Piezoelectric Harvesting System Research Articles

3-DOF X-structured piezoelectric harvesters for multidirectional low-frequency vibration energy harvesting

Nonlinear energy harvesters with specially-designed nonlinear characteristics (e.g., quasi-zero stiffness, multi-stability, and internal resonance) have been extensively studied to develop broadband harvested energy at low and ultra-low frequencies. Nevertheless, most developed energy harvesting devices were restricted to unidirectional energy harvesting, which is a limitation in many applications. This paper proposes a novel 3-degrees-of-freedom (3-DOF) X-structured piezoelectric harvesting system, enabling simultaneous & enhanced multidirectional low-frequency energy harvesting. It is shown that the developed 3-DOF X-harvester can produce useful & powerful motion coupling effect and unique band-pass-like property of two peaks and large frequency range due to nonlinear dynamics incurred by the specially designed X-mechanism, and can thus offer greater flexibility in tuning structural parameters to achieve broadband and higher low- and ultralow-frequency energy harvesting in multi-directions, compared to many other literature results. In experiments, with 300 kΩ and two piezoelectric beams connected in-series, the prototyped 3-DOF X-harvester achieved peak power outputs of 2.5 mW in the z-DOF at 9 Hz and 2 mm, 41.2μW in the x-DOF at 13.5 Hz and 2 mm, and 86.2μW in the ψ-DOF at 13.5 Hz and 1.7 mm, much better than many other literature results. In real-world applications with multidirectional vibrations, the harvested power will definitely have a wider bandwidth and higher peak outputs due to the motion coupling effect, allowing for enhanced ultralow-frequency energy harvesting.

Control and modelling evaluation of a piezoelectric harvester system

The predominant role of a piezoelectric harvester system in Vibration Energy Harvesting (VEH) is to gather vibrations energy caused by road profile disturbances. In this paper, a new piezoelectric harvester model with two degrees of freedom is modelled by the Bond Graph technics and simulated in a 20-Sim environment connected to MATLAB/Simulink software. The proposed modelling techniques have the ability to extend the ride comfort of the driver when the electric vehicle is moving upon different types of road profiles such as random road surfaces. The proposed harvester system is used to examine and ensure the health criterion and ride comfort of drives. Further, simulation results in the time domain and electrical power spectrum density analysis are carried out for the EV and proposed modelling techniques. The simulation results confirm that the proposed piezoelectric harvester system is more efficient in all different dimensions, and significantly improves the ride comfort, and increases the power quantity for the three different road classes. Finally, the results are illustrated and discussed graphically for various particular cases.

Performance enhancement of cantilever piezoelectric energy harvesters by sizing analysis

ABSTRACT 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 1.817 mW at 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 is met with the application of proof mass and thinner substrate and piezoelectric layers. Abbreviations: : Generalized coordinates vector; : The electrode area; A: The amplitude vector of generalized coordinates; : Width; : Initial width; C : Damping matrix; : Capacitance of the one piezoelectric layer; : Effective (equivalent) capacitance of the piezoelectric layers; : Piezoelectric strain coefficient; : The electric displacement; : Young’s modulus; : The electrical field along the thickness direction; F: Dynamic force vector; : The translation part of base motion; : Shear modulus; : Piezoelectric layers’ thickness; : Initial thickness of substrate layer; : Imaginary number; : Current output; : Shear correction factor; K : Global stiffness matrix; : Length of the beam; : The length of one element; M : Global mass matrix; : Polynomial’s degree; : Matrices of shape functions (1×4 for one element); : The input mechanical power; : The output electrical power; : Electric charge output; R : Displacement vectors of the generic point S (3×1); : External load resistance; : Velocity vector of the generic point S (3×1); : Time; : Kinetic energy; : Axial displacement; : Potential energy; : Transversal displacements; : Volume; : The generated piezoelectric voltage: Displacements on the middle-plane; : Positions of a general point in the relative coordinates system; : The amplitude of the effective displacement, ; : The dielectric permittivity of piezoelectric layer at constant stress; : The dielectric permittivity of piezoelectric layer at constant strain; : The electromechanical coupling vector (3×1 for one element); : The binding rotation of the cross section; : Transverse shear strain; : Axial strain; : Axial stress; : Transverse shear stress: Shape functions of superconvergent element, ; : Generalized coordinate elements, ; : Mass density; : The efficiency of harvesting; : Excitation frequency; : Constant of mass proportionality; Constant of stiffness proportionality; : Damping ratio; : Width taper ratio; : Height taper ratio; : The symbol of virtual work; : The internal electrical energy; : The non-conservative mechanical force; RD: Relative difference; PEHs: Piezoelectric energy harvesters; FEM: Finite element method; FRFs: Frequency response functions; DOF: Degree-of–freedom; MEMS: Micro-electromechanical system; MPGs: Micro-power generators; SCE: Superconvergent element; : Piezoelectric layer properties; : Substrate layer properties; : Partial differentiation with respect to x; : Partial differentiation with respect to t.

A Piezoelectric Energy-Harvesting System With Parallel-SSHI Rectifier and Integrated Maximum-Power-Point Tracking

A piezoelectric energy-harvesting system, including a parallel-synchronized-switch harvesting-on-inductor (SSHI) rectifier and integrated maximum-power-point tracking (MPPT), is presented. The perturb & observe (P&O) algorithm is adopted for the MPPT of the parallel-SSHI rectifier. Furthermore, an output power evaluation algorithm for the P&O MPPT is proposed and its detailed implementation in the full analog domain is analyzed. Fabricated in 130-nm CMOS, measurement results show the piezoelectric harvesting system achieves a 417% energy-extraction improvement for the rectifier and a maximum 97% tracking efficiency for the MPPT, which makes the system achieve high energy-extraction improvement and MPPT efficiency simultaneously.

Resonant Frequency Reduction of Piezoelectric Voltage Energy Harvester by Elastic Boundary Condition

ABSTRACTMost vibration-based energy harvesters, including piezoelectric harvester system, perform efficiently at only its resonant frequency as linear resonators, usually at very high frequency which are out of the range of frequency of interest. In real life applications, these linear resonators are impractical since real ambient vibrations are simply having varying lower frequencies. Hence, design a tuneable vibration energy harvester at a lower and useful frequency range of interest are essential in allowing promising energy output to meet intended power input at a more practical approach. In this paper, the piezoelectric voltage energy harvester (PVEH) was designed with a flexible fixture with the aim to reduce its first fundamental natural frequency. Two thickness of elastic fixtures were applied to generate power on PVEH. Three experimental techniques were used to measure the vibration characteristics of PVEH. First, the full-field optical technique, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) measured simultaneously the resonant frequencies and mode shapes. This is followed by the pointwise measurement system, laser Doppler vibrometer (LDV) in which the resonant frequencies were measured by dynamic signal swept-sine analysis. The resonant frequencies and anti-resonant frequencies were also obtained by impedance analysis. The results obtained from experimental measurements were compared with finite element numerical calculation. It is found that the boundary conditions under the elastic fixtures can effectively reduce the resonant frequency of the PVEH with a reasonable voltage output. The fundamental natural frequency of PVEH with the thickness of 0.58-mm elastic fixture is reduced to 37 Hz maintaining at 7.1 volts (1.2 mW), in comparison with the natural frequency on cantilevered PVEH at 78 Hz that produces 7.7 volts (6.5 mW).

Virtual instrument to obtain electrical models of piezoelectric elements used in energy harvesting

ABSTRACTA new virtual instrument (VI) has been designed to obtain the Fourier model of piezoelectric devices under test (PDUT) in road traffic environments, and the linear electrical model of the piezoelectric harvester circuit involved in energy harvesting applications. The VI provides a high grade of automatisation and high accuracy in the characterisation procedure of a piezoelectric harvesting system. The maximum power can be predicted and the number of piezoelectric elements can be calculated to achieve a given power value. The VI system controls the test bench (patent protected), which simulates the effect of the road traffic, and obtains the Fourier model of the PDUT. The VI controls the switched circuit’s matrix of the harvesting electronic hardware (HEH) to select the PDUTs and the rectifier topology. The VI also connects capacitors and load resistors of the HEH and computes the key parameters of the piezoelectric harvester model.

Numerical Modelling of a Piezo Roof Harvesting System: The Right Component Selection

Abstract The present work focuses on a first study for a piezoelectric harvesting system, finalized to the obtaining of electrical energy from the kinetic energy of rainy precipitation, a renewable energy source not really considered until now. The system, after the realization, can be collocated on the roof of an house, configuring a “Piezo Roof Harvesting System”. After presenting a state of art of the harvesting systems from environmental energy, linked to vibrations, using piezoelectric structures, and of piezoelectric harvesting systems functioning with rain, the authors propose an analysis of the fundamental features of rainy precipitations for the definition of the harvesting system. Then, four key patterns for the realization of a piezoelectric energy harvesting system are discussed and analysed, arriving to the choice of a cantilever beam scheme, in which the piezoelectric material works in 31 mode. An electro-mechanical model for the simulation of performance of the unit for the energetic conversion, composed of three blocks, is proposed. The model is used for a simulation campaign to perform the final choice of the more suitable piezoelectric unit, available on the market, which will be adopted for the realization of the “Piezo Roof Harvesting System”.

A Novel Frequency Tunable Mechanism for Piezoelectric Energy Harvesting System

This work proposes a novel frequency tunable mechanism for piezoelectric harvester system. The piezoelectric harvester is constructed by a cantilever base beam and piezoelectric elements coupled with the base beam in a certain manner. By modifying the electrical boundary conditions of the piezoelectric elements, the resonant frequency of the composite beam structure changes accordingly. Two kinds of coupling modes, d31 mode and d33 mode, were investigated and verified with simulations and experiments. The results showed that the d33 mode surpassed the d31 mode with a resonant frequency variation ratio of 28.59%.

Analysis of Piezoelectric Energy Harvesting Systems with Non-linear Circuits Using the Harmonic Balance Method

There is substantial promise in the use of piezoelectric energy harvesting systems to power electronics and devices through the conversion of ambient vibrations into electrical energy. Accurately predicting the energy harvesting capability in these systems is of paramount importance as the harvesting structure and the associated circuit must be ‘tuned’ in concert to the signature of the ambient vibrations. Here, we develop a numerical simulation methodology for piezoelectric harvesting systems that allows for high-fidelity finite element models of the harvester electromechanics as well as realistic non-linear circuits models. Our approach synthesizes conventional harmonic finite element analysis and a harmonic balance approach that accounts efficiently for the non-linear circuit behavior, bypassing the need for computationally expensive time marching schemes. The proposed methodology solves, via an iterative residual reduction scheme, for the coupled electrical output and structural dynamics of the piezoelectric harvesting structure. The proposed method is well suited for integration into model-predictive design methods. By numerical examples we illustrate the capability of the proposed approach to predict previously unreported coupling phenomena between the non-linear circuit response and piezoelectric structural behavior. The increased accuracy in the circuit model and flexibility of this method over current models outweighs the increased numerical costs.