Improved Flow-Induced Vibration Energy Harvester by Using Magnetic Force: An Experimental Study

Energy harvesting induced from flowing fluids (e.g., air and water flows) is a well-known process, which can be regarded as a sustainable and renewable energy source. In addition to traditional high-efficiency devices (e.g., turbines and watermills), the micro-power extracting technologies based on the flow-induced vibration (FIV) effect have sparked great concerns by virtue of their prospective applications as a self-power source for the microelectronic devices in recent years. This article aims to conduct a comprehensive review for the FIV working principle and their potential applications for energy harvesting. First, various classifications of the FIV effect for energy harvesting are briefly introduced, such as vortex-induced vibration (VIV), galloping, flutter, and wake-induced vibration (WIV). Next, the development of FIV energy harvesting techniques is reviewed to discuss the research works in the past three years. The application of hybrid FIV energy harvesting techniques that can enhance the harvesting performance is also presented. Furthermore, the nonlinear designs of FIV-based energy harvesters are reported in this study, e.g., multi-stability and limit-cycle oscillation (LCO) phenomena. Moreover, advanced FIV-based energy harvesting studies for fluid engineering applications are briefly mentioned. Finally, conclusions and future outlook are summarized.

A piezoelectric vibration energy harvester is designed to generate electricity under the weight of passing crowds. The piezoelectric beam buckles to a controlled extent when the device is stepped on. The device is a seven bar mechanism. The upper and lower bars as well as the lateral links are rigid. The middle horizontal beam is a bimorph piezoelectric beam. Damages to the piezoelectric beam are avoided by constraining its axial deformation. This constrain is implemented by limiting squeezing of the mechanism. When a person moves over the mechanism or steps off the devices it causes the bimorph to buckle or return to the unbuckled condition. The transitions result in vibrations of the piezoelectric beam and thus generate energy. In this paper, the energy harvester is analytically modeled. The electro-mechanical coupling and the geometric nonlinearities have been included in the model for the piezoelectric beam. The design criteria for the device are discussed. It is demonstrated that the device can be realized with commonly used piezoelectric patches and can generate hundreds of milliwatts of power. A three part beam is also investigated. The effect of design parameters on the generated power and required tolerances are illustrated. The proposed device could be implemented in the sidewalks producing energy from the weight of people passing over it. Other possible applications are portable smart phones chargers and shoe hill energy harvesting. Dance floor of a club is another applicable example for using this harvester. The main advantage of using horizontal configuration instead of a vertical arrangement is the ease of placement in the pavements.

Vibrational energy harvesters, also referred to as MEMS (Micro-Electro-Mechanical Systems) piezoelectric energy harvesters, have garnered significant attention for their potential to power wireless sensor networks and low-power electronics without external power sources. Piezoelectric materials, due to their high energy conversion efficiency and seamless integration into microsystems, are widely utilized in such designs. In this study, we simulate MEMS piezoelectric energy harvesters using PZT (lead zirconate titanate) material, each constructed with a silicon core layer and PZT piezoelectric layers. The simulations, conducted using COMSOL Multiphysics, analyze the performance of cantilever-shaped harvesters under identical boundary conditions, including solid mechanics, electrostatics, and an electric circuit with a 10 kΩ resistive load. The results show that natural frequencies range from 100 Hz to 500 Hz depending on the cantilever shape, with the generated voltage varying between 1.2 V and 3.5 V and corresponding power outputs ranging from 0.2 μW to 1.5 μW. These variations highlight the influence of cantilever geometry on energy harvesting efficiency. The study also identifies specific advantages, such as higher power density and tunable frequency ranges, making these harvesters suitable for powering remote sensing devices and microscale electronics. By quantifying performance metrics and demonstrating shape-dependent benefits, this research provides valuable insights into the design and optimization of MEMS piezoelectric harvesters for diverse applications.Keywords: Piezoelectric vibration energy harvesters, COMSOL simulation, MEMS vibrational energy harvesters, bimorph design.

Similarity and duality of electromagnetic and piezoelectric vibration energy harvesters

Vibration energy harvesters (VEHs) can transform ambient vibration energy to electricity and have been widely investigated as promising self-powered devices for wireless sensor networks, wearable sensors, and applications of a micro-electro-mechanical system (MEMS). However, the ambient vibration is always too weak to hinder the high energy conversion efficiency. In this paper, the integrated frame composed of piezoelectric beams and mechanical amplifiers is proposed to improve the energy conversion efficiency of a VEH. First, the initial structures of a piezoelectric frame (PF) and an amplification frame (AF) are designed. The dynamic model is then established to analyze the influence of key structural parameters on the mechanical amplification factor. Finite element simulation is conducted to study the energy harvesting performance, where the stiffness characteristics and power output in the cases of series and parallel load resistance are discussed in detail. Furthermore, piezoelectric beams with variable cross-sections are introduced to optimize and improve the energy harvesting efficiency. Advantages of the PF with the AF are illustrated by comparison with conventional piezoelectric cantilever beams. The results show that the proposed integrated VEH has a good mechanical amplification capability and is more suitable for low-frequency vibration conditions.

Vibration energy harvesting using the piezoelectric effect has recently attracted significant attention from scholars. The main concern in the research of piezoelectric vibration energy harvesters is to improve the operating bandwidth and output power in low-frequency vibration environments with random and time-varying nature. A novel piezoelectric vibration energy harvester (PVEH) with three parallel cantilevers and repulsive magnet pair structures is proposed in this work to achieve the above goal. The proposed PVEH has the potential to take full advantage of the synergistic effect of the multi-frequency and magnetic nonlinear performance enhancement techniques. The characteristics of the harvester are systematically studied by theoretical modeling, simulation, and experiments. The influence of the critical parameters (i.e. the tip mass of the inner beam, the tip mass of the outer beam, and the magnet spacing) on the output performance of the PVEH is discussed and optimized in detail, and then the internal mechanism of the proposed energy harvesting method based on multi-frequency and magnetic cooperation is revealed. The results show that the improvement rate of the output power of the fabricated prototype under the condition of first-order and second-order operating frequency reaches 23.35% and 38.10%, respectively, compared with the non-magnetic structure. Finally, the optimal configuration of the harvester ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> =6.70 g, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> =5.00 g, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> =22 mm) obtains a maximum half-power bandwidth of 1.052 Hz and a maximum output power of 2.80 mW under 0.2g with 0.155 MΩ load resistance. The proposed energy harvesting system is expected to be a promising alternative to efficient vibration energy harvesters.

Compact reliable structure and strong electromechanical coupling are hot pursuits in piezoelectric vibration energy harvester (PVEH) design. PVEH with a static arc stopper makes piezoelectric stress uniformly distributed and widens the frequency band by collision but wastes space. This Article proposes a hinged PVEH with two arc mass stoppers (AS-H-PVEH). Two arc stoppers as movable masses increase the vibration energy and the effective electromechanical coupling coefficient to achieve strong electromechanical coupling. AS-H-PVEH generates a 4.1 mW power output at 11.6-12.0 Hz and 0.2 g. AS-H-PVEH sustains 4 g acceleration vibration for 10 min without attenuation. To offset the resonance frequency increase caused by arc contact, we discuss the magnetic coupling, and axial force effects are discussed. The design of the arc stopper radius, nonlinear electromechanical coupling model, and system parameter identification method are presented. The displacement varied mechanical quality factor and effective electromechanical coupling coefficient are considered in the modified model for the first time. The model obtained good agreement under experiments. The power generation and driven wireless sensor performance of AS-H-PVEH was verified. This research has important theoretical and application value for the performance optimization of PVEH with an arc stopper.

In the field of rail transport and aerospace field, vibration energy harvesting is inevitably subjected to coupled excitations, including train wheel–track interaction induced friction heat and forced vibration, periodic thermal radiation, and vibration excitation. This paper investigates a coupled thermo-electric-elastic piezoelectric vibration energy harvester with axial movement under external heat flux and mechanical force load. The coupled forced vibration equation, coupled electric equation, and coupled thermoelastic heat conduction equation are derived and solved by Green's function theory. To analyze the effect of excitations on the response characteristics, the decoupled method is utilized to solve the coupled multi-field equations and obtain the displacement, electric, and temperature distribution closed-form solutions. The displacement coupling effect induced temperature distribution and the thermo-electric coupling effect triggered displacement are respectively decoupled and analyzed. The obtained closed-form temperature distribution and displacement solutions are verified by the finite element method. To further verify the obtained solutions, a numerical method is conducted by decoupling the coupled multi-field equations and comparing them with prior solutions. Additionally, the different height-to-length ratios, axially moving speeds, and external force load are analyzed in detail. The results indicate that the displacement, temperature distribution, and output voltage vary with external conditions due to the coupled multi-field effect. Overall, this work investigates the thermo-electric-elastic coupling effect on the axially moving piezoelectric energy harvesting, which is beneficial to promote theoretical investigations of the coupled multi-field energy harvesting system and accelerate the practical applications in the aerospace field.

Modeling and design of V-shaped piezoelectric vibration energy harvester with stopper for low-frequency broadband and shock excitation

In order to reduce the natural frequency of the piezoelectric vibration energy harvester, improve performance of the piezoelectric vibration energy harvester, and meet the requirements of energy acquisition in the low-frequency vibration environment, a variable-section circular piezoelectric vibration energy harvester is presented. The dynamic model and electromechanical coupling model of variable-section circular piezoelectric vibration energy harvester are established. The main factors affecting the output performance of piezoelectric vibration energy harvester are analyzed. The structure parameters of piezoelectric vibration energy harvester are optimized by orthogonal experiment. An experimental platform is built to test output voltage and output power of piezoelectric vibration energy harvester. The experimental results show that when the number of energy harvester is 4 and the external load is 180KΩ, the parallel output power can reach 0.213mW, which can meet the requirements of micro-power device power supply.

Flow-induced vibration in nuclear reactors: A review

Nonlinear vibration energy harvester: Design and oscillating stability analyses

A new class of vibration energy harvester based on magnetostrictive material (MsM),Metglas 2605SC, is designed, developed and tested. It contains two submodules: an MsMharvesting device and an energy harvesting circuit. Compared to piezoelectric materials,the Metglas 2605SC offers advantages including higher energy conversion efficiency, longerlife cycles, lack of depolarization and higher flexibility to survive in strong ambientvibrations. To enhance the energy conversion efficiency and alleviate the need of a biasmagnetic field, Metglas ribbons are transversely annealed by a strong magnetic fieldalong their width direction. To analyze the MsM harvesting device a generalizedelectromechanical circuit model is derived from Hamilton’s principle in conjunction withthe normal mode superposition method based on Euler–Bernoulli beam theory. The MsMharvesting device is equivalent to an electromechanical gyrator in series with an inductor.In addition, the proposed model can be readily extended to a more practical case of acantilever beam element with a tip mass. The energy harvesting circuit, whichinterfaces with a wireless sensor and accumulates the harvested energy into anultracapacitor, is designed on a printed circuit board (PCB) with plane dimension25 mm × 35 mm. It mainly consists of a voltage quadrupler, a 3 F ultracapacitor and a smartregulator. The output DC voltage from the PCB can be adjusted within 2.0–5.5 V. Inexperiments, the maximum output power and power density on the resistor can reach200 µW and 900 µW cm−3, respectively, at a low frequency of 58 Hz. For a working prototype undera vibration with resonance frequency of 1.1 kHz and peak acceleration of8.06 m s−2 (0.82 g), the average power and power density during charging the ultracapacitor can achieve576 µW and 606 µW cm−3, respectively, which compete favorably with piezoelectric vibration energy harvesters.

State of art: Piezoelectric Vibration Energy Harvesters

Zinc oxide (ZnO) thin film piezoelectric microelectromechanical systems (MEMS) based vibration energy harvesters with two different designs are presented. These harvesters consist of a silicon cantilever, a silicon proof mass, and a ZnO piezoelectric layer. Design I has a large ZnO piezoelectric element and Design II has two smaller and equally sized ZnO piezoelectric elements; however, the total area of ZnO thin film in two designs is equal. The ZnO thin film is deposited by means of radio-frequency magnetron sputtering method and is characterized by means of XRD and SEM techniques. These ZnO energy harvesters are fabricated by using MEMS micromachining. The natural frequencies of the fabricated ZnO energy harvesters are simulated and tested. The test results show that these two energy harvesters with different designs have almost the same natural frequency. Then, the output performance of different ZnO energy harvesters is tested in detail. The effects of series connection and parallel connection of two ZnO elements on the load voltage and power are also analyzed. The experimental results show that the energy harvester with two ZnO piezoelectric elements in parallel connection in Design II has higher load voltage and higher load power than the fabricated energy harvesters with other designs. Its load voltage is 2.06 V under load resistance of 1 MΩ and its maximal load power is 1.25 μW under load resistance of 0.6 MΩ, when it is excited by an external vibration with frequency of 1300.1 Hz and acceleration of 10 m/s(2). By contrast, the load voltage of the energy harvester of Design I is 1.77 V under 1 MΩ resistance and its maximal load power is 0.98 μW under 0.38 MΩ load resistance when it is excited by the same vibration.