Piezoelectric-electromagnetic Energy Harvester Research Articles

Design and evaluation of a piezoelectric-electromagnetic energy harvester with a lever structure

This paper proposes a piezoelectric-electromagnetic energy harvester with a lever structure. The prototype combines electro-magnetic energy harvester (EMH) and piezoelectric energy harvester (PEH) organically, which improves the efficiency of energy harvesting. Combining Faraday’s law of electromagnetism with a spring-mass damped system, a physical model is developed and dynamic curves are predicted at different speeds. The output voltage and power of PEH and EMH are compared theoretically and experimentally, EMH performs better at lower loads and PEH is more dominant when the load resistance is high. Experiments have demonstrated that the coupling effect of EMH and PEH is relatively weak. Consequently, it is advisable to utilise the respective advantages of these two concepts by separating them. When the number of rotor contacts is 3, and the magnet diameter and number are 20 mm and 8 respectively, the prototype output is optimal. When the external load is 2KΩ, EMH reaches a maximum power of 5.06mW, whereas PEH output reaches a maximum of 1.04mW when the external load is 10KΩ. A series of experimental tests demonstrate that the prototype is capable of simultaneously providing power to two devices.

Study of vibration suppression and energy harvesting for a Vibration-based Piezoelectric–Electromagnetic energy harvester with nonlinear energy sink

Vibration-based energy harvesting devices are prone to excessive displacement response. The effective vibration suppression is critical to the longevity and safety of energy harvesting systems. In this work, the vibration-based Piezoelectric–Electromagnetic energy harvester with nonlinear energy sink (NES-VBPEEH) is proposed to achieve the dual efficacy goals of vibration suppression and vibration energy harvesting. The electromechanical-coupled distributed governing equations are derived through Hamilton’s principle, Euler’s Bernoulli theory, Gauss’s law and Faraday’s law of electromagnetic induction. The output performances of the degradation model of the NES-VBPEEH are validated by previous work. Parameter analysis indicates that the external resistance of the piezoelectric energy harvester significantly affects the electrical damping of the system and ultimately affects the output response of the NES-VBPEEH. The external resistance and coil turns of the electromagnetic vibration energy harvester can significantly affect the output response of the NES-VBPEEH. The output power of both types of energy harvesters is maximized with respect to the resistance and the coil turns. The output response of the NES-VBPEEH exhibits certain nonlinear characteristics as the external excitation amplitude increases to a certain value. The damping and nonlinear stiffness of the NES can significantly affect the output power of the NES-VBPEEH, and appropriate parameter selection can help to achieve the dual efficacy goals of vibration suppression and vibration energy harvesting for the energy harvester.

A hybrid piezoelectric-electromagnetic energy harvester used for harvesting and detecting on the road

At present, some piezoelectric energy harvesters (PEH) have been widely used in various small wireless electronic devices and micro intelligent sensing devices for self-power supply, but PEH still needs to be further improved in the effective acquisition of road vibration energy at low frequency (<10 Hz), especially at ultra-low frequency (<5 Hz) and broadening the capture energy band. Based on this, this paper proposes a hybrid piezo-electromagnetic road vibration energy harvesting device -TPEH (Triple piezoelectric energy harvester) suitable for road deceleration belts. Spring is introduced as the key to improve the efficiency of energy harvesting. Firstly, the vibration environment of the deceleration belts is surveyed, and then the influence of different K, frequencies, vehicle types and impedance on the energy capture effect is observed in the experiment. The experimental results show that: first of all, K = 20 N/kg main spring has the best resilience; Secondly, with the increase of excitation frequency from 0 Hz to 10 Hz, the maximum peak voltage of TPEH increases from 5.7V to 31.2V, and reaches the full bandwidth in the low frequency range of 0–10 Hz, especially the frequency band widening in the range of 0–1 Hz has ma de a breakthrough. Then, the total output power of TPEH reaches a maximum of 10.29 mW under the optimal load condition of 10 kΩ. Finally, TPEH is applied to the speed strip of a local road section. Through reasonable distribution of vibration signals, TPEH could accurately wireless communication module.

Design and analysis of the piezoelectric-electromagnetic energy harvester based on magnetically coupled structures

This paper proposes a piezoelectric-electromagnetic energy harvester based on magnetic coupling for wind energy harvesting. The prototype utilizes magnetic force between the rotating magnets and fixed magnets to transmit mechanical energy and generate electricity through the piezoelectric energy harvester (PEH) and electromagnetic energy harvester (EMEH) components. The magnetic coupling exerts a non-contact force extending the PZT's lifespan, while the presence of multiple magnets introduces frequency up-conversion, contributing to an increase of the output power. Meanwhile, the rational arrangement of the magnets results in a small start-up wind speed for the harvester. The electromechanical coupling of the wind energy harvester (WEH) is modeled, and the key parameters affecting the characteristics of PEH and EMEH are thoroughly analyzed through experiments and simulations. By synergising the advantages of PEH and EMEH, WEH is capable of effectively charging a 470 μF capacitor to 13.44 V in 50 s.

Design and research of hybrid piezoelectric-electromagnetic energy harvester based on magnetic couple suction-repulsion motion and centrifugal action

In this paper, a hybrid piezoelectric-electromagnetic energy harvester (HEH) based on magnetic couple suction-repulsion motion and centrifugal action is proposed. Using a control variable approach, the effect of two variables on the output performance was investigated under different parameter conditions in order to maximize the output power. At a mounting angle of 60 degrees for the piezoelectric cantilever beam and a mass of 3.2 g for the rectangular magnet, the entire piezoelectric-electromagnetic harvester can produce 13.32 mW of power, which can successfully power low-power electronic devices such as light-emitting diodes (LEDs). The power generated by mixing piezoelectricity and electromagnetism is 1.16 times greater than the power generated by the piezoelectric generation unit alone and 70.1 times greater than the power generated by the electromagnetic generation unit alone. The composite piezoelectric-electromagnetic hybrid mechanism greatly increases the power output of the entire structure compared to the single generation mode. The suction-repulsion process is accomplished using magnetic coupling. This makes the piezoelectric cantilever beam deformed by the magnetic force and has power output. At the same time, the magnetic suction-repulsion makes the circular magnet complete cutting magnetic induction line motion at the same time, which cleverly combines piezoelectricity and electromagnetism. The form of reciprocating motion of the magnet in the coil frame using suction-repulsion is also proposed for the first time. In addition, compared with those structures that strike the piezoelectric cantilever to generate electricity, this paper uses magnetic coupling, which makes the piezoelectric cantilever beam more durable and longer in use. In summary, this structure has good prospects for application in the direction of powering wireless networks or low-power electronic devices.

A hybrid piezoelectric-electromagnetic energy harvester from vortex-induced vibrations in fluid-flow; the influence of boundary condition in tuning the harvester

In this paper, a hybrid piezoelectric-electromagnetic energy harvester is proposed to harvest energy from fluid flow around a bluff-body using vortex-induced vibration (VIV). The hybrid piezoelectric-electromagnetic harvester combines the two electromechanical transduction mechanisms through the bluff body excited by VIV: piezoelectric macro-fiber composite and an electromagnetic system. The piezoelectric composite is glued to a substrate beam to convert mechanical strain into electricity. A novel implementation of an internal electromagnetic harvester where the change in magnetic flux inside a coiled holder transduces change in magnetic flux to electricity. An analytical model is used to investigate the narrowband synchronization properties in VIV for different submerged conditions that can be tuned for vibration-based energy harvesting. Under synchronization, the structural natural frequency is the same as the vortex shedding frequency, which leads to the generation of a higher output voltage during frequency matching. Therefore, the effects of added mass and boundary conditions are validated experimentally in water flow to tune the submerged energy harvester with the new hydrodynamic properties to increase the harvesting performance. The results show that fully submerging the energy harvester increases the overall added mass, whilst confining it inside a submerged pipe adds stiffness and damping. This means the overall energy harvesting performance decreases with submerging depth and proximity to the boundary. The maximum voltage output occurs within the synchronization region, with piezoelectric output performing best when partially submerged while the electromagnetic oscillator performs best when fully submerged. Implementing a hybrid piezoelectric-electromagnetic energy harvesting system increased the voltage output by up to 23% compared to a conventional piezoelectric energy harvester.

Research on cam frequency-increasing hybrid piezoelectric electromagnetic energy harvester with center symmetric structure

This paper proposes a cam frequency-increasing hybrid piezoelectric electromagnetic energy harvester with center symmetric structure (C-HEH). The use of the cam structure allows the harvester to increase the efficiency of energy harvester per unit time, while the center symmetric structure of the entire harvester allows for maximum energy output in a limited size. This paper studies the influence of the number of cam protrusions and the length of the cylindrical permanent magnet on the output voltage signal at different rotation speeds. When the number of cam protrusions is 3 and the length of the cylindrical magnet is 10 mm, the maximum peak-to-peak voltages of the piezoelectric and the electromagnetic power generation unit are 53.74 V and 3.16 V, respectively. The effective value power of the hybrid energy harvester can be obtained as 1.49 mW. A series of application experiments were carried out to verify the performance of the C-HEH. The hybrid energy harvester can easily light up 86 light-emitting diodes (LEDs) lights and make the scientific calculators work stably after rectification. These results demonstrate the giant prospect of piezoelectric-electromagnetic energy harvesters for supplying wireless sensor networks and low-power electronic devices.

Electromechanical Performance Analysis of the Hybrid Piezoelectric-Electromagnetic Energy Harvester under Rotary Magnetic Plucking Excitation

This paper presents an analysis of the hybrid piezoelectric-electromagnetic energy harvester (P-EMEH) driven by contactless rotary magnetic plucking. A lumped-parameter model of the hybrid P-EMEH is developed, and the model parameters are determined from the finite element analysis (FEA) method. A parametric study is conducted to investigate the effects of driving force parameters, load resistance, and electromechanical coupling strengths (EMCSs) on the maximal displacements and velocities, average power inputs and outputs, and energy efficiencies of the system for indicating the performance of the hybrid P-EMEH. The results show that the hybrid P-EMEH can obtain the improved power inputs by reducing the gyration radii of the rotary magnet and shortening the gaps between the two magnets. The structural vibrations can be strongly suppressed owing to the optimal piezoelectric power outputs, which can lead to the occurrence of valleys’ power of the electromagnetic element. At weak coupling, the hybrid P-EMEH can achieve higher power outputs than the single piezoelectric energy harvester (PEH) and the single electromagnetic energy harvester (EMEH). At strong coupling, the use of the PEH is more advantageous for energy harvesting due to wider power bandwidths at high dimensionless frequencies when compared with the hybrid P-EMEH. This work provides a fundamental understanding on the effect of load resistance and EMCSs on the dynamic and electrical characteristics of the magnetically plucked hybrid P-EMEH.

A Piezoelectric and Electromagnetic Hybrid Galloping Energy Harvester with the Magnet Embedded in the Bluff Body.

To meet the needs of low-power microelectronic devices for on-site self-supply energy, a galloping piezoelectric–electromagnetic energy harvester (GPEEH) is proposed. It consists of a galloping piezoelectric energy harvester (GPEH) and an electromagnetic energy harvester (EEH), which is installed inside the bluff body of the GPEH. The vibration at the end of the GPEH cantilever drives the magnet to vibrate, so that electromagnetic energy can be captured by cutting off the induced magnetic field lines. The coupling structure is a two-degree-of-freedom motion, which improves the output power of the energy harvester. Based on Hamilton’s variational principle and quasi-static hypothesis, the piezoelectric–electromagnetic vibrated coupling equation is established, and the output characteristics of GPEEH are obtained by the method of numerical simulation. Using the method of numerical simulation, studies a series of parameters on the output performance. when the wind speed is 9 m/s, the effective output power of the GPEEH is compared with the classical galloping piezoelectric energy harvester (CGPEH) who is no magnet. It is found that the output power of GPEEH 121% higher than the output power of CGPEH. Finally, set up an experimental platform, and test and verify. The experimental analysis results show that the simulated output parameter curves are basically consistent with the experimental drawing curves. In addition, when the wind speed is 9 m/s, under the same parameters, the effective output power of the GPEEH is 112.5% higher than that of the CGPEH. The correctness of the model is verified.

Numerical research on a vortex shedding induced piezoelectric-electromagnetic energy harvester

To widen the operation wind speed bandwidth of a classic vortex shedding induced vibration piezoelectric energy harvester, a piezoelectric-electromagnetic hybrid energy harvester based on vortex shedding induced vibration is designed. The hybrid vortex shedding induced vibration energy harvester (HVSIVEH) includes a vortex shedding induced vibration piezoelectric energy harvester (VSIVPEH) and an electromagnetic vibration energy harvester (EVEH). The electromechanical coupled vibration model of the hybrid structure was established. By comparing the variations of the output power as a function of the wind speed of the HVSIVEH and the classic VSIVPEH, it is found that the power response curve of the HVSIVEH has two peaks. The hybrid structure can broaden the working wind speed range. The lower the requirement on the output power level, the more obvious the effect of widening the wind speed range. By the solution and analysis of the electromechanical coupled model, better values of related parameters of the HVSIVEH are obtained. The first and second peaks of the output power of the HVSIVEH show better values of 1.9 and 2.2 mW, respectively, under these parameters.

Nonlinear Dynamics and Power Generation on a New Bistable Piezoelectric-Electromagnetic Energy Harvester

This paper focuses power generation and nonlinear dynamic behaviors on a new bistable piezoelectric-electromagnetic energy harvester. Three different kinds of piezoelectric cantilever beam structures, which include the monostable piezoelectric cantilever beam, the bistable piezoelectric cantilever beam with spring and magnet, and the bistable piezoelectric cantilever beam with spring, magnet, and coil, are designed. The power generation efficiency and dynamic behaviors for each structure are experimentally studied, respectively. Due to the spring introduced, the system easily goes through the potential barrier. Experimental results show that the power generation structure of the bistable piezoelectric-electromagnetic harvester can vibrate between two steady states in a wider range of the frequency. Therefore, the effective frequency bandwidth is broadened about 2 Hz when the spring is introduced under the condition of the suitable magnetic distance. Comparing with the power generation efficiency for three different kinds of structures, it is found that the bistable piezoelectric-electromagnetic harvester has the optimum characteristics, which include the optimal magnetic distance of 15 mm, the optimal load of 8 MΩ, and the parameters variation law of coils. For this structure, the influences of the external excitation and the magnetic distance on the output voltage and dynamic behaviors of the system are examined.

Design and performance of hybrid piezoelectric-electromagnetic energy harvester with trapezoidal beam and magnet sleeve

At present, piezoelectric energy harvesters are disadvantaged by their low efficiency and high operating frequencies. To address these shortcomings, we propose herein a hybrid piezoelectric-electromagnetic energy harvester (HPEH) for the low-frequency vibration environment, which is composed of a piezoelectric part featured with a double-clamped trapezoidal beam and an electromagnetic part featured with a magnet sleeve and plane coils. The modeling and experiment of the HPEH were carried out to optimize the structure and performance. We find experimentally that the proposed device not only increases the piezoelectric output but also highly improves the electromagnetic output. At the excitation acceleration 2 m/s2, the average output power of the piezoelectric part and the electromagnetic part is increased by 30.5% and 20 times, respectively. The total output power of the HPEH is increased by 52.4%, reaching 0.637 mW. The results show that the proposed HPEH can efficiently use vibration energy to improve its output performance, which has the potential to power wireless intelligent sensor network and wearable electronic devices.

Design and Test of the MEMS Coupled Piezoelectric–Electromagnetic Energy Harvester

This paper researches on the design and test of the output performance of double-end clamped MEMS coupled piezoelectric–electromagnetic energy harvester. It establishes the theoretical output model of the double-end clamped rectangular beam and trapezoidal beam piezoelectric–electromagnetic energy harvester, and optimizes the structure parameters of piezoelectric and electromagnetic unit with simulation analysis. It also respectively realizes the processing of piezoelectric and electromagnetic unit by MEMS and flexible PCB technology, and completes the performance test of structure prototype through the experimental system. The result showed that the capacity of MEMS coupled piezoelectric–electromagnetic energy harvester, which taked four coil piezoelectric with integrated electromagnetic in series, was 12.23 times higher than that of piezoelectric energy harvester. Also the output voltage and power of coupled trapezoidal beam energy harvester were respectively increased 18.89% and 2.26%, compared with coupled rectangular beam energy harvester.

Hybrid piezoelectric-electromagnetic energy harvester for scavenging energy from low-frequency excitations

Capturing mechanical energy from our living environment is an effective approach for implementing self-sustained electronics. One of the key challenges is how to generate more electricity from the low-frequency and multi-directional excitations. To address this interesting issue, this paper reports a hybrid energy harvester (HEH) that consists of a piezoelectric energy harvester (PEH) and an electromagnetic energy harvester (EMEH), which can scavenge energy from both low-frequency and bi-directional excitations. The PEH is composed of two piezoelectric cantilever beams, each of which can deliver a peak power of approximately 0.13 mW when excited directly by a harmonic vibration of 0.8 g. A spherical magnet is utilized to not only trigger the PEH to function, which endows the PEH with bi-directional energy-harvesting capability, but also induce the coil to generate electricity, achieving the integration of EMEH with PEH. When the magnet is subjected to a sinusoidal excitation of 1.24 g, each beam of the PEH generates a peak power of 0.058 mW at 7 Hz and the coil outputs a peak power of 2.94 mW at 7.2 Hz. The HEH exhibits a better charging performance than the PEH or EMEH for charging a capacitor, and the fabricated HEH prototype can light up tens of light-emitting diodes (LEDs) when excited by hand-shaking vibrations.

A multimodal hybrid energy harvester based on piezoelectric-electromagnetic mechanisms for low-frequency ambient vibrations

In this paper, we proposed and experimentally validated a vibration-based multimodal hybrid piezoelectric–electromagnetic energy harvester having multiple mechanical degrees-of-freedom. This multimodal hybrid energy harvester (MHEH) has a unique design, which helps it to achieve multiple close resonant modes of vibration in a certain frequency range. Using a low-spring-stiffness material (polyacrylate) as a substrate assists MHEH in reducing the higher resonant frequencies into a low frequency range. The two combined conversion mechanisms (piezoelectric–electromagnetic) are exploited to obtain higher output power from low input accelerations at ambient vibrations. The finite element method simulation model is employed to predict and optimize the mode shapes of the proposed MHEH for different vibration modes. The simulation and experimental result imply that the proposed MHEH can operate at four resonant modes of vibration in the range of 12–22 Hz, which are concentrated around 12, 15, 17, and 22 Hz. An MHEH prototype is fabricated, where four lead-zirconate-titanate elements are used as piezoelectric materials, and NdFeB magnets with conductive coils are used as electromagnetic parts in the same system. Here, a single piezoelectric generator can produce a maximum of 250.23 µW of power across an optimum load of 90 KΩ at the 3rd resonant mode (17 Hz) under 0.4 g (3.92 ms−2) acceleration. On the other hand, a single electromagnetic generator can deliver a maximum power of 244.17 µW to a 10 Ω optimum load under the same conditions. Meanwhile, all eight generators of the MHEH operate simultaneously at their respective resonant frequencies.

A 2DOF hybrid energy harvester based on combined piezoelectric and electromagnetic conversion mechanisms

This paper presents a two-degree-of-freedom (2DOF) hybrid piezoelectric-electromagnetic energy harvester (P-EMEH). Such a 2DOF system is designed to achieve two close resonant frequencies. The combined piezoelectric-electromagnetic conversion mechanism is exploited to further improve the total power output of the system in comparison to a stand-alone piezoelectric or electromagnetic conversion mechanism. First, a mathematical model for the 2DOF hybrid P-EMEH is established. Subsequently, the maximal power output of the 2DOF hybrid P-EMEH is compared both experimentally and theoretically with those from the 1DOF piezoelectric energy harvester (PEH), 1DOF electromagnetic energy harvester (EMEH), 2DOF PEH, and 2DOF EMEH. Based on the validated mathematical model, the effect of the effective electromechanical coupling coefficients (EMCC) on the maximal power outputs from various harvester configurations is analyzed. The results indicate that for the 2DOF hybrid P-EMEH, although the increase of the power output from one electromechanical transducer will lead to the decrease of the power output from the other, the overall performance of the system is improved in weak and medium coupling regimes by increasing electromechanical coupling. In weak and medium coupling scenarios, the hybrid energy harvester configuration is advantageous over conventional 1DOF or 2DOF harvester configurations with a stand-alone conversion mechanism.

Coupling effect analysis for hybrid piezoelectric and electromagnetic energy harvesting from random vibrations

Through establishing the electroelastic model of hybrid piezoelectric(PE) and electromagnetic(EM) energy harvesting from random vibrations, normalized expressions of mean amplitude, voltage, current, power and their spectral density (SD) are derived, and effects of electromechanical coupling strength on harvester’s performances are studied by numerical calculation and experimental test. It is found that the stronger coupling effect, the smaller amplitude and working space required, and the bigger mean voltage, current and power output until up to their maximums. Furthermore, variation extent of mean voltage, current and power with the PE and EM load increasing varies with the coupling strength. Besides, coupling strength changes the SD distributing in frequency domain. In the weak coupling, maximal SD of voltage, current and power are at the natural frequency of harvester. However, with the coupling effect strengthening, the frequency corresponding to peak spectral density is bigger than the natural frequency, and the 3dB bandwidth of harvester is much larger accordingly; moreover, the bandwidth decreases with EM load increasing while it rises firstly and fall later with PE load increasing, which reaches the maximum at the optimal load. The analysis results can provide certain criteria for hybrid piezoelectric-electromagnetic energy harvester design.

A new energy harvester using a piezoelectric and suspension electromagnetic mechanism

This study presents a new design of a piezoelectric-electromagnetic energy harvester to enlarge the frequency bandwidth and obtain a larger energy output. This harvester consists of a primary piezoelectric energy harvesting device, in which a suspension electromagnetic component is added. A coupling mathematical model of the two independent energy harvesting techniques was established. Numerical results show that the piezoelectric-electromagnetic energy harvester has three times the bandwidth and higher power output in comparison with the corresponding stand-alone, single harvesting mode devices. The finite element models of the piezoelectric and electromagnetic systems were developed, respectively. A finite element analysis was performed. Experiments were carried out to verify the validity of the numerical simulation and the finite element results. It shows that the power output and the peak frequency obtained from the numerical analysis and the finite element simulation are in good agreement with the experimental results. This study provides a promising method to broaden the frequency bandwidth and increase the energy harvesting power output for energy harvesters.