Wanlu Zhou

An efficient vibration energy harvester with a multi-mode dynamic magnifier

A novel piezoelectric energy harvester with a multi-mode dynamic magnifier, which is capable of significantly increasing the bandwidth and the energy harvested from the ambient vibration, is proposed and investigated in this paper. The design comprises a multi-mode intermediate beam with a tip mass, called a ?dynamic magnifier?, and an ?energy harvesting beam? with a tip mass. The piezoelectric film is adhered to the harvesting beam to harvest the vibration energy. By properly designing the parameters, such as the length, width and thickness of the two beams and the weight of the two tip masses, we can magnify the motion virtually in all the resonance frequencies of the energy harvesting beam, in a similar way as designing a new beam-type tuned mass damper (TMD) to damp the resonance frequencies of all the modes of the primary beam. Theoretical analysis, finite element simulation, and the experiment study are carried out. The results show that voltage produced by the harvesting beam is amplified for efficient energy harvesting over a broader frequency range, while the peaks of the first three modes of the primary beam can be effectively mitigated simultaneously. The experiment demonstrates 25.5 times more energy harvesting capacity than the conventional cantilever type harvester in the frequency range 3?300?Hz, and 100?1000 times more energy around all the first three resonances of the harvesting beam.

Energy harvesting using a PZT ceramic multilayer stack

In this paper, the interdisciplinary energy harvesting issues on piezoelectric energy harvesting were investigated using a ‘33’ mode (mechanical stress and/or electric field are in parallel to the polarization direction) lead zirconate titanate multilayer piezoelectric stack (PZT-Stack). Key energy harvesting characteristics including the generated electrical energy/power in the PZT-Stack, the mechanical to electrical energy conversion efficiency, the power delivered from the PZT-Stack to a resistive load, the electrical charge/energy transferred from the PZT-Stack to a super-capacitor were systematically addressed. Theoretical models for power generation and delivery to a resistive load were proposed and experimentally affirmed. In a quasi-static regime, 70% generated electrical powers were delivered to matched resistive loads. A 35% mechanical to electrical energy conversion efficiency, which is more than 4 times higher than other reports, for the PZT-Stack had been obtained. The generated electrical power and power density were significantly higher than those from a similar weight and size cantilever-type piezoelectric harvester in both resonance and off-resonance modes. In addition, our study indicated that the capacitance and piezoelectric coefficient of the PZT-Stack were strongly dependent on the dynamic stress. (Some figures may appear in colour only in the online journal)

Vibration and wave propagation attenuation for metamaterials by periodic piezoelectric arrays with high-order resonant circuit shunts

Beam or plate metamaterials with periodic piezoelectric arrays have attracted more and more attention in recent years for wave propagation attenuation and the corresponding vibration reduction. Conventional designs use resistive shunt (R-shunt) and resistor-inductor shunt (RL-shunt). An innovative metamaterial with a high-order resonant shunt circuit is proposed and investigated for vibration and wave propagation attenuation in this paper. The proposed high-order resonant shunt circuit can introduce two local resonances in series around the tuning frequency to broaden the attenuation bandwidth, or can create two separate resonances to achieve two separate bandgaps. Finite element modeling of the beam metamaterial with wave propagation and vibration in the transverse direction is established. Simulations have been conducted to compare the vibration attenuation performances among R-shunt, RL-shunt, and the proposed high-order shunt. An impedance-based method has been presented for the parameter design of electrical components in the proposed high-order shunt for bandgaps at two desired frequencies.

A Novel Piezoelectric Multilayer Stack Energy Harvester With Force Amplification

A piezoelectric lead zirconate titanate (PZT) multilayer stack flextensional energy harvester (PZT-Stack-FEH) was designed and characterized in this paper. An elastic flextensional frame for force amplification was optimally designed to transmit more mechanical energy with high efficiency to the PZT-Stack-FEH. Instead of 31-mode single layer piezoelectric component, a 33-mode piezoelectric PZT multilayer stack was employed to increase mechanical-to-electrical energy conversion efficiency. The power delivery ratio of the electrical power dissipated by resistive load over the total generated electrical power from PZT stack was studied. Theoretical analysis and experiments were carried out. The experiment results show that the mechanical-to-electrical energy conversion efficiency of the PZT-Stack-FEH is 19%, 48.6 times more mechanical energy can be transmitted to PZT-Stack-FEH, and 26.5 times more electrical energy can be generated by using the PZT-Stack-FEH than directly applying force to the PZT multilayer stack. The maximum power delivery ratio can attain 70% when the resistive load matches the impedance of piezoelectric stack. The power generation performance of the PZT-Stack-FEH with a proof mass was also studied. Experiment results show that he peak power/acceleration can attain 2400mW/g when the PZT-Stack-FEH is connected with a proof mass of 200 grams and 3280 mW/g with a proof mass of 500 grams.Copyright

Multi-source energy harvester for wildlife tracking

Sufficient power supply to run GPS machinery and transmit data on a long-term basis remains to be the key challenge for wildlife tracking technology. Traditional way of replacing battery periodically is not only time and money consuming but also dangerous to live-trapping wild animals. In this paper, an innovative wildlife tracking device with multi-source energy harvester with advantage of high efficiency and reliability is investigated and developed. This multi-source energy harvester entails a solar energy harvester and an innovative rotational electromagnetic energy harvester is mounted on the “wildlife tracking collar” which will remarkably extend the duration of wild life tracking. A feedforward and feedback control of DC-DC converter circuit is adopted to passively realize the Maximum Power Point Tracking (MPPT) logic for the solar energy harvester. The rotational electromagnetic energy harvester can mechanically rectify the irregular bidirectional motion into unidirectional motion has been modeled and demonstrated.

Optimal design of force magnification frame of a piezoelectric stack energy harvester

With the rapid development of portable electrical devices, the demand for batteries to power these portable devices increases dramatically. However, the development of the battery technology is slow in energy storage capability and cannot meet such requirements. This paper proposed an optimal frame design for a kind of portable piezoelectric stack energy harvesters, with large force magnification ratio and high energy transmission ratio. Two kinds of design approaches have been studied and explored, i.e., flexure compliant mechanism math based and finite element analysis (FEA) based. Prototypes are fabricated and assembled. Experiments with both static test and dynamic test have been conducted to approve the effectiveness of the proposed design. The measured force magnification ratio of 6.13 times and 21.8 times for the first-stage harvester and the dual-stage harvester are close to the design objective of 7.17 times and 24.4 times. The designed single stage harvester can generate 20.7mW/g2 at resonance frequency of 160Hz with optimal resistance of 393Ω under 0.8g base excitation with 100gram top mass, and the dual stage harvester has power generation of 487mW/g2 at resonance frequency of 38.9Hz with optimal resistance of 818Ω under 1.94g base excitation with 100gram top mass. The proposed two-stage PZT energy harvester can be used to develop portable power regenerator to compensate the urgent battery needs in remote area for both civic and military application.

Piezoelectric Energy Harvesting From Torsional Vibration

Torsional vibration is present in various applications, such as in oil drilling pipes, engine crankshafts, and wind turbine gearboxes. In the case of oil drilling, ever deeper wells are being drilled and sensors used to gather data from the bottom of the well. Providing an energy source for these sensors is a big challenge. Harvesting energy from torsional vibrations presents a promising solution for powering the sensors on rotational systems. We investigated the concept of torsional vibration energy harvesting using a piezoelectric transducer attached to a shaft at an arbitrary angle with respect to the axis of the shaft. A comprehensive theoretical model considering all the working modes, including d15, d31, and d33 mode, has been developed to express the voltage outputs as functions of the mounting angle. The frequency responses of the voltage outputs over the input torque have also been studied and compared. A finite element model was also implemented to verify the theoretical results and illustrate the voltage distribution within the piezoelectric material under an external torque input.Copyright

A Piezoelectric PZT Ceramic Mulitlayer Stack for Energy Harvesting Under Dynamic Forces

In this paper, we report the study of a “33” longitudinal mode, piezoelectric PZT ceramic multilayer stack (PZT-Stack) with high effective piezoelectric coefficient for broader bandwidth high-performance piezoelectric energy harvesting transducers (PEHTs). The PZT-Stack is composed of 300 layers of 0.1 mm thick PZT plates, with overall dimensions of 32.4 mm × 7.0 mm × 7.0 mm. Experiments were carried out with dynamic forces in a broad bandwidth ranging from 0.5 Hz to 25 kHz. The measured results show that the effective piezoelectric coefficients (EPC, deff ) of the PZT-stack is about 1 × 105 pC/N at off-resonance frequencies and 1.39 × 106 pC/N at resonance, which is order of magnitude larger than that of traditional PEHTs. The EPC do not change significantly with applied dynamic forces having root mean square (RMS) values ranging from 1 N to 40 N. In resonance mode, 231 mW of electrical power was harvested at 2,479 Hz with a dynamic force of 11.6 Nrms , and 7.6 mW of electrical power was generated at a frequency of 2,114 Hz with 1 Nrms dynamic force. In off-resonance mode, an electrical power of 18.7 mW was obtained at 680 Hz with a 40 Nrms dynamic force. A theoretical model of energy harvesting for the PZT-Stack was established. The modeled results matched well with experimental measurements. This study demonstrated that structures with high EPC enable PEHTs to harvest more electrical energy from mechanical vibrations or motions, suggesting an effective design for high-performance low-profile PEHTs with potential applications in military, aerospace, and portable electronics. In addition, this study provides a route for using piezoelectric multilayer stacks for active or semi-active adaptive control to damp, harvest or transform unwanted vibrations into useful electrical energy.Copyright

A self-powered piezoelectric vibration control system with switch pre-charged inductor (SPCI) method

A self-powered piezoelectric vibration control system is proposed and investigated for flexible structures in this paper. The objective of the system is to minimize the vibration of the flexible structure and at the same time to harvest energy for the self-powered control implementation. The whole system is comprised of four parts, i.e., flexible-beam mechanism, H2 control algorithm, switch pre-charged inductor (SPCI) based control implementation, and energy storage unit. A cantilever beam with a tip mass, which is a typical type of flexible structures, is partly covered by a PZT film at the fixed end. The output feedback H2 control algorithm produces desired values of control voltage. The circuit part uses a novel SPCI technique to realize the desired control voltage. The energy storage unit has both functions of accumulating energy and providing electricity needed in the control. Theoretical analysis and simulation are carried out. The simulation results show that the vibration of the cantilever beam can be effectively reduced under white-noise random excitation. It also indicates that the accumulated harvested energy is more than the consumed energy in the system.

Multi-Mode Vibration Energy Harvester and Tuned Mass Damper Using Double-Beam Structure

A novel piezoelectric energy harvester with multi-mode dynamic magnifier is proposed and investigated in this paper, which is capable of significantly increasing the bandwidth and the energy harvested from the ambient vibration. The design comprises of an multi-mode intermediate beam with a tip mass, called “dynamic magnifier”, and an “energy harvesting beam with a tip mass. The piezoelectric film is adhered to the harvesting beam to harvest the vibration energy. By properly designing the parameters, such as the length, width and thickness of the two beams and the weight of the two tip masses, we can virtually magnify the motion in all the resonance frequencies of the energy harvesting beam, in a similar way as designing a new beam-type tuned mass damper (TMD) to damp the resonance frequencies of all the modes of the primary beam. Theoretical analysis, finite element simulation, and the experiment study are carried out. The results show that voltage produced by the harvesting beam is amplified for efficient energy harvesting over a broader frequency range, while the peaks of the first three modes of the primary beam can be effectively mitigated simultaneously. The experiment demonstrates 25.5 times more energy harvesting capacity than the conventional cantilever type harvester in broadband frequency 3–300Hz, and over 1000 times more energy close to the first three resonances of harvesting beam.Copyright