Piezoelectric Vibration Harvester Research Articles

Piezoelectric vibration harvester with excitation direction conversion

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Non-linear losses study in strongly coupled piezoelectric device for broadband energy harvesting

Piezoelectric vibration harvesters with strong electromechanical coupling coefficients have recently been combined with nonlinear electrical techniques capable of tuning their resonant frequency as a solution to provide energy to wireless sensor nodes from wideband vibrations. To be fully competitive, this approach requires piezoelectric generators with strong global electromechanical coupling coefficients k2. However, the presence of non-linear dielectric and piezoelectric losses in piezoelectric materials significantly reduces the power harvested when strongly coupled materials are used. This paper presents a non-linear model that allows for a better consideration of losses for such piezoelectric harvesters. An experimental validation is performed with a strongly coupled cantilever based on a PMN-PT material (k2 = 16 %). The results reveal the importance of considering non-linear dielectric losses. Indeed, we show thanks to the model that neglecting these losses can induce an 18 % overestimation of the harvested power for the presented prototype driven at 0.5 m/s2 amplitude ambient acceleration.

Active Interface for Piezoelectric Harvesters Based on Multi-Variable Maximum Power Point Tracking

An active electronic interface for maximizing the power extracted from a resonant piezoelectric vibration harvester by means of a multi-variable Maximum Power Point Tracking (MPPT) technique is presented. The input voltage of the electronic interface is dynamically adapted in order to ensure that the maximum power is extracted even if the vibration characteristics change with time. The digital control unit updates the amplitude, the phase and the frequency of such an input voltage without requiring the high-frequency sampling and elaboration of the harvester current or voltage. The unit exploits only the information on the vibration frequency kept from a small piezo accelerometer and a low-frequency sampling of the DC current. The implemented algorithm is as simple as the widespread Perturb & Observe algorithm, but it allows the extraction of significantly more power from the harvester. The power increase for a piezoelectric harvester with the proposed electronic interface is investigated both theoretically and experimentally. By using a commercially available piezoelectric harvester, the maximum power tracking performance of the proposed active interface is experimentally compared with that of a usual AC/DC converter with Perturb & Observe MPPT control.

Design of a Wireless and Energy Autonomous Sensor Network for Condition Monitoring of Tram Drive Components

Although condition monitoring is very important for a reliable operation of tram powertrain components, conventional wired sensor systems do not manage to find wide acceptance because of installation and security costs. To address those issues, we propose a novel condition monitoring system based on a wireless and energy self-sufficient sensor network, where the individual sensor nodes harvest energy from vibrations, occurring while the tram is in motion. First, we performed an experimental investigation to identify the most important boundary conditions for the system design. Second, we designed individual sensor nodes using parameters derived from the previous investigation. Finally, the sensor network was deployed and tested on the tram gearboxes. The obtained measurement data were recorded at a sufficient sampling rate of 4.56 kHz and were successfully transferred from the tram gearbox to the network base station within a radius of 10 m inside the tram despite factors such as reflections, fading and electromagnetic compatibility. A piezoelectric vibration harvester is the power supply for the sensor nodes and it delivers up to 21.22 mW for relevant vibration frequency range between 10 Hz and 30 Hz, thus enabling deployment of autonomous sensor nodes.

Efficiency Evaluation of a MOSFET bridge rectifier for Powering LEDs using Piezo-electric Energy Harvesting Systems

Harvesting energy from the renewable energy sources plays a very important role in recent days. Researchers are using various methods to capture the energy for different sources. One of the most prominent methods of energy harvesting from vibrations is by using piezo-electric material. Piezo-electric vibration harvesting is smart mainly due to the simplicity of piezoelectric transduction and the piezoelectric systems can be easily implemented into a wide variety of applications. Due to wide range of AC output voltage and low power, the piezo-electric generator cannot directly prop up the AC or DC electrical appliances. Hence in the majority applications the AC signal created by this generator needs to be rectified. In this paper a new highly efficient MOSFET full bridge AC to DC converter for piezoelectric energy harvesting is planned, which enhances the power extracted from the piezo-electric crystal. The proposed AC to DC converter reduces the voltage drop along the conduction path and thereby increases the power extraction and conversion capability. The proposed circuit is replicated in PSpice software package and then in the experimental setup. The performance is evaluated and compared.

Efficiency Evaluation of a MOSFET bridge rectifier for Powering LEDs using Piezo-electric Energy Harvesting Systems

Harvesting energy from the renewable energy sources plays a very important role in recent days. Researchers are using various methods to capture the energy for different sources. One of the most prominent methods of energy harvesting from vibrations is by using piezo-electric material. Piezo-electric vibration harvesting is smart mainly due to the simplicity of piezoelectric transduction and the piezoelectric systems can be easily implemented into a wide variety of applications. Due to wide range of AC output voltage and low power, the piezo-electric generator cannot directly prop up the AC or DC electrical appliances. Hence in the majority applications the AC signal created by this generator needs to be rectified. In this paper a new highly efficient MOSFET full bridge AC to DC converter for piezoelectric energy harvesting is planned, which enhances the power extracted from the piezo-electric crystal. The proposed AC to DC converter reduces the voltage drop along the conduction path and thereby increases the power extraction and conversion capability. The proposed circuit is replicated in PSpice software package and then in the experimental setup. The performance is evaluated and compared.

Self-sufficient electronic control for nonlinear, frequency tunable, piezoelectric vibration harvesters

Research in vibration energy harvesting focuses increasingly on nonlinear harvesters. In comparison to linear harvesters they show an inherent larger bandwidth through hardening or softening effects and higher conversion efficiency. A further increase of the bandwidth and thus a higher energy yield can be achieved by controlled tuning of such a nonlinear system. In this paper a self-sufficient tuning control electronic, which is directly powered by the harvester, is presented.

A multi-degree of freedom piezoelectric vibration energy harvester with piezoelectric elements inserted between two nearby oscillators

A novel piezoelectric vibration energy harvesting system is proposed whose harvesting performance could be significantly enhanced by introducing one or multiple additional piezoelectric elements placed between every two nearby oscillators. The proposed two degree-of-freedom piezoelectric vibration harvester system is expected to extract 9.78 times more electrical energy than a conventional two degrees of freedom harvester system with only one piezoelectric element inserted close to the base. A parameter study of a multiple degree-of-freedom piezoelectric vibration energy harvester system has been conducted to provide a guideline for tuning its harvesting bandwidth and optimizing its design. Based on the analysis method of the two degrees of freedom piezoelectric vibration harvester system, a generalised MDOF piezoelectric vibration energy harvester with multiple pieces of piezoelectric elements inserted between every two nearby oscillators is studied. The harvested power values of the piezoelectric vibration energy harvesters of 1 to 5 degree-of-freedom have been compared while the total mass and the mass ratio of the oscillators are kept as constants. It is found that the greater numbers of degree-of-freedom of a PVEH with the more additional piezoelectric elements inserted between every two nearby oscillators would enable that system to harvest more energy. The first mode resonant frequency will be shifted to a low-frequency range when the numbers of degree-of-freedom increase.

Piezoelectric Vibration Harvesters Based on Vibrations of Cantilevered Bimorphs: A Review

With the advancement in the technologies around the world over the past few years, the microelectromechanical systems (MEMS) have gained much attention in harvesting the energy for wireless, self-powered and MEMS devices. In the present era, many devices are available for energy harnessing such as electromagnetic, electrostatic and piezoelectric generator and these devices are designed based on its ability to capture the different form of environment energy such as solar energy, wind energy, thermal energy and convert it into the useful energy form. Out of these devices, the use of a piezoelectric generator for energy harvesting is very attractive for MEMS applications. There are various sources of harvestable energy including waste heat, solar energy, wind energy, energy in floating water and mechanical vibrations which are used by the researchers for energy harvesting purposes. This paper reviews the state-of-the-art in harvesting mechanical vibrations as an energy source by various generators (such as electromagnetic, electrostatic and piezoelectric generators). Also, the design and characteristics of piezoelectric generators, using vibrations of cantilevered bimorphs, for MEMS have also been reviewed here. Electromagnetic, electrostatic and piezoelectric generators presented in the literature are reviewed by taking into an account the power output, frequency, acceleration, dimension and application of each generator and the coupling factor of each transduction mechanism has also been discussed for all the devices.

Degradation of Piezoelectric Materials for Energy Harvesting Applications

The purpose of energy harvesting is to provide long term alternatives to replaceable batteries across a number of applications. Piezoelectric vibration harvesting provides advantages over other transduction methods due to the ability to generate large voltages even on a small scale. However, the operation in energy harvesting is different from typical sensors or actuators. The applied stress is often at the material limit in order to generate the maximum power output. Under these conditions, the degradation of the materials becomes an important factor for long term deployment. In this work bimorph piezoelectric beams were sub jected to lifetime testing through electromagnetic tip actuation for a large number of cycles. The results of two measurement series at different amplitudes are discussed. The dominant effect observed was a shift in mechanical resonance frequencies of the beams which could be very detrimental to resonant harvesters.

Piezoelectric Energy Harvesting in Automobiles

Powering the distributed or embedded wireless sensors from ambient vibration energy has attracted many attentions. It will reduce the installment trouble and maintenance costs. This work reports on vibration levels detected in automobiles during road test as a potential energy source for automobile sensors. A piezoelectric vibration harvester was designed and equipped with a simple harvesting circuit. The measurement results showed that the vibrations in the automobiles are large enough to possibly supply a wireless sensor.

Self-powered piezoelectric energy harvester for bicycle

Powering from ambient energies various electric accessories on bicycles like lamps, on-board computer, communication devices, or even wireless sensor nodes will avoid the use of batteries and improves the availability of these devices when the bicycle is not used for a long time. This paper reports on vibration resources detected in a bicycle as a potential energy source for supplying these on-board devices. The measurements showed that the bandwidth of the energy vibration is reduced with speed. For this application, a piezoelectric vibration harvester was designed and equipped with a self-powered voltage switching interface circuit. Within the field test, it is demonstrated that sufficient energy is harvested.

Shock Reliability of Vacuum-Packaged Piezoelectric Vibration Harvester for Automotive Application

This paper reports for the first time the shock reliability of vacuum-packaged piezoelectric vibration harvesters for automotive application. Experimental study on >80 devices shows that the failure is induced by the impact between seismic mass and glass package. The statistical results obtained for various types of harvesters have shown a trend of higher shock reliability for a higher resonance frequency. The influence of beam thickness on the shock reliability is then discussed. The trade-off between the power output and shock reliability is elaborated. To further improve the reliability to the level of automotive application, the idea of stepped cavity is discussed and implemented. The experimental results confirmed a significantly enhanced reliability increased by ~50%, up to maximum 2000 g, for the same type of device under shock excitations.

Vibration harvesting in traffic tunnels to power wireless sensor nodes

Monitoring the traffic and the structural health of traffic tunnels requires numeroussensors. Powering these remote and partially embedded sensors from ambient energieswill reduce maintenance costs, and improve the sensor network performance.This work reports on vibration levels detected in railway and road tunnels as apotential energy source for embedded sensors. The measurement results showed thatthe vibrations at any location in the road tunnel and at the wall in the railwaytunnel are too small for useful vibration harvesting. In contrast, the railway sleeperfeatures usable vibrations and sufficient mounting space. For this application site, arobust piezoelectric vibration harvester was designed and equipped with a powerinterface circuit. Within the field test, it is demonstrated that sufficient energyis harvested to supply a microcontroller with a radio frequency (RF) interface.

Monomorph piezoelectric wideband energy harvester integrated into LTCC

In this paper the first fully LTCC embedded piezoelectric vibration harvester is demonstrated and characterized. Using ordinary LTCC processes a 39mm×39mm×3mm package containing 25mm co-fired PZT discs was made. Three laser cut beams of different lengths provided a 5.4% frequency bandwidth for 3dB attenuation and a power of 32μW at 1g acceleration delivered into a 33.9kΩ resistive load. The packaged structure was compared to a bare monomorph reference sample and showed less crosstalk, better frequency control and more power generated. The experiments showed that integration of LTCC and PZT bulk materials by co-firing is a very feasible way to realise energy harvesters for wireless technologies, sensors and autonomous System-On-a-Package.

Piezoelectric vibration harvesting device with automatic resonance frequency tracking capability

AbstractFurther development in the area of vibration energy harvesting is limited by the lack of efficient methods to adapt the harvester to its surroundings. To this end, we propose an innovative passive way of automatic passive resonance frequency tracking.We present a new approach employing mechanical non-linear behaviour of the system to track the vibration frequency peak. An analytical model representing these nonlinear harvesting systems has been developed and analysed. Experimental results obtained with custom fabricated MEMS devices show an experimentally verified frequency adaptability of over 36% for a clamped-clamped beam device at 2g (1g=9.81m.s-2) input acceleration. We believe that the proposed solution is perfectly suited for autonomous industrial machinery surveillance systems, where vibrations with high accelerations that are necessary for enabling this solution are abundant.

Fabrication, modelling and characterization of MEMS piezoelectric vibration harvesters

Piezoelectric converters designed for harvesting energy from mechanical vibrations have been fabricated by micromachining technologies. They are characterized by applying a sinusoidal oscillation as mechanical input and by using a resistive load to measure the output power of the system. A maximum output power of 40μW has been measured for a PZT based harvester excited by an input vibration having a frequency of 1.8kHz and an amplitude of 180nm. Preliminary experimental results on AlN based devices are also presented. A model capable of estimating the output power as a function of material parameters and device dimensions has been developed. Theoretical estimations have been compared with experimental results.

Experimental Verification of Models for Microfabricated Piezoelectric Vibration Energy Harvesters

Experiments have been performed to verify power-optimized modal models of piezoelectric vibration harvesters for microelectromechanical systems. Such harvesters can power a variety of sensors, and there have been recent national workshops dedicated to harvesting. Detailed experimental results, including displacement histories and electrical output, are provided over a range of frequencies and electrical loadings to compare with (optimized) modal models. The harvester geometry considered is that of a symmetric bimorph macroscale cantilever. Although some experimental work for cantilevered bimorph harvesters has been published, key testing and/or device parameters needed for model verification are missing and/or data at and near power optima (the most interesting operating points) are not provided. Therefore, a detailed set of experiments was performed using power-optimized modeling results to guide the test matrix. Over the broad range of parameters tested, the models accurately predicted all trends and device performance away from device resonances (resonance and antiresonance frequencies). Near the resonance frequencies, the model consistently underpredicts electrical performance, which is satisfactorily attributed (and experimentally supported) to the well-known piezoelectric coupling nonlinearity in the large-strain region. The data presented herein can serve as benchmark data to verify other modeling efforts. The verified models have been used to optimally design microelectromechanical system harvesters for commercial aircraft and microfabrication is ongoing.