Cantilever-based Energy Harvester Research Articles

Free and forced vibrations of elastically restrained cantilever with lumped oscillator

The efficiency assessment of cantilever-based energy harvesters relies on vibrational analysis, which necessitates modifications aimed at enhancing efficiency. These modifications involve manipulating the fundamental frequency to lower values and encompassing a wider range of resonances within a specified bandwidth. Consequently, this paper introduces an original analytical-numerical exploration into the vibratory response of a cantilever with a novel boundary condition involving an elastically restrained oscillator-spring arrangement. At the microbeam's tip, an oscillator is elastically confined by a linear spring, resulting in a novel set of coupled governing equations and a distinct shearing boundary condition. Microbeam equations is derived from the modified couple stress theory to capture size dependency. During free vibration analysis, a previously unreported characteristic equation is derived. This nonlinear transcendental equation is numerically solved utilizing root-solver algorithms, such as those available in MATLAB. Significantly, it is discovered that the inclusion of a lumped oscillator with an elastic support induces a minimal (new) natural frequency. Applying the extended Hamilton's principle, the effect of the lumped oscillator emerges both on the governing equations of motion and boundary conditions of the microbeam. Novelty of the paper focuses on the both characteristic equation and transmissibility by adopting the Galerkin’s modal decomposition technique. This finding carries vital implications as the efficiency of cantilever-based energy harvesters is directly contingent upon the resonance frequency. Notably, the oscillator mass and spring constant are two parameters that directly influence the vibratory response of the microbeam. In the context of forced vibrations, harmonic base excitation is considered as the input excitation, and the mechanical frequency response function is provided. The proposed system offers two distinct advantages for energy harvester systems: the creation of minimal resonance at lower values and the potential to manipulate the system's resonance toward a desired frequency spectrum.Article HighlightsModifying the boundary conditions of a cantilever beam with lumped-parameter system, can significantly change the behavior of the vibratory response.The boundary condition directly impact the resonance frequencies; which influences the maximum amount of harvestable voltage in vibration-based energy harvesters.Spring constant and mass of the lumped oscillator, are the key factors to alter the vibratory behavior and bandwidth of frequencies. Optimizing such mentioned parameters can help reaching to the maximum harvesting of energy.

A piezoelectric cantilever-asymmetric-conical-pendulum-based energy harvesting under multi-directional excitation

This paper introduces a novel approach to address the challenges faced by traditional unidirectional cantilever-based energy harvesters in adapting to multi-directional vibration environments. The proposed solution combines a flexible cantilever with an asymmetric-conical-pendulum structure which consists of two different concentrated end masses and a rigid thin rod By investigation of energy interchange relationship between the kinetic feature of the asymmetric pendulum and beam bending vibration under horizontal and vertical excitations respectively from base movements, utilizing the Lagrange's theorem and multiple-scale method, 1:2 internal resonance can be induced for enabling the delivery of multi-directional motion of pendulums to the unidirectional bending of cantilever. On this basis, the advantages of the proposed system are revealed by comparing with traditional piezoelectric cantilever and piezoelectric cantilever-single-pendulum systems. Furthermore, the performance of the voltage amplitude and operational bandwidth was potentially improved up to 128.5 % and 229.8 % under x-direction. In addition, it is confirmed that its maximum voltage RMS value is 57.9 % and 11.4 % higher than that of the piezoelectric cantilever-single-pendulum in the x- and z-directions, owing to its multi-peak energy harvesting over variable excitation amplitudes. Therefore, the feasibility and superiorities of the proposed configuration are demonstrated theoretically and numerically in this paper.

Optimisation of Cantilever Based Energy Harvester Design for Railway Bridges

AbstractIn this paper, the authors investigate energy harvesting on railway bridges. A tuning process based on a statistical analysis of the mechanical energy generated by a lumped‐mass model is presented and validated. A cantilever‐based energy harvester configuration is applied, and the optimal design of 3D printed energy harvesters is studied. The electromechanical behaviour of the device is represented by an analytical model for the estimation of the energy harvested from train‐induced bridge vibrations. A genetic algorithm constrained to geometry and structural integrity is used to solve the optimisation problem. The design flexibility and energy performance are maximised by 3D printing of the substructure of the harvester. An optimal device prototype with PAHT CF15 substructure is designed and manufactured for a real bridge in the Madrid‐Sevilla High‐Speed line. The prototype is experimentally validated under laboratory conditions. Finally, the performance of energy harvesting is evaluated from in situ experimental data measured by the authors. The results allow quantifying the energy harvested in a time window of five hours and twenty‐seven train passages.

A Proof-of-Concept Study on an Internal-Resonance-Based Piezoelectric Energy Harvester With Coupled Three-Dimensional Bending-Torsion Motions

Abstract By exchanging the internal energy between coupled vibration modes, internal-resonance-based energy harvesters may provide an effective solution to broadening and enhancing bandwidth and power performance in dealing with natural vibration sources. With the development of piezoelectric-based transducers, thickness and face shear coefficients in proper piezoelectric elements can also generate power output from shear deformation on the core vibrating elements. However, in most cantilever-based energy harvesters that focused on bending modes, the shear responses were neglected. In this paper, we present an internal-resonance-based piezoelectric energy harvester with three-dimensional coupled bending and torsional modes, for the first time. The fine-tuned system leverages a two-to-one internal resonance between its first torsion and second bending modes to enhance the power output with piezoelectric effects. The dynamic behavior implies the coexistence of in-plane and out-of-plane motions under a single excitation frequency, and the corresponding strain changes in the bending and shear directions are captured by bonded piezoelectric transducers. Dependence between excitation levels and the internal-resonance phenomenon is justified as a critical system parameter study; the results also indicate that an intriguing non-periodic region exists near the center frequency. The outcomes of this study feature a multi-directional and multi-modal energy harvester that displays rich dynamic behaviors. The operational bandwidth is promising for broadband energy harvesting, and the output voltage is enhanced by capturing both in-plane and out-of-plane motions at the same time.

Electromechanical Performance of Biocompatible Piezoelectric Thin-Films

The present study analyzed a computational model to evaluate the electromechanical properties of the AlN, BaTiO3, ZnO, PVDF, and KNN-NTK thin-films. With the rise in sustainable energy options for health monitoring devices and smart wearable sensors, developers need a scale to compare the popular biocompatible piezoelectric materials. Cantilever-based energy harvesting technologies are seldom used in sophisticated and efficient biosensors. Such approaches only study transverse sensor loading and are confined to fewer excitation models than real-world applications. The present research analyses transverse vibratory and axial-loading responses to help design such sensors. A thin-film strip (50 × 20 × 0.1 mm) of each sample was examined under volumetric body load stimulation and time-based axial displacement in both the d31 and d33 piezoelectric energy generation modes. By collecting evidence from the literature of the material performance, properties, and performing a validated finite element study to evaluate these performances, the study compared them with lead-based non-biocompatible materials such as PZT and PMN-PT under comparable boundary conditions. Based on the present study, biocompatible materials are swiftly catching up to their predecessors. However, there is still a significant voltage and power output performance disparity that may be difficult to close based on the method of excitation (i.e., transverse, axial, or shear. According to this study, BaTiO3 and PVDF are recommended for cantilever-based energy harvester setups and axially-loaded configurations.

A cantilever-driven rotor for efficient vibration energy harvesting

The pervasive renewable vibration energy has been considered as a promising alternative to electrochemical energy of batteries for powering wireless sensors and wearable electronics, but its efficient harvesting is still an unsolved problem. To tackle this issue, this paper presents an innovative mechanical modulation mechanism, which we name ‘cantilever-driven rotor’, to convert vibrations to uni-directional rotation aiming to achieve improved energy harvesting performance. Compared with the conventional cantilever-based energy harvesters (CBEHs), the rotor-based energy harvester (RBEH) can provide both enhanced output power (1.8 mW versus 0.3 mW) and extended working bandwidth (4.5 Hz versus 1.9 Hz) under a harmonic vibration of 0.8 g (1 g = 9.8 m/s2). Moreover, electric outputs of the RBEH can persist for 27 s after the external excitation vanishes. With the electric energy generated by the RBEH from the harmonic vibration, a wireless acceleration sensor could be powered to perform with its full functionality. When attached to the human ankle, the RBEH can maintain the normal operation of a Timer under a walking speed of 6 km/h. This work provides a basically different vibration-to-rotation conversion mechanism with superior performance in vibration energy exploitation and potential applications in self-sustained wireless sensors and wearable electronics.

Design and Performance of ScAlN/AlN Trapezoidal Cantilever-Based MEMS Piezoelectric Energy Harvesters

In this work, we report a method to enlarge the trapezoidal cantilever-based harvester power by using the high-performance Sc <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.8</sub> N/aluminum nitride (AlN) composite film and introducing symmetrical corners to both sides of the beam. Energy harvesters with variable beam structure and piezoelectric film are designed and evaluated by simulations and experiments. The trapezoid with corners (TWCs) cantilever is verified to improve the output power by a factor of five times when compared with the conventional trapezoidal cantilever without corners. The maximum power density of the ScAlN/AlN-based TWC cantilever harvester is about twice that of the AlN-based harvester, reaching 2.054 mW ·g <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> ·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> at a frequency of 330.25 Hz. The optimization of piezoelectric film and structure can give an inspiration for further improving the performance of cantilever-based energy harvesters.

A distributed-parameter electromechanical coupling model for a piezoelectric energy harvester with variable curvature

Enabling technologies for harvesting ambient vibration energy have attracted considerable attention in research communities from different disciplines in the last decades. Among the various devices, straight cantilever-based energy harvesters have been widely investigated from the perspective of designs, modeling, simulation and experiments. In this study, we propose curved piezoelectric energy harvesters (PEHs) with variable curvature to further broaden application scenarios. Within the framework of the Euler–Bernoulli beam theory, we develop a distributed-parameter electromechanical coupling model for a curved segmented unimorph with variable curvature by Hamilton’s Principle and solve it using the Rayleigh–Ritz method. The convergence and accuracy of the model are validated by finite element simulation and experiments. Based on the proposed model, we perform a systematic parameter study and discuss the effects of the proof mass, Young’s modulus of the substrate, the thickness ratio of the substrate to the total thickness, the curvature of the substrate and the piezo patch on the mechanical and electrical responses of the structures. The theoretical model will help engineers to design and optimize new PEHs and serve as a benchmark solution for future research in this field.

A groove engineered ultralow frequency piezomems energy harvester with ultrahigh output voltage

In this paper, for the first time, a new design for a MEMS cantilever-based energy harvester (EH) has been proposed which takes advantage of two engineered piezoelectric layers. The output voltage of the EH has been increased by the aid of making grooves in the piezoelectric layers. By application of the grooves in the piezoelectric layers, the sensitivity of the cantilever as the vibration sensor or the EH has been improved. Results have shown that these grooves can increase the output voltage and decrease the resonance frequency which are desired changes in designing EHs. The single and double groove bimorph cantilevers have been compared and discussed. The position, length and depth of the grooves have been used as optimization parameters and consequently an optimal design has been proposed at the end of the paper. In the optimal design the top and the bottom piezoelectric layers have not covered the entire beam and have different lengths to produce maximum voltage. By means of groove engineering, we could rise the voltage from 5.395 V to 28.35 V which is considered a great improvement compared to other structures reported previously.

Piezoelectric energy harvester for pacemaker application: a comparative study

This study proposes the cantilever design of piezoelectric energy harvester scavenging energy from blood pressure variation in cardiac cycle. The harvester could be a perennial source of power for a typical pacemaker. The concept of three cm long and 72 μm thin cantilever based energy harvester having natural frequency close to that of heartbeat has been proposed. Considering a huge difference between shear (d15) and transverse (d31) piezoelectric coefficient the harvester was operated in two different modes. A number of materials (single and polycrystalline ceramics) along with Pb[ZrxTi1−x]O3 (PZT-5A) were operated in transverse and shear modes. The maximum open circuit voltage found for all cases was ∼6 V which was yielded by Pb(Zn1/3Nb2/3)O3–(6–7)% PbTiO3 (PZN-PT) when operating in shear mode. Further, the optimum resistance was calculated for all the materials under study operating in d15 and d31 modes for a wide frequency range. It was found that the maximum power among all materials under study was given by PZN-PT which is ∼13 μW while operating in shear mode. Such high magnitude of power harvested is due to its giant d15 which is 6000 pC N−1 and is sufficient to power a typical pacemaker.

Two-dimensional concentrated-stress low-frequency piezoelectric vibration energy harvesters

Vibration-based energy harvesters using piezoelectric materials have long made use of the cantilever beam structure. Surmounting the deficiencies in one-dimensional cantilever-based energy harvesters has been a major focus in the literature. In this work, we demonstrate a strategy of using two-dimensional beam shapes to harvest energy from low frequency excitations. A characteristic Zigzag-shaped beam is created to compare against the two proposed two-dimensional beam shapes, all of which occupy a 25.4 × 25.4 mm2 area. In addition to maintaining the low-resonance bending frequency, the proposed beam shapes are designed with the goal of realizing a concentrated stress structure, whereby stress in the beam is concentrated in a single area where a piezoelectric layer may be placed, rather than being distributed throughout the beam. It is shown analytically, numerically, and experimentally that one of the proposed harvesters is able to provide significant increase in power production, when the base acceleration is set equal to 0.1 g, with only a minimal change in the resonant frequency compared to the current state-of-the-art Zigzag shape. This is accomplished by eliminating torsional effects, producing a more pure bending motion that is necessary for high electromechanical coupling. In addition, the proposed harvesters have a large effective beam tip whereby large tip mass may be placed while retaining a low-profile, resulting in a low volume harvester and subsequently large power density.

Finite element analysis of vibration energy harvesting using lead-free piezoelectric materials: A comparative study

In this article, the performance of various piezoelectric materials is simulated for the unimorph cantilever-type piezoelectric energy harvester. The finite element method (FEM) is used to model the piezolaminated unimorph cantilever structure. The first-order shear deformation theory (FSDT) and linear piezoelectric theory are implemented in finite element simulations. The genetic algorithm (GA) optimization approach is carried out to optimize the structural parameters of mechanical energy-based energy harvester for maximum power density and power output. The numerical simulation demonstrates the performance of lead-free piezoelectric materials in unimorph cantilever-based energy harvester. The lead-free piezoelectric material K0.5Na0.5NbO3-LiSbO3-CaTiO3 (2 wt.%) has demonstrated maximum mean power and maximum mean power density for piezoelectric energy harvester in the ambient frequency range of 90–110 Hz. Overall, the lead-free piezoelectric materials of K0.5Na0.5NbO3-LiSbO3 (KNN-LS) family have shown better performance than the conventional lead-based piezoelectric material lead zirconate titanate (PZT) in the context of piezoelectric energy harvesting devices.

Performance of lead-free piezoelectric materials in cantilever-based energy harvesting devices

Energy harvesting is one of the emerging applications of piezoelectric materials. In order to replace conventional lead-based materials with lead-free materials, it is important to evaluate their performance for such applications. In the present study, finite element method-based simulation shows mean power density produced from ( K0.475Na0.475Li0.05)( Nb0.92Ta0.05Sb0.03) O3add with 0.4 wt.% CeO2and 0.4 wt.% MnO2(KNLNTS) bimorph is 96.64% of lead zirconate titanate ( Pb [ ZrxTi1-x] O3) (PZT) ceramics. Load resistance (R), length of proof mass (Lm) and thickness of host layer (th) are optimized (using genetic algorithm) for maximum power density and tuning the operating frequency range which is near to natural frequency of the structure. The lead-free piezoelectric material KNLNTS has comparable results to that of PZT for piezoelectric energy harvester in the ambient frequency range of 90 Hz to 110 Hz. Results show that KNLNTS ceramics can be potentially used in energy harvesting devices.

Energy harvesting from ambient low-frequency magnetic field using magneto-mechano-electric composite cantilever

A magneto-mechano-electric (MME) composite cantilever for energy harvesting from ambient low-frequency magnetic field has been investigated in this study. The MME composite cantilever is made of a piezoelectric bimorph with NdFeB magnets attached at its tip. The properties of the MME composite cantilever based energy harvester were theoretically predicted by using the equivalent circuit model. The experimental results show that the maximum power density for excitations at the short- and open-circuit resonance frequencies (&amp;lt;100 Hz) is 11.73 μW/Oe2 cm3, which is one order of magnitude higher than that of previously reported magnetoelectric energy harvester. The research has proved the potential application of the composite cantilever for harvesting ambient low-frequency magnetic field energy.

A Bulk Micromachined Lead Zinconate Titanate Cantilever Energy Harvester with Inter-Digital IrO&lt;SUB&gt;&lt;I&gt;x&lt;/I&gt;&lt;/SUB&gt; Electrodes

A piezoelectric vibration energy harvester with inter-digital IrO(x) electrode was developed by using silicon bulk micromachining technology. Most PZT cantilever based energy harvesters have utilized platinum electrode material. However, the PZT fatigue characteristics and adhesion/delamination problems caused by the platinum electrode might be serious problem in reliability of energy harvester. To address these problems, the iridium oxide was newly applied. The proposed energy harvester was comprised of bulk micromachined silicon cantilever with 800 x 1000 x 20 microm3, which having a silicon supporting membrane, sol-gel-spin coated Pb(Zr52, Ti48)O3 thin film, and sputtered inter-digitally shaped IrO(x) electrodes, and silicon inertial mass with 1000 x 1000 x 500 microm3 to adjust its resonant frequency. The fabricated energy harvester generated 1 microW of electrical power to 470 komega of load resistance and 1.4 V(peak-to-peak) from a vibration of 0.4 g at 1.475 kHz. The corresponding power density was 6.25 mW x cm(-3) x g(-2). As expected, its electrical failure was significantly improved.

2P4-18 Output Estimation and Demonstration of Cantilever based Energy Harvesters(Poster Session)

2P4-18 Output Estimation and Demonstration of Cantilever based Energy Harvesters(Poster Session)

Analysis and simulation of multi-mode piezoelectric energy harvesters

Theoretical analysis is performed on a multi-mode energy harvester design with focus on the first two vibration modes. Based on the analysis, a modification is proposed for designing a novel adaptive multi-mode energy harvester. The device comprises a simply supported beam with distributed mass and piezoelectric elements, and an adaptive damper that provides a 180 degree phase shift for the motions of two supports only at the second vibration mode. Theoretical analysis and numerical simulations show that the new design can efficiently scavenge energy at the first two vibration modes. The energy harvesting capability of the multi-mode energy harvester is also compared with that of a cantilever-based energy harvester for single-mode vibration. The results show that the energy harvesting capacity is affected by the damping ratios of different designs. For fixed damping ratio and design dimensions, the multi-mode design has higher energy harvesting capacity than the cantilever-based design.

PZT 압전재료를 이용한 외팔보 구조의 에너지 수집기에 관한 연구

Nowadays, the increasing demands upon mobile devices such as wireless sensor networks and the recent advent of low power electrical devices such as MEMS make such renewable power sources attractive. A vibration-driven MEMS lead zirconate titanate <TEX>$Pb(Zr,Ti)O_3$</TEX> (PZT) cantilever device is developed for energy harvesting application. This paper presents a piezoelectric based energy harvester which is suitable for power generating from conventional vibration and has in providing energy for low power electron ic devices. The PZT cantilever is used d33 mode to get the electrical power. The PZT cantilever based energy harvester with the dimension of 7 mm<TEX>${\times}$</TEX>3 mm<TEX>${\times}$</TEX>0.03 mm is fabricated using micromachining technologies. This PZT cantilever has the mechanical resonance frequency with a 900 Hz. With these conditions, we get experimentally the 37 uW output power from this device with the application of 1g acceleration using the 900 Hz vibration. From this study, we show the feasibility of one of energy harvesting candidates using PZT based structure. This PZT energy harvester could be used for various applications such a batteryless micro sensors and micro power generators.