Energy Harvesting Structure Research Articles

A Triboelectric Nanogenerator Utilizing a Crank-Rocker Mechanism Combined with a Spring Cantilever Structure for Efficient Energy Harvesting and Self-Powered Sensing Applications

With the advancement of industrial automation, vibrational energy generated by machinery during operation is often underutilized. Developing efficient devices for vibration energy harvesting is thus essential. Triboelectric nanogenerators (TENGs) based on spring and cantilever beam structures show considerable potential for industrial vibration energy harvesting; however, traditional designs often fail to fully harness vibrational energy due to their structural limitations. This study proposes a triboelectric nanogenerator (TENG) based on a crank-rocker mechanism and a spring cantilever structure (CR-SC TENG), which combines a crank-rocker mechanism with a spring cantilever structure, designed for both energy harvesting and self-powered sensing. The CR-SC TENG incorporates a spring cantilever beam, a crank-rocker mechanism, and lever amplification principles, enabling it to respond sensitively to low-frequency, small-amplitude vibrations. Utilizing the crank-rocker and lever effects, this device significantly amplifies micro-amplitudes, enhancing energy capture efficiency and making it well suited for low-amplitude, complex industrial environments. Experimental results demonstrate that this design effectively amplifies micro-vibrations and markedly improves energy conversion efficiency within a frequency range of 1–35 Hz and an amplitude range of 1–3 mm. As a sensor, the CR-SC TENG’s dual-generation units produce output signals that precisely reflect vibration frequencies, making it suitable for the intelligent monitoring of industrial equipment. When placed on an air compressor operating at 25 Hz, the first-generation unit achieved an output voltage of 150 V and a current of 8 μA, while the second-generation unit produced an output voltage of 60 V and a current of 5 μA. These findings suggest that the CR-SC TENG, leveraging spring cantilever beams, crank-rocker mechanisms, and lever amplification, has significant potential for micro-amplitude energy harvesting and could play a key role in smart manufacturing, intelligent factories, and the Internet of Things.

A straight-arch-straight beam tandem quasi-zero stiffness structure

Extremely low dynamic stiffness is essential for the successful utilization of quasi-zero stiffness (QZS) structures for vibration isolation, energy harvesting, and micromechanical sensing. However, most conventional QZS structures are based on a parallel connection of positive and negative stiffness mechanisms, which poses challenges for stiffness matching, structure design, and fabrication. We propose a QZS structure based on a straight-arch-straight (SAS) tandem connection, in which the integrated design of the structure overcomes the problem of stiffness matching, and more importantly, the simple design of the structure greatly reduces the difficulty of fabrication and enables the design of a wide range of load-carrying capacity by only adjust the ratio of the length of the straight beam to the arch and the ratio of the height of the arch to the thickness. The symmetric deformation of the SAS structure extends the working range of the QZS structure, which can be further extended several times or divided into several different QZS intervals by connecting several identical or different SAS units in parallel. The experimental results show that the SAS structure has excellent vibration isolation performance in the low-frequency region, and more importantly, the low preload requirement also provides an important reference for structural design in the field of micromechanical sensing.

A hybrid piezoelectric–electromagnetic body energy harvester: design and experiment validation

Abstract The rapid advancement of electronic devices and wireless sensors has heightened the demand for energy sustainability and portable power solutions. Traditional human energy harvesters have limitations in harvesting energy from ultra-low-frequency human motion due to issues related to unstable energy output and wearing comfort. To address this challenge, a piezoelectric–electromagnetic hybrid energy harvesting (HP-EEH) structure designed for the hip joint area. This innovative design employs magnetically coupled frequency boosting alongside electromagnetic energy capture to achieve high output power. Firstly, the structure and principle of the energy capture device are introduced, and the electromechanical coupling model of the energy harvester is derived using Hamilton’s principle. Furthermore, the system is numerically simulated, and the voltage output characteristics of the piezoelectric unit and the electromagnetic unit are analyzed by using the finite element analysis software. Finally, the experimental setup of the (HP-EEH) is constructed, and the voltage output characteristics are tested for different swinging angles and positions. The results show that two parts of energy can be captured simultaneously under ultra-low-frequency motion conditions. At a swing angle of 50 degrees, the piezoelectric and electromagnetic units achieved maximum output power values of 14.96 µW at 0.8 Hz and 10.4 µW at 1.2 Hz, respectively. Incorporating the output power of the electromagnetic unit aims to address the power consumption requirements of low-power devices better.

Visible Light Active 0.95KNbO3‐0.05Ba(Nb1/2Sc1/2)O3 Ferroelectric for Enhanced Photocatalytic Activity

AbstractThis study reports a visible light active Ba/Sc co‐doped potassium niobate (KNbO3) ferroelectric material for enhanced photocatalytic applications. Through 5% Ba and Sc co‐doping in KNbO3 (i.e., 0.95KNbO3‐0.05Ba(Nb1/2Sc1/2)O3), the electronic band gap (Eg) is narrowed down to the visible range of the solar spectrum. The prepared samples are systematically examined by using X‐ray diffraction and Raman spectroscopy, which confirms the successful incorporation of Ba and Sc ions into the KNbO3 lattice. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis reveal particle morphology and chemical homogeneity of prepared samples. The UV–vis spectroscopy and ferroelectric PE‐loop demonstrate enhanced optical absorption compared to host KNbO3 while retaining ferroelectric behavior. The photoelectrochemical (PEC) measurements under visible light irradiation demonstrate a notable enhancement in the photocurrent for 0.95KNbO3‐0.05Ba(Nb1/2Sc1/2)O3 (hereafter denoted by 5KBSNO) compared to undoped KNbO3. Additionally, the 5KBSNO sample displays enhanced RhB dye degradation efficiency, reaching ≈50% compared to parent KNbO3 (≈30%) under light irradiation. First‐principles density functional theory (DFT) calculations are employed to understand the mechanism responsible for the reduced band gap. This study presents a promising material for developing advanced ferroelectric photocatalysts with tailored band structures for efficient solar energy harvesting for energy conversion and contamination remediation applications.

Modelling and performance enhancement of the fluid coupling interface for hydraulic pressure energy harvesting by superposition of the static mean pressure and pressure fluctuations

The monitoring and control of hydraulic systems in an autonomous and battery-free manner is receiving increasing attention to improve both safety and performance. In this regard, the conversion of pressure ripples within a hydraulic system into electric energy using hydraulic pressure energy harvesting (HPEH) is attractive due to the high energy intensity associated with dynamic pressure fluctuations. In this paper, a new theoretical model of the fluid to mechanical interface is established based on a central piezoelectric stack subject to a superimposed dynamic pressure fluctuation and a mean static pressure. A lumped-parameter model of the electromechanical coupling system is employed to study the overall harvesting performance of the system, and the force–deflection behavior of a circular edge-clamped plate with a lumped mass and a superimposed excitation is determined. The influence of static pressure on harvesting performance is explored in detail, where the mean static pressure introduces a softening nonlinearity to the harvester which decreases the power output and harvesting bandwidth. To reduce the negative impact of static pressure on power output, an optimized structure based on a quasi-zero stiffness (QZS) disc spring is proposed. The nonlinear restoring force of the circular plate interface on a central piezoelectric stack and disc spring is determined and the electromechanical coupling equations of the quasi-zero stiffness hydraulic pressure energy harvesting (QZS-HPEH) structure is established. Our theoretical analysis shows that the power output is improved using the novel QZS-HPEH structure, in particular at the high static loads presented in hydraulic systems. Experimental validation is performed, where good agreement is observed between model results and experimental measurements. The proposed model and experimental validation provide important new insights into the optimization of power output and application of HPEH devices in practical hydraulic systems.

Complexity and response of bio-inspired energy harvesters based on wing-beat pattern

This paper aims to investigate the dynamical mechanism of bio-inspired energy harvesters based on wing-beat pattern under harmonic excitation. Due to the existence of the gravity force in the established model, the harmonic balance method is utilized to calculate the theoretical results, which has the advantage to keep the influence of gravity force. Multiple solutions are found in the high frequency region, and they are very close in the amplitude of displacement and voltage due to the special structure of the bio-inspired energy harvester. Direct time-domain analysis verifies the effectiveness of theoretical results. The influence mechanism of the equivalent stiffness is also explored, which leads to the appearance of different states. Then, the root mean square (RMS) voltage and average power are analyzed. It is observed that a smaller damping coefficient and equivalent capacitance enhance the average electrical output and achieve greater output power. Subsequently, the bifurcation and complexity properties of the harvester are discussed. Complex phenomena are observed under different external excitations and equivalent damping, including double periodic bifurcation, multiple periodic bifurcation, and chaos phenomena. The complexity analyses confirm the effectiveness of the bifurcation results. The distribution of complexity also exhibits significant fluctuations, closely correlated with the trend of the bifurcation diagram.

A Kelp Inspired High‐Power Density Triboelectric Nanogenerator with Stacking Structure for Multiple Directional Ocean Wave Energy Harvesting

AbstractOcean wave energy is one of the most promising green energies in the wild. However, it is still challenging to effectively collect wave energy due to its randomness and irregularity. In this work, a kelp inspired high‐power density triboelectric nanogenerator (K‐TENG) is presented for harvesting wave energy with characteristics in multiple directions. The proposed K‐TENG consists of a series of stacked leaf‐like units. The influence of configuration parameters, including pellet diameters, pellet numbers, unit sizes, oscillation frequency, swing amplitude, and wave directions on output performances of leaf‐like units, are extensively investigated. Experimental data indicates that a single leaf‐like unit can achieve a maximum output voltage of 623.14 V as well as a maximum current of 1.48 µA and realize energy harvesting from different wave directions. A K‐TENG composed of 15 leaf‐like units demonstrates a high‐power density of 18.77 W m−3 at a wave frequency of 2.5 Hz, which successfully powers a digital watch and 414 light‐emitting diodes (LEDs). This work is hoped to provide a simple and reliable route to effectively harvest ocean wave energy.

Multi-functional periodically heterogeneous structures for energy harvesting and vibration attenuation-effects of piezoelectricity and shunting circuits

Abstract We explore a kind of metamaterial plate structures intended for simultaneous energy harvesting and vibration control. These structures are designed using a periodically perforated piezoelectric plate (the matrix) with elastic inclusions situated in the holes and serving for the resonators. The design options comprise two- and three-phase configurations related to the mechanical connection between the matrix and inclusions. By introducing a singularity—the focal spot created as a defect in the perfectly periodic structure and using the theory of super-cell, an enhanced piezoelectric energy harvester is obtained. It is observed that such a meta-structure serves as a dual-purpose system: efficiently capturing vibrational energy at a focal spot while maintaining the overall vibration attenuation throughout the structure. The band gap analysis based on the Bloch’s wave decomposition theory shows that by concentrating energy and halting vibration propagation, approximately 10 times energy harvesting enhancement and a remarkable 100 dB reduction in vibrations are achieved simultaneously. Besides the passive response of these meta-structures, we consider its extension by an external electric circuit (EC). Such modified configurations enable to exploit ‘actively’ the piezoelectric plate property to transmit the mechanical response between two, or more distant locations. Due to nonlocal interactions introduced by means the controllable EC, we consider optimization of the EC impedance to reduce the vibrations at a selected location of the whole structure without any external energy supply. The computational study discovers perspectives and benefits of designing such active self-powered meta-structures.

Design and experimentation of width tapered meandered array structure for low frequency broadband vibration energy harvesting

A novel 6DoF Tapered beam energy harvester, capable of operating across a broad and low frequency range, is proposed in this work. The hybrid structure incorporates regular beam array and zig-zag sections, enhancing deformation and bending. Width tapering with constant thickness optimizes the structural performance and energy harvesting capabilities of the beam. Tapering ensures even strain distribution, reducing the risk of structural failure. The proposed structure demonstrates wide band characteristics at low frequencies, delivering higher power output compared to an array of cantilevers for a given area. FEM analysis is conducted to optimize proof mass, aiming for closely spaced resonance frequencies and high-power output. Experimental validation on a prototype confirms the accuracy of the frequency response predicted by the models. Under harmonic base excitation of 0.4 g, the harvester yields an average DC power of 2497 μW, accounting for signal conditioning losses, within the frequency range of 9–20 Hz. The suggested structure offers excellent design flexibility, allowing adjustment of resonant frequencies by varying the number of beams, the slope and the proof mass of individual beams. The geometry of the proposed structure provides versatility, mechanical resilience, uniform strain distribution make it suitable for developing MEMS energy harvesters.

Galfenol-based Magnetostrictive Sensors: comparative analysis of various structures for efficient energy harvesting

Galfenol-based Magnetostrictive Sensors: comparative analysis of various structures for efficient energy harvesting

Power absorption and flow-field characteristics analysis for oscillating coaxial twin-buoy wave energy converter by using CFD

The energy conversion capacity of wave energy conversion devices highly depends on the hydrodynamic characteristics of the energy-harvesting structure. To investigate the effect of hydrodynamic performance on the power conversion characteristics, a twin-buoy wave energy converter (WEC) was investigated by using a three-dimensional numerical wave pool based on the Computational Fluid Dynamics (CFD) method. Several factors are examined, including the elasticity coefficient of the anchor chain, the bottom configuration of the floating body, and the power take-off (PTO) damping coefficient. The heave displacement, heave velocity, and heave force of the converter are calculated under specific wave parameters, and the flow field cloud diagram during the heave motion is analyzed. The results indicate that a wave energy converter with a hemispherical floating body exhibits the best kinematic performance. The influence of the mechanical damping coefficient on the energy conversion performance of the device is studied. By appropriately reducing the mechanical damping coefficient, the energy capturing capability of the device can be increased to a certain extent. These findings can serve as a theoretical basis for the application of deep-water wave energy conversion in engineering and the optimization of future WEC designs.

Finite Element Analysis and Optimization of the Piezoelectric Circular Diaphragm Energy Harvester

The effectiveness of power generation of the piezoelectric energy harvester (PEH) depends on the coupling between its resonant frequency and the oscillation frequency of the vibration source. The resonant frequency of a PEH is determined by its structural design, and therefore, to improve piezoelectric energy harvester performance, the piezoelectric energy harvester must be optimally designed to achieve the resonant frequency that matches the excitation frequency of the vibration source. This paper presents the design and detailed calculation of the piezoelectric energy harvester in the form of a bimorph piezoelectric circular diaphragm (PCD) structure by finite element analysis (FEA) using the software package ANSYS. Based on analyses and calculations, the optimal structure of the piezoelectric circular diaphragm energy harvester is proposed to meet the specified resonant frequency response matching the vibration source frequency. Detailed calculations of the PEH were performed with an excitation frequency of 100 Hz. With an optimal load resistor of 10.1 kΩ, an output power of 0.287 W was generated at 100 Hz (equal to the resonant frequency of the PEH) under an amplitude of harmonic excitation of 0.1mm. In addition, the research results can be used to fabricate piezoelectric circular diaphragm energy harvester operating at a resonant frequency suitable for the available vibrations.

Transparent Photovoltaics with Array ZnO/NiO Structure for Energy Harvesting and Human Interface Applications

In this study, a proof of concept for seamless energy flow is demonstrated by converting light energy into electrical energy and then storing it. A simple heterojunction structure of an FTO/ZnO/NiO/AgNWs/ZnO array transparent photovoltaic (TPV) device is employed to ensure an excellent average visible transmittance value of 67.7% while storing light energy as electrical energy in a capacitor bank. By simple and stable array connection of unit cell devices, the power leakage is minimized while maximizing output voltage. In the array TPV device, an open‐circuit voltage of 1.4 V is achieved under 365 nm illumination, with a voltage of 1.26 V stored in the capacitor bank, accumulating to over 6 V. The stored electrical energy is successfully converted for use by an light‐emitting diode (LED) light source, demonstrating sustained light‐up for over 30 s. This work explores facile energy generation, storage and utilization through TPVs, with a good potential for transparent energy harvesting and human interface applications.

(Invited) A CNT Binding Bis(Zinc Porphyrin)Bodipy-C60 Nano Tweezer: Charge Stabilization in Supramolecular C60-Bodipy-(ZnP)2:SWCNT Hybrids

Single-wall carbon nanotubes (SWCNT) coupled with either electron donor or acceptor are promising functional structures for light energy harvesting and molecular optoelectronics applications. For building such hybrids involving SWCNTs, the p-stacking ability of large aromatic compounds is one of the commonly employed approaches.1-2 Often, the desired donor or acceptor entities are functionalized to carry one or more aromatic entities and allowed to interact with CNTs. However, due to close proximity, the role of SWCNTs in stabilizing the electron transfer product has been a challenge.3 Recently, we overcame this hurdle by employing a multi-modular approach to build donor-acceptor hybrids and successfully demonstrated charge stabilization in the presence of SWCNTs.4 In the present study, we have further improved our design by newly synthesizing a nano tweezer comprised of covalently linked BODIPY-C60 carrying two zinc porphyrin arms as shown in the figure. This compound was further allowed to interact with SWCNT(6,5) and SWCNT(7,6) to form the supramolecular C60-BODIPY-(ZnP)2:SWCNThybrids. Upon spectral, electrochemical, and computational characterization, femtosecond pump-probe spectroscopic studies were performed to establish the occurrence of photoinduced charge separation and charge stabilization. Extending the lifetime of the charge-separated states upon SWCNT binding has been successfully demonstrated in the present molecular design strategy. D’Souza, F.; Sandanayaka, A. S. D.; Ito, O. ‘SWNT-Based Supramolecular Nanoarchitectures with Photosensitizing Donor and Acceptor Molecules’ Phys. Chem. Letts. 2010, 1. 2586-2593.B. KC, G. N. Lim, and F. D’Souza, ‘Accelerated Charge Separation in Graphene Decorated Multi-Modular Tripyrene-Subphthalocyanine-Fullerene Donor-Acceptor Hybrids,’ Angew. Chem. Int. Ed. 2015, 54, 5088-5092.Barrejon, L. M. Arellano, F. D’Souza, F. Langa, ‘Bidirectional charge transfer in carbon-based hybrid nanomaterials’ Nanoscale, 2019, 11, 14978-14992.Kazemi, Y. Jang, A. Liyanage, P. A. Karr, and F. D’Souza, A Carbon Nanotube Binding Bis(pyrenylstyryl)BODIPY-C60 Nano Tweezer: Charge Stabilization through Sequential Electron Transfer, Angew. Chem. Int. Ed. 2022, 61, e202212474 (1-7). Figure 1

Theoretical and experiment optimization research of a frequency up-converted piezoelectric energy harvester based on impact and magnetic force

Harvesting environmental vibrations to power electronic components is an essential approach for addressing the power supply challenge in MEMS. However, conventional vibration energy harvesting systems frequently suffer from limited frequency bandwidth and high-frequency deficiencies. This paper proposes a novel up-frequency structure for piezoelectric vibration energy harvesting (VEH) that relies on both nonlinear magnetic force and piecewise linear force. The proposed VEH’s nonlinear dynamic characteristics are analyzed theoretically, and an experimental prototype machining and vibration test platform are constructed. Theoretical and experimental results are compared and analyzed by conducting basic experiments and key parameter optimization experiments. The research results demonstrate that the proposed VEH can efficiently harvest vibration energy in low-frequency and wide-band environments. Regarding the system parameters, higher vibration acceleration results in increased output voltage and wider working frequency bandwidth. Reducing the gap distance enhances piecewise linear vibration, which broadens the working frequency bandwidth. Furthermore, the proposed VEH’s ability to harvest low-frequency vibrations can be enhanced by reducing the magnet distance, thereby reducing the linear resonance frequency of the system. The findings of this study offer valuable insights for advancing the engineering application of MEMS self-power supply technology.

Exploiting internal resonance of 3D-printed weakly coupled structures for piezoelectric energy harvesting

Exploiting internal resonance of 3D-printed weakly coupled structures for piezoelectric energy harvesting

Case study: Design and properties of acoustic energy harvester

Converting acoustic energy into electric energy can not only suppress environmental noise but also provide energy supply, which is a potential way to solve the bottleneck problem of energy supply in wireless sensor networks (WSNs). An acoustic energy harvester structure and circuit system combining Helmholtz resonance effect with piezoelectric effect are proposed in this article. The band gap characteristics of the designed acoustic energy harvester are analyzed by plane wave expansion (PWE) theory and experiment. The substrate of Helmholtz resonator is made from piezoelectric sheet, and the acoustic energy harvester structure is arranged periodically. When the incident noise frequency keeps coincidence with the resonant frequency, the conversion efficiency goes high up to 21.3%. The influence of series and parallel connection of piezoelectric elements on the acoustic to electric energy is observed. The AC-DC conversion circuit is designed with rectifier bridge, and the energy storage circuit is designed with supercapacitor. The power obtained from the acoustic to electric energy conversion system is 1523 mW. Application tests indicate that the noise suppresses, energy conversion, and energy storage can be realized at the same time by the proposed acoustic energy harvester system.

A piezoelectric and electromagnetic hybrid energy harvester based on two-stage magnetic coupling

Traditional piezoelectric energy harvesters cannot adapt to environmental energy with low frequency, wideband, and randomness because of the narrow working bandwidth. The introduction of magnetic coupling can improve the narrow-band characteristics of piezoelectric energy harvesting structures. To explore more efficient broadband methods, this paper designs a piezoelectric and electromagnetic hybrid energy harvester (PEEH) based on two-stage magnetic coupling to realize the expansion of piezoelectric energy harvesting bandwidth. In this paper, the magnetic pole alternating frequency is changed and the output of the structure is tested, and the operating frequency bands under different alternating frequencies are compared according to the test results. It can be seen from the experimental results that the output performance of the structure is obviously improved by increasing the AC frequency of the magnetic pole while reducing the optimal frequency point of the structure. When the number of magnets in the rotor magnet array is 6, increasing the pole alternating frequency can effectively improve the output performance of the electromagnetic unit when the rotor speed is low, and can also increase the maximum output voltage and energy harvest bandwidth of the piezoelectric unit by 189% and 150%, respectively. Therefore, by increasing the alternating frequency of magnetic poles, the output voltage of the structure can be improved, and the bandwidth of the structure can be broadened.

The Latest Advances in Ink-Based Nanogenerators: From Materials to Applications.

Nanogenerators possess the capability to harvest faint energy from the environment. Among them, thermoelectric (TE), triboelectric, piezoelectric (PE), and moisture-enabled nanogenerators represent promising approaches to micro-nano energy collection. These nanogenerators have seen considerable progress in material optimization and structural design. Printing technology has facilitated the large-scale manufacturing of nanogenerators. Although inks can be compatible with most traditional functional materials, this inevitably leads to a decrease in the electrical performance of the materials, necessitating control over the rheological properties of the inks. Furthermore, printing technology offers increased structural design flexibility. This review provides a comprehensive framework for ink-based nanogenerators, encompassing ink material optimization and device structural design, including improvements in ink performance, control of rheological properties, and efficient energy harvesting structures. Additionally, it highlights ink-based nanogenerators that incorporate textile technology and hybrid energy technologies, reviewing their latest advancements in energy collection and self-powered sensing. The discussion also addresses the main challenges faced and future directions for development.

Bionic dragonfly staggered flapping hydrofoils triboelectric-electromagnetic hybrid generator for low-speed water flow energy harvesting

Water flow energy harvesting with triboelectric nanogenerators (TENGs) is in the spotlight. However, existing front-end energy harvesting structures have drawbacks, such as traditional turbines requiring higher flow speed to start-up, and devices based on vortex-induced vibration exhibiting a lock-in phenomenon, which severely limits the performance of the TENGs in low-speed water environments. Here, a bionic dragonfly flapping hydrofoils-driven triboelectric-electromagnetic hybrid generator (BDFH-TEHG) is reported. The dragonfly-wing-like staggered tandem hydrofoil configuration enables the BDFH-TEHG continuous energy harvesting in the entire time domain. Meanwhile, the power generation part and front-end structure parameters are optimized to enhance the electrical output of the harvester. As a result, the BDFH-TEHG exhibits a low starting flow speed, and efficient power generation at different flow speeds. At the flow speed of 0.21 m/s, the triboelectric nanogenerator (TENG) and electromagnetic generator (EMG) achieve peak powers of 4.19 mW and 8.01 mW, respectively. Furthermore, the BDFH-TEHG can power the wireless water quality sensor and provide early warning successfully for agricultural activities. This work provides a valid method for low-speed water flow energy harvesting, toward practical applications of water environment monitoring in smart agriculture.