The last two decades have witnessed several advances in microfabrication technologies and electronics, leading to the development of small, low-power devices for wireless sensing, data transmission, actuation, and medical implants. Unfortunately, the actual implementation of such devices in their respective environment has been hindered by the lack of scalable energy sources that are necessary to power and maintain them. Batteries, which remain the most commonly used power sources, have not kept pace with the demands of these devices, especially in terms of energy density. In light of this challenge, the concept of vibratory energy harvesting has flourished in recent years as a possible alternative to provide a continuous power supply. While linear vibratory energy harvesters have received the majority of the literature’s attention, a significant body of the current research activity is focused on the concept of purposeful inclusion of nonlinearities for broadband transduction. When compared to their linear resonant counterparts, nonlinear energy harvesters have a wider steady-state frequency bandwidth, leading to a common belief that they can be utilized to improve performance in ambient environments. Through a review of the open literature, this paper highlights the role of nonlinearities in the transduction of energy harvesters under different types of excitations and investigates the conditions, in terms of excitation nature and potential shape, under which such nonlinearities can be beneficial for energy harvesting. [DOI: 10.1115/1.4026278]

On the Role of Nonlinearities in Vibratory Energy Harvesting: A Critical Review and Discussion

The dramatic reduction in power consumption of current integrated circuits has evoked great research interests in harvesting ambient energy, such as vibrations, as a potential power supply for electronic devices to avoid battery replacement. Currently, most vibration-based energy harvesters are designed as linear resonators to achieve optimal performance by matching their resonance frequencies with the ambient excitation frequencies a priori. However, a slight shift of the excitation frequency will cause a dramatic reduction in performance. Unfortunately, in the vast majority of practical cases, the ambient vibrations are frequency-varying or totally random with energy distributed over a wide frequency spectrum. Hence, developing techniques to increase the bandwidth of vibration-based energy harvesters has become the next important problem in energy harvesting. This article reviews the advances made in the past few years on this issue. The broadband vibration-based energy harvesting solutions, covering re...

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Toward Broadband Vibration-based Energy Harvesting

This paper reviews possible strategies to increase the operational frequency range of vibration-based micro-generators. Most vibration-based micro-generators are spring-mass-damper systems which generate maximum power when the resonant frequency of the generator matches the frequency of the ambient vibration. Any difference between these two frequencies can result in a significant decrease in generated power. This is a fundamental limitation of resonant vibration generators which restricts their capability in real applications. Possible solutions include the periodic tuning of the resonant frequency of the generator so that it matches the frequency of the ambient vibration at all times or widening the bandwidth of the generator. Periodic tuning can be achieved using mechanical or electrical methods. Bandwidth widening can be achieved using a generator array, a mechanical stopper, non-linear (e.g. magnetic) springs or bi-stable structures. Tuning methods can be classified into intermittent tuning (power is consumed periodically to tune the device) and continuous tuning (the tuning mechanism is continuously powered). This paper presents a comprehensive review of the principles and operating strategies for increasing the operating frequency range of vibration-based micro-generators presented in the literature to date. The advantages and disadvantages of each strategy are evaluated and conclusions are drawn regarding the relevant merits of each approach.

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Strategies for increasing the operating frequency range of vibration energy harvesters: a review

The last decade has witnessed significant advances in energy harvesting technologies as a possible alternative to provide a continuous power supply for small, low-power devices in applications, such as wireless sensing, data transmission, actuation, and medical implants. Piezoelectric energy harvesting (PEH) has been a salient topic in the literature and has attracted widespread attention from researchers due to its advantages of simple architecture, high power density, and good scalability. This paper presents a comprehensive review on the state-of-the-art of piezoelectric energy harvesting. Various key aspects to improve the overall performance of a PEH device are discussed, including basic fundamentals and configurations, materials and fabrication, performance enhancement mechanisms, applications, and future outlooks.

A comprehensive review on piezoelectric energy harvesting technology: Materials, mechanisms, and applications

In an effort to eliminate the replacement of the batteries of electronic devices that are difficult or impractical to service once deployed, harvesting energy from mechanical vibrations or impacts using piezoelectric materials has been researched over the last several decades. However, a majority of these applications have very low input frequencies. This presents a challenge for the researchers to optimize the energy output of piezoelectric energy harvesters, due to the relatively high elastic moduli of piezoelectric materials used to date. This paper reviews the current state of research on piezoelectric energy harvesting devices for low frequency (0–100 Hz) applications and the methods that have been developed to improve the power outputs of the piezoelectric energy harvesters. Various key aspects that contribute to the overall performance of a piezoelectric energy harvester are discussed, including geometries of the piezoelectric element, types of piezoelectric material used, techniques employed to match the resonance frequency of the piezoelectric element to input frequency of the host structure, and electronic circuits specifically designed for energy harvesters.

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Energy harvesting from low frequency applications using piezoelectric materials

We study the effects of a varying cross-section on the performance of Rosen piezoelectric transformers operating with length extensional modes of rods. A theoretical analysis is performed using an extended version of a one- dimensional model developed in a previous paper. Numerical results based on the theoretical analysis are presented.

Analysis of Rosen piezoelectric transformers with a varying cross-section

Based on the von Karman thin circular plate theory, we report in this paper the analysis of the nonlinear behavior of a power harvester consisting of a circular piezoelectric plate and an electric resistance. Dependence of the output power of the harvester upon driving frequency for different electric loads and different applied forces is obtained. Numerical results show that the output power exhibits multi- valuedness and a jump phenomenon near resonance.

Nonlinear characteristics of a circular plate piezoelectric harvester with relatively large deflection near resonance

The effects of first-order strain gradient in micro piezoelectric-bimorph (PB) power harvesters are investigated by including the first-order gradient terms in the energy density functions. For a PB, the gradient effects can be focused on the analysis of the strain gradient effect in the thickness direction through choosing the strains and the electric displacements as the independent constitutive variables. It is shown theoretically that the first-order gradient effects have raised the natural frequency of the PB and effectively enhanced the output power density of the harvester.

The effects of first-order strain gradient in micro piezoelectric-bimorph power harvesters

We study stress fields near the edge of an electrode by finite element method. Von Mises Stress near an electrode edge is calculated. The effect of the curvature of the electrode is examined. Stress concentration is observed and a technique for its reduction is suggested.

Finite element analysis of stress field concentration near the edge of an electrode

A piezoelectric energy captor enabling to capture energy and store energy effectively consists of piezoelectric beam formed by two layers of piezoelectric ceramic plates and intermediate sandwich layer, electrode prepared by plating metal silver on ceramic plate, inductance coil with control switch, bridge type of rectifier, rectifying capacitor, Cuk type of dc-dc converter formed by transistor switch and electric inductance as well as diode, filtering capacitor for stabilizing charge current, and energy storing battery.

Huan Xue

Papers

Analysis of Rosen piezoelectric transformers with a varying cross-section

Nonlinear characteristics of a circular plate piezoelectric harvester with relatively large deflection near resonance

The effects of first-order strain gradient in micro piezoelectric-bimorph power harvesters

Finite element analysis of stress field concentration near the edge of an electrode

Piezoelectric energy trapping device capable of efficient trapping energy and energy-storaging