Energy harvesting technologies have been explored by researchers for more than two decades as an alternative to conventional power sources (e.g. batteries) for small-sized and low-power electronic devices. The limited life-time and necessity for periodic recharging or replacement of batteries has been a consistent issue in portable, remote, and implantable devices. Ambient energy can usually be found in the form of solar energy, thermal energy, and vibration energy. Amongst these energy sources, vibration energy presents a persistent presence in nature and manmade structures. Various materials and transduction mechanisms have the ability to convert vibratory energy to useful electrical energy, such as piezoelectric, electromagnetic, and electrostatic generators. Piezoelectric transducers, with their inherent electromechanical coupling and high power density compared to electromagnetic and electrostatic transducers, have been widely explored to generate power from vibration energy sources. A topical review of piezoelectric energy harvesting methods was carried out and published in this journal by the authors in 2007. Since 2007, countless researchers have introduced novel materials, transduction mechanisms, electrical circuits, and analytical models to improve various aspects of piezoelectric energy harvesting devices. Additionally, many researchers have also reported novel applications of piezoelectric energy harvesting technology in the past decade. While the body of literature in the field of piezoelectric energy harvesting has grown significantly since 2007, this paper presents an update to the authors' previous review paper by summarizing the notable developments in the field of piezoelectric energy harvesting through the past decade.

https://iopscience.iop.org/article/10.1088/1361-665X/ab36e4/pdf

A review of energy harvesting using piezoelectric materials: state-of-the-art a decade later (2008–2018)

Energy harvesting for the purpose of powering low power electronic sensor systems has received explosive attention in the last few years. Most works using deterministic approaches focusing on using the piezoelectric effect to harvest ambient vibration energy have concentrated on cantilever beams at resonance using harmonic excitation. Here, using a stochastic approach, we focus on using a stack configuration and harvesting broadband vibration energy, a more practically available ambient source. It is assumed that the ambient base excitation is stationary Gaussian white noise, which has a constant power-spectral density across the frequency range considered. The mean power acquired from a piezoelectric vibration-based energy harvester subjected to random base excitation is derived using the theory of random vibrations. Two cases, namely the harvesting circuit with and without an inductor, have been considered. Exact closed-form expressions involving non-dimensional parameters of the electromechanical system have been given and illustrated using numerical examples.

/pdf/piezoelectric-energy-harvesting-from-broadband-random-4c9bspjxla.pdf

Piezoelectric energy harvesting from broadband random vibrations

In this paper, a summary of published techniques for power conditioning within energy harvesting systems is presented. The focus is on low-power systems, e.g, <;10 mW, for kinetic energy harvesting. Published concepts are grouped according to functionality and results contrasted. The various techniques described are considered in terms of complexity, efficiency, quiescent power consumption, startup behavior, and utilization of the harvester compared to an optimum load. This paper concludes with an overview of power management techniques that aim to maximize the extracted power and the utilization of the energy harvester.

Review of Power Conditioning for Kinetic Energy Harvesting Systems

Piezoelectric energy harvesting has attracted wide attention from researchers especially in the last decade due to its advantages such as high power density, architectural simplicity, and scalability. As a result, the number of studies on piezoelectric energy harvesting published in the last 5 years is more than twice the sum of publications on its electromagnetic and electrostatic counterparts. This paper presents a comprehensive review on the history and current state-of-the art of piezoelectric energy harvesting. A brief theory section presents the basic principles of piezoelectric energy conversion and introduces the most commonly used mechanical architectures. The theory section is followed by a literature survey on piezoelectric energy harvesters, which are classified into three groups: (i) macro- and mesoscale, (ii) MEMS scale, and (iii) nanoscale. The size of a piezoelectric energy harvester affects a variety of parameters such as its weight, fabrication method, achievable power output level, and potential application areas. Consequently, size-based classification provides a reliable and effective basis to study various piezoelectric energy harvesters. The literature survey on each scale group is concluded with a summary, potential application areas, and future directions. In a separate section, the most prominent challenges in piezoelectric energy harvesting and the studies focusing on these challenges are discussed. The conclusion part summarizes the current standing of piezoelectric energy harvesters as possible candidates for various applications and discusses the issues that need to be addressed for realization of practical piezoelectric energy harvesting devices.

Piezoelectric energy harvesting: State-of-the-art and challenges

Recent advances in wide bandgap semiconductor biological and gas sensors

This talk presents the development of an acoustic energy harvester using an electromechanical Helmholtz resonator (EMHR). The EMHR consists of an orifice, cavity, and a piezoelectric diaphragm. When the acoustic wave is incident on the EMHR, a portion of acoustic energy is converted to electrical energy via piezoelectric transduction in the diaphragm of the EMHR. Moreover, the diaphragm is coupled with energy reclamation circuitry to increase the efficiency of the energy conversion. Two power converter topologies are adopted to demonstrate the feasibility of acoustic energy reclamation using an EMHR. The first is comprised of only a rectifier, and the second uses a rectifier connected to a flyback converter to improve load matching. Experimental results indicate that approximately 30 mW of output power is harvested for an incident sound pressure level of 160 dB with a flyback converter. Such power level is sufficient to power a variety of low power electronic devices.

Acoustic energy harvesting using an electromechanical Helmholtz resonator.

This paper demonstrates the system operation of a self-powered active liner for the suppression of aircraft engine noise The fundamental element of the active liner system is an electromechanical Helmholtz resonator (EMHR), which consists of a Helmholtz resonator with one of its rigid walls replaced with a circular piezoceramic composite plate For this system demonstration, two EMHR elements are used, one for acoustic impedance tuning and one for energy harvesting The EMHR used for acoustic impedance tuning is shunted with a variable resistive load, while the EMHR used for energy harvesting is shunted to a flyback power converter and storage element The desired acoustic impedance conditions are determined externally, and wirelessly transmitted to the liner system The power for the receiver and the impedance tuning circuitry in the liner are supplied by the harvested energy Tuning of the active liner is demonstrated at three different sound pressure levels (148, 151, and 153dB) in order to show the robustness of the energy harvesting and storage system An acoustic tuning range of approximately 200Hz is demonstrated for each of the three available power levels

Demonstration of a wireless, self-powered, electroacoustic liner system.

A self-powered wireless hydrogen sensor node has been designed and developed from a system level approach. By using multi-source energy harvesting circuitry such as scavenged or “reclaimed” energy from light emitting and vibrational sources as the source of power for commercial low power microcontrollers, amplifiers, and RF transmitters, the sensor node is capable of conditioning and deciphering the output of hydrogen sensitive ZnO nanorods sensors. Upon the detection of a discernible amount of hydrogen, the system will ‘wake’ from an idle state to create a wireless data communication link to relay the detection of hydrogen to a central monitoring station. Two modes of operation were designed for the use of hydrogen detection. The first mode would sense for the presence of hydrogen above a set threshold, and alert a central monitoring station of the detection of significant levels of hydrogen. In the second mode of operation, actual hydrogen concentrations starting as low as 10 ppm are relayed to the receiver to track the amount of hydrogen present.

A hydrogen leakage detection system using self-powered wireless hydrogen sensor nodes

For piezoelectric-based, vibration energy harvesting systems, a simplified resonant model is typically used to represent the piezoelectric transducer. Furthermore, the total amount of harvested power is calculated assuming an ideal and lossless power converter. A coupled, system-level model is developed that includes parasitic losses in the power converter for a system comprised of a cantilevered transducer beam and pulsed resonant converter. The accuracy of the system-level model is validated with experimental data, and it is shown that the simplified resonant model underpredicts the total harvested power by approximately 30% for the implemented system. In addition to capturing the electrical domain behavior of the system, the system-level model is also shown to accurately predict the effect of energy harvesting on the beam mechanics.

System Modeling of Piezoelectric Energy Harvesters

Passive circuits and active circuits (i.e., switched-mode power converters) for vibration-energy harvesting are reviewed, focusing on power-extraction efficiency (PEE). Optimal battery voltage and resistance are given for maximal power extraction by passive circuits. Switched-mode converters are reviewed as means to match the actual battery voltage or load resistance to the optimal ones. To emulate the optimal battery voltage or load resistor, these converters could be controlled by pulse-width modulation (PWM) or by resonance, could operate in continuous or discontinuous conduction modes (CCM or DCM), and could leverage the piezoelectric (PZT) impedances in the energy extraction process. The large filter capacitor usually found after the bridge rectifier actually degrades the PEE. Resonance between the output capacitor of the PZT and the converter inductor improves the PEE at the expense of higher voltage and current stresses.Copyright © 2006 by ASME

Alex Phipps

Papers

Acoustic energy harvesting using an electromechanical Helmholtz resonator.

Demonstration of a wireless, self-powered, electroacoustic liner system.

A hydrogen leakage detection system using self-powered wireless hydrogen sensor nodes

System Modeling of Piezoelectric Energy Harvesters

Power Converters for Piezoelectric Energy Extraction