Piezoelectric Energy Harvesting System Research Articles

A piezoelectric energy harvesting concept for an energy-autonomous instrumented total hip replacement

To improve the clinical outcome of total hip replacements (THRs), instrumented implants with sensory functions for implant monitoring and diagnostics or actuators for therapeutic measures are a promising approach. Therefore, an adequate energy source is needed. Batteries and external power supplies bring shortcomings e.g. limited lifetime or dependency on external equipment. Energy harvesting has the clear benefit of providing continuous and independent power for fully autonomous implants. Our present study evaluates by means of finite element analysis (FEA) the capabilities of a concept of a piezoelectric energy harvesting system (ring shaped multilayer piezoelectric element of 5 mm diameter and 2.5 mm height) integrated in a femoral hip stem. The deformations from a modified load-bearing implant are used to generate electric power for various instrumentation purposes. Besides the expected amount of converted energy, the influence on the stress distribution of the instrumented implant is analysed. The results show that the local stress increase for the modified implant geometry does not exceed the stress of the original reference model. The maximum generated open circuit voltage of 11.9 V can be processed in standard energy harvesting circuitry whereas an average power output amounts up to 8.1 µW. In order to increase the electric power in an upcoming design optimization, a sensitivity analysis is performed to identify the most important influencing parameters with regard to power output and implant safety.

Experimental and Numerical Studies of a Soft Impact Piezoelectric Energy Harvesting Using an MR Fluid

Numerical and an experimental study of a soft impact-based piezoelectric energy harvesting system employing a thin layer of magnetorheological (MR) fluid as the impact object is presented in this paper. MR fluid devices are mostly used as vibration suppressors in automobiles and other machinery. MR fluids exhibit variable rheological properties in the presence of a magnetic field, which makes them excellent vibration attenuation devices with easily adaptable damping forces. This behavior can be exploited in vibration energy harvesting to aid frequency up-conversion. The study is carried by solving the theoretical equations numerically and then validating the results experimentally. The Heaviside function is used to model the piecewise nonlinear dynamics of the proposed system. In this way, the sticky and inelastic behavior of the fluid, which causes a time-delay in the oscillations of the beam is best described. The results obtained indicated that increasing the magnetic field increases the voltage generated through frequency amplification. The voltage obtained with a load resistance of 200 k $\Omega $ increased from 9.29 V to 9.42 V when the magnetic field increases from 0.04T to 0.08T for the numerical study and 7.71 V to 8.46 V when the field increased from 0.044T to 0.085T in the experimental study. The frequency is amplified from 59.58 Hz at 0.04T to 82.76 Hz at 0.08T for the numerical results and from 61.02 Hz at 0.044T to 83.04 at 0.085T for the experimental results. The MR fluid acts as a soft impact object in this work.

IMPACT-BASED PIEZOELECTRIC ENERGY HARVESTING SYSTEM EXCITED FROM DIESEL ENGINE SUSPENSION

Vibration energy harvesting systems are using real ambient sources of vibration excitation. In our paper, we study the dynamical voltage response of the piezoelectric vibrational energy harvesting system (PVEHs) with a mechanical resonator possessing an amplitude limiter. The PVEHs consist of the cantilever beam with a piezoelectric patch. The proposed system was subjected to the inertial excitation from the engine suspension. Impacts of the beam resonator are useful to increase of system’s frequency transition band. The suitable simulations of the resonator and piezoelectric transducer are performed by using measured signal from the engine suspension. Voltage outputs of linear (without amplitude limiter) and nonlinear harvesters were compared indicating better efficiency of the nonlinear design.

Behavioral modeling of a piezoelectric harvester with adaptive energy-investment for improved battery charging

This work describes the behavior of a piezoelectric energy harvesting system that uses a single inductor and the concept of energy investment for the whole of building a behavioral model for the harvester and a high-level system analysis approach. The harvester modules and control were specified and described in Verilog-A to fully model the energy harvester operation. Simulation results have shown the harvesting mechanism based on the concept of energy-investment and model accuracy, and the effect of the invested energy on the battery charging profile, highlighting the trade-off a constant energy investment time poses to the harvester, unable to meet the requirements a non-constant input vibration sets to system. An adaptive energy investment time based on a P&O algorithm was proposed to cope with this trade-off and added to the harvester model. Performed simulations with adaptive energy investment have shown improved energy harvesting, and that such improvement increases as the input power increases, since the system can tune the energy investing mechanism to the input vibrations.

Phononic band gap of a quarter-wave stack for enhanced piezoelectric energy harvesting

Extraordinary phenomenon (e.g., band gap) exhibited by a phononic crystal (PnC) has recently been incorporated into piezoelectric energy harvesting (PEH) as a means to amplify input waves for improving the power generation capability. For a systematic design of PnC-based PEH using band gap reflection, it is required to identify a standing wave pattern (i.e. location of nodes and antinodes) in order to determine the optimal placement of a piezoelectric layer. In this context, we propose a quarter-wave stack (QWS)-based PEH system under elastic waves. The foundational idea of this study is to manipulate a standing wave pattern formed in a host medium by considering the phase change within the QWS. The key to creating an optimal standing wave for PEH is to intentionally form a displacement node at the interface between the host medium (here, continuous copper bar) and QWS at a target design frequency; thereby, the placement of the piezoelectric layer can be systematically determined in order that its center is aligned with the strain antinode to generate the maximum output power. To deeply explore the effect of the standing wave pattern on the output performances of the QWS-based PEH system, two key parameters are thoroughly investigated: 1) the number of unit cells and 2) the excitation frequency. Numerical analysis results suggest the followings: First, an increase in the number of unit cells corresponds to the effect of amplifying input loading for enhanced PEH; thereby, the output performances increase gradually and converge asymptotically. Second, since the standing wave pattern varies with the excitation frequency, the electroelastic coupling varies accordingly. These new findings provide guidelines on design parameters that can be manipulated to yield the best performance of the QWS-based PEH system under elastic waves for various potential applications.

Dynamics of a Nonlinear Energy Harvesting System in Time-Delayed Feedback Control under Stochastic Excitations

A time-delayed feedback control is applied to a nonlinear piezoelectric energy harvesting system excited by additive and multiplicative Gaussian white noises to improve its energy harvesting performance. An equivalent decoupling system can be obtained by using a variable transformation. Based on the standard stochastic averaging method, the Fokker–Plank–Kolmogorov equation and the stationary probability density functions of the amplitude, displacement, and velocity of the harvester are obtained, respectively. In addition, the approximate expressions of mean square electric voltage and the mean extracted output power are derived. Finally, the paper explores the influences of parameters on the mean square electric voltage. The results show that noise intensity, time delay, feedback strength, time constant ratio, and coupling coefficients have great influences on the mean square electric voltage. The accuracy of the theoretical method is verified by the Monte Carlo simulation.

On the Effects of Structural Coupling on Piezoelectric Energy Harvesting Systems Subject to Random Base Excitation

The current research investigates the novel approach of coupling separate energy harvesters in order to scavenge more power from a stochastic point of view. To this end, a multi-body system composed of two cantilever harvesters with two identical piezoelectric patches is considered. The beams are interconnected through a linear spring. Assuming a stochastic band limited white noise excitation of the base, the statistical properties of the mechanical response and those of the generated voltages are derived in closed form. Moreover, analytical models are derived for the expected value of the total harvested energy. In order to maximize the expected generated power, an optimization is performed to determine the optimum physical and geometrical characteristics of the system. It is observed that by properly tuning the harvester parameters, the energy harvesting performance of the structure is remarkably improved. Furthermore, using an optimized energy harvester model, this study shows that the coupling of the beams negatively affects the scavenged power, contrary to the effect previously demonstrated for harvesters under harmonic excitation. The qualitative and quantitative knowledge resulting from this analysis can be effectively employed for the realistic design and modelling of coupled multi-body structures under stochastic excitations.

Enhancing Performance of a Piezoelectric Energy Harvester System for Concurrent Flutter and Vortex-Induced Vibration

This paper proposes a novel and efficient energy harvester (EH) system, for capturing simultaneously flutter and vortex-induced vibration. There exists a coupling effect between flexible spring energy harvester (FSEH) and cantilever beam energy harvester (CBEH) in aerodynamic response and output characteristic. Many prototypes of the harvester were manufactured to explore the coupling effect in a wind tunnel. The experimental results demonstrate that FSEH is mainly subjected to flutter-induced vibration and CBEH undergoes vortex-induced vibration. Disturbance of FSEH first takes place, a limited oscillation cycle then occurs, and chaos ultimately happens as airflow velocity increase. Root mean square voltages are more than 11 V for FSEH at beyond 10.52 m/s, which shows the better output performance over the existing harvesters. Vibration response and output voltage of various harvesters are mutually enhanced with each other. An enhancing ratio for FSEH-130-25 is up to 69.6% over FSEH-130-0, while the enhancing ratio for CBEH-130-30 is 198.3% compared to CBEH-0-30. Field application testing manifests that discharging time to power the pedometer is almost twice as long as the charging one for FSEH-130-25 at 14.48 m/s. The current research offers a suggestive guidance for promoting future practical application in micro airfoil aircrafts.

Vibration analysis of transverse galloping of different bluff bodies

The purpose of this research is to identify the best Blunt Body (BB) configuration for a piezoelectric wind energy harvesting system. The bluff body configurations studied are square, trapezoid, cone, cylinder, and aerofoil which are experimented on the rectangular and triangular cantilever beam. The increase in displacement and vibration velocity with respect to incident wind velocity is reported experimentally. Experimental findings suggest square BB and triangular cantilever are best suited for transverse galloping. A comprehensive study of galloping of the cantilever beams on its various regions with respect to the wind velocity is done. An overall increase of 27% displacement is reported in the triangular cantilever beam when compared to the rectangular cantilever beam. Cut–in speed for the above configurations is also studied and results are plotted. Results prove Trapezoidal BB and aerofoil BB has the least and highest cut-in speed respectively.

System level design of wireless sensor node powered by piezoelectric vibration energy harvesting

This paper proposes a design of wireless sensor node powered by piezoelectric vibration energy harvesting system. A complete system level coupling circuit model is established to predict the performance characteristics. The piezoelectric vibration energy harvester (PVEH) is based on a PZT bimorph cantilever, in which a big proof mass is introduced to decrease resonant frequency and a shell served as a stopper to avoid overload. Lumped parameters of the model are identified by experiments and calculations. Electromechanical analogy model of PVEH is simulated in LTspice software. The power consumption of a temperature WSN is tested and the equivalent load model is simulated. A power management circuit (PMC) with LTC3588-1 is designed for rectifying and regulating output of PVEH. Electrical energy is stored in a capacitor. Finally, a system level coupling model is established. Time domain circuit simulation can provide the detailed parameters about the WSN powered by PVEH such as full charge time and sustainable time of the system. Test curves of capacitor charging and WSN power supply in prototype testification show good consistency with the simulation results in LTspice. An application for temperature WSN powered by PVEH is testified as an example. The method and model proposed in this paper can set up a reference to optimize system parameters for WSN powered by PVEH.

A State-Of-The-Art Review of Car Suspension-Based Piezoelectric Energy Harvesting Systems

One of the most important techniques for energy harvesting is the clean energy collection from the ambient vibration. Piezoelectric energy harvesting systems became a hot topic in the literature and attracted most researchers. The reason behind this attraction is that piezoelectric materials are a simple structure and provide a higher power density among other mechanisms (electromagnetic and electrostatic). The aim of this manuscript is to succinctly review and present the state of the art of different existing vibrational applications utilizing piezoelectric energy harvesting technique. Meanwhile, the main concentration is harvesting energy from a vehicle suspension system. There is a significant amount of dissipated energy from the suspension dampers that is worthy of being harvested. Different mathematical car models with their experimental setup are presented, discussed, and compared. The piezoelectric material can be mounted in different locations such as suspension springs, dampers, and tires. The technique of implementing the harvester and the amount of power harvested from each location are analyzed. The evaluation of the electrical harvesting circuits and different storage devices for the harvested power are also discussed. The paper will also shed light on the variety of potential applications of the harvested energy.

Wind energy harvesting using piezoelectric macro fiber composites based on flutter mode

Mechanical energy such as the wind flow widely exists in nature as renewable and sustainable energy source. It could be converted into electrical energy throughout piezoelectricity which has capability for converting mechanical energy into electrical energy. In this paper, an innovation piezoelectric energy harvesting (PEH) system is proposed by using the piezoelectric macro fiber composites (MFC) based on flutter mode. It is demonstrated that this PEH-MFC system exhibits the excellent characteristic of flexibility on large deformation and reliability in energy harvesters and effectively captures power from wind energy. The PEH-MFC system is composed of a soft substrate linked with a polymer triangular leaf by a copper hinge. The active MFC is attached at the bottom of the soft substrate as the core component of system. A series of experiments on energy harvesting systems for various substrate materials and various types of MFC are performed in wind tunnel. The flutter mode is obtained under the critical flutter wind speed in order to acquire the excellent behavior of extracting power through this innovation PEH-MFC system. The experimental results show that the thickness and stiffness of PEH substrate have significant effects on the performance of energy harvesting. The maximum peak-to-peak open circuit voltage of 82 V is obtained using the MFC-2807 with Al substrate at the wind speed of 7.5 m/s. The resulting direct voltage and electric power are 25.8 V and 0.54 mW with a load resistance of 680 kΩ, respectively. It is concluded that the proposed energy harvesting system using MFC based on flutter mode can generate a power efficiency of 9.18 mW/cm3 which can meet the requirement of conventional MEMS.

Elastic wave localization and harvesting using double defect modes of a phononic crystal

Phononic crystals (PnCs) have been utilized to amplify the amount of input energy transferred to a piezoelectric energy harvesting (PEH) device by manipulating elastic wave propagation. When introducing a defect that has material properties and/or geometry different from a unit cell, mechanical resonance of the defect leads to localizing elastic waves inside the defect. This is called a defect mode. Several prior studies have explored a defect mode for PEH purpose; however, they have focused only on a single defect. When introducing an additional defect into a PnC, the coupling between two defects leads to splitting the defect band. Incorporating such split defect band phenomena into PEH can potentially widen frequency bandwidth and realize broadband energy harvesting. Thus, this study newly proposes a PnC-based PEH system that uses double defect modes under elastic waves. In particular, this study examines how an electrical circuit connection (i.e., Independent, Series, or Parallel) between two PEH devices attached on each defect affects PEH performances. Key findings from this study include (1) the shift in split defect bands as well as harvesting performance varies with the type of electrical circuit connection; (2) split defect band phenomena amplify the output electric power at double resonance peaks in an Independent connection; and (3) despite displacement amplification at certain resonance frequencies, no peak output voltage occurs due to the current source direction (for Series connections) and voltage cancellation (for Parallel connections). These key findings can provide design and selection guidelines for electrical circuit configurations between double defects for enhanced PEH.

Designing a phononic crystal with a defect for energy localization and harvesting: Supercell size and defect location

Metamaterial-based energy harvesting (MBEH) has recently received much attention due to its capability of amplifying input mechanical wave transferred to a piezoelectric energy harvesting (PEH) device. A phononic crystal (PnC), one representative example of a metamaterial, is an artificially-engineered structure constituted by a periodic repetition of unit cells that can manipulate the propagation of elastic waves at the scale of the wavelength. If a defect is introduced in the PnC by replacing one unit cell with another cell that has different geometric or material properties, the periodicity of the PnC is locally broken; thereby, defect bands are created within the band gap. Since the defect can mechanically resonate with a certain defect mode shape at the defect band frequency, an evanescent wave can be localized inside the defect. By attaching the PEH device to the defect, the output electric power can be dramatically enhanced. However, there is presently no thorough design rationale to inform decisions on supercell size and optimal defect location of a PnC for energy localization and harvesting. Thus, this study investigates effects of supercell size and defect location on energy localization and harvesting performances. For a given defect location, the output performance of the PnC-based PEH system monotonically increases and converges toward the maximum value as the supercell size increases. For a given supercell size, there exists an optimal defect location where maximum output performances of the PnC-based PEH system can be achieved. The key findings of this study lie in that there is a trade-off relationship between the fulfillment of resonance formation and the attenuation of evanescent waves. It can be concluded from this study that the supercell size and defect location can be properly designed to improve the output performances of a PnC-based PEH system under elastic waves.

Analytical and Experimental Studies of Double Elastic Steel Sheet (DESS) Vibration Energy Harvester System

This study provides a double elastic steel sheet (DESS) piezoelectric energy harvester system, in which the vibration generated by the deformation and clap of two elastic steel sheets is assisted by a piezo patch to generate electric energy. The system is combined with energy storage equipment to propose a complete solution forgreen energy integration. This study buildsexperimentallyon the model of the proposed system to explore its voltage, power output and energy collection efficiency. This study also builds atheoretical model of a nonlinear beam with the piezo patch, including the piezoelectric coupling coefficient and current equation. This nonlinear problem is analyzed by the method of multiple scales (MOMS). The system frequency response wasobserved using fixed points plots. The perturbation technique and numerical method wereused to mutually validate the experimental results; the concept of DESS vibration energy harvester (DESS VEH) is proved feasible. In order to prolong the lifetime of the clapping of DESS piezo patch, a camber protector design is proposed. The findings show that the power-generating effect is best when the piezo patch is placed at the peak of the third mode of the DESS system, and the high camber protector is used to generate electric energy.

Development of Micro-Mobility Based on Piezoelectric Energy Harvesting for Smart City Applications

This study investigates the use of an alternative energy source in the production of electric energy to meet the increasing energy requirements, encourage the use of clean energy, and thus reduce the effects of global warming. The alternative energy source used is a mechanical energy by piezoelectric material, which can convert mechanical energy into electrical energy, that can convert mechanical energy from pressure forces and vibrations during activities such as walking and traveling into electrical energy. Herein, a pilot device is designed, involving the modification of a bicycle into a stationary exercise bike with a piezoelectric generator, to study energy conversion and storage generated from using the bike. Secondly, the piezoelectric energy harvesting system is used on bicycles as a micro-mobility, light electric utility vehicle with smart operation, providing a novel approach to smart city design. The results show that the energy harvested from the piezoelectric devices can be stored in a 3200 mAh, 5 V battery and power sensors on the bicycle. Moreover, 13.6 mW power can be generated at regular cycling speed, outputting 11.5 V and 1.2 mA. Therefore, the piezoelectric energy harvesting system has sufficient potential for application as a renewable energy source that can be used with low power equipment.

Electrical impedance matching based on piezoelectric ceramics for energy harvesting application

ABSTRACT Piezoelectric energy harvesting is one of the promising energy sources for wireless sensor networks and integrated devices. One way to enhance the efficiency of energy harvesting is through the electrical impedance matching. In piezoelectric energy harvesting system, the electrical impedance matching can increase the output voltage and energy from the generated electrical energy to the harvesting circuit. In this paper, the electrical impedance matching technologies for energy harvesting circuit to transfer the accumulated electrical energy to various output loads, including conventional electrolytic capacitors, supercapacitors and rechargeable Ni MH batteries, were intensively investigated to obtain maximum output energy. The harvested power through AC-DC rectifier circuit was used to light the LED lamp, which provides a prospect application in wireless sensor networks and portable devices.

A Sensorless Self-Tuning Resonance System for Piezoelectric Broadband Vibration Energy Harvesting

This article presents a broadband piezoelectric vibration energy harvesting system. It can actively tune its resonant frequency to match the frequency of the ambient vibration excitation. The energy harvester is comprised of a movable mass attached to a piezoelectric cantilever beam. And a microstepper is employed to adjust the position of the mass for regulating the resonant frequency. Furthermore, in this article, a new method is proposed for the online dynamic detection of the piezoelectric transducer (PZT) vibration statement without any additional sensors. A circuit is proposed to detect the ambient vibration excitation frequency deviation against the resonant frequency only by measuring the phase difference between the open-circuit voltage and the short-circuit current of the PZT. Experimental results indicate a frequency broadening rate of up to 60.56%, while the maximum extraction efficiency is 84.8%. It can harvest vibration energy and self-power the system in a wide broadband ambient excitation vibration frequency for the wireless sensor network nodes.

New insight into piezoelectric energy harvesting with mechanical and electrical nonlinearities

This letter investigates the piezoelectric energy harvesting system with mechanical and electrical nonlinearities. Through impedance model, nonlinear interface circuits for energy harvesting purpose can be simplified as an electrical impedance with real and imaginary parts. Their effects on the mechanical structure can be regarded as circuit-induced damping and stiffness. The resulted equivalent mechanical vibratory system allows us to analytically obtain the system responses under different excitation and loading conditions by harmonic balance method. Furthermore, it becomes possible to achieve a comprehensive comparison among different nonlinear interface circuits, including the standard energy harvesting circuit, synchronized electric charge extraction circuit, series synchronized switching on inductor circuit, parallel synchronized switching on inductor circuit and parallel synchronized triple bias-flip circuit. The results from the theoretical model and experiments together reveal that the nonlinearities play a significant role in the energy harvester’s hysteresis region size, displacement amplitude, and piezoelectric voltage level. This investigation provides an insight into the design, optimization and implementation for the nonlinear energy harvester.

Piezoelectric vortex induced vibration energy harvesting in a random flow field

Vibration-based energy harvesters have significant potential for sustainable energy generation from ambience for micro-scale systems like wireless sensor networks and similar low power electronic devices. Vortex-induced vibration (VIV) is one of the richest sources for such power generation for devices installed within a fluid environment. However, uncertainty in the direction and magnitude of the free stream velocity could affect the performance of such systems. We have first developed the mathematical model of a piezoelectric cantilever beam with end mass vibrating under the influence of VIV. The piezo patch is assumed to be in the unimorph and bimorph configurations. From the unimodal dynamic response of the system, an equivalent single degree of freedom mechanical model is developed. This is further integrated with the electrical model of the piezoelectric system without and with an inductor. The energy harvested from the deterministic harmonic excitation is estimated against the non-dimensional velocity parameter. A random process model is developed considering the excitation force due to vortex shedding to be a bounded, weakly stationary and narrowband random process. The power spectral density of the random process is obtained using the Fourier transform of the auto-correlation function. The dynamic response of the energy harvester is obtained against such random excitations. The expressions of the mean power are obtained in closed-form corresponding to the cases without and with the inductor integrated to the electrical circuit. It is observed that while for cases without the inductor, the average harvested power monotonically decreases with increase in damping ratio and decrease in the coupling factor; for models with the inductor, an optimal inductor constant exists corresponding to the maximum mean-power condition. The extensive analytical modelling and initial representative results are expected to pave the way for the practical design of VIV based piezoelectric energy harvesting system subjected to stochastic excitation.