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 is the most effective way to respond to the energy shortage and to produce sustainable power sources from the surrounding environment. The energy harvesting technology enables scavenging electrical energy from wasted energy sources, which always exist everywhere, such as in heat, fluids, vibrations, etc. In particular, piezoelectric energy harvesting, which uses a direct energy conversion from vibrations and mechanical deformation to the electrical energy, is a promising technique to supply power sources in unattended electronic devices, wireless sensor nodes, micro-electronic devices, etc., since it has higher energy conversion efficiency and a simple structure. Up to now, various technologies, such as advanced materials, micro- and macro-mechanics, and electric circuit design, have been investigated and emerged to improve performance and conversion efficiency of the piezoelectric energy harvesters. In this paper, we focus on recent progress of piezoelectric energy harvesting technologies based on PbZrxTi1-xO3 (PZT) materials, which have the most outstanding piezoelectric properties. The advanced piezoelectric energy harvesting technologies included materials, fabrications, unique designs, and properties are introduced to understand current technical levels and suggest the future directions of piezoelectric energy harvesting.

/pdf/recent-progress-on-pzt-based-piezoelectric-energy-harvesting-3dcjyip2x7.pdf

Recent Progress on PZT Based Piezoelectric Energy Harvesting Technologies

This chapter contains sections titled: Introduction Node Platforms Techniques of Energy Harvesting Prediction Models Protocols for EHWSNs References

/pdf/wireless-sensor-networks-with-energy-harvesting-1f2f8j9q43.pdf

Wireless Sensor Networks with Energy Harvesting

Wearable devices are drawing increasing attention in both academia and industry in that they can offer unprecedented information related to human health in real-time and human–machine interactions, which is expected to enable a paradigm shift in the digital world. For this shift to occur, green and sustainable energy technology for powering flexible wearable devices is a roadblock. This paper is dedicated to reviewing cutting-edge wearable power generation methodologies, for which we discuss their pros and cons, underlying physics, and general design/evaluation criteria. Sensor types, materials, processing technology, power consumption, and methods of testing the stretchability and flexibility of wearable devices are also summarized. Based on application scenarios in healthcare, industrial inspection, structural monitoring, armed forces and consumer electronics, an integrated system architecture of wearable, flexible systems is presented. Finally, future perspectives of wearable technologies are outlined by covering the aspects of all-in-one printable wearable electronics, fiber and textile electronics, self-powered self-awareness wearable systems, hybrid-integrated Systems on a Chip (SoC) for flexible electronics, and Internet of Things (IoT)-enabled self-contained systems towards full life cycle monitoring.

Power generation for wearable systems

A study of vortex-induced energy harvesting from water using PZT piezoelectric cantilever with cylindrical extension

In this paper, micro-fabricated electromagnetic power generator is presented to convert the low level ambient vibration into electric energy. The proposed micro-power generator is comprised of three micro-components such as bulk-micromachined silicon spiral spring, low loss copper micro-coil, and NdFeB magnet to be assembled with low cost PDMS packaging substrate. In order to maximize the output power, magnet is applied as inertial mass at the center of silicon spiral spring to adjust its resonant frequency. Especially, NdFeB discrete/miniaturized magnet and copper wire wounded micro-coil were utilized to avoid the performance deterioration of the proposed device due to its miniaturization. It was specially designed for scavenging low ambient vibration of several tens of hertz and low acceleration under 1g. The fabricated device generated output power of 115.1 W and load voltage of 68.2 mV to the load resistance of 18.1 from the vibration of 54 Hz with acceleration of 0.57 g. The normalized power density was 590.4 ?W/cm3g2.

Micro-Fabricated Electromagnetic Power Generator to Scavenge Low Ambient Vibration

Asymmetric PZT bimorph cantilever for multi-dimensional ambient vibration harvesting

This paper presents a micro-fabricated electromagnetic power generator for an ambient vibration energy harvesting system. The proposed power generator utilized a bulk micro-machined silicon spring, a copper coil, and NdFeB magnet. In order to reduce the resonant frequency and increase the displacement of the proof mass, we developed a gimbal suspension structure for the fabrication of the silicon spring. The NdFeB permanent magnet was applied as an inertial mass to increase the effective mass of the total spring system. The fabricated spring was assembled using a lowcost Polydimethylsiloxane (PDMS) packaging substrate with a micro-coil, which had a lower DC resistance than a micro-fabricated planar coil. The system was specially designed to scavenge low ambient vibrations of several tens of hertz and low accelerations of under 1 g. The fabricated energy harvester had a 1 × 1 × 0.6 cm size and generated 102 μW of electrical power to a 100 Ω load at 201 mVpeak-to-peak from a vibration of 0.4 g at 53 Hz. The normalized power density was 1.06 mW/cm·g.

Jong Cheol Park

Papers

Micro-Fabricated Electromagnetic Power Generator to Scavenge Low Ambient Vibration

Asymmetric PZT bimorph cantilever for multi-dimensional ambient vibration harvesting

A Bulk Micromachined Electromagnetic Micro-Power Generator for an Ambient Vibration-energy-harvesting System

Wideband LC balun transformer using coupled LC resonators embedded into organic substrate