Piezoelectric energy harvesting solutions

This paper reviews the state of the art in piezoelectric energy harvesting. It presents the basics of piezoelectricity and discusses materials choice. The work places emphasis on material operating modes and device configurations, from resonant to non-resonant devices and also to rotational solutions. The reviewed literature is compared based on power density and bandwidth. Lastly, the question of power conversion is addressed by reviewing various circuit solutions

Chapter Vibration Energy Harvesting: Linear and Nonlinear Oscillator Approaches

Optical physic

Review of nonlinear vibration energy harvesting: Duffing, bistability, parametric, stochastic and others

Vibration energy harvesting typically involves a mechanical oscillatory mechanism to accumulate ambient kinetic energy, prior to the conversion to electrical energy through a transducer. The convention is to use a simple linear mass-spring-damper oscillator with its resonant frequency tuned towards that of the vibration source. In the past decade, there has been a rapid expansion in research of vibration energy harvesting into various nonlinear vibration principles such as Duffing nonlinearity, bistability, parametric oscillators, stochastic oscillators and other nonlinear mechanisms. The intended objectives for using nonlinearity include broadening of frequency bandwidth, enhancement of power amplitude and improvement in responsiveness to non-sinusoidal noisy excitations. However, nonlinear vibration energy harvesting also comes with its own challenges and some of the research pursuits have been less than fruitful. Previous reviews in the literature have either focussed on bandwidth enhancement strategies or converged on select few nonlinear mechanisms. This article reviews eight major types of nonlinear vibration energy harvesting reported over the past decade, covering underlying principles, advantages and disadvantages, and application-specific guidance for researchers and designers

Stochastic analysis of a bistable piezoelectric energy harvester with a matched electrical load

We present the analysis of a bistable piezoelectric energy harvester with matched electrical load, subject to random mechanical vibrations. The matching network optimizes the average energy transfer to the electrical load. The system is described by a set of nonlinear stochastic differential equations. A perturbation method is used to find an approximate solution of the stochastic system in the weak noise limit, and this solution is used to optimize the circuit parameters of the matching network. In the strong noise limit, the state equations are integrated numerically to determine the average power absorbed by the load and the power efficiency. Our analysis shows that the application of a properly designed matching network improves the performances by a significant amount, as the power delivered to the load improves of a factor about 17 with respect to a direct connection

Energy Harvesters and Self-powered Sensors for Smart Electronics

This book is a printed edition of the Special Issue “Energy Harvesters and Self-Powered Sensors for Smart Electronics” that was published in Micromachines, which showcases the rapid development of various energy harvesting technologies and novel devices. In the current 5G and Internet of Things (IoT) era, energy demand for numerous and widely distributed IoT nodes has greatly driven the innovation of various energy harvesting technologies, providing key functionalities as energy harvesters (i.e., sustainable power supplies) and/or self-powered sensors for diverse IoT systems. Accordingly, this book includes one editorial and nine research articles to explore different aspects of energy harvesting technologies such as electromagnetic energy harvesters, piezoelectric energy harvesters, and hybrid energy harvesters. The mechanism design, structural optimization, performance improvement, and a wide range of energy harvesting and self-powered monitoring applications have been involved. This book can serve as a guidance for researchers and students who would like to know more about the device design, optimization, and applications of different energy harvesting technologies

A comparison of linear and non-linear strategies for energy harvesting from mechanical vibrations

Energy Harvesting strategies coupled with the improvement of electronics and the progressive reduction of power requirements have been widely recognized as fundamental to enable self-powered (or autonomous) devices. Among all the potential energy sources, kinetic energy stemming from mechanical vibrations has been particularly extensively investigated for EH purposes due to its characteristics of heterogeneity and ubiquity. To exploit such energy sources, a suitable coupling mechanism to convert vibrations into electric charge is required; it must take into account the wide frequency bandwidth of mechanical vibrations as encountered in everyday scenarios. This review offers an overview of linear vs. non-linear strategies for EH, with a specific focus on different approaches to implement efficient coupling mechanisms; the performances of the specific solutions covered in this work are discussed

Structural vibration energy harvesting via bistable nonlinear attachments

A vibration-based bistable electromagnetic energy harvester coupled to a directly excited host structure is theoretically and experimentally examined. The primary goal of the study is to investigate the potential benet of the bistable element for harvesting broadband and low-amplitude vibration energy. The considered system consists of a grounded, weakly damped, linear oscillator (LO) coupled to a lightweight, damped oscillator by means of an element which provides for both cubic nonlinear and negative linear stiness components and electromechanical coupling elements. Single and repeated impulses with varying amplitude applied to the LO are the vibration energy sources considered. A thorough sensitivity analysis of the system's key parameters provides design insights for a bistable nonlinear energy harvesting (BNEH) device able to attain robust harvesting efficiency. Energy localization into the bistable attachment is achieved through the exploitation of three BNEH main dynamical regimes; namely, periodic cross-well, aperiodic (chaotic) cross-well, and in-well oscillations. For the experimental investigation on the performance of the bistable device, nonlinear and negative linear terms in the mechanical coupling are physically realized by exploiting the transverse displacement of a buckled slender steel beam; the electromechanical coupling is accomplished by an electromagnetic transducer

USE OF A TRIBOELECTRIC GENERATOR FOR A TUNABLE WIDEBAND ENERGY HARVESTER AND A THRESHOLD SHOCK SENSOR

The prevalence of triboelectricity as a transduction mechanism has increased rapidly in recent years. We will discuss two uses for triboelectric generators. One design is a tunable wideband energy harvester. An axial force and amplitude limiter work together to create an energy harvester that can accommodate various frequency sources and have a large operating bandwidth. The addition of the compressive axial force also softens the system, which allows for higher voltage outputs. A proof of concept of a threshold shock sensor is proposed that incorporates bi-stability along with the triboelectric effect. A clamped-clamped buckled beam will switch stable states when a threshold shock amplitude is experienced and a voltage peak will occur during this switching of states. Levels of input acceleration can be related to voltage output, which increases the value of the concept. Thorough continuous electro-mechanical models will be produced for each design and the validity of these models will be tested

Dynamic analysis and fabrication of a bi-stable structure designed for MEMS energy harvesting applications.

Thanks to the rapid growth in demand for power in remote locations, scientists’ attention has been drawn to vibration energy harvesting as an alternative to batteries. Over the past ten years, the energy harvesting community has focused on bistable structures as a means of broadening the working frequency range and, by extension, the effective efficiency of vibration-based power scavenging systems. In the current study, a new method is implemented to statically and dynamically analyze a bistable buckled, multi-component coupled structure designed specifically for low-frequency vibration energy harvesting systems in both macro and MEMS-scale sizes. Furthermore, several micro-fabrication steps using advanced manufacturing technology methods were applied to design and fabricate a micro-scale version of the energy harvester at the University of Louisville Micro/Nano Technology Center. First, previously efforts performed on different aspects of vibration energy harvesting systems are reviewed to show the current challenges associated with such devices. The coupled structure proposed in this project is then introduced and its equations of motion are developed based on nonlinear Euler-Bernoulli beam theory. These governing equations are discretized and solved using a Galerkin method in two different approaches: with some known shape functions which only satisfies the geometrical boundary conditions; with the exact shape functions obtained from solving the linearized coupled structure as a one single system. An experimental setup is also used to verify the advantages of designed structure in capturing bistable motion at low-frequency range. To validate the modeling approaches, the obtained results are compared with the ones captured from both FEA model and the experimental setup, which shows the superiority of the proposed approach in which exact shape functions of the system are used as the basis in the discretization process. After the validation of the proposed approach, it is applied on a micro-scale version of the system in which structural, piezoelectric, and electrode layers are all considered as they exist in an actual device. Furthermore, a different bistable system, which was previously studied by other researchers in the area, is analyzed by this method to show the reliability of the proposed model. For all these cases, the amplitude-frequency response of the system and snap-through regime with the variation of various parameters, including exciting frequency, base vibration, and buckling loads are investigated based on the developed model. It is shown that bisatble motion and other nonlinear phenomena such as super-harmonic behavior in the system can be captured under certain circumstances, which can significantly impact major system functionalities such as output voltage response and is crucial for the performance of energy harvesting devices. As mentioned above, various micro-fabrication techniques were also used to design and fabricate a micro-scale version of the proposed system, which eventually led to the successful fabrication of a MEMS device as a result of experimental efforts performed to overcome the challenges and issues associated with the designed manufacturing process

A broadband bistable piezoelectric cantilever-based vibration energy harvester with nonlinear high power extraction

This work presents a nonlinear vibration energy harvester, which combines a nonlinear bistable broadband piezoelectric cantilever used to transduce ambient vibration energy, with synchronized capture for efficient harvesting over broadband sources. An accurate model of the bistable transducer, that augments the Butterworth van Dyke piezoelectric model to capture the external magnetic force added as a bias to the external vibrations, is presented. Its validity has been demonstrated through physical implementation and experimental validation against simulation of the mathematical model. For efficient extraction of the transduced energy, nonlinear extraction circuits, namely synchronous charge extraction (SCE) and parallel synchronized switch harvesting on inductor (SSHI), are employed. The switching in these circuits is implemented using a fully self-propelled, low-power electronic breaker circuit, capable of detecting extrema in the waveform to perform switching. Both simulated and experimental power outputs from the bistable harvester have been presented, with the SCE and parallel-SSHI providing average outputs with more than one-hundred (100) fold increase over the harvested power reported in literature for the same input, and further, even more significant gains are observed for broadband excitations. For the above mentioned harvester, bistability is introduced through the use of two repelling magnets, one mounted on the cantilever tip and the other at a fixed location opposite it. Excitations that can overcome the repulsive magnetic force cause the cantilever to snap between its two equilibrium states, increasing amplitude and velocity of vibration, resulting in higher power outputs. This improved performance is observed whenever the cantilever operates in the bistable mode. Lower-amplitude excitations are unable to overcome the repulsive force, causing the cantilever to vibrate around one of its equilibrium states, and with smaller amplitudes in the presence of the opposing repulsion. To circumvent this issue, the second part of the work presents a completely mechanical way of increasing the range of excitation amplitudes over which the system remains bistable, by spring-loading the previously fixed-positioned magnet, and restricting its motion in the horizontal direction, towards and away from the cantilever. Then, whenever the cantilever moves towards the spring-loaded magnet, the latter is pushed away due to the repulsive force, increasing the distance between the magnets, thereby reducing the repulsive force required to be overcome for bistable operation. The opposite occurs when the cantilever moves away. Thus, the role of spring-loading is to introduce a type of negative feedback, through the self-adjustment of the distance between the magnets, favoring bistable operation over a larger range of excitations, and this is accomplished without an added energy cost. A 90% gain in power output levels over the fixed magnet system was observed