Cantilever Piezoelectric Energy Harvester Research Articles

There Is Plenty of Room inside a Bluff Body: A Hybrid Piezoelectric and Electromagnetic Wind Energy Harvester

In this paper, a piezoelectric and electromagnetic hybrid wind energy harvester is proposed. The general design of the harvester comprises multiple cantilever piezoelectric energy harvesters (PEHs) and electromagnetic energy harvesters (EEHs) embedded inside the bluff body that is attached to the free end of PEHs. This research work investigates utilizing the room inside the bluff body to enclose harvesters to have a more compact and efficient harvesting system. A comprehensive coupled dynamic model of the harvester (HEH) is developed using Lagrange’s formulation. The electromechanical and electromagnetic coupling coefficient equations are derived. The coupled equations of motion are solved analytically and numerically with an exact agreement. A parametric analysis is conducted to study the effect of the design parameters on the overall performance of the harvester in terms of output power and bandwidth. The proposed design evidently presents itself as a promising concept in utilizing the room inside a bluff body.

Experimental investigation on performance improvement of cantilever piezoelectric energy harvesters via escapement mechanism from extremely Low-Frequency excitations

In this paper, we first design a frequency tuning device that enables the piezoelectric cantilever to operate under extremely low-frequency (below 2 Hz) excitations. Our design is mainly composed of three sections: coil spring for energy conversion and storage, escapement mechanism for frequency tuning, and piezoelectric cantilever for power generation. The prototype is capable of converting random excitation into regulated high-frequency oscillations, rendering the PEH to perform continuous high output voltage and attain low matched impedance. In experiments, this device successfully tuned the 0.75 Hz excitation into a 12.15 Hz oscillation, which is 0.68 Hz lower than the resonant frequency of the PEH. With this frequency tuning design, the performance of the PEH is less dependent on the external excitation. The instantaneous output power from the PEH on the frequency tuning device is 38.12 μW under 1 Hz excitation, which is 91 % of the output power of the same PEH vibrating under 0.35 g acceleration, 13.2 Hz harmonic excitation. Our design can be of great significance when harnessing energy from extremely low-frequency excitation such as ocean waves.

Nonlinear Dynamic Analysis of Bistable Piezoelectric Energy Harvester with a New-Type Dynamic Amplifier.

A distributed parametric mathematical model of a new-type dynamic magnifier for a bistable cantilever piezoelectric energy harvester is proposed by using the generalized Hamilton principle. The new-type dynamic magnifier consists of a two-spring-mass system, one is placed between the fixed end of the piezoelectric beam and the L-shaped frame, and the other is placed between the L-shaped frame and the base structure. We used the harmonic balance method to obtain the analytical expressions for the steady-state displacement, steady-state output voltage, and power amplitude of the system. The effect of the distance between the magnets, the spring stiffness ratio and mass ratio of the two dynamic magnifiers, and the load resistance on the performance of the harvester is investigated. Analytical results show that compared with the bistable piezoelectric energy harvester with a typical spring-mass dynamic magnifier, the proposed new-type energy harvester system with a two-spring-mass dynamic magnifier can provide higher output power over a broader frequency band, and increasing the mass ratio of the magnifier tip mass to the tip magnet can significantly increase the output power of the BPEH + TDM system. Properly choosing the stiffness ratio of the two dynamic amplifiers can obviously improve the harvested power of the piezoelectric energy harvester at a low excitation level.

Tuning the resonance frequency of piezoelectric energy harvesters by applying direct current electric field on piezoelectric elements

Different from previous strategies utilized to improve the energy conservation efficiency of piezoelectric energy harvesters (PEHs) from the environment, by broadening the frequency-bandwidth of energy harvesters using a specifically designed structure or tuning their resonance frequency (RF) through changing the geometrical/dynamical constraints, we report a method—by applying a direct current (DC) electric field on piezoelectric elements—to tune the RF of PEH based on the phenomenon that the elastic parameters of piezoelectric material are related to its electric field boundary condition. The results of a confirmatory experiment revealed that with a pre-loading DC electric field of −0.5 to 0.75 kV/mm, the RF of a piezoelectric cantilever energy harvester can be tuned from 144 to 156 Hz. The effectiveness of this strategy was further verified by comparing the energy conservation output of the PEH at a frequency that deviates from its RF, and at the same frequency, with pre-loading DC electric field adjustment.

Dynamic Characteristics Analysis of Tri-Stable Cantilever Piezoelectric Energy Harvester with a Novel-type Dynamic Amplifier

In this paper, a non-linear tri-stable piezoelectric cantilever energy harvester with a novel-type dynamic magnifier was proposed to achieve more effective broadband energy harvesting under low-level ambient excitations. According to the generalized Hamilton principle, a mathematical distributed parameter model of the piezoelectric energy harvester was proposed. The novel-type dynamic magnifier is a system consisting of two spring masses, one placed between the fixed end of the piezoelectric beam and the L-shaped frame, and the other, between the L-shaped frame and the base. The harmonic balance method was adopted to work out the analytical expressions of the steady-state displacement, steady-state output voltage and power amplitude of the energy harvester system. The effects of the distance between the magnets, the spring stiffness of the dynamic magnifier, and the load resistance on the performance of the system were also investigated. The results show that different from that of the conventional tri-stable piezoelectric energy harvester, the frequency response curve of the proposed novel-type energy harvester system with a two-spring-mass dynamic magnifier exhibits two peaks as a result of the interactions of the coupled elastic system, where the left peak stands for the resonant value of the tri-stable piezoelectric energy harvester, while the right one the resonant value of the dynamic magnifier. It is able to achieve higher output power over a broader frequency band under low-level environmental excitations, and the harvested power can be significantly strengthened if the mass and stiffness of the dynamic magnifier are selected properly.

Multicriteria Approach for Design Optimization of Lightweight Piezoelectric Energy Harvesters Subjected to Stress Constraints

In this work a multicriteria optimization approach to minimize weight and maximize power output in piezoelectric energy harvesting systems for aerospace applications is studied. The design variables are the geometric and electric circuit parameters of the vibration-based piezoelectric energy harvester (PEH). A finite element model is developed to model the dynamic behavior of the composite plate-type harvester with embedded piezoelectric layers. The cantilever PEH structure is subjected to constraints in the bending stresses which must be lower than or equal to the tensile yield strength of the piezoelectric material. For solving the multi-objective optimization problem, the Non-dominated Sorting Genetic Algorithm II (NSGA-II), the Non-dominated Sorting Genetic Algorithm III (NSGA-III) and the Generalized Differential Evolution 3 (GDE3) algorithm are employed. It is shown that the proposed algorithms are effective in developing optimal Pareto front curves for maximum electrical power output and minimum mass of the PEH system. A comparative assessment of the solutions generated on the Pareto Front show that GDE3 achieved solutions that generate higher maximum power output and performs better compared to the two other algorithms.

Application of [001]-textured (K, Na)(Nb, Sb)O3-CaZrO3 thick films to piezoelectric energy harvesters

A (K, Na)NbO3 (KNN)-based lead-free piezoceramic for a piezoelectric energy harvester (PEH) should exhibit a large kij, Qm, dij, and a small εT33 to generate a large power output. Texturing was used to enhance the piezoelectricity of KNN-related piezoceramics. In particular, the kij and dij values of the KNN-based piezoceramics were considerably improved after texturing along the [001] direction, with a small change in the εT33/ε0 value, indicating that the [001]-textured KNN-based thick films are good candidates for use in PEHs. The 0.97(K0.5Na0.5)(Nb0.93Sb0.07)O3-0.03CaZrO3 [KN(N0.93S0.07)-CZ] thick film was textured along the [001] direction, and this thick film exhibited a large kp (0.57) and d33 × g33 (25.7 pm2/N), which is the largest d33 × g33 of the KNN-based piezoceramics reported to date. A cantilever PEH fabricated using the textured KN(N0.93S0.07)-CZ thick film exhibited a power density of 21.4 μW/mm3 at the resonance frequency. This is the highest power density observed for PEHs fabricated using lead-free piezoceramics. The PEH also exhibited a power density of 0.023 μW/mm3 at the off-resonance frequency. Therefore, the textured KN(N0.93S0.07)–CZ thick film is a good candidate for use in PEHs.

Artificial neural network (ANN)-based optimization of a numerically analyzed m-shaped piezoelectric energy harvester

In this research work, the M-shaped cantilever piezoelectric energy harvester is modeled and optimized using advanced artificial intelligence algorithms. The proposed harvester adopts a single structure geometrical configuration in which two secondary beams are being connected to the principal bimorph. Finite element analysis is carried out on COMSOL Multiphysics to analyze the efficiency of the proposed energy harvester. The influence of frequency, load resistance, and acceleration on the electrical performance of the harvester is numerically investigated to enhance the bandwidth of the piezoelectric vibrational energy harvester. Numerical analysis is also utilized to obtain the iterative dataset for the training of the artificial neural network. Furthermore, a genetic multi-objective optimization approach is implemented on the trained artificial neural network to obtain the optimal parameters for the proposed energy harvester. It is observed that optimization using modern artificial intelligence approaches implies nonlinearities of the system and therefore, machine learning-based optimization has shown more convincing results, as compared to the traditional statistical methods. Results revealed the maximum output values for the voltage and electrical power are 15.34 V and 4.77 mW at 51.19 Hz, 28.09 k[Formula: see text], and 3.49 g optimal design input parameters. Based on the outcomes, it is recommended to utilize this reliable harvester in low-power micro-devices, electromechanical systems, and smart wearable devices.

T-type Piezoelectric Cantilever-Beam Energy Harvester based on Vortex-Induced Vibration

A new piezoelectric cantilever energy harvester based on vortex-induced vibration was proposed. The influence of some parameters was by mathematical modeling, numerical simulation and experimental testing. The results showed that the voltage value increased with the increase of wind speed within the test range. When the bluff body was a cylinder with a diameter of 0.02 m, a height of 0.05 m, and the ratio of the distance between bluff body and harvester and bluff body diameter was 2, the maximum voltage of the T-type piezoelectric cantilever beam energy harvester was 1.02 V. It provided theoretical and experimental references for energy harvesting in the wind.

Analysis of Dynamic Characteristics of Tristable Piezoelectric Energy Harvester Based on the Modified Model

Taking into account the gravitational potential energy of the piezoelectric energy harvester, the size effect, and the rotary inertia of tip magnet, a more accurate distributed parametric electromechanical coupling equation of tristable cantilever piezoelectric energy harvester is established by using the generalized Hamilton variational principle. The effects of magnet spacing, the mass of tip magnet, the thickness ratio of piezoelectric layer and substrate, and the load resistance and piezoelectric material on the performance of piezoelectric energy capture system are studied by using multiscale method. The results show that the potential well depth can be changed by reasonably adjusting the magnet spacing, so as to improve the energy capture efficiency of the system. Increasing the mass of tip magnet can enhance the output power and frequency bandwidth of the interwell motion. When the thickness of the piezoelectric beam remains unchanged, the optimal load impedance of the system increases along with the increase of thickness ratio of piezoelectric layer and substrate. Compared with the traditional model, which neglects the system gravitational potential energy, the eccentricity, and the rotary inertia of the tip magnet, the calculation results of the frequency bandwidth and the peak power of the modified model have significantly increased.

Synchronized switch piezoelectric energy harvesting using rotating magnetic ball and reed switches

Synchronized switch harvesting on inductor (SSHI) interface circuit has been developed to boost the harvesting capability of piezoelectric energy harvesters (PEHs). Although some electronic self-powered peak-detector and switching circuits have been proposed to support the practical realization of SSHI, the energy dissipation and voltage drops in transistors and diodes of the self-powered circuits might significantly deteriorate the actual energy harvesting performance. Some mechatronic designs were proposed as well. However, most of their switches are activated by touch impacts, which might introduce undesired high-order vibrations to the main structure. In this paper, rather than using the impact-engaged strategy discussed in the literature, a new mechanism using a magnetic ball for vibration synchronization and reed switches for switching operation is proposed. A PEH shunted to an SSHI interface circuit using the proposed mechatronic approach has been prototyped. Since the peak-detection and switching operations are completed by a mechanical mechanism, less passive electrical components, which consume extra energy, are required in our proposed design. Therefore, the overall energy harvesting performance is improved. Numerical simulations and experimental tests have validated the feasibility of the proposed design. The experimental results have shown that the power output produced by the proposed mechatronic self-powered SSHI design can be increased by and , as compared with the cases using a benchmark standard energy harvesting bridge rectifier and an electronic self-powered SSHI solutions, respectively. Moreover, owing to the new mechatronic design, the auxiliary mechanical components are embedded in the tip block of the cantilevered PEH, rendering the whole system to be a compact design.

Enhanced low-frequency vibration energy harvesting with inertial amplifiers

Piezoelectric vibration energy harvesters have demonstrated the potential for sustainable energy generation from diverse ambient sources in the context of low-powered micro-scale systems. However, challenges remain concerning harvesting more power from low-frequency input excitations and broadband random excitations. To address this, here we propose a purely mechanical approach by employing inertial amplifiers with cantilever piezoelectric vibration energy harvesters. The proposed mechanism can achieve inertial amplification amounting to orders of magnitude under certain conditions. Harmonic, as well as broadband random excitations, are considered. Two types of harvesting circuits, namely, without and with an inductor, have been employed. We explicitly demonstrate how different parameters describing the inertial amplifiers should be optimally tuned to maximise harvested power under different types of excitations and circuit configurations. It is possible to harvest five times more power at a 50% lower frequency when the ambient excitation is harmonic. Under random broadband ambient excitations, it is possible to harvest 10 times more power with optimally selected parameters.

Embedded Metamaterial Subframe Patch for Increased Power Output of Piezoelectric Energy Harvesters

AbstractThese days, piezoelectric energy harvesting (PEH) is introduced as one of the clean and renewable energy sources for powering the self-powered sensors utilized for wireless condition monitoring of structures. However, low efficiency is the biggest drawback of PEHs. This paper introduces an innovative embedded metamaterial subframe (MetaSub) patch as a practical solution to address the low throughput limitation of conventional PEHs whose host structure has already been constructed or installed. To evaluate the performance of the embedded MetaSub patch (EMSP), a cantilever beam is considered as the host structure in this study. The EMSP transfers the auxetic behavior to the piezoelectric element (PZT) wherever substituting a regular beam with an auxetic beam is either impracticable or suboptimal. The concept of the EMSP is numerically validated, and the comsol multiphysics software was employed to investigate its performance when a cantilever beam is subjected to different amplitude and frequency. The finite element model results demonstrate that the harvesting power in cases that use the EMSP can be amplified up to 5.5 times compared to a piezoelectric cantilever energy harvester without patch. This paper opens up a great potential of using EMSP for different types of energy harvesting systems in biomedical, acoustics, civil, electrical, aerospace, and mechanical engineering applications.

Optimization of Substrate Layer Material and Its Mechanical Properties for Piezoelectric Cantilever Energy Harvesting System

AbstractA cantilever piezoelectric energy harvester (PEH) is a popular choice to harvest energy for applications with natural or unnatural vibrations. Other than the choice of piezoelectric material, the substrate layer material also plays an important role to increase the energy harvesting in PEH. Earlier researches have emphasized on selecting a few substrate materials than all available in literature. However, we argue that the choice of the substrate material and its mechanical properties depend on the design of the PEH. We establish this fact by designing 20 different PEH models by varying the size of cantilever, substrate layer thickness, and types of the piezoelectric materials. These models are simulated in COMSOL with every known substrate material to select the best substrate material. We also propose a greedy approach to further increase the energy harvesting by optimizing the mechanical properties of the best substrate material. In all models, the best substrate material harvests at least 2 × more energy. The greedy approach increases energy harvesting in almost 50% of the models. Some of the substrate materials with optimized mechanical properties are reported in literature, however, this research opens up a discussion to manufacture new substrate materials to increase energy harvesting in PEH.

Power Density Improvement of Piezoelectric Energy Harvesters via a Novel Hybridization Scheme with Electromagnetic Transduction.

A novel hybridization scheme is proposed with electromagnetic transduction to improve the power density of piezoelectric energy harvester (PEH) in this paper. Based on the basic cantilever piezoelectric energy harvester (BC-PEH) composed of a mass block, a piezoelectric patch, and a cantilever beam, we replaced the mass block by a magnet array and added a coil array to form the hybrid energy harvester. To enhance the output power of the electromagnetic energy harvester (EMEH), we utilized an alternating magnet array. Then, to compare the power density of the hybrid harvester and BC-PEH, the experiments of output power were conducted. According to the experimental results, the power densities of the hybrid harvester and BC-PEH are, respectively, 3.53 mW/cm3 and 5.14 μW/cm3 under the conditions of 18.6 Hz and 0.3 g. Therefore, the power density of the hybrid harvester is 686 times as high as that of the BC-PEH, which verified the power density improvement of PEH via a hybridization scheme with EMEH. Additionally, the hybrid harvester exhibits better performance for charging capacitors, such as charging a 2.2 mF capacitor to 8 V within 17 s. It is of great significance to further develop self-powered devices.

Experimental investigation of T-shaped piezoelectric energy harvester activating coupled transverse and shear mode

During the past decade, the researchers have explored some of the valuable energy sources that are wasted if these are not being utilized like heat and vibration. These energy sources can be converted into micro electric power which is required in numerous electronic applications like wireless sensors, actuators etc. Many of researchers have been working on extracting the energy from ambient vibration because of its free availability in ambient. In the present study, the T-shaped cantilever beam is presented for harvesting energy from vibration under shear mode using PZT-5H (Lead Zirconate Titnate) piezoelectric material. Experimental analysis is conducted to obtain open circuit voltage response over frequency for all the configurations of piezoelectric energy harvester under study. The experimental results presented in this study concludes that the open circuit voltage developed under shear mode is maximum (5.26 V) and significantly equal to the voltage corresponding to bending mode (5.41 V) for T-shaped piezoelectric cantilever energy harvester when proof mass of 100 g is placed only at one end. Output voltage developed under shear mode for the T-shaped cantilever configuration with 100 g proof mass on one end is observed higher by approximately 12.87%, 5.83% and 5.17% than voltage for T-shaped energy harvester configuration with 50-50 g, 70-30 g masses and 85-15 g proof masses respectively. It is interesting to note that the output voltage under bending mode is reduced approximately by 15% and increased approximately by 80.07% under twisting mode for T-shaped piezoelectric energy harvester with 100 g proof mass at one extreme end compared to the T-shaped piezoelectric energy harvester with 100 g proof mass at center.

Investigation of the energy harvesting performance of a Lambda-shaped piezoelectric energy harvester using an analytical model validated experimentally

The principal objective of this paper is to show the efficient and reliable energy harvesting performance of a Lambda-shaped piezoelectric energy harvester (LPEH). The equations of motion of the harvester were derived based on Euler–Bernoulli beam theory. The accuracy of the analytical model was validated by the finite element method and experiment. Then, using the analytical model, the energy harvesting performance of the harvester was compared to that of a conventional cantilever piezoelectric energy harvester. It was found that the LPEH generated much more power than the cantilever piezoelectric harvester when the same amount of substrate and piezoelectric materials were used. Additionally, the effects of the harvester shape angle and excitation direction of the proposed harvester on the energy harvesting performance were investigated. The results showed that the LPEH could produce reliable power even though the harvester shape angle and excitation direction varied. Owing to such reliable energy harvesting characteristics, the proposed harvester has the practical advantages of fitting within limited space and functioning under uncertain excitation direction conditions.

Non-uniform electric field in cantilevered piezoelectric energy harvesters: An improved distributed parameter electromechanical model

In the existing electromechanical model for cantilevered piezoelectric energy harvesters, the electric field in the piezoelectric layer is generally considered as a uniform field. In the present study, it is found and described in detail that the oversimplified uniform electric field assumption could lead to critical issues regarding the fundamental of piezoelectricity. Further, inspired by the electric field distribution obtained using the exact solutions for plane problems, a non-uniform electric field is proposed. Accordingly, an improved distributed parameter electromechanical model for cantilevered piezoelectric energy harvesters including both unimorph and bimorph configurations is established, in which the bending stiffness term involved in the electromechanical governing equations is explicitly corrected, and the aforementioned critical issues are perfectly addressed. The present proposed non-uniform electric field is then validated by comparing the static analysis results of the present model with finite element results and the results obtained using exact solutions for plane problems. Dynamic analysis of the present model is also conducted, and the electromechanical characteristic corrections for the traditional distributed parameter model adopting uniform electric field assumption is carried out including bending stiffness correction, resonant frequency correction, voltage output correction and power output correction.

A cantilevered piezoelectric energy harvester excited by an axially pushed wedge cam using repulsive magnets for rotary motion

Harvesting energy from the rotary environment to replace the conventional electrochemical batteries has gained considerable interest. Different from the existing rotation-induced energy harvesters based on the bidirectional deformation of piezoelectric vibrators, a novel cantilevered piezoelectric energy harvester excited by an axially pushed wedge cam using repulsive magnets for rotary motion was presented and fabricated in this paper. The new piezoelectric rotary energy harvester (PREH) was characterized by the simultaneous realization of unidirectional deformation and limited amplitude for piezoelectric vibrators. To verify the feasibility of the proposed principle and design, a theoretical model was established based on Fourier series as well as superposition principle. Meanwhile, the influence of the system parameters on the response characteristic of the presented PREH were obtained by simulation. And then, the experiments of rotating speed response were performed to evaluate the energy harvesting performance in terms of the deformation and open-circuit voltage. Both simulation and experimental results showed that the amplitude of the piezo-cantilever could be limited by using the cam mechanism and there were obvious resonance peaks on the amplitude-rotary speeds curves. Thus, the relatively stable output voltage could be maintained over a broad rotating speed range. Also, the stable voltage increased with the increasing of cam lift, but the effective rotating speed range became narrow. With the increasing of the cam angle, the effective rotating speed bandwidth could be increased, whereas the self-locking phenomenon of the piezo-cantilever would occur when the angle was increased to some extent. Besides, the bandwidth could be adjusted by changing the number of exciting magnets and stiffness of cam system. Under the optimum matching parameters, the maximum power 10.88 mW was reached for the presented PREH.

Design, modeling, and experiment of a multi-bifurcated cantilever piezoelectric energy harvester

A multi-bifurcated cantilever piezoelectric energy harvester (BCPEH) is designed and verified to achieve a wide and adjustable response frequency band. The theoretical model is derived based on the Euler-Bernoulli beam theory and continuity boundary conditions to investigate the dynamic response of the BCPEH. The displacement frequency response function and the voltage frequency response function of the BCPEH are deduced based on the Galerkin method, and the theoretical results of a typical multi-bifurcated cantilever piezoelectric energy harvester, the Y-shaped BCPEH, are verified by the finite element method (FEM) and experiments. In addition, by comparing experimental output power of the Y-shaped BCPEH with that of the traditional cantilever-based piezoelectric energy harvester with the same mass of the bifurcated part at the beam-tip, it demonstrates that the Y-shaped BCPEH has a wider operational frequency band. Moreover, it is found that the Y-shaped BCPEH can be designed with an asymmetric configuration to adjust its response frequency distribution. The number of resonant frequencies and the output power of the asymmetric Y-shaped BCPEH are higher than that of the symmetric Y-shaped BCPEH. And the Y-shaped BCPEH has even better performance than L-shaped BCPEH. This study provides a new design concept for enhanced energy harvester.