Research on piezoelectric vibration energy harvester with variable section circular beam

Investigation upon the performance of piezoelectric energy harvester with elastic extensions

We demonstrate a piezoelectric vibration energy harvester with the ZnO piezoelectric film and an improved synchronous electric charge extraction energy harvesting circuit on the basis of the beam-type mechanical structure, especially investigate its output performance in vibration harvesting and ability to generate charges. By establishing the theoretical model for each of vibration and circuit, the numerical results of voltage and power output are obtained. By fabricating the prototype of this harvester, the quality of the sputtered film is explored. Theoretical and experimental analyses are conducted in open-circuit and closed-circuit conditions, where the open-circuit mode refers to the voltage output in relation to the ZnO film and external excitation, and the power output of the closed-circuit mode is relevant to resistance. Experimental findings show good agreement with the theoretical ones, in the output tendency. It is observed that the properties of ZnO film achieve regularly direct proportion to output performance under different excitations. Furthermore, a maximum experimental power output of 4.5 mW in a resistance range of 3 kΩ–8 kΩ is achieved by using an improved synchronous electric charge extraction circuit. The result is not only more than three times the power output of classic circuit, but also can broaden the resistance to a large range of 5 kΩ under an identical maximum value of power output. In this study we demonstrate the fundamental mechanism of piezoelectric materials under multiple conditions and take an example to show the methods of fabricating and testing the ZnO film. Furthermore, it may contribute to a novel energy harvesting circuit with high output performance.

State of art: Piezoelectric Vibration Energy Harvesters

Piezoelectric energy harvesting and charging performance of Pb(Zn1/3Nb2/3)O3–Pb(Zr0.5Ti0.5)O3 nanoparticle-embedded P(VDF-TrFE) nanofiber composite sheets

Vibrational energy harvesters, also referred to as MEMS (Micro-Electro-Mechanical Systems) piezoelectric energy harvesters, have garnered significant attention for their potential to power wireless sensor networks and low-power electronics without external power sources. Piezoelectric materials, due to their high energy conversion efficiency and seamless integration into microsystems, are widely utilized in such designs. In this study, we simulate MEMS piezoelectric energy harvesters using PZT (lead zirconate titanate) material, each constructed with a silicon core layer and PZT piezoelectric layers. The simulations, conducted using COMSOL Multiphysics, analyze the performance of cantilever-shaped harvesters under identical boundary conditions, including solid mechanics, electrostatics, and an electric circuit with a 10 kΩ resistive load. The results show that natural frequencies range from 100 Hz to 500 Hz depending on the cantilever shape, with the generated voltage varying between 1.2 V and 3.5 V and corresponding power outputs ranging from 0.2 μW to 1.5 μW. These variations highlight the influence of cantilever geometry on energy harvesting efficiency. The study also identifies specific advantages, such as higher power density and tunable frequency ranges, making these harvesters suitable for powering remote sensing devices and microscale electronics. By quantifying performance metrics and demonstrating shape-dependent benefits, this research provides valuable insights into the design and optimization of MEMS piezoelectric harvesters for diverse applications.Keywords: Piezoelectric vibration energy harvesters, COMSOL simulation, MEMS vibrational energy harvesters, bimorph design.

A theoretical model of a micro piezoelectric energy harvester is proposed based on the nonlocal elasticity theory, which is operated in the flexural mode for scavenging ambient vibration energy. A nonlocal scale is defined as the product of internal characteristic length and a constant related to the material. The dependences of performance of the harvester upon the nonlocal scale and the scale ratio of the nonlocal scale to the external characteristic parameter are investigated in detail. Numerical results show that output power of the harvester decreases, and resonance frequency reduces gradually at first then increases rapidly when nonlocal scale increases. The results of nonlocal elasticity theory are compared with that of classic beam theory. All the results are helpful for material and structure design of the micro piezoelectric energy harvester.

Similarity and duality of electromagnetic and piezoelectric vibration energy harvesters

Nonlinear multi-stable piezoelectric energy harvesters show broadband frequency spectra and excellent energy harvesting performance, owing to their high output power related to inter-well transitions. However, existing quad-stable piezoelectric energy harvesters contain too many structural parameters, which makes the systems clumsy, and increases the difficulties of dynamic analysis and structural optimization. Herein, a nonlinear quad-stable piezoelectric energy harvester, with only one external magnet, is proposed based on the magnetic force characteristics between a ring magnet and a rectangular magnet. Under selected structural parameters, as the magnet spacing increases, the stability characteristic of the harvester changes from quad-stability to bi-stability, and then to mono-stability. The transformation of the stability characteristic results from the changes in the variation rate of the vertical magnetic force. Subsequently, under the filtered Gaussian white noise within the frequency range of 0–120 Hz, the energy harvesting performance of the harvester is simulated by the classic fourth-order Runge-Kutta method. Simulation results show that the performance of the harvester under the quad-stable structural parameters is better than that under the bi-stable structural parameters, independent of whether the excitation acceleration is small or large. This result is related to the potential well characteristics under the quad-stable and bi-stable structural parameters. More specifically, the potential well depths under the quad-stable and bi-stable structural parameters are almost the same, but the distance between the two outer potential wells under the quad-stable structural parameters is larger than that under the bi-stable structural parameters. Finally, a fabricated prototype is used to measure the experimental performance of the harvester. The experimental data and the estimated data share the same trend. This study provides a new conception and technical method for the design, optimization, and application of quad-stable piezoelectric energy harvesters.

Output Performance of Piezoelectric Vibration Energy Harvester Considering Inductive Loads

Modeling and design of V-shaped piezoelectric vibration energy harvester with stopper for low-frequency broadband and shock excitation

All structures in nature have vibration energy which can be converted into Electrical energy. This electrical energy can be used as a source of energy to operate sensors thereby replacing limited storage capacity equipment's such as battery. Piezoelectric vibration energy harvesting scheme utilizes direct piezoelectric effect to convert mechanical energy into electrical energy. The output voltage from the piezoelectric vibration energy harvester depends on the relative motion between the base and proof mass. The resulted mechanical strain developed on the PZT patches is converted into electrical power because of direct coupling piezo electric effect. This article present a study of the effect of length of PZT patch on single modal linear vibration based piezo electric energy harvester (PEH). A coupled series piezo patch-electrical circuit finite element model is used to analyze the power output of a vibration based piezoelectric energy-harvesting device (EHD) when it is connected to a load resistor. Mathematical model of linear single modal Vibration -based Energy harvester is developed using Ansys APDL (Ansys parametric design Language). The modeling configuration is done with a series configuration of piezo electric layers. Accuracy of the developed FEM model is validated against the existing coupled FEM model. First modal analysis is performed to find the natural frequency of the piezoelectric energy harvester. Then harmonic analysis is carried out to estimate the voltage responses and power output which are measured through the PZT patches.

Cantilever-based piezoelectric energy harvesters have been utilized as structures to extract mechanical energy from the ambient mechanical vibrations and transfer it into the electrical output. In this article, the performance of bimorph piezoelectric beam energy harvesters is investigated. The cantilever beam is modeled by using both Timoshenko and Euler–Bernoulli beam theories. The equations are discretized using the conventional finite element method and superconvergent element. Besides the high rate of convergence, easy switching between the above beam theories is enabled by such type of element. The current model is presented for a Timoshenko beam model, but it could as well be used for a Euler–Bernoulli beam model. In addition, voltage, current, and power frequency response functions for different ranges of load resistance varying from the short-circuit to open-circuit conditions are determined to reach the maximum values. Effects of the slenderness ratio and the required beam model based on the geometric properties of the piezoelectric energy harvesters are discussed in the final part of this study. The results show that only for smaller values of the slenderness ratio (below 5), it is necessary to model the beam using the Timoshenko assumptions; otherwise both beam theories provide approximately the same responses.

Vibration energy harvesting has attracted considerable attention because of its application prospects for charging or powering micro-electro-mechanical system. Abundant hydrokinetic energy of water at low velocity is contained in the fluid environment, such as rivers and oceans, which are widely existing in nature. In this paper, a flow-induced piezoelectric vibration energy harvester (PVEH) with magnetic force enhancement, which is integrated by piezoelectric beam, circular cylinder bluff body and magnets, is proposed and experimental investigated. It could transfer the hydrokinetic energy, both the vortex-induced vibration and magnetic force excitation underwater, into electricity. First, the frequency sweep experiment of the piezoelectric cantilever beam is carried out to determine the resonance frequency where the effect of magnetic force on the vibration characteristic is obtained. Furthermore, the flow-induced vibration experiment platform is setup and the energy harvesting performance of the PVEH is investigated in detail. The effects of the magnet property, flow velocity and the magnetic poles distance on the vibration frequency and the acquisition voltage are demonstrated and discussed. The results show that it could improve the harvesting performance by introducing magnetic force. It has advantages in higher output voltage for the flow-induced PVEH, especially in low velocity water flow, when the flow velocity is 0.35 m/s, the PVEH under attractive magnetic force with magnetic distance of 20 mm scavenges the higher acquisition voltage of 5.2 V, which is increased by 225% than the PVEH with non-magnetic. The results can be applied to guide further fabrication process and optimized design of the proposed flow-induced PVEH underwater with low flow velocity.

In the process of energy harvesting, vibration energy harvesting still has several disadvantages, including a high-threshold excitation and a narrow working bandwidth. Therefore, a 2-degrees-of-freedom piezoelectric energy harvester is proposed. By introducing a nonlinear magnetic force to the system, the working bandwidth and the energy-harvesting efficiency of three magnetically coupled piezoelectric cantilever beams can be effectively improved. In this paper, a mathematical model consisting of three electrically coupled magnetically coupled piezoelectric cantilever beam systems is established, and the governing equations of electric coupling are solved numerically and verified experimentally. The dynamic characteristics under different excitations and frequencies are studied. The experiment shows that the working bandwidth can be increased by controlling the distance between three pairs of circular magnets and changing the excitation and frequency to induce resonance. Thus, the self-power requirement of micro-power devices can be realized. Overall, this study provides a promising solution for improving the performance of piezoelectric energy harvesters and offers theoretical insights for designing vibrating piezoelectric energy harvesters.

To address the self-powered issue of micro-sensors, an integrated piezoelectric energy harvester was proposed, which utilized wake-induced vibration (WIV). Utilizing the wind-induced vibration energy harvesting test bench and a two-way fluid–structure interaction calculation approach, the output performance of the energy harvester under vortex-induced vibration (VIV)and WIV was compared. The study investigated the effects of wind speed, diameter ratio, and aspect ratio on the output performance of the integrated piezoelectric energy harvester. The response mechanism to WIV was elucidated. The findings indicated that the energy harvester performed more effectively under WIV than under VIV. With a diameter ratio of 1.0, the upstream interfering column exerted an inhibitory effect, resulting in the poorest output performance for the integrated piezoelectric energy harvester. At a diameter ratio of 1.5, the maximum effective power of the integrated piezoelectric energy harvester reached 44.28 μW, a 4.65-fold increase over the previous condition. Based on variations in the aspect ratio, the wake region could be categorized into an extended body region, a reattachment region, and a common shedding region. Within these, the integrated piezoelectric energy harvester demonstrated the best output performance in the reattachment region. These findings provide a theoretical foundation for the application of wake excitation in piezoelectric energy harvesting and offer guidance for advancements in micro-sensor self-powered technology.