Cantilevered Harvester Research Articles

Numerical Investigation of Piezoelectric Energy Harvesting From a Multi-Mode T-Shaped Structure

In this work, energy harvesting from a proposed three-mode T-shaped structure, composed of a vertical beam, two horizontal beams, a center mass, and tip masses, is investigated to expand the frequency bandwidth for energy harvesting, without compromising the power density due to the additional mass of the structure, as is the case with most multi-mode harvesters. The aim is to cleverly use and position the additional mass to help induce higher and more uniform strain levels throughout the piezoelectric patch, leading to greater power generation to help counteract the added mass. A numerical model was developed to analyze the structure, to obtain voltage and power frequency responses, taking into effect the load resistance modeling and the accurate evaluation of resonance peaks by estimating each mode damping ratio. The validity of the model was confirmed by comparisons with previous experiments involving other structures, which demonstrated strong agreement. The excitation load was strategically applied to induce maximum displacement of the center and tip masses relative to the fixed ends in each mode. The outcomes reveal that the T-shaped configuration exhibits the capacity to generate higher maximum strain and a more uniform strain distribution across the piezoelectric patch when compared to previous L-shaped and traditional cantilever harvesters' designs. These characteristics yielded a power density higher than that of the L-shaped structure by approximately 70% with only around 20% addition in structure mass. Additionally, the multi-mode T-shaped structure boasts a significantly broader harvesting bandwidth due to the additional mode, without compromising power density, as was the case with L-shaped structures. Furthermore, the positioning of the tip mass was systematically altered to assess its impact on the frequency bandwidth and power output of the horizontal and vertical beams in the three bending modes, demonstrating great robustness and tuning capabilities.

Multi-Variable Optimization to Enhance the Performance of a Cantilevered Piezoelectric Harvester

Over the past decade, various researchers have shown the practicality of extracting electrical energy from vibrating structures. The primary objective of this research was to optimize the parameters of a basic cantilever harvester to maximize the energy production of electricity from surrounding mechanical energy. A distributed parameter model and its modal solution were utilized to determine the design variables via a parametric investigation. It is important to ensure sufficient power generation when there is a wide range of frequencies being excited, without any specific frequency being emphasized. The cost function for the optimization problem was defined as the average power within a specific frequency range, considering geometric and physical restrictions. It was discovered that different parameters’ values can be utilized to generate varying maximum power levels for different frequency ranges. Furthermore, a comparative analysis was performed between the finite element method (FEM) using ANSYS and the current harvesting model. The comparison demonstrated a high level of concordance, enabling the utilization of the finite element method (FEM) for subsequent investigation.

Performance of a Piezoelectric Energy Harvester with Rubber Compound Modification

Recently, there has been a significant increase in the research on Piezoelectric energy harvester. Piezoelectric energy harvester is capable of producing electrical charge when mechanically deformed. The application is to be used to power up mobile electronic. The common problem in the piezoelectric energy harvester is the material is brittle and causes fatigue failure at the same time the material is relatively costly. One of the method to address this problem is to add a rubber compound layer which can improve the flexibility and power output of the energy harvester. It can also improve the cost per output density of the piezoelectric energy harvester because the rubber compound has low cost. But, currently none of existing literatures explore into this type application. Thus, the objective of this paper is to investigate the voltage output and effectiveness of piezoelectric energy harvester with rubber compound modification. The test in the laboratory was set up to optimize PZT (Lead Zirconate Titanate) Energy Harvester cantilever beams using rubber compound layer as modification. The tests were conducted using frequency range of 30 Hz to 70 Hz with fixed RMS 0.25g acceleration. The result shows promising output for the PZT energy harvester with rubber compound, with an increase of between 16.6% to 61.2% open circuit voltage when compared to the standard PZT.

Low-temperature co-fired multilayer cantilevers based on relaxor–Pb(Zr,Ti)O3 for enhanced piezoelectric power generation at nonresonant frequency

Improving piezoelectric power-generation capability has been explored by modulating materials chemistry and device structure for specific low-power applications. Herein, high-performance multilayer cantilever structures based on perovskite 0.4Pb(Zn1/3Nb2/3)O3–0.6Pb(Zr0.5Ti0.5)O3 (0.4PZN–0.6PZT) with CuO additives are proposed as an example of electromechanical energy harvester utilizing nonresonant-frequency mechanical source. Even with low-temperature co-firing at 900 °C for 2 h to use inexpensive Ag inner electrodes, an optimized unimorph single-layer cantilever exhibited the best normalized power density of ∼10.8 mW cm−2 g−2 Hz−1 at 2 Hz with an acceleration of 0.028 g, which is far better than typical values reported for cantilever harvesters. The power value itself increased from ∼142.7 to ∼508.5 μW with four layers while maintaining the high power density. The enhanced power with multilayers was attributed to the increased current due to extensive surface-charge polarization as the effective electrode coverage area was approximately quadrupled.

Dynamic Behavior of Galloping Micro Energy Harvester with the Elliptical Bluff Body Using CFD Simulation

Energy extraction from flow-induced oscillations based on piezoelectric structures has recently been tackled by several researchers. This paper presents a study of the dynamic behavior analysis and parametric characteristics of a galloping piezoelectric micro energy harvester (GPEH) applied to self-powered micro-electro-mechanical systems (MEMS). The mechanical performance of a piezoelectric micro energy harvester cantilever beam with two layers of elastic silicon and piezoelectric (PZT-5A) attached to a tip elliptical cylinder is numerically simulated. Using size-dependent beam formulation on the basis of the modified couple stress theory and Gauss’ law, the coupled electro-mechanical non-linear governing equations of the energy harvester are obtained. The mode summation and Galerkin methods are used to derive the extracted power from the system. The study also models the flow field effect on the beam oscillations via CFD simulation. The effect of elliptical cylinder mass, damping ratio, beam thickness, and load resistance on the dynamic behavior and harvested power of the system is studied. Findings reveal that increasing the normalized tip mass from 0 to 0.5 and 1 increases the output power density from 0.12 to 0.2 and 0.22, respectively, and the corresponding electrical load resistance of maximum power increases from 175 to 280 kΩ and 375 kΩ, respectively. An approximately linear relation between the elliptical cylinder mass and the load resistance is observed. By increasing/decreasing the cylinder mass, the required electrical load resistance for maximum output power proportionally changes. The damping analysis shows that a higher damping ratio increases the onset velocity of galloping and decreases the extracted power.

Design and Analysis of an Extended Simply Supported Beam Piezoelectric Energy Harvester

The harvesting efficiency of a cantilevered piezoelectric energy harvester is limited by its uneven strain distribution. Moreover, a cantilevered harvester requires a large workspace due to the large displacement of its free end. To address these issues, a novel piezoelectric energy harvester based on an extended simply supported beam is proposed. The proposed design features a simply supported piezoelectric main beam with an extended beam attached to its roller end and a tip mass to reduce the resonant frequency. The theoretical model of the proposed piezoelectric energy harvester is developed based on the Euler–Bernoulli beam theory. The model has been experimentally validated through the fabrication of a prototype. The extended beam and tip mass are adjusted to see their influence on the performance of the harvester. The resonant frequency can be maintained by shortening the extended beam and increasing the tip mass simultaneously. A shorter extend beam leads to a more even strain distribution in the piezoelectric layer, resulting in an enhanced output voltage. Moreover, the simulation results show that a torsional spring is installed on the roller joint which greatly influences the voltage output. The strain distribution becomes more even when proper compressive preload is applied on the main beam. Experiments have shown that the proposed design enhances the output power by 86% and reduces tip displacement by 63.2% compared to a traditional cantilevered harvester.

Effect of major factors on broadband natural frequency energy harvesting for rectangular and L- shaped cantilever harvesters

A small amount of natural frequency deviation extremely decreases the output power. So, a multi-mass single harvester (bending harvester) was utilized to enlarge the bandwidth of the natural frequency. We constructed three models to study the effect of increasing the concentrated masses on increasing the bandwidth natural frequency. We used Finite Element Metho (FEM (COMSOL to model and simulate the three models. Moreover, we constructed an L-shaped harvester with concentrated masses to compare the rectangular harvester with concentrated masses. The results prove that increasing the number of concentrated masses increases the output power and broadband natural frequency. Moreover, the results indicate that the harvester cantilever with concentrated masses gives more output power and broadband than the L- shaped harvester for the same volume. Also, our research studied the harvester parameter effects on the output power. This study found that the increase in beam length and mass height increases the output power while the increase in piezoelectric thickness and damping ratio decreases the output power and bandwidth frequency. We validated our proposed model through a comparison with others’ preceding experimental results and it showed a good agreement. The harvester with a high width/length ratio gives a larger wideband natural frequency.

Numerical Investigation of Piezoelectric Vibration Energy Harvesting with L-shaped Beam

Energy harvesting efficiency is a crucial problem in practical engineering applications of piezoelectric vibration energy harvester. L-shaped piezoelectric vibration energy harvester has the potential of broadband and high energy harvesting efficiency. Different vibration energy harvesting structures are numerically investigated here to compare their energy harvesting efficiencies, including traditional cantilever beam structure and L-shaped structures. Verification and validation of the numerical simulation approach adopted here are conducted firstly, through comparing the numerical results with the theoretical and experimental results respectively. Modal analysis and harmonic response analysis are conducted consequently to obtain the natural frequencies and voltage outputs of different harvesters. Numerical results show that, L-shaped harvester is a potential broadband energy harvesting structure with higher energy harvesting efficiency compared with traditional cantilever harvester.

Four-point bending piezoelectric energy harvester with uniform surface strain toward better energy conversion performance and material usage

Improving the energy conversion efficiency of piezoelectric energy harvesters is of great importance, and one approach is to make more uniform use of the working material by ensuring a uniform strain state. To achieve better performance, this paper presents a four-point bending piezoelectric energy harvester with extensive investigation and modeling to identify the influential parameters. An electromechanical analytical model is presented and verified by experimental data. The frequency-domain method extracts the solutions for a general time-variable force and impact. Four-point bending is compared with the standard cantilever harvesters regarding voltage generation, mechanical strain, and figure of merit. Strain contours are analyzed and interpreted for this innovative approach, and the power generation by the optimal resistance load is studied. Dimensionless parameters are introduced and investigated to find the optimal operating conditions for the four-point bending harvester. Finally, the four-point bending performance and the best figure of merit are discussed with a view to the long-term fatigue life of the harvester. The results show that in the best four-point bending energy conversion conditions; the energy conversion coefficient is more than three times higher than that of typical cantilever energy harvesters. The results also illustrate that the axial strain experienced in a standard cantilever harvester is more than three times higher than that of the four-point bending harvester, suggesting the latter device may have favorable fatigue performance. Overall, the presented piezoelectric harvester has improved energy conversion efficiency and experiences a reduced and uniform surface strain, making it appropriate for high-efficiency energy harvesting systems.

A graded metamaterial for broadband and high-capability piezoelectric energy harvesting

This work proposes a graded metamaterial-based energy harvester integrating the piezoelectric energy harvesting function targeting low-frequency ambient vibrations (<100 Hz). The harvester combines a graded metamaterial with beam-like resonators, piezoelectric patches, and a self-powered interface circuit for broadband and high-capability energy harvesting. Firstly, an integrated lumped parameter model is derived from both the mechanical and the electrical sides to determine the power performance of the proposed design. Secondly, thorough numerical simulations are carried out to optimize both the grading profile and wave field amplification, as well as to highlight the effects of spatial-frequency separation and the slow-wave phenomenon on energy harvesting performance and efficiency. Finally, experiments with realistic vibration sources validate the theoretical and numerical results from the mechanical and electrical sides. Particularly, the harvested power of the proposed design yields a five-fold increase with respect to conventional harvesting solutions based on single cantilever harvesters. Our results reveal that by bridging the advantages of graded metamaterials with the design targets of piezoelectric energy harvesting, the proposed design shows significant potential for realizing self-powered Internet of Things devices.

Nonlinear Dynamic Analysis of Hybrid Piezoelectric-Magnetostrictive Energy-Harvesting Systems

To progress the proficiency and broaden the action bandwidth of vibration energy harvesters, this paper presents a cantilever piezoelectric-magnetostrictive bistable hybrid energy harvester with a dynamic magnifier. The hybrid energy-harvesting system comprises two vibration degrees of freedom and two electrical degrees of freedom. It consists of a composite cantilever beam made of three layers, in which the magnetostrictive and piezoelectric layers are attached to the top and bottom of the base layer. The electromechanically coupled vibration equations of the whole hybrid structure were established with the lumped-parameter model while taking into account the magnetic interaction of two magnets. The nonlinear frequency-response of vibrations for the hybrid harvester is calculated using the harmonic balance method, and the model has been validated by literature. The time response and phase portraits of oscillation for the cantilever harvester and its performance in generating electrical power under different magnet distances, dynamic magnifier features, and excitation levels are analyzed. Numerical results have shown that the hybrid structure can harvest additional electrical power and operates at larger bandwidth than routine bistable piezoelectric or magnetostrictive energy harvesters.

A Versatile Model for Describing Energy Harvesting Characteristics of Composite-Laminated Piezoelectric Cantilever Patches.

Vibration-based energy harvesters consisting of a laminated piezoelectric cantilever have recently attracted attention for their potential applications. Current studies have mostly focused on the harvesting capacity of piezoelectric harvesters under various conditions, and have given less attention to the electromechanical characteristics that are, in fact, crucial to a deeper understanding of the intrinsic mechanism of piezoelectric harvesting. In addition, the current related models have mostly been suitable for harvesting systems with very specific parameters and have not been applicable if the parameters were vague or unknown. Drawing on the available background information, in this study, we conduct research on a vibration-based cantilever beam of composite-laminated piezoelectric patches through an experimental study of its characteristics as well as a modeling study of energy harvesting. In the experimental study, we set out to investigate the harvesting capacity of the system, as well as the electromechanical (voltage/current-strain and power-strain relationships) characteristics of the cantilever harvester. In addition, we summarize some pivotal rules with regard to several design variables, which provide configuration design suggestions for maximizing energy conversion of this type of harvesting system. In the modeling study, we propose a coupled electromechanical model with a set of updated parameters by using an optimization program. The preceding experimental data are used to verify the superiority of the model for accurately predicting the amount of harvested energy, while effectively imitating the characteristics of a cantilever harvesters. The model also has merit since it is suitable for diversified harvesters with vague or even unknown parameters, which cannot be dealt with by using traditional modeling methods. Overall, the experimental study provides information on a comprehensive way to enhance the harvesting capacity of piezoelectric cantilever transducers, and the modeling study provides a wide scope of applications for cantilever harvesters even if precise information is lacking.

Design and development of a high-performance tensile-mode piezoelectric energy harvester based on a three-hinged force-amplification mechanism

When considering durability and reliability, flexible piezoelectric materials, such as PVDF and macro-fiber composite, are preferable to piezoceramics due to the brittleness of piezoceramics. However, flexible piezoelectric materials cannot sustain compressive loads so they need to be operated in either tensile or bending mode. The tensile mode has the advantage of uniform strain distribution over the bending mode. This study proposes a novel tensile-mode piezoelectric energy harvester based on a three-hinged force amplification mechanism. The proposed design consists of a rigid beam and an elastic PVDF film connected to each other via a revolute joint. The assembly is attached to a base via revolute joints with the PVDF film pre-stretched. The PVDF film bears a dynamic tensile load when the harvester is under harmonic excitations. A theoretical model of the proposed harvester is developed and experimentally validated. The simulation and experimental results show that the proposed design exhibits a strong hardening effect due to the nonlinear geometry of the three-hinged mechanism. The effect of preloads and mass distributions are explored to see their impact on the harvesting performance. It is shown that the peak voltage and bandwidth of the harvester decline as the preload increases. By properly tuning the mass distribution, the performance of the harvester can be enhanced. Compared with a bending-mode cantilevered harvester, the voltage output and harvesting bandwidth of the proposed harvester can be improved by 500% and 1250%, respectively.

Performance of Fe–Ga alloy rotational vibration energy harvester with centrifugal softening

With the development of vibration energy harvesting, sensor nodes for wireless monitoring are being increasingly powered by harvesting vibrations in rotating environments such as car tires and fan blades. Considering the diverse installation positions of vibration energy harvesters on rotating carriers, the centrifugal forces of the cantilever beams exhibit remarkable differences during rotation. Crucial factors for the performance of vibration energy harvesting include the deformation of the harvester cantilever beam, which is affected by the centrifugal force, and the influence of the pre-magnetization field on the Villari effect of specific alloys. We propose a rotational vibration energy harvester based on an Fe–Ga alloy and establish a mathematical model for magnetostrictive vibration energy harvesting by leveraging centrifugal softening. In addition, we perform a systematic theoretical analysis of the factors influencing the harvester performance considering centrifugal softening, rotation radius, and arrangement of the pre-magnetization field. The theoretical findings are verified on a prototype, and the system characteristics are investigated experimentally. The maximum output voltage reaches 3.36 V, and the energy harvesting efficiency reaches 22.86% when the harvester undergoes rotation at 330 r min−1. Moreover, the harvester is applied in a low-power temperature sensor for real-time temperature monitoring, indicating the validity and applicability of the proposed rotational vibration energy harvester. The results demonstrate that an appropriate use of the centrifugal softening and the pre-magnetization field can enhance the energy harvesting efficiency of a harvester operating at a low rotational frequency.

Working characteristics of a magnetostrictive vibration energy harvester for rotating car wheels.

The practice of harvesting vibration energy from machine tools, windmill blades, etc., and converting it into electric energy to power low-power electronic circuits has attracted wide attention from experts and scholars. Abundant vibrations that exist in the moving vehicle can be harvested to power sensors in tire pressure monitoring. In this paper, for the first time, a device is proposed to harvest the rotational vibration energy with the iron-gallium alloy (magnetostrictive material) as the core material. Such a device utilizes the coupling characteristics of Villarreal effect and Faraday electromagnetic effect to convert the vibration energy generated by the moving vehicle into electric energy. Upon completion of the design of the magnetostrictive rotational vibration energy harvester, the influence law of key factors, including substrate material, substrate size, and pre-magnetization field arrangement on the harvesting capability of the device, was studied in detail through experiments. An electric motor and vibration exciter were used to apply varied excitation forms to the harvester, and the output patterns of the harvester under conditions of wheel rotation, road bumps, and random vibration were fully analyzed. In addition, the correlation between the deformation of the cantilever beam and harvester performance was also investigated. The results have shown that at the acceleration of 9.6 g and the rotational speed of 90 r/min, the harvester can reach the output voltage of 1.22 V. Consequently, it demonstrates the feasibility of employing the magnetostrictive harvester to gather rotational vibration energy and provides theoretical guidance for further and deeper research on the harvester.

Electromechanical metastructures for simultaneous wave attenuation and energy harvesting

Periodic architectures designed with piezoelectric materials are favorable due to their potential to control waves without any need for structural modifications and also due to their multifunctional abilities, such as energy harvesting and vibration mitigation. This talk focuses on the latter and introduces a piezoelectric-based metastructure with broadband capability of low-frequency elastic wave energy conversion. Unlike the phononic crystal concepts consisting of piezoelectric patch arrays with heavy masses or resonance-based piezoelectric cantilever harvester arrays with tip mass attachments used for harvesting standing waves, our goal is to exploit the properties of locally-resonant metamaterials and phononic crystals within the same structure and harvest energy from travelling elastic waves. Specifically, we merge locally resonant and Bragg band gaps to achieve a multifunctional metastructure, which is capable for maximum energy conversion and wave attenuation in a broadband fashion. To this end, we develop a new wave-based fully coupled electroelastic transfer matrix method and study multifunctional harvesting and attenuation performance of the electromechanical metastructure. The theoretical frameworks and the applicability of the proposed metastructure are also validated using a full-scale experimental setup.

Vibration Energy Harvesting from Raindrops Impacts: Experimental Tests and Interpretative Models

The kinetic energy of raindrops is a large and renewable source of energy that nowadays can be exploited by means of piezoelectric harvesters. This study focuses on a new cantilever harvester that uses the impact of a drop on a liquid surface created on the harvester in order to improve the conversion from kinetic energy to electric energy. Experimental tests, carried out both outdoors and indoors, were performed to assess the validity of the proposed design. The voltage obtained with the impact on the liquid surface was about four times larger than the one obtained with the impact on a dry surface. The phenomena that lead to the increased performance of the harvester were analyzed both experimentally, by means of a high-speed camera, and analytically, by means of a mathematical model. The camera footage showed a clear relationship between the waveform of the generated voltage and the various phases of the impact (crown formation, crown collapse, and sloshing). The mathematical model developed herein, which was based on the oscillation of the liquid mass caused by the impact and on the linear momentum equation, is simple and can be used to estimate the measured voltage within a good approximation.

Vibration Energy Harvesting by Means of Piezoelectric Patches: Application to Aircrafts.

Vibration energy harvesters in industrial applications usually take the form of cantilever oscillators covered by a layer of piezoelectric material and exploit the resonance phenomenon to improve the generated power. In many aeronautical applications, the installation of cantilever harvesters is not possible owing to the lack of room and/or safety and durability requirements. In these cases, strain piezoelectric harvesters can be adopted, which directly exploit the strain of a vibrating aeronautic component. In this research, a mathematical model of a vibrating slat is developed with the modal superposition approach and is coupled with the model of a piezo-electric patch directly bonded to the slat. The coupled model makes it possible to calculate the power generated by the strain harvester in the presence of the broad-band excitation typical of the aeronautic environment. The optimal position of the piezoelectric patch along the slat length is discussed in relation with the modes of vibration of the slat. Finally, the performance of the strain piezoelectric harvester is compared with the one of a cantilever harvester tuned to the frequency of the most excited slat mode.

Development and characterisation of a self-powered measurement buoy prototype by means of piezoelectric energy harvester for monitoring activities in a marine environment

&lt;p class="Abstract"&gt;In the interest of our society, for example in Smart City but also in other specific backgrounds, environmental monitoring is an essential activity to measure the quality of different ecosystems. In fact, the need to obtain accurate and extended measurements in space and time has considerably become relevant. In very large environments, such as marine ones, technological solutions are required for the use of smart, automatic, and self-powered devices in order to reduce human maintenance service. This work presents a simple and innovative layout for a small self-powered floating buoy, with the aim of measuring and transmitting the detected data for visualization, storage and/or elaboration. The power supply was obtained using a cantilever harvester, based on piezoelectric patches, converting the motion of ripple waves. Such type of waves is characterized by frequencies between 1.50 Hz and 2.50 Hz with oscillation between 5.0 ° and 7.0 °. Specifically, a dedicated experimental setup was created to simulate the motion of ripple waves and to evaluate the suitability of the proposed design and the performance of the used harvester. Furthermore, a dynamic analytical model for the harvester has been defined and the uncertainty correlated to the harvested power has been evaluated. Finally, the harvested voltage and power have shown how the presented buoy behaves like a frequency transformer. Hence, although the used cantilever harvester does not work in its resonant frequency, the harvested electricity undergoes a significant increase.&lt;/p&gt;&lt;p class="Abstract"&gt;&lt;span lang="EN-US"&gt;&lt;br /&gt;&lt;/span&gt;&lt;/p&gt;

POTENTIAL OF TWIN-SCREW COMPRESSOR AS VIBRATION SOURCE FOR ENERGY HARVESTING APPLICATIONS

The paper presents the vibrational behaviour of a twin-screw compressor at various functioning regimes. The speed is varied by means of a 250 kW electric driving motor, via a frequency converter. The compressor can supply pressurized air up to ~16 bar into a buffer tank. The air is used for testing various equipment on test bench, such as expanders, pneumatic starters for gas turbine engines, or other compressors and blowers used for compressing air starting from a pressure higher than the atmospheric pressure. Like all other industrial equipment, compressors experience inherent vibrations in operation. The pulsatory effects of the air within the compressor also give birth to harmonics. The study herein involves gathering vibration data and represent it as vibration spectra. Raw vibration signals, employed for assessing the condition of the machinery, may not always be clear in the frequency spectrum for vibration analysis, thus being required to apply Fast Fourier Transform for converting the time waveform into frequency spectrum. The study herein pursues a future application of energy harvesting from vibrations, and outlines that the spectral analysis of the compressor is convenient for piezoelectric cantilever harvesters in terms of vibration frequency and amplitude.