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)

Design and experiment of a human-limb driven, frequency up-converted electromagnetic energy harvester

An electromagnetic rotational energy harvester using sprung eccentric rotor, driven by pseudo-walking motion

Optimizing orientation of piezoelectric cantilever beam for harvesting energy from human walking

Improving efficiency of piezoelectric based energy harvesting from human motions using double pendulum system

An impact-driven piezoelectric energy harvester from human motion is proposed in this paper. A high-frequency PZT-5A bimorph cantilever beam with attached proof mass at the free end was selected. A frequency up-conversion strategy was realized using impulse force generated by human motion. An aluminum prototype was attached to the leg of a person on a treadmill and measurements taken of the dissipated electric energy across multiple resistances over a range of walking speeds. The outer dimensions of this prototype are 90 mm × 40 mm × 24 mm. It has been shown that the average output voltage generated by the piezoelectric bimorph increases sequentially with a faster walking speed, the power varies with the external resistances and maximum levels occur at the optimal resistance, which is consistent with the simulation result. An open circuit voltage of 2.47 V and maximum average power of 51 μW can be achieved across a 20 kΩ external load resistance and 5 km h−1 walking speed. Experimental results reveal that the impact-driven piezoelectric energy harvesting system mounted on a person’s leg has the potential for driving wearable devices.

https://iopscience.iop.org/article/10.1088/0964-1726/22/10/105020/pdf

Modeling and experimental investigation of an impact-driven piezoelectric energy harvester from human motion

This paper proposes and tests an impact-excited piezoelectric energy harvester, which converts human kinetic energy into electrical energy. While the impulses between the ridges and the proof mass lead the piezoelectric bimorph vibrating at its resonant frequency with decaying amplitude, sequent and reasonable impulses provide higher generating electrical energy. The research described herein highlights the effect of the impact interval/vibration period ratio on the energy conversion of the aforementioned harvester. The interval between consecutive impulses, Δti, with respect to the space distance between the two ridges, Δd, and the vibration period, T, are analyzed. The fabricated prototypes provide various Δti/T that can be investigated for their effect on output performance. A series of experiments demonstrate that output power is reduced by 48% with a longer interval and by 27% with a shorter interval compared to the optimized design.

Experimental analysis of optimized impact interval/vibration period ratio on piezoelectric energy harvesting

This paper presents a two-PZT beam impact-excited energy harvester. It utilizes the unused space in the one-PZT beam impact-excited harvester to integrate the second PZT beam to increase the output power, which shares common parts such as cylinder, shaft and tube with the first PZT beam. An electrical signal processing and storage circuit has been developed for the harvester. The prototype is fabricated and tested. Experimental results show that the power density of the two-PZT beam harvester is 50.7% higher than that of the previously reported one-PZT beam harvester.

Hong Hu

Papers

Modeling and experimental investigation of an impact-driven piezoelectric energy harvester from human motion

Experimental analysis of optimized impact interval/vibration period ratio on piezoelectric energy harvesting

A Two-PZT Beam Impact-Excited Energy Harvester