Vibration Energy Harvesting Applications Research Articles

A multi-directional broadband piezoelectric-electromagnetic-magnetic coupling compound energy harvester for vibration energy harvesting applications

Currently, common vibration energy harvesters can only capture vibration energy in a unidirectional or fixed plane, posing issues such as high collection frequency, limited frequency range, and low output power. This paper proposes a multi-directional broadband piezoelectric-electromagnetic-magnetic coupling composite vibration energy harvester. It achieves three-directional energy harvesting while broadening the harvesting frequency and having a higher power density compared to current state-of-the-art research. Comprising a piezoelectric system and an electromagnetic system, the harvester leverages theoretical analysis to design the piezoelectric cantilever beam with a branching structure, enhancing its broad frequency characteristics. In addition, the magnetic coupling effect is added to the device so that the cantilever beam in three directions can work when the device receives unidirectional vibration excitation. Building on theoretical analysis, the COMSOL 5.6 software is utilized to conduct simulation analysis and optimize the size of the designed piezoelectric cantilever beam structure. This process validates theoretical analysis accuracy and improves energy capture capability. To confirm device viability and simulation accuracy, a physical model is fabricated, and vibration tests are executed. The energy harvester generates two peaks (10 Hz, 27 Hz) when vibration excitation is applied, which effectively broadens the collection frequency. Under the vibration frequency excitation in the X and Y directions, the total composite output power of the multidirectional broadband piezoelectric-electromagnetic-magnetic coupling composite vibration energy harvester is 17.72 mW and 30.22 mW, and the power density can reach 32.85 mW·cm−3, which significantly strengthened the captured energy efficiency of the energy harvester compared with the energy harvester without magnetic coupling, with the total composite output power increased by 352.0% and 165.8%, respectively; under the excitation of the Z-direction vibration frequency, the total composite output power was 42.42 mW and 44.80 mW, and the power density could reach 48.70 mW·cm−3.

Synthesis of a Stable and High-Concentration BaHfxTi1−xO3 Sol–Gel for High Electromechanical Performance of Bulk Ceramics

Lead-based materials are widely used in piezoceramics due to their high electromechanical properties. However, due to environmental protection and sustainable development, the use of the toxic element lead (Pb) in electronic devices is strictly restricted, therefore requiring the rapid development of piezoelectric-based devices with lead-free ceramics. In this context, a lead-free doped barium titanate was studied with a dual objective. First, a new sol–gel method to synthesize Hf4+-doped BaHfxTi1−xO (BHT) with x = 0.05, 0.075, and 0.10 is presented. Such BHT sols were prepared at high concentrations of up to 1 M. Dilution in ethylene glycol allowed parameters (viscosity, colloid sizes, etc.) to be controlled, which ensured a time-stable sol for several months at room temperature. Second, densified bulk ceramics with attrited powders were obtained from these sols and showed very good electromechanical properties, with a thickness coupling factor of kt = 47% (BaHf0.05Ti0.95O3 sintered at 1500 °C/6 h). These results are a first step that will allow the processing of lead-free piezoelectric thick films using a sol–gel composite method for vibrational energy harvesting applications.

Experimental analysis of nonlinear piezo-electromagnetic composite human energy harvester

To better harvest the kinetic energy of the human and broaden the energy harvest frequency band, a nonlinear piezo-electromagnetic composite human energy harvester (NPE-HEH) is proposed. A magnetic repulsion force between the two groups of magnets makes the energy harvester nonlinear. The excitation experiment and the actual experiment of the human are carried out for the harvester. The excitation experiment results show that there is an optimal resistance value of the harvester to maximize the output power value. When the excitation acceleration is 0.4 g and the excitation frequency is 9 Hz, the output voltage value and the output power of the electromagnetic part of the energy harvester are 0.86 V and 2.47 mW respectively, and the output performance is excellent. When the energy harvester is installed in a backpack with a moving speed of 9 km/h, it can generate 0.7 mW of power. When the energy harvester is placed on the leg, the output performance is good and the output power can reach 1.3 mW. The energy harvester can efficiently harvest energy at low frequencies. This harvester is efficient at low frequencies, compact in size, and easy to carry, making it highly suitable for human vibration energy harvesting applications.

Enhancing Electrical Generation Efficiency through Parametrical Excitation and Slapping Force in Nonlinear Elastic Beams for Vibration Energy Harvesting.

This study aims to enhance conventional vibration energy harvesting systems (VEHs) by repositioning the piezoelectric patch (PZT) in the middle of a fixed-fixed elastic steel sheet instead of the root, as is commonly the case. The system is subjected to an axial simple harmonic force at one end to induce transversal vibration and deformation. To further improve power conversion, a baffle is strategically installed at the point of maximum deflection, introducing a slapping force to augment electrical energy harvesting. Employing the theory of nonlinear beams, the equation of motion for this nonlinear elastic beam is derived, and the method of multiple scales (MOMS) is used to analyze the phenomenon of parametric excitation. This study demonstrates through experiments and theoretical analysis that the second mode yields better power generation benefits than the first mode. Additionally, the voltage generation benefits of the enhanced system with the added baffle (slapping force) surpass those of traditional VEH systems. Overall, the proposed model proves feasible and holds promising potential for efficient vibration energy harvesting applications in various industrial sectors.

(Invited) Harvesting Energy from Freestanding Graphene Thermal Fluctuations

Highly flexible, electrically conductive freestanding graphene membranes hold great promise for vibration energy harvesting applications. In this study, we present numerical results for a graphene ripple treated as a Brownian particle coupled to an energy harvesting circuit. When circuit and particle are at the same temperature, the second law forbids harvesting energy from the thermal motion of the Brownian particle, even if the circuit contains a rectifying diode. However, when the circuit contains a junction followed by two diodes wired in opposition, a special ultraslow convergence to equilibrium may be imposed. Detailed balance is temporarily broken as current flows between the two diodes and charges two storage capacitors. The harvested energy is taken from the surrounding thermal environment, and we show that the system obeys the first and second laws of thermodynamics. Experimental results will also be presented for a custom designed integrated circuit built by TSMC combined with post-processing lithography on bare die followed by graphene suspension. Figure 1

High-fidelity dynamics of piezoelectric covered metamaterial Timoshenko beams using the spectral element method

Piezoelectric metamaterial beams have received enormous research interest for the applications of vibration attenuation and/or energy harvesting in recent years. This paper presents a generic modelling approach for predicting the high-frequency dynamics of piezoelectric metamaterial beams. The spectral element method (SEM) is used to derive the dynamic stiffness matrix of a composite piezoelectric beam segment. Boundary condition implementations are demonstrated. Both band structure and transmittance analyses are realized. Several case studies for piezoelectric metamaterial beams configured in different geometric/electrical forms are carried out. The corresponding finite element (FE) models are built for verification, and a comparison study with the transfer matrix method (TMM) is conducted. For the uniform configurations, an almost indistinguishable difference is noted between the theoretical and FE results. For the stepped configurations, only minor discrepancies are observed in the high-frequency responses. The improved robustness and stability of the SEM method compared to the TMM method are demonstrated. A further discussion has been provided to explain the cause of the high-frequency discrepancies: sudden changes in the cross-section of the beam result in the stress concentration effect and reduce the bending stiffness at the junction connection. Finally, the value of the high-fidelity modelling approach is reflected through a parametric-based optimization study towards merging the Bragg scattering and locally resonant band gaps in an example piezoelectric metamaterial beam to achieve a wide band gap.

Flexible ZnO:PVDF based free standing piezoelectric nanogenerator for vibrational energy harvesting and wearable shoe insole pedometer sensor

The increasing demand of energy harvesting and wearable electronics applications requires the development of flexible and highly durable piezoelectric nanogenerators (PENG). In this work, We have fabricated flexible ZnO:PVDF based PENGs for vibrational energy harvesting and shoe insole pedometer applications. ZnO nanorods were grown by hydrothermal method and incorporated into PVDF matrixes in the concentration range of 5–15 wt%. These homogeneous ZnO:PVDF composite films were sandwiched between Al electrodes to realize flexible free standing PENGs. The open circuit voltage (Voc), short circuit current (Isc) and instantaneous power density of PENGs increased from ∼ 4 V, 0.4 µA and 1.6 µW/cm2 to ∼ 14.6 V, 0.6 µA and 21.3 µW/cm2 respectively when ZnO nanorods concentration in PVDF increased from 0 to 10 wt% and decreased with further increase in ZnO nanorods concentration. The enhancement in output characteristics of ZnO:PVDF PENG with increasing ZnO concentration was attributed to β-phase crystallization of PVDF, which was confirmed by XRD and FTIR measurements. The deterioration in output characteristics beyond 10 wt% of ZnO nanorods concentration was explained considering the variation of dielectric constant and remnant polarization. The rectified output of the PENGs was effectively stored in various commercially available capacitors and used to power LEDs and stopwatch displays. The PENG with 10 wt% ZnO concentration was used to develop shoe insole pedometer which was interfaced with android based mobile application via Bluetooth. The shoe insole pedometer was successfully tested for 5000 steps at different walking frequencies ranging from 0.5 Hz to 2 Hz in the speed range of ∼ 1.4 km/h to 5.5 km/h. This study not only gives an insight into the mechanism of ZnO:PVDF based PENGs but also opens up their potential in vibration energy harvesting and shoe insole pedometer applications.

Optimised Voltage Distribution on Piezoelectric Actuators for Modal Excitations Damping in Tapered Beams

Vibration mitigation is a prominent matter in several engineering fields. Several adverse phenomena are related to vibrations, such as fatigue, noise, etc. The availability of smart materials increases the solutions for both vibration damping and energy harvesting applications. Piezoelectric materials seem to be the most promising for these applications. However, their positioning significantly affects their efficiency. Several studies were performed on the positioning of piezoelectric actuators to dampen a target resonance in cantilever beams with constant cross-sections. Here, an analytical model for the optimal voltage distribution on an array of piezoceramic (PZT) actuator pairs is proposed in the case of tapered beams. The effect of tapering on the optimal voltage distribution was investigated for several eigenmode excitations and tapering ratios. The model outcomes were corroborated via FEM simulations and a fair agreement was found for each considered case.

Design and Optimization of a Boost Interface for Magnetostrictive Energy Harvesting

Magnetostrictive alloys are very promising for Vibration Energy Harvesting applications to supply power to Wireless Sensor Network (WSN) and Internet of Things (IoT) devices, especially because of their intrinsic robustness. Typically, vibration energy sources are random in nature, usually providing exploitable voltages much lower than the electronic standards 1.6, 3.3 and 5 V. Therefore, a Power Electronic Interface (PEI) is needed to improve the conversion to DC output voltage from AC input over a wide range of frequencies and amplitudes. Very few or no conversion techniques are available for magnetostrictive devices, although several have been presented over the years for other smart materials, such as piezoelectrics. For example, hybrid buck–boost converters for piezoelectrics use one or more external inductors with a high-frequency switching technique. However, because of the intrinsic nature of harvesters based on magnetostrictive materials, such energy conversion techniques are proved to be neither efficient nor applicable. An improved AC–DC boost converter seems very promising for our purpose instead. The key feature is represented by the direct exploitation of the active harvester coil as a storage element of the boost circuit, without using other passive inductors as in other switching methods. Experimental tests of such a converter, driven with a real-time operating Arduino controller to detect the polarity of the input voltage, are presented with the aim to assess the potentiality of the scheme with both sinusoidal and impulse-like inputs. Simulations have been performed with LTspice, and the performance and efficiency have been compared with other energy conversion techniques.

Energy harvester using two-phase flow conditions

Single-phase flow-induced vibration energy harvesting approaches, such as vortex-induced vibration, galloping, and flutter, have received considerable attention from researchers in recent years. However, the challenges and potential applications of multi-phase flow-induced vibration energy harvesting have rarely been explored. To bridge the research gap in the present energy harvesting studies based on two-phase flow, we investigated in detail the mechanism and potential benefits of the fluid–structure interaction between smart structures and two fluid phases (water and air) on the vibration energy harvesting performance. A piezoelectric energy harvester using air–water two-phase flow conditions is proposed for potential multifunctional applications. A T-shaped piezoelectric cantilever was used to harvest liquid sloshing energy in the proposed structure. A fluid–structure interaction containing two fluid phases (water and air) was theoretically modelled using the arbitrary Lagrangian-Eulerian technique. The experimental results showed that a prototype of the proposed structure can be used as a smart water bottle that simultaneously performs human-motion energy collection and acts as a drinking water bottle. The prototype achieved its maximum peak-to-peak voltage value (12.08 V) at 5 km/h for powering wireless IoT (Internet of Things) nodes. Furthermore, it can be used as an energy regenerative shock absorber to perform the dual functions of vibration damping and energy harvesting. Therefore, multi-phase flow-induced vibration energy harvesting shows great application potentials.

High output power density owing to enhanced charge transfer in ZnO-based triboelectric nanogenerator

We have fabricated triboelectric nanogenerarators (TENGs) using ZnO and polydimethylsiloxane (PDMS) in which ZnO growth temperature was varied in the range from 450 °Ct 750 °C. The output voltage/current of TENGs increases with increase of ZnO growth temperature up to 600 °C and then decreases with further increase of growth temperature up to 750 °C. TENG fabricated with ZnO grown at 600 °C exhibits maximum electrical output with peak to peak voltage of ∼210 V, current ∼95 μA and power density ∼8.8 mW/cm2 upon application of a periodic force of ∼30 N @ 6 Hz, which is higher than the power densities reported till date in the case of ZnO-based TENGs. This enhanced output power density can be mainly attributed to the large effective work function difference obtained between ZnO and PDMS. Electrical, photoluminescence and ultra-violet photoelectron spectroscopy measurements clearly suggest the dominant role of electron transport in the charge transfer between ZnO and PDMS. Practical applications of TENGs have been demonstrated by powering 38 LEDs and a stopwatch display. This study not only deepens the understanding of contact electrification between ZnO and PDMS, but opens up the immense potential of ZnO-based TENGs for possible vibration energy harvesting applications.

Auxetic hexachiral cantilever beams for piezoelectric vibration energy harvesting

This work presents an auxetic hexachiral cantilever substrate for low-frequency vibration energy harvesting applications. Auxetics are materials with negative Poisson’s ratio that develop stresses of the same nature under mechanical loading, which can be advantageously used in designing energy harvesters with enhanced power output. The proposed harvester is fabricated by attaching a piezo patch on a 3D printed polylactic acid hexachiral substrate to convert the mechanical response to electrical output. Experiments are conducted to characterize the vibration and electrical properties of the harvester. A 3D finite element (FE) model is developed and validated with experimental voltage obtained for different electrical resistance. As the first mode generates maximum power, an equivalent single degree of freedom semi-analytical model is formulated and validated with experiments and FE results. The proposed harvester has a natural frequency of 23 Hz with a voltage output of 9.1 V at 250 kΩ. The developed models are used to study the influence of hexachiral geometry, electrical and mechanical loading on the electro-mechanical response. The harvester voltage is influenced by the ligament thickness and is found to increase linearly with an increase in mechanical loading. Further, the enhancement in performance by the addition of hexachiral sub patch to a plain beam is investigated, followed by a comparison with harvesters having plain, hexagonal and re-entrant geometries. The results show that the hexachiral harvester has the lowest first mode frequency with a power output about 20 and 3 times the plain and re-entrant harvesters, respectively. Finally, random vibration analysis of the hexachiral harvester is carried out to evaluate its performance under ambient loading, and the results show that the semi-analytical model is a computationally efficient alternative to study the first mode behavior. The findings of the study demonstrate the potential of the proposed hexachiral harvester for low-frequency applications.

Oxygen annealing induced enhancement in output characteristics of ZnO based flexible piezoelectric nanogenerators

Piezoelectric nanogenerators (PENG), which convert random mechanical energy into electrical energy, have attracted considerable attention due to their application potential in self-powered micro and nano electronics devices, wearable electronics, sensors etc. PENGs based on ZnO nanostructures are particularly important due to their low cost, flexibility and bio-compatibility. Flexible PENGs based on ZnO nanostructures dispersed in Polydimethylsiloxane (PDMS) in ITO/ZnO:PDMS/ITO device configuration were fabricated and characterized for vibration energy harvesting applications. Surfactant free ZnO nanostructures were grown using co-precipitation route and ZnO:PDMS nano-composite films with ZnO content varying in the range of 1.5–7.5 wt% were deposited on ITO/PET substrates for PENG fabrication. The maximum open circuit voltage and short circuit current of ~ 2.5 V and ~ 4 µA respectively were obtained in PENG fabricated with 6 wt% ZnO. The output characteristics were further enhanced to 5 V and 6 µA with flowing oxygen ambient annealing of ZnO nanostructures generating an instantaneous power density of ~9.55 µWcm −2 . X-ray photoelectron spectroscopy studies confirmed reduction in oxygen vacancy and enhancement in oxygen interstitial concentrations on oxygen annealing which leads to the suppression of free carrier induced internal screening in ZnO nanostructures. This suppression of internal screening effect is the possible reason for the enhancement in output characteristics of ZnO:PDMS PENG fabricated with oxygen annealed ZnO nanostructures. The electrical energy generated by the ZnO:PDMS PENG was rectified and effectively stored in capacitors and used to power LEDs and LCD display. • ZnO nanostructures were grown by co-precipitation method with air and oxygen annealing. • ZnO:PDMS PENG with variable wt% of ZnO in PDMS were fabricated in ITO/ZnO:PDMS/ITO configuration. • The output performance of ZnO:PDMS PENG is improved significantly by annealing ZnO nanostructures in flowing oxygen ambient. • XPS established a correlation between the oxygen related point defects in ZnO and output characteristics of ZnO based PENG. • The output energy from ZnO:PDMS PENG was rectified and effectively stored in capacitor to flash LEDs and LCD display.

Electromechanical simulation and analysis of perovskite piezoelectric ‎unimorph cantilever nanogenerator with interdigitated electrodes in ‎vibration energy harvesting application

This paper addresses a unimorph cantilevered piezoelectric nanogenerator having high ‎output power through vibrational energy harvesting that is simulated using finite element ‎method (FEM). The simulations are done for three types of perovskite piezoelectric ‎materials including PZT, PMN-PT and MAPbI3. The interdigitated electrodes were ‎exploited‏ ‏to obtain longitudinal vibration mode using d33 mode of piezoelectric layer during ‎the bending of nanogenerator structure. The presented structure consists of a piezoelectric ‎nanolayer with gold interdigitated electrodes on it, which is placed on a flexible PET ‎polymeric substrate. To encapsulate the piezoelectric layer, an SU-8 epoxy is placed over ‎the surface. The poling process is also simulated by applying high voltage through IDs to ‎piezoelectric layer. Generally, the electric potential distribution of the piezoelectric layer ‎must be performed by applying mechanical loadings. Then the output voltage, ‎power for free vibrations and base excitation (0.25-2g) of the nanogenerator at resonance ‎frequency are investigated. The resonance frequency of the PZT, PMN-PT, and MAPbI3 were ‎calculated to be 549 Hz, 560.5 Hz and 631 Hz, respectively. We found that PZT ‎piezoelectric materials yields maximum output voltage and electrical power values of 91.69 ‎V and 350 mW which shows better performance in vibrational energy harvesting ‎application. In comparison, the results of the simulation implied a good agreement with ‎other experimental studies. The unimorph piezoelectric energy harvester system generates ‎high voltage and output power in response to sub-kilohertz ambient vibration‎.‎‎

A novel high-power density, low-frequency electromagnetic vibration energy harvester based on anti-phase motion

The paper proposes a novel electromagnetic vibration energy harvester based on the concept of anti-phase vibration. Anti-phase motion is desirable in electromagnetic vibration energy harvesting applications as it results in a higher power output due to the increase in the relative velocity between the coil and the magnet components. The proposed device achieves anti-phase motion at any driving frequency due to a developed new design. The harvester was experimentally tested under a base input of 0.49 g, 0.38 g and 0.36 g, recording a power density of 765.3 Wm−3, 420.8 Wm−3 and 587.2 Wm−3 respectively under a resonant frequency of 11.8 Hz. Although the device has not yet been optimised, these values obtained are already comparable, if not higher than the recent previous works on vibration energy harvesting. In addition, the observed experimental results have well agreed with the results obtained through the mathematical model, derived in this study. The original design was then optimised to determine the optimum load resistance, mechanical arm length and component dimensions that would result in the maximum power output. Considering a base input of 0.36 g and the same friction and damping forces as obtained from the experiment, a power density of 1708.5 Wm−3 could theoretically be achieved under the same natural frequency.

Fabrication and characterization of PU/NKLNT/CFs based lead-free piezoelectric composite for energy harvesting application

ABSTRACT For vibration energy harvesting applications, a flexible composite material based on a polyurethane (PU) polymer matrix filled with polycrystalline particles (Na0.535K0.48)0.966 Li0.058 Nb0.9Ta0.1O3 (NKLNT) and crushed carbon fibers (CFs) has been developed by tape-casting method. NKLNT was synthesized by the solid-state route. The powder mixture of NKLNT and CFs was dispersed in the solution obtained by dissolving polyurethane in Cyclohexane. A maximum electrical power has been obtained for 0.5 wt.% at an electrical resistance of 5.105 Ω, which allows us to supply low-power electronic systems. A high piezoelectric charge coefficient (d33 = 147pC.N−1) of NKLNT indicates its potential application in flexible energy harvesting.

Mechanisms and applications of vibration energy harvesting in solid rocket motors

Energy harvesting has become a fascinating topic of research. As the world moves towards reducing its dependency on fossil fuels, new and innovative techniques of energy harvesting have been tested and developed. The use of piezoelectric materials to harvest the ambient vibrations from the surroundings is one method that has seen a dramatic rise in use for power harvesting. Remote sensors can be powered by these piezoelectric materials and could potentially act as a continuous source of energy. In space vehicles, energy is generated using solar panels which are bulky, heavy and expensive. Instead piezoelectric harvesters can be used to generate power and are much lighter, compact and relatively cheap when produced in bulk. This paper presents a theoretical study on energy harvesting from structural vibration caused by combustion instability of a solid rocket motor through the motor burnout. Vibration data of tested solid rocket motor was taken as a reference and was inputted as the boundary condition. The 3-D model of the harvester system was designed on Fusion360 and the simulation was performed on COMSOL. Finally, improvements needed in the system to enhance practicality were discussed.

The effect of substrate bias on the piezoelectric properties of pulse DC magnetron sputtered AlN thin films

Substrate bias was applied for AlN deposition on rolled Ni sheet during pulse DC reactive sputtering to overcome the difficulty caused by thermal expansion mismatch between Ni substrate and AlN upon substrate heating. It was shown by Piezoresponse Force Microscopy (PFM) that the quality of the deposited AlN layer depends strongly on the negative substrate bias, i.e., the energy transferred via the bombardment of the accelerated positive ions on the sample. As the negative substrate bias becomes larger, the so formed layer shows higher piezoresponse, and better homogeneity. A Z-cut LiNbO3 single crystal was used as a reference to correct the PFM signals. The highest average d33 piezoelectric coefficient value, achieved at − 100 V substrate bias, is 3.4 pm/V indicating the feasibility of AlN deposition on rolled Ni substrate for vibration energy harvesting applications.

On a self-tuning sliding-mass electromagnetic energy harvester

Prior research has investigated resonators capable of self-tuning through the use of a sliding mass. This passive tuning mechanism can be utilized to improve vibration control; however, little is known about the nonlinear dynamic interactions between the vibrating beam and sliding mass, particularly as these apply to vibration energy harvesting applications. This paper investigates this problem by numerically and experimentally examining the response of an electromagnetic self-tuning energy harvester. We present the governing equations of this electromagnetic cantilever beam with a sliding mass using the extended Hamilton principle. These equations are then discretized using the Galerkin method and solved numerically. An experiment is carried out to validate the numerical analysis. Parametric studies are conducted to examine the effect of different system parameters on the performance of the self-tuning harvester.

Sacrificial Water-Soluble BaO Layer for Fabricating Free-Standing Piezoelectric Membranes.

The use of a sacrificial water-soluble BaO layer was investigated for the purpose of fabricating free-standing single-crystalline BaTiO3 membranes for vibrational energy harvesting applications. An epitaxial BaTiO3/SrTiO3/BaO heterostructure was deposited on a SrTiO3(001) substrate by pulsed laser deposition. The sacrificial BaO layer was dissolved by immersing the heterostructure in water. A single-crystalline BaTiO3 membrane was thereby released from the SrTiO3(001) substrate and transferred onto a glass or polyethylene terephthalate (PET) substrate coated with a polydimethylsiloxane (PDMS) adhesion layer. A 200 nm-thick BaTiO3 membrane was sandwiched between two flexible PDMS/ITO/PET electrode layers, forming a vibrational energy harvester test device that could operate at an average electrical power output of over 1 μW. This membrane fabrication process is applicable to various flexible structures and materials in vibrational energy harvesting or dynamic strain-sensing applications.