Energy Harvesting Characteristics Research Articles

Enhancing Energy Harvesting Efficiency of Flapping Wings with Leading-Edge Magnus Effect Cylinder.

According to the Magnus principle, a rotating cylinder experiences a lateral force perpendicular to the incoming flow direction. This phenomenon can be harnessed to boost the lift of an airfoil by positioning a rotating cylinder at the leading edge. In this study, we simulate flapping-wing motion using the sliding mesh technique in a heaving coordinate system to investigate the energy harvesting capabilities of Magnus effect flapping wings (MEFWs) featuring a leading-edge rotating cylinder. Through analysis of the flow field vortex structure and pressure distribution, we explore how control parameters such as gap width, rotational speed ratio, and phase difference of the leading-edge rotating cylinder impact the energy harvesting characteristics of the flapping wing. The results demonstrate that MEFWs effectively mitigate the formation of leading-edge vortices during wing motion. Consequently, this enhances both lift generation and energy harvesting capability. MEFWs with smaller gap widths are less prone to induce the detachment of leading-edge vortices during motion, ensuring a higher peak lift force and an increase in the energy harvesting efficiency. Moreover, higher rotational speed ratios and phase differences, synchronized with wing motion, can prevent leading-edge vortex generation during wing motion. All three control parameters contribute to enhancing the energy harvesting capability of MEFWs within a certain range. At the examined Reynolds number, the optimal parameter values are determined to be a∗ = 0.0005, R = 3, and ϕ0 = 0°.

Realization of multi-functional features with ZnO nanosheets/p-Si based electronic device for energy harvesting and memristive switching

This work investigates and reports on the fabrication of a ZnO nanosheets/p-Si heterojunction energy harvester. The proposed nanostructure device exhibits two key functionalities: energy harvesting and memristive characteristics. This allows the device to perform multiple tasks. The ZnO nanostructure sheet was grown using a hydrothermal method. To minimize defect states at the electrode-substrate interface, an optimal phosphorus doping process was employed to achieve minimal substrate sheet resistance. Under an applied pushing force of 0.259 kgf, the energy harvester generated an output voltage and current of 0.5548 V and 44 μA, respectively. The proposed structure produces an output of 24.41 μW at 13 Hz for 2000 cycles. Investigation of the device's transfer characteristics revealed memristive behavior with an on/off ratio of 107. These findings suggest that the multifunctional ZnO nanosheets/p-Si electronic device reported here has promising potential for applications in the Internet of Things (IoT).

Study of Hydrokinetic Energy Harvesting of Two Tandem Three Rigidly Connected Cylinder Oscillators Driven by Fluid-Induced Vibration

This study utilizes a bidirectional fluid–structure interaction numerical method to investigate the hydrodynamic and energy harvesting characteristics of two tandem three rigidly connected cylinder oscillators with different inter-oscillator spacing ratios. The analysis considers inter-oscillator spacing ratios of 8, 12, and 16 within a reduced velocity range of U* = 2–13 (equivalent to flow velocities of 0.18–1.16 m/s). The research explores the hydrodynamic interference features, energy harvesting variations, and the efficiency and density of energy harvesting of both upstream and downstream three-cylinder oscillators. The findings indicate that with increasing reduced velocity and inter-oscillator spacing ratio, the mutual interference between upstream and downstream oscillators diminishes. Wake patterns observed in the two series-connected three-cylinder oscillators include 2P, 2S, and 2T patterns, with fragmented vortices and banded vortices at specific reduced velocities. The most significant disparity in energy harvesting efficiency between upstream and downstream oscillators is observed at U* = 9.

Energy harvesting technology for AC overhead insulated transmission line based on electric field induction

AbstractTo solve the problem of the energy harvesting (EEH) effect of the condition monitoring devices power supply on the transmission line is not ideal. The authors designed three kinds of EEH schemes based on AC electric field induction, which can effectively improve the output power of load power supply. The EEH principle of each scheme was analysed in detail, and the influence factors such as the shape of outer energy harvester, capacitance compensation and impedance matching characteristics were analysed. Finally, the experiment showed that 140.9 mW of power was obtained in direct‐mode field EEH when the line voltage level was 10 kV. The high‐potential field EEH mode obtained 4.1 mW of power. The harvesting effect of the inner energy harvester with the same potential as the aluminium wire was obviously better, and 30.7 mW of power was obtained. Finally, based on the third mode, when the load resistance was 2200 Ω, the rectifier received 23.7 mW DC output. The experimental results are in agreement with the theoretical analysis, which verifies the effectiveness of the electric field induction power supply technology.

Experimental-numerical analyses on energy harvesting characteristics of non-conventional T-shaped beams with varied piezoelectric patch location and anchor position

Recently, researchers have studied innovative beam structures in a quest to maximize the energy conversion capability of piezoelectric (PZT) transducers coupled with the shims. A T-shaped beam is one of the structural elements used for harvester design owing to its exceptional geometrical advantage. While a number of research papers have reported its performance characteristics, its potential for harnessing the vibration energy at much lower resonance frequency and damping has not been explored. This paper presents non-conventional T-shaped beam harvesters, namely, the Uniform Tapered T-shaped Beam (UTB) and the Reversed Tapered T-shaped Beam (RTB), with the purpose of enhancing the T-shaped beam functionality. A performance analysis between the UTB, RTB and a conventional T-shaped beam (CTB) harvester of equal mass was conducted, where experimental results show that the RTB harvester has a lower fundamental resonance frequency of 12.3% and 28.3% when compared to the CTB and UTB, respectively. Also, a maximum terminal voltage of 82.8 V and an output peak power of 4.6 mW were produced by the RTB harvester when the PZT patch was placed near its clamped end. In addition, we investigated the effect of the anchor position of the beams on their energy harvesting performance using a finite element analysis (FEA) tool. The numerical results show that the position of the anchor has a considerable effect on the overall characteristics of the configurations.

Research on energy harvesting characteristics of a flapping foil with trailing edge jet flap

Flapping foils offer a potential means for extracting hydrokinetic energy from ocean and river flows by utilizing a combined pitching and heaving motion of the airfoil. In this paper, the effectiveness of trailing edge active flow control in enhancing the energy harvesting performance of the conventional flapping foil is examined through numerical simulations. In this approach, an injections slot is opened at the trailing edge of the flapping foil, from which a high velocity jet is discharged into ambient water. Since the water jet is issued vertically downwards perpendicular to the airfoil surface, it operates like a Gurney flap and thus is known as jet flap in aeronautics. Parametric studies show that the optimal injection position should be as far as possible from the leading edge of the flapping foil. In addition, it is also found when the width of the exit slot of jet equals to 2.6 % of the airfoil chord and the momentum coefficient of jet is 0.02, the flapping foil with the jet flap can increase the maximum net energy harvesting efficiency obtained after deducting the energy consumption for the flow control from 39.22 % to 47.6 % compared to its baseline counterpart, indicating the effectiveness of this method. Furthermore, the dynamic mode decomposition (DMD) method is also adopted to reveal the spatial-temporal features of the coherent structures in the wake flow behind the proposed flapping foil in an attempt to gain a deep understanding of the underlying flow mechanism involved in promoting its energy harvesting performance.

Adaptive Data Transmission Protocols for Energy Harvesting WSNs Used in Agriculture

Energy consumption is a major concern in wireless sensor networks (WSNs) as it affects the lifespan of sensor nodes. Battery-based WSNs have a short operating period, which makes them impractical for real-time applications, for instance in agriculture. Energy harvesting and suitable medium access control (MAC) protocols have been used to extend the lifetime of nodes. Receiver-initiated protocols have been proved to be the best solution for energy harvesting WSNs. However, they suffer from a key disadvantage, i.e. an increase in collision rate. These collisions need to be reduced using a multi-layer protocol structure. In such a context, a new solar-based hybrid MAC (SHMAC) protocol relying on receiver-initiation and characterized by a multi-layer structure is proposed. It is an adaptive protocol capable of adapting to changing weather conditions. The nodes with a high energy harvesting rate have a higher level of residual energy and are active for longer time periods compared with those with low energy harvesting characteristics. The proposed work has shown improvements in two major MAC layer parameters, i.e. collision rate and energy neutrality operation ratio (ENO).

Performance study of an energy harvester with multiple piezoelectric disks in parallel connection for water pressure pulsation

Water hydraulic pump is a crucial component of the water hydraulic system, and it generates periodic pressure pulsation due to its inherent characteristics. To harvest the vibration energy from the pressure pulsation, an energy harvester with multiple piezoelectric disks in parallel connection is proposed. Two prototypes are fabricated to analyze the effect of the number of piezoelectric disks on the energy harvesting characteristics under different pressures and resistances. Parameter matching is also carried out to obtain high root mean square (RMS) voltage and average power. For both prototypes, the cyclical change of deformation is caused by the pressure pulsation, leading to transient variation of voltage. Moderate thickness of piezoelectric ceramic and small thickness of copper substrate are advantageous for generating higher electrical energy output. Pressure pulsation significantly affects the harvested voltage and power, with the main influencing factor being the pulsation amplitude rather than static pressure. Additionally, transient voltage and RMS voltage increase with increasing resistance, while average power first rises and then falls. Comparing the two prototypes, both voltage and optimal resistance decrease when the number of piezoelectric disks in parallel connection increases. The average power and power density with two piezoelectric disks can reach 447 μW and 4.56 mW cm−3 under 3 MPa and at a resistance of 20 KΩ. This research provides guidance for the design, optimization and application of piezoelectric energy harvesters in water hydraulic system.

Effect of dimension size on electromagnetic radiation energy characteristics of lead zirconate titanate under drop weight impact load

This article presents a study on Electromagnetic radiation (EMR) energy harvesting characteristics of lead zirconate titanate (PZT) of soft grade (SP 5 A) samples under drop weight impact load. In the present study, four samples having different diameter to thickness (d/t) ratio were used. A possible EMR energy harvesting mechanism from these samples under impact loading has been discussed. It is found that the EMR parameters viz. EMR voltage, generated EMR energy, and so on, depend on the dimension of the sample and applied mechanical energy. The sample having highest t/d 2 (0.069) produces maximum EMR voltage, that is, 2.31 V. Also for the same sample, EMR parameters increase with the increase in applied mechanical energy. Also an increasing pattern of EMR energy was observed with the increase in the capacitance value of the capacitor. The results obtained suggest the possibility of using PZT as a better option for energy harvesting, sensing, and structural health monitoring applications. Also the results suggest EMR technique as an alternative option for harnessing energy from piezoelectric ceramics.

A phase change material based annular thermoelectric energy harvester from ambient temperature fluctuations: Transient modeling and critical characteristics

Annular thermoelectric power generator has been increasingly considered in application of ambient energy harvesting owing to the advantages of simple structure and no pollution. To improve thermal stability and energy harvesting performance of this system, the latent heat of phase change materials to improve thermal management and the high thermal conductivity of the heat sink to enhance heat transfer with the ambient are harness to annular thermoelectric power generator. Motivated by this, a phase change material based annular thermoelectric energy harvester (PCM-ATEH) with fins is developed for ambient energy harvesting and its three-dimensional transient model is also built up through jointly with thermo-electric and phase change processes. This paper considers the influence of key parameters such as temperature fluctuation amplitude, temperature fluctuation period, height ratio of PCM and thermoelectric generator (TEG) and melting temperature on liquid fraction, temperature difference, voltage and power density. Moreover, the comparison of PCM-ATEH and PCM based thermoelectric energy harvester (PCM-TEH) with/without fins is further conducted in this study to explore thermal management and energy harvesting performance. The energy harvesting characteristics of PCM-ATEH with fins is developed concerning the combination of power generation of TEG and melting process of PCM. Based on the results, it is found that the temperature difference and power density of PCM-ATEH with fins vary periodically with the sinusoidal temperature boundary, and results show that increasing temperature fluctuation period is not always feasible. Additionally, the comparative results indicate that the peak power density and energy efficiency of PCM-ATEH with fins are increased by 0.126 W/m2 and 0.02 % compared with PCM-TEH with fins, and increased by 0.195 W/m2 and 0.041 % compared with PCM-ATEH without fins. The results of energy harvesting characteristics show that a maximum of 0.77$ per watt can be reached to power generation cost of PCM-ATEH with fins. This paper can provide theoretical guidance for thermal management and energy conversion of energy harvesting system.

Numerical study of wake induced vibration(WIV) and energy harvesting characteristics under different stable conditions

In order to better capture energy from natural water flow, we designed a novel captive energy model using wake induced vibration (WIV) combined with multi-stable theory. The model consists of an upstream stationary square cylinder and a downstream vibrating circular cylinder. The multi-stable characteristics are achieved by controlling the horizontal distance (l) and vertical distance (d) between the tip magnet of the vibrating cylinder and the stationary magnets. We simulate the capture energy characteristics of the harvester for different stable conditions at 0.1 m/s-0.8 m/s (i.e., 1990 ≤ Reynolds number ≤ 15,923) using the computational fluid dynamics (CFD) method. The simulation results show that when fixing l = 0.020, d = 0.016 and d = 0.017 are bi-stable systems, and at the same time, it will be trapped in a potential well at a flow velocity of 0.1 m/s, resulting in a lower amplitude and vibration frequency. When d is fixed at 0.017 m, l = 0.021 and l = 0.022 are tri-stable systems with a wider flow velocity interval corresponding to its high amplitude. Different magnet positions affect the phase between the lift coefficients and displacements of the bluff body. At flow velocities from 0.1 m/s to 0.4 m/s, the energy harvesting effect of the with-magnet system is better than that of the non-magnet system.

Effect of boundary conditions on energy harvesting of a flow-induced snapping sheet at low Reynolds number

Recent studies on the snap-through motion of elastic sheets have attracted intense interest in energy-harvesting applications. However, the effect of boundary conditions (BCs) on energy extraction performance still remains an open question. In this study, we explored the snapping dynamics and energy-harvesting characteristics of the buckled sheet at various conditions using fluid–structure interaction simulations at a Reynolds number Re = 100. It was found that the front boundary condition (BC) dramatically affects the sheet's snapping dynamics, e.g., the pinned or relatively soft front BC triggers the sheet's instability easily and thus boasts the collection of potential energy. In the snap-through oscillation state, a stiffer rear BC results in a larger improvement in the sheet's energy collection compared with a minor effect of front BC. Meanwhile, the enhancement can also be achieved by adjusting the rear rotational spring stiffness up to 1.125 × 10−4, after which it remains nearly constant, as observed in the case of EI* = 0.004. This introduction of an elastic BC with krs* = 1.125 × 10−4 not only efficiently enhances energy extraction but significantly reduces stress concentration and, as a result, greatly prolongs the sheet's fatigue durability, especially for the stiffer sheet with EI* = 0.004. The effect of three other governing parameters, including the length ratio ΔL*, sheet's bending stiffness EI*, and mass ratio m*, on the sheet's energy-harvesting performance were also explored. The result shows that increasing ΔL* and EI* could improve the total energy harvested, primarily by enhancing the elastic potential energy, particularly in the aft half of the sheet. In contrast, increasing m* mainly enhances the kinetic energy collected by the sheet's central portion, thus improving the total energy-extracting performance. This study provides an in-depth insight into the dynamics of a buckled sheet under various BCs, which may offer some guidance on the optimization of relevant energy harvesters.

Study on the Influence of Coil Arrangement on the Output Characteristics of Electromagnetic Galloping Energy Harvester.

The arrangement of the induction coil influences the electromagnetic damping force and output characteristics of electromagnetic energy harvesters. Based on the aforementioned information, this paper presents a proposal for a multiple off-center coil electromagnetic galloping energy harvester (MEGEH). This study establishes both a theoretical model and a physical model to research the influence of the position and quantity of the induction coils on the output characteristics of an energy harvester. Additionally, it conducts wind tunnel tests and analyzes the obtained results. With the increase in the number of induction coils, there is a significant improvement in the duty cycle and output power of the MEGEH, resulting in an amplified energy conversion efficiency. At a wind speed of 9 m/s, the duty ratios of a single set of coils (SC), two sets of coils (TC), and multiple sets of coils (MC) are 30%, 51%, and 100%, respectively. The total output powers are 0.4 mW, 0.62 mW, and 0.72 mW. However, the rate of output growth has decreased from 55% to 16%. The position of the coils affects the initial electromagnetic damping of the energy harvester. Changing the position can reduce the initial electromagnetic damping, thereby decreasing the critical wind speed. The critical wind speed of the MEGEH decreases as the induction coil is positioned further away from the vibration center. When the distance is sufficiently large, the electromagnetic damping force becomes negligible. When the induction coil is positioned centrally, the MEGEH demonstrates its maximum critical wind speed, which has been measured at 4.01 m/s. When the initial distance between the induction coil and the vibrating component is increased to 10 mm, the critical wind speed reaches its minimum value of 2.23 m/s. Therefore, it is necessary to optimize the arrangement of the coils. The coils of the MEGEH should be arranged with the MC and a 10 mm offset from the center.

Vortex-induced vibrations in an active pitching flapping foil power generator with two degrees of freedom

The energy harvesting characteristics of actively pitching flapping foils under a two-degrees-of-freedom (2DOF) system were investigated through numerical simulations. At a Reynolds number of 1100, the effects of the pitching amplitude, reduced frequency, and structural parameters on the energy harvesting performance were compared with the traditional one-degree-of-freedom (1DOF) case. The optimal pitching amplitude (85°), reduced frequency (0.16), and structural parameters (bx*=0.5, kx*=0.7) of the streamwise vibrating flapping foil were determined. The additional velocity generated by streamwise vibrations increased the optimal reduced frequency and pitching amplitude over the traditional case. Streamwise vibrations accelerate the wake propulsion, and the wake vortevx spacing is about 0.8 times the chord length larger than that of the traditional case. Furthermore, the 2DOF case allows the vortex-shedding process of the flapping foil to participate in wake propulsion. The trajectory of the streamwise vibrating flapping foil was observed to be a figure “8” shape. The “8” shape gradually regularizes with an increased streamwise damping coefficient. There is an ideal parameter combination at the optimal reduced frequency that allows the flapping foil to reach the most unstable motion mode. The energy harvesting efficiency of the flapping foil can be increased by up to 25% due solely to vortex-induced vibrations of the 2DOF.

Sustainable Porous Scaffolds with Retained Lignin as An Effective Light-absorbing Material for Efficient Photothermal Energy Conversion.

Organic phase change materials (PCMs) are promising to utilize thermal energy from solar radiation for photothermal energy conversion. However, the issues of poor photo absorption and liquid leakage greatly restrict their practical application. Herein, a sustainable porous scaffold comprising periodate oxidized wood (POW) as the supporting material and in situ retains lignin as the light-absorber dopant are demonstrated. The π-π stacking ability of lignin molecules endows the retained lignin with efficient photonic energy harvesting characteristics for fast thermal conductivity to reach a higher maximal energy storage volume. The inherently porous structure of the POW scaffold enables excellent shape-stability, which bypasses the liquid leakage problem. The resulting POW/PCM composites exhibit superior comprehensive performance, including enhanced light absorption capacity, high photothermal conversion efficiency (≈86.7%), and high latent heat of 151 J g-1 . Furthermore, the POW/PCM composites also possess the ability to maintain a relatively constant indoor temperature when fixed atop the model house roof, showing great potential for their practical applications in the thermal regulation of intelligent buildings. This work not only paves a new way to obtain sustainable and effective porous scaffolds for sufficient photothermal energy conversion but also provides more possibilities for their practical application in the future.

The performance investigation of flow-induced motion energy-harvesting by applying time-varying stiffness in the dynamic ocean environment

Ocean water exhibits periodic motion both temporally and spatially. However, no time-varying mechanism has been studied for harvesting energy from dynamic ocean. This paper presents an enhanced mechanism for harvesting the energy of ocean flows by applying time-varying stiffness adaptation in dynamic ocean environments, resulting in superior performance. By conducting numerical simulations and experiments, this study investigates the motion response and energy harvesting characteristics of a single oscillating cylinder equipped with time-varying stiffness. The research focuses on examining its behavior in both uniform flow and shear flow conditions, and presents several noteworthy findings. First, in comparison to impulse and trapezoid patterns, the sin-patterned time-varying stiffness demonstrates superior energy harvesting performance in both uniform flow and time-varying flow conditions. Second, the frequency of the sin-patterned time-varying stiffness is a critical parameter that influences the energy harvesting performance. Setting the sin-patterned time-varying stiffness frequency to ωv = 0.75ωn (natural frequency of constant stiffness) yields optimal performance under both uniform and time-varying flow conditions. At ωv = 0.75ωn, the energy-harvesting power can be increased by more than 30 times compared to the case of constant stiffness. Simultaneously, the oscillator's motion frequency experiences a reduction of over 40%. It is within this frequency range that the energy-harvesting power is maximized across the entire frequency spectrum. Third, as the frequency of sin-patterned time-varying stiffness increases, there is a decrease in both the energy harvesting power and efficiency. At a frequency of ωv/ωn* = 1.5, the advantage over the constant stiffness oscillator becomes negligible. Fourth, the energy harvesting performance of time-varying stiffness is superior in a time-varying flow condition compared to a uniform flow condition. The maximum energy harvesting power is achieved at ωv/ωn* = 0.75 in the time-varying flow condition, surpassing the corresponding value in the uniform flow condition. Fifth, the phase-shift resonance between the shedding frequency and the frequency of time-varying stiffness significantly enhances the energy harvesting performance of the time-varying stiffness oscillator. The optimal time-varying frequency is determined to have a phase difference of 0.15ωn. Sixth, the power harvesting efficiency can be improved by up to 1.5 times on average using the time-varying stiffness mechanism (sin-patterned, 10% additional power required) compared to state-of-the-art technologies employing constant stiffness. Finally, matching the form and dominant frequency of the excitation force with those of the time-varying stiffness can greatly improve the energy harvesting power and motion amplitude of the oscillator. This paper explores a performance-based approach to energy harvesting in dynamic ocean environments by applying sin-patterned time-varying stiffness with ωv = 0.75ωn.

Investigation of a Novel Ultra-Low-Frequency Rotational Energy Harvester Based on a Double-Frequency Up-Conversion Mechanism.

Due to their lack of pollution and long replacement cycles, piezoelectric energy harvesters have gained increasing attention as emerging power generation devices. However, achieving effective energy harvesting in ultra-low-frequency (<1 Hz) rotational environments remains a challenge. Therefore, a novel rotational energy harvester (REH) with a double-frequency up-conversion mechanism was proposed in this study. It consisted of a hollow cylindrical shell with multiple piezoelectric beams and a ring-shaped slider with multiple paddles. During operation, the relative rotation between the slider and the shell induced the paddles on the slider to strike the piezoelectric beams inside the shell, thereby causing the piezoelectric beams to undergo self-excited oscillation and converting mechanical energy into electrical energy through the piezoelectric effect. Additionally, by adjusting the number of paddles and piezoelectric beams, the frequency of the piezoelectric beam struck by the paddles within one rotation cycle could be increased, further enhancing the output performance of the REH. To validate the output performance of the proposed REH, a prototype was fabricated, and the relationship between the device's output performance and parameters such as the number of paddles, system rotation speed, and device installation eccentricity was studied. The results showed that the designed REH achieved a single piezoelectric beam output power of up to 2.268 mW, while the REH with three piezoelectric beams reached an output power of 5.392 mW, with a high power density of 4.02 μW/(cm3 Hz) under a rotational excitation of 0.42 Hz, demonstrating excellent energy-harvesting characteristics.

High Roughness Induced Pearl Necklace‐Like ZIF‐67@PAN Fiber‐Based Triboelectric Nanogenerators for Mechanical Energy Harvesting

AbstractTechnological developments and innovations in the wearable device field have created huge consumer demand. Hence, designing energy harvesting devices are of utmost importance. Of the various types of energy harvesting devices, triboelectric nanogenerators (TENGs) have come to the fore, as it can efficiently harvest electrical energy from mechanical motions. To date, polymers and metals have dominated the triboelectric series, but there is a need to develop novel composite materials and 2D materials to enhance the performance of TENGs. In this study, electrospun polyacrylonitrile nanofibers are prepared and decorated with zeolitic imidazole framework‐67 (ZIF‐67@PAN) to form pearl‐necklace‐like fibers. ZIF‐67@PAN nanofibers are prepared by immersing PAN nanofibers for different hours (1, 5, 10, and 24 h) in ZIF‐67 solution, they provide more roughness, and efficient surface contact area. The immersion of PAN fibers in ZIF solution for longer times increases overall energy harvesting efficiency. Different amounts of MXene are deposited on PVDF; the inclusion of MXene improves the charge transfer properties of TENGs. PAN@ZIF‐67 is used as a positive tribolayer and PVDF@MXene as a negative tribolayer. The optimized TENG device has 305 V, 10.6 µA, and 10.9 W/m2 power and demonstrated promising energy harvesting characteristics and self‐powered sensing efficiency.

Performance study of a control valve with energy harvesting based on a modified passive model

GreenValve (integrating a runner into a ball valve) is a highly promising solution for harvesting excess water energy from the pipe to power the electrical equipment in the pipe network. In order to better match the actual operation of the GreenValve and to realise the simulation of the non-stationary operation process of the GreenValve, a modified passive model is proposed in this paper. The model is based on the idea of incoming flow induced rotor rotation and on a modification of the 6-DOF model that takes into account the added mass of the fluid. Based on the model, the energy harvesting characteristics and fluid regulation characteristics of the GreenValve with a modified Savonius runner with different number of blades and hollow ratios are investigated. Numerical results show that at an inlet flow rate of 15.7 × 103 m3/s, with the increase in the number of blades, the movement of the runner tends to be smooth, and the power and efficiency of the GreenValve gradually increases, up to 245 W of power and 13.6% of efficiency; the increase in the hollow ratio from 0.25 to 0.33 improves the overall performance of the GreenValve.

Theoretical model and experimental study on working characteristics of electromagnetic damper

An analysis model for electromagnetic damper is proposed in order to obtain the working characteristics of electromagnetic damper under different working conditions. Firstly, the inertia force and the electromagnetic force of electromagnetic damper are calculated, and the friction force is tested. Secondly, by combining the theoretical results and the test data, the working characteristic analysis model for electromagnetic damper is established. Finally, the damping characteristics and energy harvesting characteristics of the electromagnetic damper under multiple working conditions are discussed by using the present model. The working condition characteristic surface of the electromagnetic damper is obtained by using the recovered energy and equivalent damping coefficient as the coordinate plane. The results show that the error between the calculated results and the test results is below 10%. The damping force and output voltage of the electromagnetic damper are positively correlated with excitation frequency and amplitude. The excitation amplitude and frequency influence the energy harvesting characteristic and damping property deeply, respectively. The increase in load resistance reduces the energy regenerative capacity and damping capacity of the electromagnetic damper.