COUPLED ANALYSIS FOR THE HARVESTING STRUCTURE AND THE MODULATING CIRCUIT IN A PIEZOELECTRIC BIMORPH ENERGY HARVESTER

The authors analyze a piezoelectric energy harvester as an electro-mechanically coupled system. The energy harvester consists of a piezoelectric bimorph with a concentrated mass attached at one end, called the harvesting structure, an electric circuit for energy storage, and a rectifier that converts the AC output of the harvesting structure into a DC input for the storage circuit. The piezoelectric bimorph is assumed to be driven into flexural vibration by an ambient acoustic source to convert the mechanical energies into electric energies. The analysis indicates that the performance of this harvester, measured by the power density, is characterized by three important non-dimensional parameters, i.e., the non-dimensional inductance of the storage circuit, the non-dimensional aspect ratio （length/thickness） and the non-dimensional end mass of the harvesting structure. The numerical results show that： （1） the power density can be optimized by varying the non-dimensional inductance for each fixed non-dimensional aspect ratio with a fixed non-dimensional end mass; and （2） for a fixed non-dimensional inductance, the power density is maximized if the non-dimensional aspect ratio and the non-dimensional end mass are so chosen that the harvesting structure, consisting of both the piezoelectric bimorph and the end mass attached, resonates at the frequency of the ambient acoustic source.

Nonlinear characteristics of circular-cylinder piezoelectric power harvester near resonance based on flow-induced flexural vibration mode

The nonlinear behaviors of a circular-cylinder piezoelectric power harvester （CCPPH） near resonance are analyzed based on the flow-induced flexural vibration mode. The geometrically-nonlinear effect of the cylinder is studied with considering the in-plane extension incidental to the large defection. The boundary electric charges generated from two deformation modes, flexure and in-plane extension, were distinguished with each other because the charge corresponding to the latter mode produces no contribution to the output current. Numerical results on output powers show that there are multi- valuedness and jump behaviors.

Performance of beam-type piezoelectric vibration energy harvester based on ZnO film fabrication and improved energy harvesting circuit

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 kΩis 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 kΩunder 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.

Finite Element Analysis on a Square Canister Piezoelectric Energy Harvester in Asphalt Pavement

A novel square canister piezoelectric energy harvester was proposed for harvesting energy from asphalt pavement. The square of the harvester was of great advantage to compose the harvester array for harvesting energy from the asphalt pavement in a large scale. The open circuit voltage of the harvester was obtained by the piezoelectric constant d33 of the piezoelectric ceramic. The harvester is different from the cymbal harvester which works by the piezoelectric constant d31. The finite element model of the single harvester was constructed. The open circuit voltage increased with increase of the outer load. The finite element model of the single harvester buried in the asphalt pavement was built. The open circuit voltage, the deformation difference percent and the stress of the ceramic of the harvester were obtained with different buried depth. The open circuit voltage decreased when the buried depth was increased. The proper buried depth of the harvester should be selected as 30 - 50 mm. The effects of structure parameters on the open circuit voltage were gotten. The output voltage about 64.442 V could be obtained from a single harvester buried under 40 mm pavement at the vehicle load of 0.7 MPa. 0.047 mJ electric energy could be gotten in the harvester. The output power was about 0.705 mW at 15 Hz vehicle load frequency.

Design and Modelling of Piezoelectric Road Energy Harvesting

In recent years, road piezoelectric energy harvesting (RPEH) has attracted great attention from industry and academia, as it can provide power to traffic ancillary facilities and low-power wireless sensor devices to support car networking and intelligent transportation. The output power of RPEH in a recent research project demonstrated a watt level RPEH. In this proposal, we propose to harvest energy from piezoelectric modules (also called stacks) to power selected highways, tolls, and bridges in Pennsylvania. The project incorporates electrical, mechanical, and civil engineering works. The proposed smart highway RPEH will be conducted using optimization parameters to evaluate the system performance and trade-offs. MATLAB will be used with other optimization solvers in problem modeling and optimization. During this project, an RPEH hardware system will be constructed. The system will include a piezoelectric module, rectifier (AC-DC), Storage battery, data acquisition system (DAQ), and computer. The captured data will be analyzed using MATLAB/Simulink. The results show that optimum harvested parameters were addressed when the thickness is selected as 2 mm.

Experimental and Simulation Validation of Piezoelectric Road Energy Harvesting

This project strived to develop a prototype road piezoelectric energy harvester RPEH system using five Lead Zirconate Titanate (PZT) PZT 5H modules (stacks) that are embedded in the road by means of a housing unit to harvest energy from vehicles stressing the modules. The work is an extension of our previous published work in the same journal. The design considered many factors to optimize the harvested energy. The proposed system first captures mechanical energy using a designed module that transfers the energy to the piezoelectric stacks. Then the captured energy will be converted into electrical energy by the piezoelectric phenomenon. The harvested energy is stored in a storage device, then analyzed by an oscilloscope through the acquisition of the harvested voltage, current, power, and energy. When testing the RPEH with the wheel tracking machine, varying resistor loads where connected to the output of the RPEH to address the optimum power delivered to the load. The optimum load was found to be 950 kΩ, and the optimal harvested energy was recorded as 45 uJ.

Design of piezoelectric energy harvesting devices subjected to broadband random vibrations by applying topology optimization

Converting ambient vibration energy into electrical energy by using piezoelectric energy harvester has attracted a lot of interest in the past few years.In this paper,a topology optimization based method is applied to simultaneously determine the optimal layout of the piezoelectric energy harvesting devices and the optimal position of the mass loading.The objective function is to maximize the energy harvesting performance over a range of vibration frequencies.Pseudo excitation method （PEM） is adopted to analyze structural stationary random responses,and sensitivity analysis is then performed by using the adjoint method.Numerical examples are presented to demonstrate the validity of the proposed approach.

Pedestrian walking characteristics at stairs according to width change for application of piezoelectric energy harvesting

This work aims at finding pedestrian walking characteristics at U-type stairs according to the width change of stairs and appropriate spot for installing piezoelectric energy harvesting.The number of pedestrian at two kinds of stairs(one is stairs with 1.5 m in width and the other is stairs with 3 m in width) was estimated by calculating the number of steps on the stairs by a zone which is divided into 30 cm×30 cm.The result shows high density in the middle in the case of narrow stairs but traffic is concentrated on stair inside(pillar side) in stairs with large width.In conclusion,the location for installation of piezoelectric energy harvesting system should be considered differently on stairs width and the number of installation depends on total expected traffic and the expected traffic for a device.

Enhanced galloping energy harvester with cooperative mode of vibration and collision

The low power and narrow speed range remain bottlenecks that constrain the application of small-scale wind energy harvesting.This paper proposes a simple,lowcost,and reliable method to address these critical issues.A galloping energy harvester with the cooperative mode of vibration and collision(GEH-VC)is presented.A pair of curved boundaries attached with functional materials are introduced,which not only improve the performance of the vibration energy harvesting system,but also convert more mechanical energy into electrical energy during collision.The beam deforms and the piezoelectric energy harvester(PEH)generates electricity during the flow-induced vibration.In addition,the beam contacts and separates from the boundaries,and the triboelectric nanogenerator(TENG)generates electricity during the collision.In order to reduce the influence of the boundaries on the aerodynamic performance and the feasibility of increasing the working area of the TENG,a vertical structure is designed.When the wind speed is high,the curved boundaries maintain a stable amplitude of the vibration system and increase the frequency of the vibration system,thereby avoiding damage to the piezoelectric sheet and improving the electromechanical conversion efficiency,and the TENG works with the PEH to generate electricity.Since the boundaries can protect the PEH at high wind speeds,its stiffness can be designed to be low to start working at low wind speeds.The electromechanical coupling dynamic model is established according to the GEH-VC operating principle and is verified experimentally.The results show that the GEH-VC has a wide range of operating wind speeds,and the average power can be increased by 180%compared with the traditional galloping PEH.The GEH-VC prototype is demonstrated to power a commercial temperature sensor.This study provides a novel perspective on the design of hybrid electromechanical conversion mechanisms,that is,to combine and collaborate based on their respective characteristics.

A modified airfoil-based piezoaeroelastic energy harvester with double plunge degrees of freedom

In this letter, a piezoaeroelastic energy harvester based on an airfoil with double plunge degrees of freedom is proposed to additionally take advantage of the vibrational energy of the airfoil pitch motion. An analytical model of the proposed energy harvesting system is built and compared with an equivalent model using the well-explored pitch-plunge configuration. The dynamic response and average power output of the harvester are numerically studied as the flow velocity exceeds the cut-in speed （flutter speed）. It is found that the harvester with double-plunge configuration generates 4%-10% more power with varying flow velocities while reducing 670 of the cut-in speed than its counterpart.

Experiment and performance analysis of serpentine-shaped cantilever beam for pipeline vibration-based piezoelectric energy harvester prototype development

Pipelines produce vibrations during fluid or gas transportation.These vibrations are less likely to cause structural failure as they exist with a small magnitude and can be harvested into useful energy.This paper presents a study on the piezoelectric energy-harvesting method converting mechanical energy from pipeline vibration into electrical energy.The performance of the serpentine-shaped piezoelectric cantilever beam was observed to check whether the design can produce the highest output voltage within the allowable vibration region of the pipeline from 10 to 300 Hz through finite element analysis using COMSOL Multiphysics software(Supplementary Material).In addition,this study investigates the energy-harvesting potential of the proposed design under real pipeline vibration conditions through a lab vibration test.The harvested energy output is evaluated based on various vibration frequencies and amplitudes,which gives an idea of the device and its performance under different operating conditions.The experiment result shows that the energy harvester produced an open-circuit voltage of 10.28-15.45 V with 1 g of vibration acceleration.The results of this research will contribute to the development of efficient piezoelectric energy harvesters adapted for pipeline environments.

Experimental study on broadband bistable energy harvester with L-shaped piezoelectric cantilever beam

This paper presents an experimental study of the broadband energy harvesting and dynamic responses of an L-shaped piezoelectric cantilever beam.Experimental results show that the L-shaped piezoelectric beam generates two optimal voltage peaks when the horizontal beam size is similar to the vertical beam size.Several optimized L-shaped piezoelectric cantilever beam structures are proposed.Power generation using the inverted bistable L-shaped beam is better.It is observed experimentally that the inverted bistable L-shaped beam structure shows obvious bistable characteristics and hard spring characteristics.Furthermore,the corresponding relationship between the bistable phase portrait and the potential energy curve is found in the experiment.This is the first time that a phase portrait for stiffness hardening of an L-shaped beam has been found experimentally.These results can be applied to analysis of new piezoelectric power generation structures.

Analytical and finite-element study of optimal strain distribution in various beam shapes for energy harvesting applications

Owing to the increasing demand for harvesting energy from environmental vibration for use in self-powered electronic applications, cantilever-based vibration energy harvesting has attracted considerable interest from various parties and has become one of the most common approaches to converting redundant mechanical energy into electrical energy. As the output voltage produced from a piezoelectric material depends largely on the geometric shape and the size of the beam, there is a need to model and compare the performance of cantilever beams of differing geometries.This paper presents the study of strain distribution in various shapes of cantilever beams, including a convex and concave edge profile elliptical beam that have not yet been discussed in any prior literature. Both analytical and finite-element models are derived and the resultant strain distributions in the beam are computed based on a MATLAB solver and ANSYS finite-element analysis tools. An optimum geometry for a vibration-based energy harvesting system is verified.Finally, experimental results comparing the power density for triangular and rectangular piezoelectric beams are also presented to validate the findings of the study, and the claim, as suggested in the literature, is verified.

Prompt efficiency of energy harvesting by magnetic coupling of an improved bi-stable system

In order to improve the transform efficiency of bi-stable energy harvester（BEH）,this paper proposes an advanced bi-stable energy harvester（ABEH）,which is composed of two bi-stable beams coupling through their magnets.Theoretical analyzes and simulations for the ABEH are carried out.First,the mathematical model is established and its dynamical equations are derived.The formulas of magnetic force in two directions are given.The potential energy barrier of ABEH is reduced and the snap-through is liable to occur between potential wells.To demonstrate the ABEH＇s advantage in harvesting energy,comparisons between the ABEH and the BEH are carried out for both harmonic and stochastic excitations.Our results reveal that the ABEH＇s inter-well response can be elicited by a low-frequency excitation and the harvester can attain frequent jumping between potential wells at fairly weak random excitations.Thus,it can generate a higher output power.The present findings prove that the ABEH is preferable in harvesting energy and can be optimally designed such that it attains the best harvesting performance.

Suppressing friction-induced stick-slip vibration through a linear PZT-based absorber and energy harvester

In this paper,a PZT(lead zirconate titanate)-based absorber and energy harvester(PAEH)is used for passive control of friction-induced stick-slip vibration in a friction system.Its stability condition coupled with PAEH is analytically derived,whose efficiency is then demonstrated by numerical simulation.The results show that the structural parameters of the PAEH can significantly affect the system stability,which increases with the mass ratio between the PAEH and the primary system,but first increases and then decreases with the natural frequency ratio between the PAEH and the primary system.The impacts of the electric parameters of the PAEH on the system stability are found to be insignificant.In addition,the PAEH can effectively suppress the stick-slip limit cycle magnitude in a wide working parameter range;however,it does not function well for friction systems in all the working conditions.The stick-slip vibration amplitude can be increased in the case of a large loading(normal)force.Finally,an experiment on a tribo-dynamometer validates the findings of the theoretical study,in which the vibration reduction and energy harvesting performance of the PAEH is fully demonstrated.

Performance enhancement of cantilever piezoelectric energy harvesters by sizing analysis

This paper presents the results of the performance of piezoelectric cantilever beams in relation to their size.The total produced power represents the main indicator of performance of a piezoelectric harvesting system while the area of the beams stays constant.Lightweight design is an important aspect in any industry,mainly in the aerospace.In this study,the effects of non-uniformity on the efficiency and power output are studied.Finite element method(FEM)with the application of superconvergent element(SCE)is adopted here to solve the equations.It is observed that the trapezoidal geometry(converging beam)provides a higher output power while the efficiency decreases.Moreover,in order to prove that the power enhancement is achievable while the amount of piezoelectric material consumed is constant the new configuration is proposed.In the configuration,an array of uniform beams connected in series is used instead of one single rectangular beam.The proposed setting generates an output power of 1.817mWat a resonant frequency of 284.6 Hz when excited by an input acceleration of 1 g.The only challenge is the fundamental frequency difference which ismet with the application of proof mass and thinner substrate and piezoelectric layers.

Wireless Self-Powered Vibration Sensor System for Intelligent Spindle Monitoring

In recent years,high-end equipment is widely used in industry and the accuracy requirements of the equipment have been risen year by year.During the machining process,the high-end equipment failure may have a great impact on the product quality.It is necessary to monitor the status of equipment and to predict fault diagnosis.At present,most of the condition monitoring devices for mechanical equipment have problems of large size,low precision and low energy utilization.A wireless self-powered intelligent spindle vibration acceleration sensor system based on piezoelectric energy harvesting is proposed.Based on rotor sensing technology,a sensor is made to mount on the tool holder and build the related circuit.Firstly,the energy management module collects the mechanical energy in the environment and converts the piezoelectric vibration energy into electric energy to provide 3.3 Vfor the subsequent circuit.The lithium battery supplies the system with additional power and monitors’the power of the energy storage circuit in real-time.Secondly,a three-axis acceleration sensor is used to collect,analyze and filter a series of signal processing operations of the vibration signal in the environment.The signal is sent to the upper computer by wireless transmission.The host computer outputs the corresponding X,Y,and Z channel waveforms and data under the condition of the spindle speed of 50∼2500 r/min with real-time monitoring.The KEIL5 platform is used to develop the system software.The small-size piezoelectric vibration sensor with high-speed,high-energy utilization,high accuracy,and easy installation is used for spindle monitoring.The experiment results show that the sensor system is available and practical.

Experimental Investigation of Performance Characteristics of PZT-5A with Application to Fault Diagnosis

In the previous couple of decades,techniques to reap energy and empower low voltage electronic devices have received outstanding attention.Most of the methods based on the piezoelectric effect to harvest the energy from ambient vibrations have been revolutionized.There’s an absence of experiment-based investigation which incorporates the microstructure analysis and crystal morphology of those energy harvest home materials.Moreover,the impact of variable mechanical and thermal load conditions has seldom been studied within the previous literature to utilize the effectiveness of those materials in several practical applications like structural health monitoring(SHM),etc.In the proposed research work,scanning electron microscope(SEM)and energy dispersive x-ray(EDX)analysis are performed to examine the inside crystal morphology of PZT-5A and ensure the quality of the piezoelectric ceramic.Further,the performance of piezoelectric vibration-based energy harvester has been investigated in the second phase of current research work under the variable mechanical and thermal load conditions through a regular series of experiments.It’s been found that the output voltage of piezoelectric sensors will increase by increasing the applied load,whereas a decreasing trend in output voltage is noticed by increasing the applied temperature,resistance and frequency.Within the third part,a measuring setup is developed in the laboratory to further investigate the effectiveness of PZT-5A in practical applications such as electromechanical impedance(EMI)based structural health monitoring under the controlled heating environment.Therefore,this analysis not only evaluates the performance of PZT sensors under the variable operating conditions but also encourages developing a temperature compensation approach in EMI-based SHM.

Characterization the influences of diodes to piezoelectric energy harvester

This study discloses the diode’s influences on the piezoelectric energy harvesting performance.The piezoelectric-based energy harvesting system plays an important role in scavenging environment vibration energy into electrical energy,which can be utilized by low-power electronic devices.With respect to the interface circuit,a full-wave bridge circuit is usually needed to rectify the alternating current(AC)signal into a direct current(DC)signal.The full-wave bridge is composed of four diodes,whose characteristics may influence the harvested power significantly.Therefore,in this paper,the diodes’properties and influences on the energy harvesting performance are analyzed and presented via simulation and experimental studies.It is found the harvested energy has close relationship with the diode characteristics.For the high source impedance case,diode with low reverse leakage current is favorable.For the low source impedance case,diode with low forward voltage drop is favorable.The corresponding experimental study is carried out via a piezoelectric beam,which shows that the measured harvested power differences can almost be up to 800%for the same test structure.

Power Source for Wireless Sensors in Pipes

In this paper, we present investigations on energy harvesters for wireless sensors inside pipes. The harvesters are of flexible piezoelectric PVDF （Poly-Vinylidene-Di-Fluoride） and aluminum-foils as electrodes. The layers were stacked alternating on each other and wound to a spool. An LDPE （low-density polyethylene）-film wraps the spool and prevents the inflow of liquids. A ring shaped bluff body was placed inside the pipe to induce turbulence in the fluid stream. As the harvesters have been arranged downstream of the bluffbody, they were forced to oscillate independent of the media. This led to a polarization and a separation of electrical charges. Experiments were carried out in a wind channel as well as in a water pipe. In air, the spool oscillates with a frequency of about 30 Hz, at a wind speed of about 7 m/s. A voltage of about 4 V （peak-peak） was measured. This delivers in case of impedance adjustment power values of about 0.54 p.W. In water, oscillation starts at a speed above 0.6 m/s. The average oscillation frequency is about 18 Hz. At a velocity of 0.74 m/s, a peak-peak-voltage up to about 2.3 V was found. In case of impedance adjustment, the power was about 0.33 μW. This power is stored in a capacitor. Assuming a data transmission unit consumes about 0.2 mWs during one operational period of I s, the duty cycle can be calculated to about 6.2 min for air harvesting and 10.1 min for harvesting in water.