Environmental Vibration Energy Research Articles

Vacancy defect and piezoelectric field assisted photocatalytic performance of BiO(Cl1/3Br1/3I1/3)x for the degradation of organic pollutants

Semiconductor photocatalysts have been widely researched in wastewater treatment of organic dyes, among which bismuth halide semiconductors have shown great application prospects due to their unique layered structure and diverse micromorphology. As for photocatalysis, high concentration of photo-generated carriers and their effective separation are considered to be the key to obtain excellent photocatalytic performance. In view of the common issues of high bandgap energy and low carrier separation rate in bismuth halide, in this paper, the BiO(Cl1/3Br1/3I1/3)x catalysts with different proportions of Bi3+ and (Cl1/3Br1/3I1/3)- were designed and synthesized by hydrothermal method, through constructing hybrid energy levels and thus accomplishing by multi-halogen doping to widen the light absorption range. For another, the efficient separation of electrons and holes was achieved in BiO(Cl1/3Br1/3I1/3)x in virtue of a built-in field stemmed from the intrinsic piezoelectric effect, and band tilting. Meanwhile, more active sites were induced by Vo•• and VBiʹʹʹ due to the directional impact of the built-in field. Ultimately, BiO(Cl1/3Br1/3I1/3)5/7 demonstrated the optimum catalytic performance under the combined light irradiation and ultrasonic vibration, with the degradation efficiency of MB reaching 91.28% in 60 min and the k of 0.0360 min-1, and 97.44% degradation efficiency of Rh B within 18 min and the k of 0.1565 min-1 together with excellent cycling stability. The prepared BiO(Cl1/3Br1/3I1/3)5/7 catalyst has a huge application potential for the degradation of wastewater, taking full advantage of environmental vibration energy and light energy.

Electromagnetic Energy Harvester Based on Bidirectional Vibration to Unidirectional Rotation Conversion for Environmental Low-Frequency Vibration Energy Harvesting

Electromagnetic Energy Harvester Based on Bidirectional Vibration to Unidirectional Rotation Conversion for Environmental Low-Frequency Vibration Energy Harvesting

Archery-inspired catapult mechanism with controllable energy release for efficient ultralow-frequency energy harvesting

Ultralow-frequency (< 5 Hz) vibration energy is abundant in the environment, but its efficient utilization is still highly difficult due to the frequency-mismatch problem encountered by the vibratory energy harvesters and the slow rotation of rotary energy harvesters (REHs). To solve this issue, we developed herein a high-performance REH (named AI-REH) based on the archery-inspired catapult mechanism, which breaks through the limitation of the slow vibration source to the REH rotation speed through an innovative magnetic coupling strategy between the vibration source and the AI-REH. By employing an accumulator spring as the energy reservoir, the AI-REH also realizes the accumulation and controllable release of ultralow-frequency vibration energy via the interaction between the magnetic coupling and the elastic force. High-speed kinetic energy can thus be acquired for efficiently powering the rotor, contributing to significantly accelerated rotor speeds and enhanced electric outputs. Compared with the traditional counterpart, the AI-REH achieves 3.6-fold increase in rotor speed, 3.5-fold increase in output voltage and 3.0-fold increase in output power under an ultralow-frequency vibration of 4 Hz. A power backpack was also constructed and tested, which demonstrates the superior capability of the AI-REH in harnessing real ultralow-frequency amplitude-varying vibration energy. The AI-REH proposed in this study provides a new pathway for efficiently exploiting environmental ultralow-frequency vibration energy toward self-sufficient systems with various purposes.

Self-Powered Wireless Temperature and Vibration Monitoring System by Weak Vibrational Energy for Industrial Internet of Things.

Developing self-powered smart wireless sensor networks by harvesting industrial environmental weak vibration energy remains a challenge and an impending need for enabling the widespread rollout of the industrial internet of things (IIoT). This work reports a self-powered wireless temperature and vibration monitoring system (WTVMS) based on a vibrational triboelectric nanogenerator (V-TENG) and a piezoelectric nanogenerator (PENG) for weak vibration energy collection and information sensing. Therein, the V-TENG can scavenge weak vibration energy down to 80 μm to power the system through a power management module, while the PENG is able to supply the frequency signal to the system by a comparison circuit. In an industrial vibration environment where the vibration frequency and amplitude are 20 Hz and 100 μm, respectively, the WTVMS can upload temperature and frequency information on the equipment to the cloud in combination with the narrowband IoT technology to realize real-time information monitoring. Furthermore, the WTVMS can work continuously for more than 2 months, during which the V-TENG can operate up to 100 million cycles, achieving ultrahigh stability and durability. By integrating weak vibration energy harvesting and active sensing technology, the WTVMS can be used for real-time online monitoring and early fault diagnosis of vibration equipment, which has great application prospects in industrial production, machinery manufacturing, traffic transportation, and intelligent IIoT.

A Hybrid Piezoelectric and Electromagnetic Broadband Harvester with Double Cantilever Beams

Vibration-energy harvesting is an effective strategy for replacing batteries and provides a long-term power supply to microelectronic devices. Harvesting vibration energy from human motions has attracted research attention in recent years. Here, a novel low-frequency hybrid piezoelectric and electromagnetic broadband harvester is proposed. Two parallel piezoelectric cantilever beams support the harvester and capture environmental vibration energy based on the piezoelectric effect. A permanent magnet is connected by springs to the two beams, and a fixed coil surrounds the moving permanent magnet, enabling energy conversion via the electromagnetic effect and the proof mass. The parameters influencing the output power of the harvester are optimized numerically to boost the harvester's performance. The output power of the proposed hybrid harvester is compared with that of a piezoelectric harvester and an electromagnetic harvester. The simulation results show that the output power is significantly higher for the hybrid harvester than for the piezoelectric and electromagnetic harvesters, and the bandwidth is broader owing to the double cantilevers. An experiment is conducted using a prototype of the hybrid harvester to evaluate its output power. The results show multiple resonant peaks, an extended bandwidth, and a maximum power of 6.28 mW. In contrast, the maximum harvested power of the piezoelectric harvester is only 5.15 mW at 9.6 Hz.

Strongly enhanced piezocatalysis of BiFeO3/ZnO heterostructure nanomaterials

BiFeO3/ZnO heterostructures, with a strongly enhanced piezocatalytic dye decomposition performance, offer a promising option to treat wastewater through collecting environmental vibration energy.

A high-efficiency curved panel energy harvester featured by reduced stress concentration

Currently, most energy harvester designs focus on improving the efficiency of harvesting, with less attention paid to fatigue damage. In this study, a novel piezoelectric energy harvester with a curved panel is proposed. The curved panel of the harvester exhibits a bistable behavior during the deformation process so that the vibration energy can be efficiently converted into electricity. Moreover, the fatigue damage caused by stress concentration can be significantly alleviated by the real-time stress change of each curved panel. To optimize the power generation efficiency of the harvester, the design considered the influence of a number of key parameters, including panel thicknesses, mass block, excitation frequency and load resistance. Experimental results show that the maximum peak-to-peak and root-mean-square voltages under open-circuit conditions can respectively reach upmost 24.8 V and 5.66 V for the harvester with a piezoelectric film in a dimension of 30 mm × 12.1 mm × 0.28 μm, and the maximum power reach 129.4 μW. The proposed harvester has great potential for power generation and application, which provides a reference for collecting vibration energy in environment.

Environmental vibration energy collection technology based on piezoelectric and electromagnetic model

In this paper, the vibration model of the piezoelectric cantilever, the piezoelectric and electromagnetic output model are established. The simulation analysis of the cantilever vibration is performed using Comsol Multiphysics software. The effects of structural parameters, including cantilever length, cantilever thickness, piezoelectric layer length, piezoelectric layer thickness, coil size and position, on the resonance frequency and output voltage were analyzed. A cantilever vibration energy collection device is designed. The feasibility and accuracy of theoretical analysis were verified through the experiment, and the resonance frequency and the output voltage of the experiment basically agree with the theoretical calculation value.

Temperature-dependent vibration energy harvesting performance of polyimide/(Na,K)NbO3 piezoelectric composites

A composite structure of piezoelectric particles and soft polymer composite material is one of the candidates that converts environmental vibration energy into electrical energy. Presently, expanding the usage of applications is needed in terms of the working environment at harsh temperatures. Polyimide is flexible and temperature-stable polymer. In this research, we report a synthesis of polyimide/(Na,K)NbO3 (PI/NKN) flexible composites. We constructed a setup, where vibration and heat are simultaneously applied to the PI/NKN composites. The frequency and temperature dependence of the output voltage were investigated at room temperature up to 200 °C. Relative permittivity, piezoelectric constant, and output voltage of the PI/NKN showed temperature stability. Flexibility and glass transition temperature of a polymer matrix are important factors. PI/NKN composites are potential energy harvesting materials with flexibility and excellent high-temperature stability.

Vibration Energy Harvesting from the Subwavelength Interface State of a Topological Metamaterial Beam.

Topological metamaterial has been a research hotpot in both physics and engineering due to its unique ability of wave manipulation. The topological interface state, which can efficiently and robustly centralize the elastic wave energy, is promising to attain high-performance energy harvesting. Since most of environmental vibration energy is in low frequency range, the interface state is required to be designed at subwavelength range. To this end, this paper developed a topological metamaterial beam with local resonators and studied its energy-harvesting performance. First, the unit cell of this topological metamaterial beam consists of a host beam with two pairs of parasitic beams with tip mass. Then, the band structure and topological features are determined. It is revealed that by tuning the distance between these two pairs of parasitic beams, band inversion where topological features inverse can be obtained. Then, two sub-chains, their design based on two topologically distinct unit cells, are assembled together with a piezoelectric transducer placed at the conjunction, yielding the locally resonant, topological, metamaterial, beam-based piezoelectric energy harvester. After that, its transmittance property and output power were obtained by using the frequency domain analysis of COMSOL Multiphysics. It is clear that the subwavelength interface state is obtained at the band-folding bandgap. Meanwhile, in the interface state, elastic wave energy is successfully centralized at the conjunction. From the response distribution, it is found that the maximum response takes place on the parasitic beam rather than the host beam. Therefore, the piezoelectric transducer is recommended to be placed on the parasitic beam rather than host beam. Finally, the robustness of the topological interface state and its potential advantages on energy harvesting were studied by introducing a local defect. It is clear that in the interface state, the maximum response is always located at the conjunction regardless of the defect degree and location. In other words, the piezoelectric transducer placed at the conjunction can maintain a stable and high-efficiency output power in the interface state, which makes the whole system very reliable in practical implementation.

Modeling and Optimization Analysis for Base-Excited Magnetostrictive Vibration Harvester

Due to the low vibration frequency and weak vibration energy in natural environment, the vibration energy harvester is faced with the problem of low power and low adaptability and becoming particularly difficult in actual conditions. It is necessary to improve the harvesting capacity and efficiency by optimizing the parameters of the harvester, making full use of the energy of low and unstable atmospheric vibrations. In this paper, a mathematical model is established for the cantilever magnetostrictive vibration harvester under the base excitation, including the mechanical deformation of the composite beam, and the electromagnetic results produced thereof. The mechanical-magneticelectric energy conversion relationship is duly taken into account. The additional weight, coil parameters, external resistance and other parameters of the harvester are optimized and analyzed through numerical simulation. In addition, the theoretical results are analyzed and discussed via comparison with experiments. Finally, the effects of the above factors are assessed, which allows us to obtain the optimal winding length, number of turns of the coil, and optimal tip additional mass. The experiment result shows that the optimized magnetostrictive harvester can output 12.07[Formula: see text]mW power to the external resistor under the condition of 1[Formula: see text]g acceleration mechanical vibration, with normalized power density reaching 40.2[Formula: see text]mW/cm3/g. Moreover, the optimized magnetostrictive harvester can successfully supply power for the LED display screen of the temperature sensor and a low-power thermometer.

A three-degree-of-freedom bistable piezoelectric energy trapping method

The use of piezoelectric energy harvester to convert environmental low-frequency vibration energy into electrical energy has become a research hotspot in the field of new energy. However, the piezoelectric energy harvester developed at present has high natural frequency and narrow energy trapping band, which has become one of the main reasons restricting the application of this technology. To solve this problem, based on the principle of nonlinear three degrees of freedom, this paper proposes a three-degree-of-freedom bistable piezoelectric energy trapping method. Firstly, the three-degree-of-freedom bistable energy capture method is modeled, and the energy capture frequency and nonlinear force of the model are derived; then use COMSOL software to simulate the model. The simulation results prove that this model not only reduces the natural frequency of the piezoelectric energy harvester, but also the introduced nonlinear magnetic force significantly broadens the energy trapping band. Finally, the actual measurement and comparative analysis of the proposed method prove the effectiveness of the proposed method.

A magneto-mechano-electric (MME) energy harvester based on rectangular cymbal structure

In this work, we report a magneto-mechano-electric (MME) energy harvester with a rectangular cymbal structure consisting of a piezoelectric ceramic plate and magnetostrictive alloy (Metglass) foils. The magnetic field induced voltage was then predicted by using finite element analysis. Experimental results show that under a magnetic field excitation of 8 Oe at 180 Hz (resonance frequency), the MME energy harvester can generate a peak-peak output power of 5.7 mW and peak-peak current of 2.3 mA, respectively, for a load resistance of 5.6 kΩ, which allow to drive 10 LEDs lighting directly and stably. Correspondingly, its power density is 5.1 mW cm−3 at Hac =7 Oe, which is comparable with previous reports about traditional cantilever structure MME energy harvester using a piezoelectric single crystal. This work confirms that the MME energy harvester is a promising candidate for powering wireless sensors and other micro-energy smart electronics using the stray magnetic field, or even mechanical vibration energy in environment.

A Comparison of Methods to Measure the Coupling Coefficient of Electromagnetic Vibration Energy Harvesters

Vibration energy harvesters transform environmental vibration energy into usable electrical energy. The transformation is only possible because of a coupling between the mechanical part of the energy harvester and the electric circuit. This paper compares several measurement methods to determine the electromagnetic coupling coefficient. These methods are applied to various implementations of an energy harvester and the results are compared with one another and with simulation data by analyzing the magnetic flux. The average deviation between the measurement methods and the simulation data in our study was 5%. This good agreement validates the methods. Based on this, we recommend determination of the coupling coefficient and the optimum load resistance for maximum power harvesting on the basis of simulations and the open circuit method, because this procedure leads to the shortest measurement times.

Low-frequency and broadband vibration energy harvester driven by mechanical impact based on layer-separated piezoelectric beam

Vibration energy harvesting is to transform the ambient mechanical energy to electricity. How to reduce the resonance frequency and improve the conversion efficiency is very important. In this paper, a layer-separated piezoelectric cantilever beam is proposed for the vibration energy harvester (VEH) for low-frequency and wide-bandwidth operation, which can transform the mechanical impact energy to electric energy. First, the electromechanical coupling equation is obtained by the Euler-Bernoulli beam theory. Based on the average method, the approximate analytical solution is derived and the voltage response is obtained. Furthermore, the physical prototype is fabricated, and the vibration experiment is conducted to validate the theoretical principle. The experimental results show that the maximum power of 0.445 □W of the layer-separated VEH is about 3.11 times higher than that of the non-impact harvester when the excitation acceleration is 0.2 g. The operating frequency bandwidth can be widened by increasing the stiffness of the fundamental layer and decreasing the gap distance of the system. But the increasing of operating frequency bandwidth comes at the cost of reducing peak voltage. The theoretical simulation and the experimental results demonstrate good agreement which indicates that the proposed impact-driving VEH device has advantages for low-frequency and wide-bandwidth. The high performance provides great prospect to scavenge the vibration energy in environment.

The benefits of a magnetically coupled asymmetric monostable dual-cantilever energy harvester under random excitation

Piezoelectric vibration energy harvesting is a promising technique to power wireless sensor networks. This article originally presents a magnetically coupled asymmetric monostable dual-cantilever piezoelectric energy harvester consisting of a generating piezoelectric cantilever beam and an auxiliary cantilever beam. Theoretical and experimental results both verify that the asymmetric harvester has the superior performance compared with the conventional magnetically coupled symmetric bistable dual-cantilever piezoelectric energy harvester, yielding higher voltage output under different magnetic coupling intensities and different power densities of the band-limited Gaussian white noise random excitation. More importantly, the mechanical strain of the asymmetric harvester is much smaller than that of the symmetric harvester, being lower than half of the latter one under strong magnetic coupling. Therefore, due to its higher energy conversion efficiency and better durability, the proposed asymmetric harvester is beneficial for practical environment vibration energy harvesting.

High-efficient synergy of piezocatalysis and photocatalysis in bismuth oxychloride nanomaterial for dye decomposition

In this work, it is found that the hydrothermally-synthesized bismuth oxychloride can behave both the piezocatalysis and photocatalysis for the Rhodamine B dye decomposition. ∼99% decomposition efficiency is achieved after both vibrating and lighting the Rhodamine B dye solution for ∼96 min with the addition of bismuth oxychloride catalyst, while the ∼72% and ∼26% decomposition efficiencies are obtained for only photocatalysis or only piezocatalysis respectively. In bi-catalysis, the mechanical strain produced due to vibration will directly provide an electric field that will increase the separation between the photo-induced electron-hole pairs, yielding to the enhanced decomposition performance of bi-catalysis. There is no significant change in the bi-catalytic performance of bismuth oxychloride nanomaterial observed after being recycled four times. Bismuth oxychloride catalyst is potential for the bi-catalytic decomposition treatment of wastewater through harvesting both the environmental vibration energy and light energy.

Simulation and experiment on bridge-shaped nonlinear piezoelectric vibration energy harvester

There is abundant of vibration energy in environment. Using piezoelectric energy harvesters to power ultra-low power wireless sensors has become a hot topic in recent years. Most piezoelectric energy harvesters have satisfactory output only at one resonant frequency, while once the external excitation frequency deviates from the resonant frequency, the voltage output will drop significantly. Therefore, this paper proposes a bridge-shaped piezoelectric energy harvester to broaden the frequency band for energy harvesting, and the harvester can adaptively adjust the natural frequency of the system to match the external excitation. Based on the two-dimensional nonlinear Euler–Bernoulli beam hypothesis and the Hamilton principle, the distributed-parameter dynamic model of the nonlinear energy harvesting system is set up. By use of variation operator and nondimensionalization, we derive the dimensionless electromechanical coupling equations. With the harmonic balance method, the approximate equations for calculating voltage amplitude and average power are derived. And then the model is numerically solved and analyzed by considering the influence of excitation frequency, excitation amplitude, mass position and load on the output performance of the bridge-type piezoelectric energy harvester. Finally, various comprehensive experiments are performed to verify the results of simulation, and the dynamic effects of the moving mass on the output characteristics are studied. It can be noted that the moving mass can improve the voltage output of the bridge type energy harvester by changing the resonant frequency of the bridge-type piezoelectric energy harvester and impacting the piezoelectric beam. The proposed vibration energy collection device can adaptively tune the resonant frequency and has practical value in engineering.

Effects analysis of bias and excitation conditions on power output of an environmental vibration energy harvesting device using Fe-Ga slice

With the advent of low power VLSI designs and the mass manufacture of CMOS, the power consumption of wireless sensor nodes has been significantly reduced from mW to μW. This opens up a new and interesting research field, that is, the possibility of converting environmental vibration energy to electrical energy for supplying power to the sensors. In this paper, using magnetostrictive materials slice, that is Fe-Ga alloy, a device for harvesting environmental vibration energy is designed and tested. Compared with piezoelectric materials and Terfenal-D alloy, Fe-Ga alloy offers excellent properties for surviving in tough ambient vibration conditions, including higher energy conversion efficiency, longer life cycles, excellent toughness, reduced depolarization and higher flexibility, etc. The designing of vibration energy harvesting process is based on the coupling characteristics of magnetostrictive inverse effect and Faraday electromagnetic induction. The device consists of a Fe-Ga alloy cantilever beam with a magnetostrictive direction throughout the length. It has magnetostrictive inverse effect during vibration and the internal magnetization state will change. A cantilever beam is surrounded by a pickup coil and voltage is induced due to the magnetic field according to Faraday's law. The energy conversion principle among mechanical, magnetic and electric energy is described through a dynamic equation of motion and in conjunction with an electromagnetic conversion equation. The influence law of bias and excitation conditions on output voltage, power and other characteristics of device are investigated in comprehensive experiments. By knowing these influence laws, it is possible to choose an appropriate number of pick up coil for a definite load resistance, to set an appropriate working frequency range, pre-tightening force and pre-magnetized magnetic field such that a maximum power can be harvested. The results derived here can be used as a design guideline for future studies in optimal design and the modeling of vibration energy harvester and force sensor.

Characterization the influences of diodes to piezoelectric energy harvester

ABSTRACTThis study discloses the diode’s influences on the piezoelectric energy harvesting performance. The piezoelectric-based energy harvesting system plays an important role in scavenging environment vibration energy into electrical energy, which can be utilized by low-power electronic devices. With respect to the interface circuit, a full-wave bridge circuit is usually needed to rectify the alternating current (AC) signal into a direct current (DC) signal. The full-wave bridge is composed of four diodes, whose characteristics may influence the harvested power significantly. Therefore, in this paper, the diodes’ properties and influences on the energy harvesting performance are analyzed and presented via simulation and experimental studies. It is found the harvested energy has close relationship with the diode characteristics. For the high source impedance case, diode with low reverse leakage current is favorable. For the low source impedance case, diode with low forward voltage drop is favorable. The corresponding experimental study is carried out via a piezoelectric beam, which shows that the measured harvested power differences can almost be up to 800% for the same test structure.