonanza del cantilever con la vibrazione dell'ambiente per massimizzare la potenza disponibile, viene proposto un algoritmo MPPT secondo l'approccio Perturba e Osserva (P&O), al quale è fornita in ingresso la tensione efficace di un layer di materiale piezoelettrico. Valutare la sua risposta in tensione, presenta dei limiti applicativi che hanno portato a prendere in considerazione un approccio totalmente diff�erente, basato sullo sfasamento tra la tensione di un trasduttore piezoelettrico e il segnale di accelerazione impiegato come eccitazione. Misure sperimentali sono state condotte con l'obiettivo di validare l'efficacia di quest'ultimo approccio qualora si voglia sincronizzare la frequenza di risonanza dei piezo con segnali di vibrazione reali.

The performance of piezoelectric cantilever beam energy harvesters subjected to base excitation is considered in this work. Based on the linear assumption, a theoretical model is developed to predict the mechanical and electrical responses of the harvester and in comparison to other theoretical models, more accurate mode shape functions are used for the structural part of the harvester. The model is validated against experimental measurements and parameter studies are carried out to investigate the maximum power output in different situations. In some applications, like powering tyre pressure monitoring sensors (TPMS), energy harvesters are subjected to large amplitude shocks and high levels of acceleration, which can cause large bending stresses to develop in the beam, leading to mechanical failure. In this work, a bump stop is introduced in the energy harvester design to limit the amplitude of vibration and prevent large amplitude displacement. A theoretical model is developed to simulate the energy harvester impacting a stop, and the model is used to investigate how the electrical output of the harvester is affected by the stop. The work demonstrates how the model can be used as a design tool for analysing the compromise between the electrical output and structural integrity. Nonlinear behaviour of the energy harvester is observed to have a significant effect on the resonance frequencies when the harvester is subjected to large amplitude base accelerations. To correctly predict the behaviour of the harvester, piezoelectric material nonlinearity and geometric nonlinearity are incorporated in the theoretical model. It is found that the nonlinear softening effect is dominated by the material nonlinearity, while the geometric nonlinearity is less significant. The nonlinear energy harvester model is used in conjunction with the bump stop and results obtained using the linear and nonlinear models are compared to experimental measurements to investigate the importance of using a nonlinear model. The inclusion of nonlinear behaviour is shown to improve significantly the accuracy of predictions under some circumstances. The energy harvester models developed in this work are used to simulate the electrical power generated in a TPMS application, where the harvester embedded in the tyre is subjected to large radial accelerations as the tyre rolls along the road. The simulated results are compared to reported experimental work and agreement is found between the results.

Energy harvesting is a technology for generating electrical power from ambient or wasted energy. It has been investigated extensively as a means of powering small electronic devices. The recent proliferation of devices with ultra-low power consumption - devices such as RF transmitters, sensors, and integrated chipsets - has created new opportunities for energy harvesters. There is a variety of ambient energies such as vibration, thermal, solar, stray current, etc. Depending on energy sources, different kinds of energy conversion mechanism should be employed. For energy harvesters to become practical, their energy conversion efficiency must improve. This efficiency depends upon advances in two areas: the system or structural design of the energy harvester, and the properties of the materials employed in energy conversion. This dissertation explores developments in both areas. In the first area, the role of nano-, micro-, and bulk structure of the energy conversion materials were investigated. In the second area, piezoelectric energy harvesters and a magneto-thermoelectric generator are treated from the perspective of system design. In the area of materials development, PbTiO3 (PTO) nanostructures consisting of nanofibers and three-dimensional (3-D) nanostructure arrays were hydrothermally synthesized. The growth mechanism of the PTO nanofibers and 3-D nanostructures were investigated experimentally and theoretically. The PTO nanostructures were composed of oriented PTO crystals with high tetragonality; these arrays could be promising candidates for nanogenerators. Different designs for energy harvesters were explored as a means of improving energy conversion efficiency. Piezoelectric energy harvesters were designed and constructed for applications with a low frequency vibrational energy and for applications with a broadband energy spectrum. A spiral MEMS piezoelectric energy harvester design was fabricated using a silicon MEMS process and demonstrated to extract high power density at ultra-low resonance frequencies and low acceleration conditions. For a broadband energy harvester, a magnetically-coupled array of oscillators was designed and built that broadened the harvester's effective resonance frequency with considerably improved output power. A new design concept for thermal energy harvesting that employs a magneto-thermoelectric generator (MTG) design was proposed. The MTG exploits a thermally-induced second order phase transition in a soft magnetic material near the Curie temperature. The MTG harvested electric power from oscillations of the soft magnet between hot and cold sources. For the MTG design, suitable soft magnetic materials were selected and developed using La0.85Sr0.15MnO3-Ni0.6Cu0.2Zn0.2Fe2O4 magnetic composites. The MTG was fabricated from a PVDF cantilever and a gadolinium (Gd) soft magnetic material. The feasibility of the design for harvesting energy from the waste heat was demonstrated by attaching an MTG array to a computer CPU.
PHD

The urgent need for a clean and sustainable power supply for wireless sensor nodes and low-power electronics in various monitoring systems and the Internet of Things has led to an explosion of research in substitute energy technologies. Traditional batteries are still the most widely used power source for these applications currently but have been blamed for chemical pollution, high maintenance cost, bulky volume, and limited energy capacity. Ambient energy in different forms such as vibration, movement, heat, wind, and waves otherwise wasted can be converted into usable electricity using proper transduction mechanisms to power sensors and low-power devices or charge rechargeable batteries. This dissertation focuses on the design, modeling, optimization, prototype, and testing of novel piezoelectric energy harvesters for extracting energy from human walking, bio-inspired bi-stable motion, and torsional vibration as an alternative power supply for wireless monitoring systems. To provide a sustainable power supply for health care monitoring systems, a piezoelectric footwear harvester is developed and embedded inside a shoe heel for scavenging energy from human walking. The harvester comprises of multiple 33-mode piezoelectric stacks within single-stage force amplification frames sandwiched between two heel-shaped aluminum plates taking and reallocating the dynamic force at the heel. The single-stage force amplification frame is designed and optimized to transmit, redirect, and amplify the heel-strike force to the inner piezoelectric stack. An analytical model is developed and validated to predict precisely the electromechanical coupling behavior of the harvester. A symmetric finite element model is established to facilitate the mesh of the transducer unit based on a material equivalent model that simplifies the multilayered piezoelectric stack into a bulk. The symmetric FE model is experimentally validated and used for parametric analysis of the single-stage force amplification frame for a large force amplification factor and power output. The results show that an average power output of 9.3 mW/shoe and a peak power output of 84.8 mW are experimentally achieved at the walking speed of 3.0 mph (4.8 km/h). To further improve the power output, a two-stage force amplification compliant mechanism is designed and incorporated into the footwear energy harvester, which could amplify the dynamic force at the heel twice before applied to the inner piezoelectric stacks. An average power of 34.3 mW and a peak power of 110.2 mW were obtained under the dynamic force with the amplitude of 500 N and frequency of 3 Hz. A comparison study demonstrated that the proposed two-stage piezoelectric harvester has a much larger power output than the state-of-the-art results in the literature. A novel bi-stable piezoelectric energy harvester inspired by the rapid shape transition of the Venus flytrap leaves is proposed, modeled and experimentally tested for the purpose of energy harvesting from broadband frequency vibrations. The harvester consists of a piezoelectric macro fiber composite (MFC) transducer, a tip mass, and two sub-beams with bending and twisting deformations created by in-plane pre-displacement constraints using rigid tip-mass blocks. Different from traditional ways to realize bi-stability using nonlinear magnetic forces or residual stress in laminate composites, the proposed bio-inspired bi-stable piezoelectric energy harvester takes advantage of the mutual self-constraint at the free ends of the two cantilever sub-beams with a pre-displacement. This mutual pre-displacement constraint bi-directionally curves the two sub-beams in two directions inducing higher mechanical potential energy. The nonlinear dynamics of the bio-inspired bi-stable piezoelectric energy harvester is investigated under sweeping frequency and harmonic excitations. The results show that the sub-beams of the harvester experience local vibrations, including broadband frequency components during the snap-through, which is desirable for large power output. An average power output of 0.193 mW for a load resistance of 8.2 kΩ is harvested at the excitation frequency of 10 Hz and amplitude of 4.0 g. Torsional vibration widely exists in mechanical engineering but has not yet been well exploited for energy harvesting to provide a sustainable power supply for structural health monitoring systems. A torsional vibration energy harvesting system comprised of a shaft and a shear mode piezoelectric transducer is developed in this dissertation to look into the feasibility of harvesting energy from oil drilling shaft for powering downhole sensors. A theoretical model of the torsional vibration piezoelectric energy harvester is derived and experimentally verified to be capable of characterizing the electromechanical coupling system and predicting the electrical responses. The position of the piezoelectric transducer on the surface of the shaft is parameterized by two variables that are optimized to maximize the power output. Approximate expressions of the voltage and power are derived by simplifying the theoretical model, which gives predictions in good agreement with analytical solutions. Based on the derived approximate expression, physical interpretations of the implicit relationship between the power output and the position parameters of the piezoelectric transducer are given.
Doctor of Philosophy
Wireless monitoring systems with embedded wireless sensor nodes have been widely applied in human health care, structural health monitoring, home security, environment assessment, and wild animal tracking. One distinctive advantage of wireless monitoring systems is to provide unremitting, wireless monitoring of interesting parameters, and data transmission for timely decision making. However, most of these systems are powered by traditional batteries with finite energy capacity, which need periodic replacement or recharge, resulting in high maintenance costs, interruption of service, and potential environmental pollution. On the other hand, abundant energy in different forms such as solar, wind, heat, and vibrations, diffusely exists in ambient environments surrounding wireless monitoring systems which would be otherwise wasted could be converted into usable electricity by proper energy transduction mechanisms. Energy harvesting, also referred to as energy scavenging and energy conversion, is a technology that uses different energy transduction mechanisms, including electromagnetic, photovoltaic, piezoelectric, electrostatic, triboelectric, and thermoelectric, to convert ambient energy into electricity. Compared with traditional batteries, energy harvesting could provide a continuous and sustainable power supply or directly recharge storage devices like batteries and capacitors without interrupting operation. Among these energy transduction mechanisms, piezoelectric materials have been extensively explored for small-size and low-power generation due to their merits of easy shaping, high energy density, flexible design, and low maintenance cost. Piezoelectric transducers convert mechanical energy induced by dynamic strain into electrical charges through the piezoelectric effect. This dissertation presents novel piezoelectric energy harvesters, including design, modeling, prototyping, and experimental tests for energy harvesting from human walking, broadband bi-stable nonlinear vibrations, and torsional vibrations for powering wireless monitoring systems. A piezoelectric footwear energy harvester is developed and embedded inside a shoe heel for scavenging energy from heel striking during human walking to provide a power supply for wearable sensors embedded in health monitoring systems. The footwear energy harvester consists of multiple piezoelectric stacks, force amplifiers, and two heel-shaped metal plates taking dynamic forces at the heel. The force amplifiers are designed and optimized to redirect and amplify the dynamic force transferred from the heel-shaped plates and then applied to the inner piezoelectric stacks for large power output. An analytical model and a finite model were developed to simulate the electromechanical responses of the harvester. The footwear harvester was tested on a treadmill under different walking speeds to validate the numerical models and evaluate the energy generation performance. An average power output of 9.3 mW/shoe and a peak power output of 84.8 mW are experimentally achieved at the walking speed of 3.0 mph (4.8 km/h). A two-stage force amplifier is designed later to improve the power output further. The dynamic force at the heel is amplified twice by the two-stage force amplifiers before applied to the piezoelectric stacks. An average power output of 34.3 mW and a peak power output of 110.2 mW were obtained from the harvester with the two-stage force amplifiers. A bio-inspired bi-stable piezoelectric energy harvester is designed, prototyped, and tested to harvest energy from broadband vibrations induced by animal motions and fluid flowing for the potential applications of self-powered fish telemetry tags and bird tags. The harvester consists of a piezoelectric macro fiber composite (MFC) transducer, a tip mass, and two sub-beams constrained at the free ends by in-plane pre-displacement, which bends and twists the two sub-beams and consequently creates curvatures in both length and width directions. The bi-direction curvature design makes the cantilever beam have two stable states and one unstable state, which is inspired by the Venus flytrap that could rapidly change its leaves from the open state to the close state to trap agile insects. This rapid shape transition of the Venus flytrap, similar to the vibration of the harvester from one stable state to the other, is accompanied by a large energy release that could be harvested. Detailed design steps and principles are introduced, and a prototype is fabricated to demonstrate and validate the concept. The energy harvesting performance of the harvester is evaluated at different excitation levels. Finally, a piezoelectric energy harvester is developed, analytically modeled, and validated for harvesting energy from the rotation of an oil drilling shaft to seek a continuous power supply for downhole sensors in oil drilling monitoring systems. The position of the piezoelectric transducer on the surface of the shaft is parameterized by two variables that are optimized to obtain the maximum power output. Approximate expressions of voltage and power of the torsional vibration piezoelectric energy harvester are derived from the theoretical model. The implicit relationship between the power output and the two position parameters of the transducer is revealed and physically interpreted based on the approximate power expression. Those findings offer a good reference for the practical design of the torsional vibration energy harvesting system.

Ambient energy harvesting has attracted significant attention over the last years for applications such as wireless sensors, implantable devices, health monitoring systems, and wearable devices. The methods of vibration-to-electric energy conversion can be included in the following categories: electromagnetic, electrostatic, and piezoelectric. Among various techniques of vibration-based energy harvesting, piezoelectric transduction method has received the most attention due to the large power density of the piezoelectric material and its simple architectures. In contrast to electromagnetic energy harvesting, the output voltage of a piezoelectric energy harvester is high, which can charge a storage component such as a battery. Compared to electrostatic energy harvester, the piezoelectric energy harvester does not require an external voltage supply. Also, piezoelectric harvesters can be manufactured in micro-scale, where they show better performance compared to other energy harvesters, owing to the well-established thick-film and thin-film fabrication techniques. The main drawback of the linear piezoelectric harvesters is that they only retrieve energy efficiently when they are excited at their resonance frequencies, which are usually high, while they are less efficient when the excitation frequency is distributed over a broad spectrum or is dominant at low frequencies. High-frequency vibrations can be found in machinery and vehicles could be used as the energy source but, most of the vibration energy harvesters are targeting at low-frequency vibration sources which are more achievable in the natural environment. One way to overcome this limitation is by using the frequency-up-conversion technology via impacts, where the source of the impacts can be one or two stoppers or more massive beams. The impact makes the piezoelectric beam oscillate in its resonance frequency and brings nonlinear behavior into the system.

Thesis (M.S.)--University of Missouri-Columbia, 2005.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (December 18, 2006) Includes bibliographical references.

A piezoelectric energy harvesting (PEH) system can harvest electrical energy from ambient vibration energy. In a PEH system, the interface rectifier circuit is critical because it converts AC from the output of piezoelectric harvester to DC that can power the load. Hence, improving the efficiency of the interface circuit can directly increase the efficiency of the entire PEH system; consequently, more power can be harvested. Commonly used interface circuits in PEH systems, such as full-bridge and voltage- doubler rectifiers,lead to relatively simple circuit implementations but they show serious limitations in energy-harvesting efficiency. Several innovative solutions have been reported to improve the efficiency of the interface rectifiers, such as ‘switch-only’ and ‘bias-flip’ techniques [7]. Such solutions utilize additional switches or switched inductors to speed up and even quickly reverse (flip) the voltage on the rectifier input to the desired voltage-level and condition for energy transfer, ultimately improving the overall efficiency of the energy harvesting. However, such techniques rely on accurate timing and synchronization of the pulsed switches every time the current produced by the piezoelectric harvester changes polarity. This thesis studies and investigates the impact of the non-ideal switching effects on the energy efficiency of the switch-only and bias-flip interface rectifiers in a PEH system, by theoretical derivation and experimental simulation.

The goal of this thesis is to determine the fatigue life of piezoelectric energy harvesters. The harvester is a cantilever beam made from the piezoelectric ceramic lead zirconate titanate (PZT). Similar structures are used in micro electromechanical systems (MEMS) as actuators and energy harvesters to convert electrical energy to mechanical energy and vice versa. A platform was built to excite PZT cantilever beams in bending vibration, and a method was developed to detect the mechanical and electrical response of the beam, and correlate changes in these responses to the onset of damage.
Subsequently, test protocols were developed to experimentally determine the fatigue life of PZT beams by applying total life and damage tolerance approaches to fatigue testing. Total life tests were performed on pristine beams, while damage tolerance tests were performed on beams indented to induce localized damage. Rates of crack growth were measured by interrupting the fatigue tests and imaging the cracks using scanning electron microscopy. The observation of crack arrest is a major result arising from these studies. The test platform developed in this thesis can be used to explore the effects of size on the fatigue reliability of miniaturized energy harvesters.
Le but de ce projet est de déterminer la résistance en fatigue des générateurs d'énergie piézoélectrique. Le générateur est une poutre en porte-à-faux en miniature faite d'une céramique piézoélectrique de titano-zirconate de plomb (PZT). Des structures similaires sont utilisées dans des systèmes micro-électromécaniques (MEMS) tels que les actionneurs et les générateurs d'énergie pour convertir l'énergie électrique en énergie mécanique et vice versa. Un dispositif a été construit pour soumettre des poutres en miniature au cintrage par vibration et une méthodologie a été développée pour détecter la réponse mécanique et électrique des poutres, et corréler les variations de réponses observées au début de leur bris.
Par la suite, un protocole est développé pour déterminer l'endurance des poutres en miniature PZT, en adoptant l'approche de la durée de vie totale des poutres et celle de leur tolérance au bris. Les expériences de la durée de vie totale sont effectuées sur des poutres immaculées, et les autres sont faites sur des poutres cabossées afin d'introduire un défaut local. Les fréquences de la croissance des craquelures sont mesurées à l'arrêt des expériences et capture des images des craquelures à l'aide du microscope à balayage. L'observation de l'arrêt des craquelures est le résultat majeur émanant de ces études. Le dispositif d'expérimentation utilisé peut aussi servir à explorer l'ampleur des effets des générateurs d'énergie sur la fiabilité de la fatigue.

Over the last decade there has been a growing increase in research in the field of vibrational energy harvesting - devices which convert ambient vibrational energy into electrical energy. The major application area for such devices is as power sources for wireless sensors, thereby replacing currently used batteries which suffer from a finite lifespan and pose environmental issues during disposal. The vast majority of designs are cantilever beams comprising of piezoelectric layers having coverage identical to the substrate layer. It is evident from the literature that rudimentary work has been performed on design optimisation, with reliable and extensive parametric studies on geometry, especially piezoelectric layer coverage, being overlooked. As a result of this, outcomes from previous research are yet to be seen in designs for practical applications. In this work a versatile linear model is developed which can accurately predict the performance of cantilever piezoelectric energy harvesters. An integral part of the model uses a transfer matrix method to accommodate the difference in structural dynamics of both uniform and non-uniform structures with model validation provided through extensive experimental work. The linear model developed is used to carry out parametric studies on the geometry of three distinct energy harvester cases thereby providing comprehensive knowledge on key variables and geometrical changes which can improve performance. In one of the cases examined, an improvement in performance of over 100% is predicted by solely altering piezoelectric layer coverage. However, the load resistance, i.e. electrical condition, has a significant effect on the trends in generated power which led to work directed toward harvester optimisation in a more realistic electrical scenario. Investigation on harvester geometry whilst utilising an electrical scenario comprising of an energy storage medium is undertaken in this work. The developed model ensures the effects of electro-mechanical coupling remain and provides a solid basis from which users can readily apply model extensions through inclusion of further electrical components to resemble practical circuitry. Theoretically, for all examined case studies, improvements in performance were realised through alterations to piezoelectric layer dimensions with the most notable result indicating an improvement of over 200% during optimisation of piezoelectric layer length. In conjunction to theoretical findings, outcomes of extensive experimental work are provided in order to highlight the accuracy and reliability of the presented theoretical models in both electrical scenarios. Variation in mechanical damping magnitude plays a pivotal role throughout experimental testing and is one key factor in explaining why devices comprising of shorter piezoelectric layers have high performance. A methodology behind unbiased design comparisons is also provided in this work, and involves comparing devices with identical fundamental frequencies. The reasoning behind this approach is to allow for each device to perform as efficiently as possible in the same excitation scenario. Systematic alterations to multiple geometric parameters are used to achieve this. Geometric parameters such as the substrate thickness are observed to provide adequate frequency control. Using this approach, performance improvements from adjustments to piezoelectric coverage still remain. The occurrence of non-linearity in piezoelectric materials is a widely known phenomena and so lastly, a more robust model is provided which incorporates material and geometric non-linearity. This model is useful in determining dynamical responses of uniform and non-uniform piezoelectric energy harvesters when subjected to moderate-to-high acceleration levels. A thorough validation of the theoretical model is achieved using extensive experimental data obtained from a range of samples. For the harvester composition tested in this work, the occurrence of mild non-linearity at base acceleration levels as low as 1 meter per second squared is witnessed with softening behaviour causing the resonant frequency to decrease with base acceleration. In order to avoid reduced efficiency in the final application, the prediction of possible frequency shifts is vital during the design process.

Approved for public release; distribution is unlimited
The military’s dependence on fossil fuels for electric power production in isolated settings is both logistically and monetarily expen-sive. Currently, the Department of Defense is actively seeking alternative methods to produce electricity, thus decreasing dependence on fossil fuels and increasing combat power.We believe piezoelectric generators have the ability to contribute to military applications of alternative electrical power generation in isolated and austere conditions. In this paper, we use three and six variable mathemat-ical models to analyze piezoelectric generator power generation capabilities. Using mk factorial sampling, nearly orthogonal and balanced Latin hypercube (NOBLH) design, and NOBLH iterative methods, we find optimal solutions to maximize piezoelectric gen-erator power output. We further analyze our optimal results using robustness analysis techniques to determine the sensitivity of our models to variable precision. With our results, we provide analysts and engineers the optimal designs involving material parameters in the piezoelectric generator, as well as the generator’s environment, in order to maximize electric output.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, June 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 48).
This thesis presents the design and analysis of an experimental test bench for the characterization of piezoelectric microelectromechanical system (MEMS) energy harvester being developed by the Micro & Nano Systems Laboratory research group at MIT. Piezoelectric MEMS energy harvesters are micro-devices that are able to harvest energy from their ambient vibrations using piezoelectric material property, and many different designs are being researched by the Micro & Nano Systems Laboratory. In order to analyze the different designs, it is crucial to have a flexible test bench, and the test bench created in this thesis allows data to be gathered easily from different energy harvesters. After the test bench is designed and created, it is used to excite a linear cantilever beam energy harvester system at different frequencies and values for open circuit voltage, resonance frequency, and maximum power are calculated from the collected experimental data. In addition, theory behind linear and nonlinear energy harvester systems is investigated and important definitions, characteristics, and equations are summarized in this thesis.
by You C. Yoon.
S.B.

This work examines a novel concept and design of simultaneous energy harvesting and vibration control on the same host structure. The motivating application is a multifunctional composite sandwich wing spar for a small Unmanned Aerial Vehicle (UAV) with the goal of providing self-contained gust alleviation. The basic idea is that the wing itself is able to harvest energy from the ambient vibrations along with available sunlight during normal flight. If the wing experiences any strong wind gust, it will sense the increased vibration levels and provide vibration control to maintain its stability. This work holds promise for improving performance of small UAVs in wind gusts. The proposed multifunctional wing spar integrates a flexible solar cell array, flexible piezoelectric wafers, a thin film battery and an electronic module into a composite sandwich structure. The basic design factors are discussed for a beam-like multifunctional wing spar with load-bearing energy harvesting, strain sensing and self-controlling functions. Three-point bending tests are performed on the composite sandwich structure for bending strength analysis and bending stiffness prediction under a given safety factor. Additional design factors such as the configuration, location and actuation type of each piezoelectric transducer are investigated for optimal power generation. The equivalent electromechanical representations of a multifunctional wing spar is derived theoretically, simulated numerically and validated experimentally. Special attention is given to the development of a reduced energy control (REC) law, aiming to minimize the actuation energy and the dissipated heat. The REC law integrates a nonlinear switching algorithm with a positive strain feedback controller, and is represented by a positive feedback operation amplifier (op-amp) and a voltage buffer op-amp for each mode. Experimental results exhibit that the use of nonlinear REC law requires 67.3 % less power than a conventional nonlinear controller to have the same settling time under free vibrations. Nonlinearity in the electromechanical coupling coefficient of the piezoelectric transducer is also observed, arising from the piezoelectric hysteresis in the constitutive equations coupling the strain field and the electric field. If a constant and voltage-independent electromechanical coupling coefficient is assumed, this nonlinearity results in considerable discrepancies between experimental measurements and simulation results. The voltage-dependent coupling coefficient function is identified experimentally, and a real time adaptive control algorithm is developed to account for the nonlinear coupling behavior, allowing for more accurate numerical simulations. Experimental validations build upon recent advances in harvester, sensor and actuator technology that have resulted in thin, light-weight multilayered composite sandwich wing spars. These multifunctional wing spars are designed and validated to able to alleviate wind gust of small UAVs using the harvested energy. Experimental results are presented for cantilever wing spars with micro-fiber composite transducers controlled by reduced energy controllers with a focus on two vibration modes. A reduction of 11dB and 7dB is obtained for the first and the second mode using the harvested ambient energy. This work demonstrates the use of reduced energy control laws for solving gust alleviation problems in small UAVs, provides the experimental verification details, and focuses on applications to autonomous light-weight aerospace systems.
Ph. D.

The goal of this dissertation consists of improving the efficiency of energy harvesting using pyroelectric and piezoelectric materials in a system by the proper characterization of electrical parameters, widening frequency, and coupling of both effects with the appropriate parameters. A new simple stand-alone method of characterizing the impedance of a pyroelectric cell has been demonstrated. This method utilizes a Pyroelectric single pole low pass filter technique, PSLPF. Utilizing the properties of a PSLPF, where a known input voltage is applied and capacitance Cp and resistance Rp can be calculated at a frequency of 1 mHz to 1 Hz. This method demonstrates that for pyroelectric materials the impedance depends on two major factors: average working temperature, and the heating rate. Design and implementation of a hybrid approach using multiple piezoelectric cantilevers is presented. This is done to achieve mechanical and electrical tuning, along with bandwidth widening. In addition, a hybrid tuning technique with an improved adjusting capacitor method was applied. An toroid inductor of 700 mH is shunted in to the load resistance and shunt capacitance. Results show an extended frequency range up to 12 resonance frequencies (300% improvement) with improved power up to 197%. Finally, a hybrid piezoelectric and pyroelectric system is designed and tested. Using a voltage doubler, circuit for rectifying and collecting pyroelectric and piezoelectric voltages individually is proposed. The investigation showed that the hybrid energy is possible using the voltage doubler circuit from two independent sources for pyroelectrictity and piezoelectricity due to marked differences of optimal performance.

Electromechanical modeling efforts in the research field of vibration-based energy harvesting have been mostly focused on deterministic forms of vibrational input as in the typical case of harmonic excitation at resonance. However, ambient vibrational energy often has broader frequency content than a single harmonic, and in many cases it is entirely stochastic. As compared to the literature of harvesting deterministic forms of vibrational energy, few authors presented modeling approaches for energy harvesting from broadband random vibrations. These efforts have combined the input statistical information with the single-degree-of-freedom (SDOF) dynamics of the energy harvester to express the electromechanical response characteristics. In most cases, the vibrational input is assumed to have broadband frequency content, such as white noise. White noise has a flat power spectral density (PSD) that might in fact excite higher vibration modes of an electroelastic energy harvester. In particular, cantilevered piezoelectric energy harvesters constitute such continuous electroelastic systems with more than one vibration mode. The main component of this thesis presents analytical and numerical electroelastic modeling, simulations, and experimental validations of piezoelectric energy harvesting from broadband random excitation. The modeling approach employed herein is based on distributed-parameter electroelastic formulation to ensure that the effects of higher vibration modes are included. The goal is to predict the expected value of the power output and the mean-square shunted vibration response in terms of the given PSD or time history of the random vibrational input. The analytical method is based on the PSD of random base excitation and distributed-parameter frequency response functions of the coupled voltage output and shunted vibration response. The first one of the two numerical solution methods employs the Fourier series representation of the base acceleration history in a Runge-Kutta-based ordinary differential equation solver while the second method uses an Euler-Maruyama scheme to directly solve the resulting electroelastic stochastic differential equations. The analytical and numerical simulations are compared with several experiments for a brass-reinforced PZT-5H cantilever bimorph under different random excitation levels.In addition to base-excited cantilevered configurations, energy harvesting using prismatic piezoelectric stack configurations is investigated. Electromechanical modeling and numerical simulations are given and validated through experiments for a multi-layer PZT-5H stack. After validating the electromechanical models for specific experimentally configurations and samples, various piezoelectric materials are compared theoretically for energy harvesting from random vibrations. Finally, energy harvesting from narrowband random vibrationsusing both configurations are investigated theoretically and experimentally.

This work presents an investigation of a piezoelectric sensor based energy harvesting system, which collects energy from the surrounding environment. Increasing costs and scarcity of fossil fuels is a great concern today for supplying power to electronic devices. Furthermore, generating electricity by ordinary methods is a complicated process. Disposal of chemical batteries and cables is polluting the nature every day. Due to these reasons, research on energy harvesting from renewable resources has become mandatory in order to achieve improved methods and strategies of generating and storing electricity. Many low power devices being used in everyday life can be powered by harvesting energy from natural energy resources. Power overhead and power energy efficiency is of prime concern in electronic circuits. In this work, an energy harvester is modeled and simulated in Simscape™ for the functional analysis and comparison of achieved outcomes with previous work. Results demonstrate that the harvester produces power in the 0 μW to 100 μW range, which is an adequate amount to provide supply to low power devices. Power efficiency calculations also demonstrate that the implemented harvester is capable of generating and storing power for low power pervasive applications.

Advanced materials such as carbon fiber, composite materials et al. are more and more used in modern industry. They make the structures lighter and stiffer. However, they bring vibration problems. Researchers studied numerous methods to eliminate the undesirable vibrations. These treatments are expected to be a compact, light, intellectual and modular system. Recently, a nonlinear technique which is known as Synchronized Switch Damping (SSD) technique was proposed. These techniques synchronously switched when structure got to its displacement extremes that leading to a nonlinear voltage on the piezoelectric elements. This resulting voltage showed a time lag with the piezoelectric strain thus causing energy dissipation. Based on the developed SSD techniques, a new synchronized switch damping e.g. Synchronized Switch Damping with Energy Transfer (SSDET) was proposed in this document. This method damped the vibration by using the energy from other vibrating form. The objectives of the work reported in this document were threefold. The first one consisted of introduction of SSDET principle and developing its control law. This part aimed at establishing the mathematical model and verifying the proposed method by mathematical tools. Then, the experimental validations were carried out. Three experiments with different configurations demonstrated that SSDET can be implemented not only between structures but also vibrating modes in one structure. A SSDET scheme with multi-patches was also investigated for improving the damping. Finally, a bidirectional SSDET concept was introduced based on the original SSDET technique. This technique be regarded as a multimode control SSDET. Since it privileged the target vibration while keeps a decent control effect on the source vibration.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005.
Includes bibliographical references (p. 181-195).
The modeling and design of MEMS-scale piezoelectric-based vibration energy harvesters (MPVEH) are presented. The work is motivated by the need for pervasive and limitless power for wireless sensor nodes that have application in structural health monitoring, homeland security, and infrastructure monitoring. A review of prior milli- to micro-scale harvesters is provided. Common ambient low-level vibration sources are characterized experimentally. Coupled with a dissipative system model and a mechanical damping investigation, a new scale-dependent operating frequency selection scheme is presented. Coupled electromechanical structural models are developed, based on the linear piezoelectric constitutive description, to predict uni-morph and bi-morph cantilever beam harvester performance. Piezoelectric coupling non-intuitively cancels from the power prediction under power-optimal operating conditions, although the voltage and current are still dependent on this property. Piezoelectric material selection and mode of operation ([3-1] vs. [3-3]) therefore have little effect on the maximum power extracted. The model is verified for resonance and off-resonance operation by comparison to new experimental results for a macro-scale harvester. Excellent correlation is obtained away from resonances in the small-strain linear piezoelectric regime. The model consistently underpredicts the response at resonances due to the known non-linear piezoelectric constitutive response (higher strain regime). Applying the model, an optimized single prototype bi-morph MPVEH is designed concurrently with a microfabrication scheme.
(cont.) A low-level (2.5 m/s²), low-frequency (150 Hz) vibration source is targeted for anti-resonance operation, and a power density of 313 [mu]W/cm³ and peak-to-peak voltage of 0.38 V are predicted per harvester. Methodologies for the scalar analysis and optimization of uni-morph and bi-morph harvesters are developed, as well as a scheme for chip-level assembly of harvester clusters to meet different node power requirements.
by Noël Eduard du Toit.
S.M.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.
Includes bibliographical references (p. 99-100).
As MEMS and smart material technologies begin to mature, their applications, such as medical implants and wireless communications are becoming more attractive. Traditionally, remote devices have used chemical batteries to supply their energy. However, batteries are no longer suitable for many of these remote applications due to their relatively large bulk and weight, limited lifetime and high cost. The commercially sponsored Auto ID tag has demonstrated the need for a power source with the characteristics of our Piezoelectric Micro Power Generator (PMPG). The PMPG is a MEMS-based energy scavenging device which converts ambient, vibrational energy into electrical energy. It consists of a composite micro-cantilever beam with a PZT piezoelectric thin film layer and a top, interdigitated electrode structure which exploits the d₃₃ mode of the piezoelectric. When excited into mechanical resonance, the PMPG acts as a current generator whose charge can be stored by an electrical charge storage system. A single PMPG device delivered more than 1 [micro]W of DC power at 2.36 V DC to an electrical load from an ambient, vibrational energy source. The corresponding energy density is approximately 0.74 mW-h/cm2, which compares favorably to competing lithium ion battery solutions for the Auto ID tag. The PMPG power system has an electrical efficiency greater than 99%. In the near future the PMPG power system will serve as the power source for the Auto ID tag and has benefits over its competitors. Namely, the PMPG has a potentially infinite lifetime, is a cheaper, less bulky power solution versus competing lithium ion batteries, and should prove to have a better packaging scheme.
by Rajendra K. Sood.
M.Eng.

A frequency self-tuning energy harvesting methodology is proposed to achieve efficient energy harvesting. To simulate the self-tuning process, a theoretical model of the harvester made of an aluminum beam bonded with piezoelectric patches is developed for numerical simulation. The energy harvesting is realized by converting ambient vibration to electric charge through piezoelectric patches on the host beam. To accomplish the frequency self-tuning process, a control voltage is applied on a piezoelectric stack actuator to tune the natural frequency of the beam harvester matching the major excitation frequency of the ambient vibration with large power generation. Two tuning methods with different electric circuits are developed to find the efficient and feasible self-tuning process, which is then further verified by the finite element method. Research findings show that the optimal frequency self-tuning method significantly increases the power output from the harvester by more than 26 times compared with the one without tuning.
October 2016

Over the last decade, advancement of microelectronics has triggered a growing interest in ambient energy harvesting. Ambient energy can be found in various forms such as: thermoelectric, acoustic, solar, and mechanical vibrations. Most of the stated ambient energy sources have been thoroughly investigated. One of the relatively unexplored ambient energy sources is raindrop impact energy. Raindrop impact energy harvesting is achieved by converting the strain induced by an impinging raindrop on a piezoelectric beam into usable electrical energy. Most of the conducted research from the literature only considered single droplet impact on a piezoelectric beam. More interestingly, actual field test has yet to be conducted. These are the areas that the research will cover. A commercial piezoelectric beam (Mide-v25w) is utilised for this research. In this work, the piezoelectric beam is modelled as a distributed parameter system. To describe the post impact behaviours and water layer formed on the piezoelectric beam, impact coefficient and added mass coefficient are introduced for respective cases. Excitation models for single droplet, multiple droplet, artificial rain, and actual rain are developed. The models presented here were validated via experimental results. A hybrid bridge rectifier is designed and tested under actual rain. Experiment results showed that the half bridge rectifier is able to produce 95.12 % more energy than the full bridge rectifier during low voltage operation. From the actual rain experiment, the raindrop impact energy harvester was able to produce 1564 µJ energy over a rain period of 3539 s. The maximum instantaneous power generated by the piezoelectric was found to be 3.75 mW. This is higher compared the highest instantaneous power recorded in the literatures, which was 23 µW.

Harvesting Energy is a very interesting area of research in recent times. The depletion in the conventional non renewable energy sources have made researchers to look into new and alternate sources of energy. Walking is one the primary motion of human beings and with each step taken there is some amount of energy which is left behind in form of stray Vibrations. This mechanically wasted form of energy could be converted into electrical ones using piezoelectricity. This work takes a look into the possibility of harvesting such mechanical energy and converting them into the usable electrical form. A simple prototype platform is also developed and tested successfully using Piezo buzzer discs made of PZT. This study gives an simple but effective way to capture energy from human footfalls and by using proper circuitry enabling them to be stored temporarily in a storage device for future usage.

碩士
國立臺灣大學
工程科學及海洋工程學研究所
107
In order to replace the traditional battery, the concept of energy harvesting has been proposed and attracted widespread attention. Using the micro-piezoelectric transducer for extracting ambient energy is now a popular research topic. The piezoelectric energy harvesting system consists of a piezoelectric transducer, a load device, and interface circuits, which usually includes a rectifier and a DC/DC converter. In general, a full-bridge rectifier is used to convert AC source into DC voltage because it is easy to implement. However, the it has low power efficiency since its low power factor and forward voltage of the diodes consume large amounts of energy. As a result, more and more rectifiers with nonlinear synchronous switch harvesting techniques are proposed to improve the efficiency. Majority of which use inductors extract more energy by realizing voltage inversion and load independent; however, the inductor which is magnetic a component would generate electromagnetic waves and induce the electromagnetic interference. Therefore, this thesis proposes a new architecture-Synchronized Switch Harvesting using Piezoelectric Oscillators (SSHO) for solving these problem. Without bulky external inductors SSHO achieves voltage inversion which increases the voltage amplitude and then the output power. In this thesis, the SSHO rectifier fabricated in TSMC 0.25 μm HV-CMOS process has executed and tape-out. According to the post-layout simulation results, the circuit can boost the output power up to 475% when the equivalent current source of the piezoelectric source is 25 μA, the parasitic capacitance is 15 nF, and the vibration frequency is 125 Hz.

In this thesis, the energy producing capabilities and efficiency of Piezoelectric materials for ambient energy harvesting from multi-layered micro-cantilevers are analyzed. The cantilevers are then optimized utilizing a homogenization approach involving the redistribution of materials in all regions throughout the three dimensional model to yield the greatest voltage output for a specified tip force under static loading; This would be analogous to having the greatest energy production. The design of the model using the Finite Element Analysis (FEA) software ABAQUS is used in conjunction with a commercial FORTRAN optimization code, where the FEA software handles the mechanical design aspect of creating the model and determining nodal voltage quantities and the FORTRAN code executes the optimization procedure for maximizing the Voltage production. The optimization uses a Sequential Quadratic Programming (SQP) algorithm. An optimal case is found and its topology follows the expected tapered shape.

Due to decreasing power requirements for wireless networks and other microwatt devices, energy harvesting from ambient vibrations has become a realized power source. Piezoelectric cantilevers are a viable option as the transducer element for converting mechanical to electrical energy. Being able to accurately model piezoelectric cantilevers is important in designing efficient converters needed in the power management circuitry. In this thesis a method is outlined that enables the modeling of the physical behaviour of piezoelectric cantilevers with an equivalent circuit model comprised of RLC circuits. A MatLab model of piezoelectric cantilevers is developed and verified via literature comparisons. The equivalent circuit model, which is particularly important in electrical engineering of power management circuity, is demonstrated with a proof-of-concept harvester unit design. In the process and for a fraction of the traditional cost, the accuracy and usability of a low-cost vibration shaker is shown. The design is tested on two real-world applications. The first application is a transformer that has regular vibrations with low harmonic content. The second application are industrial fans with high harmonic content vibrations. The results of both applications show that energy harvesting is possible with a simplistic approach as presented. Further it is shown that high harmonic content, such as was found in the fans, can interfere with energy harvesting in both a constructive and destructive manner leading to further analysis. These findings have implications in designing vibrational energy harvester units as discussed.

碩士
國立中興大學
精密工程學系所
98
A shear mode piezoelectric energy harvester for harnessing energy from flow-induced vibration is developed. It converts flow energy into electrical energy by piezoelectric conversion with oscillation of a piezoelectric beam. A finite element model is developed in order to estimate the generated voltage of the piezoelectric beam. Prototypes of the energy harvester are fabricated and tested. Experimental results show that an open circuit output voltage of 72mVpp are generated when the excitation pressure oscillates with an amplitude of 20.80 kPa and a frequency of about 45 Hz. The solution of the generated voltage based on the finite element model is compared with the experiments. Based on the finite element model, the effects of the piezoelectric beam dimensions, the fluid pressure applied to the harvester and types of piezoelectric beam on the output voltage of the harvester can be investigated.

碩士
大葉大學
工具機產業碩士學位學程
103
Over the years, industrialized society surge in demand for energy and a limited supply of fossil fuels have become increasingly prominent, countries to develop various renewable energy sources, energy recovery technology become hot topics. Piezoelectric generator is such a technique, piezoelectric effect piezoelectric material mechanical vibrational energy into electrical energy, which will walk as human stampede, mechanical vibration, noise or vibration energy in the form of collected through energy conversion , rectifier, storage, power supply and many other areas, used in life. Piezoelectric generator having a simple structure, no heat, no electromagnetic interference, non-polluting and easy to achieve miniaturization and integration, etc., and because it can meet the energy needs of low-energy products and become one of the hot research. In this paper, MEMS technology to design and manufacture a way to produce the percussion piezoelectric kinetic energy capture device, this piezoelectric energy by piezoelectric effect extractor actuator converts kinetic energy into electrical energy, and AC generated after full-wave bridge rectifier circuit rectifying stored in the capacitor. The results that can be fixed through the condition input square wave, stainless steel thickness 300μm, the thickness of the piezoelectric sheet 100μm, the amount of displacement 1000μm, can produce voltage 10.2V the operation frequency 2 Hz, can be generated on the four piezoelectric actuators in parallel 0.73mW of power.

碩士
中原大學
機械工程研究所
97
A great deal of research has repeatedly demonstrated that piezoelectric energy harvesters by using piezoelectric direct effect hold the promise of providing an alternative power source. Ambient vibrations have been the focus as a source due to the amount of energy available in them. How to harvest the vibration energy and transfer into useful electricity and store into a battery is the primary investigation in this article. Also, efficiency of energy harvesting of a piezoelectric unimorph and mechanical to electrical conversion of a converter is studied. An overview of power storage devices explores the background of rechargeable batteries and capacitors, the advantages and disadvantages of each. Also the effectiveness of piezoelectric energy harvesting for the purpose of battery charging is explored, with particular focus on the current output of piezoelectric harvesters. Pneumatic equipment with fixed frequency is continuously press the piezoelectric unimorph to cause deformation, from which the electricity is generated. Analytical and experimental computation for the efficiency of electromechanical conversion and storage are carried out and shows a good agreement. Also, different vibration frequencies are tested. For an example of 2.5Hz, it can generate 33.84mW and obtain 13.5% electromechanical conversion efficiency, and fully charge a battery of 1800mAh NiMH 1.2V within 30 minutes for 150 and 330 seconds to achieve peak voltage of a 100µF and a 470µF capacitor respectively.

碩士
大葉大學
機械與自動化工程學系
100
Nowadays, due to the energy shortages, people begin to find new energy sources to replace the existing ones. The ways of collecting energy sources in the environment play an important role in human life where many kinds of vibration energy exist. This green energy will gradually replace the traditional energy such as fossil energy, etc. Piezoelectric materials, which have the function of electromechanical energy conversion, can be applied to converting vibration energy into electrical energy. In this study, we have proposed a piezoelectric energy harvester, which is made of MEMS technology, can capture energy from airflow-induced vibration. It converts airflow energy into electrical energy by the piezoelectric conversion effect of the oscillation of PZT wafer. Besides, we also discuss the output electrical energy caused by the controlling factors in this article. The possibility that the electrical energy can be stored in the capacitor after rectification is verified finally. Experimental results show that the harvesting device produces an output power of about 13.07μW when the excitation pressure oscillates with an amplitude of 2.0kPa and a frequency of about 52.4Hz.

For the last few decades, piezoelectric (PZT) materials have been widely used in the field of micro/nano-electromechanical systems. One of the most important applications of the PZT material is energy harvesting by absorbing ambient energy from the operational conditions and converting it into electrical energy. This energy can be used to operate sensors and actuators. Moreover, it can be stored in batteries for later tasks. In this thesis, the harvester absorbs energy from the airflow, thanks fluid-structure interaction (FSI), and converts it into useful electrical energy. To analyze FSI, it is important to consider the whole dynamics of the system formed by the structure and the flow i.e., the aeroelastic system rather than considering them as two different systems. This coupling, from the mathematical point of view, occurs because the natural boundary condition of the structure is defined by the flow pressure which is mutually influenced by the structure. This leads to a very complex phenomenon that is intrinsically non-stationary and it is no longer possible to study it by considering the structure and the flow separately. The aeroelastic system remains stable up to a critical velocity of the flow known as flutter velocity which depends on the following media and the mechanical properties of the surrounding system. After this particular velocity, the aeroelastic system is no longer stable in its unperturbed condition. The system can no longer be considered as linear and stable oscillations arise, the so-called Limit Cycle. Indeed, the interaction of the fluid in the form of airflow with structure i.e., airfoil will transfer oscillations to the PZT which will result in energy harvesting. In the present work, the possibility of extracting energy by means of PZT transduction from an aeroelastic behavior, known as the Limit Cycle Oscillation (LCO), is investigated analytically, numerically and experimentally. A suitably designed aeroelastic device which is based on the use of PZT components is presented thanks to the flag-flutter phenomenon. The presented harvester is studied from the analytical, numerical and experimental points of view. A nonlinear piezoelectric aeroelastic energy harvester (PAEH) is modeled based on the FSI that represents an important area of research for the development of innovative energy harvesting solutions. This PAEH operates on LCOs that arise after the flutter velocity. The aim of this research is to study and design a nonlinear aeroelastic energy harvester. The PZT transduction from the Limit Cycle is investigated. Particular emphasis is placed on demonstrating a correct model of unsteadiness of aerodynamics. The unsteady aerodynamic model is a critical ingredient for a sound prediction of the nonlinear behavior of an aeroelastic system. Thus, it plays a vital role in the correct evaluation of the performance of an energy harvester based on the flutter phenomenon. Moreover, it is shown that if the unsteady nature of aerodynamics is not taken into account, the evaluation of the system stability margins is totally incorrect, even if a quasi-steady hypothesis is considered. Therefore, it is emphasized that the determination of the aerodynamic model is necessary for the correct prediction of PAEH performance. Indeed, harvesting performances, flutter boundaries, aeroelastic modes, and LCOs amplitude predicted by different models, are compared with the experimental data provided by wind tunnel tests. The present harvester has various applications in the field of aerospace engineering. As a result, it is shown that the overall system is suitable for energy harvesting and can be utilized to drive microelectronics i.e., wireless sensors in sub-orbital missions, launchers, space vehicles and in various aerospace applications.