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Railway traffic plays a pivotal role within the current transportation system, with ensuring its safety being of paramount importance. Real-time monitoring of train track health through sensor technology has emerged as a significant approach for achieving this objective. However, a persistent challenge lies in providing cost-effective and stable power to sensors in remote areas. This paper proposes the utilization of a novel piezoelectric stack energy harvester in railway systems to address this issue. The substantial and consistent vibration energy produced by railway operations makes it an ideal source for energy harvesting, unaffected by environmental conditions. Through simulation analysis and experimental verification, this study explores the impact of load size, load frequency, and external resistance on the energy harvesting efficiency of the proposed piezoelectric stack energy harvester. The results indicate that the output power of the energy harvester increases with the load size. Furthermore, the frequency significantly influences the energy capture efficiency when below 8 Hz, with minimal impact on frequencies above 8 Hz. Interestingly, the load dramatically affects the energy capture efficiency, even at higher frequencies. With the external resistance set to 250 kΩ, the harvester achieves a maximum output power of 42.76 mW. [ABSTRACT FROM AUTHOR]

Batteries with a limited lifespan have gradually failed to meet the development needs of some low-power electronic products. Harvesting wind energy to power the above devices has been a promising way. Facing the time-varying characteristics of wind direction and velocity in the natural environment, an efficient orientation-adaptive energy harvester (OAEH) based on the piezoelectric effect is proposed. An experimental test system is established to probe into the output and adaptive performances of the OAEH. The experimental results indicate that improving the inertia of the tray can abate the initial wind velocity and enhance the output power to a certain extent. The relative deviation (γ) of power integration areas at different inclinations is less than 3%. The harvester has 364.86% enhancement in average power integration area comparing that with the fixed shaft. Besides, the OAEH can drive a monitoring device with a display screen and integrated sensors, which can be utilized to monitor the condition of the bridge, flyover, and so on. [ABSTRACT FROM AUTHOR]

As one of the most important modes of transportation, the safety of running trains and railway tracks is significant. It is essential to power sensors that detect and track health in remote areas. The vibration energy of the track structure is enormous, stable, and not limited by weather factors such as the sun and wind. A new type of arch beam piezoelectric stack energy harvester for railway systems is studied in this paper. Through simulation analyses and experimental verification of the energy harvester, the influences of external resistance, load, pre-stress, and load frequency on the energy harvesting performance of the piezoelectric energy harvester are discussed. When the frequency is less than 6 Hz, the energy capture efficiency is greatly affected by the frequency. When the frequency exceeds 6 Hz, the frequency has little effect and the load dramatically affects the energy capture efficiency. The pre-stress has little effect on the energy capture efficiency, but there is an optimal value at 4.5 kN. The energy harvester has an output power of 193 mW, a weight of 912 g, and the energy density can reach 211.8 μW/g. These results can provide a reference for subsequent experiments in the actual environment. [ABSTRACT FROM AUTHOR]

Industry 4.0 realizes intelligent interconnection through the sensor group of the Internet of Things. A key challenge is to achieve the self-powering of sensors and stable operation of precision instruments. This paper introduces a dual-functional structure (VIPEH) integrating energy harvesting (EH) and vibration isolation (VI) based on the quasi-zero stiffness (QZS) piezoelectric mechanism. The paper analyzes the nonlinear statics of piezoelectric flexible beams under large deformations and conducts parametric analysis. A nonlinear dynamic model with electromechanical coupling was developed to investigate the impact of mechanical and electrical parameters on the system's dynamic bifurcation behavior, EH, and VI performance. Finally, an experimental setup is created to evaluate the VIPEH's characteristics. Sweep frequency excitation experiments demonstrate that the initial isolation frequency of VIPEH is lower than 1.4 Hz. The important thing is that VIPEH can still power the sensor based on the isolation frequency, and the output power of a single piezoelectric material can reach 3.19 mW. This not only enables the isolation of low-frequency vibrations but also presents a highly promising application for achieving self-powering in sensor clusters within the context of Industry 4.0 and the IoTs. • VIPEH based on quasi-zero stiffness piezoelectric mechanism is proposed. • VIPEH achieves energy harvesting while isolating low-frequency vibrations. • The output power can reach 3.19 mW. • The initial vibration isolation frequency of VIPEH is less than 1.4 Hz. [ABSTRACT FROM AUTHOR]

• Experiments verified the performance of WMPEH with different structural parameters. • Wake excitation and magnetic coupling are used for underwater energy harvesting. • The wake excitation and magnetic coupling can enhance harvesting performance. • Reducing the fixing column diameter can increase the output voltage. • Increasing the vibrating column diameter can enhance performance. • Increasing the vibrating column mass can improve performance. [Display omitted] This paper proposes a wake-excited magnetically coupled piezoelectric energy harvester (WMPEH) to realize the self-powered function of microelectronic devices in a fluid environment. The WMPEH consists of a fixed column, a vibrating column, magnets, and a piezoelectric composite beam. A series of water tunnel experiments are conducted to prove the usefulness of wake excitation and magnetic coupling, and how it positively or negatively affects the harvester's efficacy. Different fixed and vibrating column diameters and the distance between the two columns affect the performance of the WMPEH. The influence of the wake excitation force generated by the fixed columns with diameters of 5 mm, 10 mm and 15 mm on the vibrating column is analyzed respectively in the experiment. The vibrating column diameter is D , and four different distances are considered, namely 2 D , 3 D , 4 D , and 5 D. The results show that the maximum output voltage of WMPEH is increased by 1.96 and 1.34 times, respectively, compared with that of magnetically coupled piezoelectric energy harvester (MPEH) and conventional piezoelectric energy harvester (PEH). Furthermore, increasing the fixed column diameter leads to a decrease in the output voltage of WMPEH in the case of the same vibrating column diameter. Increasing the diameter and mass of the vibrating column for a specific fixed column diameter can enhance the harvester's performance. The maximum output voltage density of the WMPEH is 75.56 V/cm3 when the vibrating column diameter, the fixed column diameter and the distance between the two columns are 20 mm, 5 mm, and 2 D , respectively. This proposed design can provide the groundwork to promote the performance of the conventional PEH, further enabling the realization of underwater self-powered systems. [ABSTRACT FROM AUTHOR]

• The proposed device contains magnetic coupling and vortex-induced vibrations. • The structural parameters of vibrating column affect the efficiency. • The magnetic repulsion system is suitable for low-speed water flow environment. • The magnetic attractive system is suitable for high-speed water flow environment. The rapid development of the fifth-generation mobile networks (5G) and the Internet of Things (IoT) is inseparable from a large number of miniature, low-cost, and low-power sensors and actuators. To solve the problem of self-powered underwater wireless sensor nodes (WSNs), this paper proposes a magnetically coupled piezoelectric energy harvester (MPEH) based on fluid-induced vibration (FIV) to achieve high-efficiency performance in low-velocity water environments. The results show that compared with the non-magnetic PEH, the initial vibration velocity, velocity bandwidth, and maximum output voltage of the magnetic attraction coupling piezoelectric energy harvester (MAPEH) are increased by 18.42%, 41.38%, and 5.79% respectively. Besides, it is also shown that the vertical distance between the magnets, the diameter, and the mass of the vibrating column have a significant effect on the vibration characteristics, water velocity bandwidth, and performance of the magnetic repulsion coupled piezoelectric energy harvester (MRPEH). The initial vibration velocity of the MRPEH is reduced by 42.1%, and when the water speed is 0.2 m/s, its output voltage is 12.21 times that of the classical configuration. This proposed structure can provide a reference for the optimization of underwater FIV-based PEH, and also lay a foundation for further interconnection of underwater self-powered sensors. [ABSTRACT FROM AUTHOR]

• When the flow rate is high, the change of the L and H has a great influence on the of the PEH array. • The single-row parallel-arranged array (PEH-2P and PEH-3P) can improve the system's initial vibration velocity and half-frequency bandwidth. • The single-row series-arranged array (PEH-2S and PEH-3S) can increase the maximum energy harvesting power. • The energy harvesting capacity of nine-vibrators square array is 102.4% higher than the reference value, and the initial vibration velocity is 25.95% lower than the reference value. This paper mainly uses simulation and experimental methods to analyze the output characteristics of different piezoelectric energy harvester (PEH) arrays based on flow-induced vibration, which is mainly used in low-velocity water in a natural environment. Each PEH consists of a piezoelectric beam and an interference cylinder. The PEH arrays presented in this paper include the double-vibrators parallel array (PEH-2P), double-vibrators serial array (PEH-2S), three-vibrators parallel array (PEH-3P), three-vibrators serial array (PEH-3S), and nine-vibrators square array (PEH-9). Prototypes of the different PEH arrays are fabricated and experiments are conducted to explore the energy harvesting capacity, the maximum energy harvesting power, initial vibration velocity and half-power bandwidth of the different PEH arrays. The experimental results demonstrated that the PEH-2P and the PEH-3P can improve the system's initial vibration velocity and half-power bandwidth, but the maximum energy harvesting power of the PEH array is relatively not good. The PEH-2S and the PEH-3S can increase the maximum energy harvesting power of the PEH array, but the initial vibration velocity and half-power bandwidth of the PEH array are relatively not good. The average value of energy harvesting capacity of the PEH-9 is the largest, which is 102.4% higher than the reference value, and the initial vibration velocity of the PEH-9 is the lowest, which is 25.95% lower than the reference value. This work provides a comprehensive experimental guideline for further designing an efficient PEH array used in the low-speed water environment. [ABSTRACT FROM AUTHOR]

• A bidirectional plucking energy harvester with an orthogonal oscillator is proposed. • Piezoelectric oscillator is excited by bidirectional magnetic component force. • Exploring bending and torsion vibrations of the orthogonal piezoelectric oscillator. • BP-RPEH has multiple resonance regions. • The charge rate could reach 0.39 V/s at 300 rpm. One key challenge of the energy harvesting technology lies in how to fully utilize external environmental excitation to collect ambient energy and convert it into electrical energy efficiently. To address this challenge, this work proposed a bidirectional non-contact plucking rotary piezoelectric energy harvester, based on the spatial distribution characteristics of magnetism. This work was initiated by establishing a mathematical model for the rotating magnetic field and calculating the magnitude of the magnetic forces. Numerical findings indicated that the quantity of rotating magnets had an impact on the magnitude and distribution of these magnetic forces. Leveraging the distinctive attributes of the rotating magnetic forces, this work introduced an orthogonal piezo-oscillator, designed to concurrently respond to magnetic forces along two orthogonal directions. Subsequently, this work conducted experimental research on the piezoelectric oscillators. The experimental results indicated that the number of magnets affects the power output bandwidth and position of the effective frequency. A mathematical relationship exists between the resonant frequency, the number of magnets, and the natural frequency. The results demonstrate that the total peak output power of the harvester could reach 3.29mW calculated by RMS voltage at 301 rpm, and the charging rate could reach 0.39 V/s at 300 rpm. [ABSTRACT FROM AUTHOR]

Vibration energy harvesting holds the promise of providing autonomous power for low-power electronic devices. To improve the issue of the limited bandwidth of the piezoelectric energy harvester, this work proposes a novel T-shaped beam bistable piezoelectric energy harvester with a moving magnet. The moving magnet can not only provide nonlinear force to adjust bandwidth, but also increase the number of system resonance peaks, which improves the utilization of the magnet, enhancing the adaptability of the vibration energy harvesting device to the environment. Established a mathematical model and validated it through experiments. Some parameters, such as external resistance, magnet spacing, and spring stiffness, are analyzed by theoretical analysis. The results indicate that, at an acceleration amplitude of 0.3 g and a frequency of 15.7 Hz, the peak output power of the main support beam is 2.36 mW. Similarly, at an acceleration amplitude of 0.3 g and a frequency of 15.6 Hz, the peak output power of the parasitic cantilever beam is 0.56 mW, demonstrating its potential to power low-power electronic components. The moving magnet provides an additional resonance peak for the harvester, offering a new method for the design of broadband magnetic nonlinear piezoelectric energy harvesters in the near future. • A novel T-shaped beam bistable piezoelectric energy harvester with a moving magnet (TBPEH) is proposed. • The moving magnet can not only provide nonlinear force to adjust bandwidth but also increase the number of system resonance peaks. • The coupling of the moving magnet and the T-shaped beam results in the generation of three voltage peaks, thereby expanding the frequency bandwidth. • The stiffness of the spring and the spacing between magnets influence both the size and position of the resonance peaks excited by the moving magnet. • In laboratory testing, the TBPEH demonstrated the capability to illuminate a light strip comprising 23 LEDs. [ABSTRACT FROM AUTHOR]