Impact Energy Harvesting Research Articles

Energy harvesting and inter-floor impact noise control using an optimally tuned hybrid damping system

Impact-loaded floor structures radiate undesired sound waves into adjacent rooms, compromising the acoustic comfort. On the other hand, substantial structural vibrations caused by the impact loading offer a promising energy source for harvesting. Nevertheless, a systematic analytical or numerical investigation of simultaneous inter-floor impact sound transmission control and energy harvesting appears to be missing. Current study describes the conceptual development of a fully coupled 3D analytical model of a dual-functional double-plate floor structure optimized for hybrid regenerative control of inter-floor impact sound transmission. Leveraging multi-mode shunted piezoelectric and Electromagnetic Damper (EMD) energy transduction mechanisms, the model structure is composed of two PZT sandwich plates, which are interlinked through a Nonlinear Vibration Absorber (NVA)-based EMD. The finite Fourier cosine transform and standard normal mode approach are employed to treat the governing acousto-elastic equations. Non-dominated Sorting Genetic Algorithm II is applied to tune the system parameters along Pareto frontiers to target maximum pressure mitigation, maximum energy harvesting, or dual-objective optimization, which hires advantageous features from both configurations for an optimal trade-off between them. Simulations reveal that elasto-acoustic response suppression and energy extraction of the employed stand-alone PZT-based conversion mechanism can be remarkably improved with the adopted optimized hybrid PZT/NVA/EMD-equipped system.

Fish-Wearable Piezoelectric Nanogenerator for Dual-Modal Energy Scavenging from Fish-Tailing.

Aiming to develop a self-powered bioelectric tag for fish behavioral studies, here we present a fish-wearable piezoelectric nanogenerator (FWPNG) that can simultaneously harvest the strain energy and the flow impact energy caused by fish-tailing. The FWPNG is fabricated by transferring a 2 μm-thick Nb0.02-Pb(Zr0.6Ti0.4)O3 (PZT) layer from a silicon substrate to a spin-coated polyimide film via a novel zinc oxide (ZnO) release process. The open-circuit voltage of the strain energy harvester reaches 2.3 V under a strain of 1% at an ultra-low frequency of 1 Hz, and output voltage of the impact energy harvester reaches a 0.3 V under a pressure of 82.6 kPa at 1 Hz, which is in good agreement with our theoretical analysis. As a proof-of-concept demonstration, an event-driven underwater acoustic transmitter is developed by utilizing the FWPNG as a trigger switch. Acoustic transmission occurs when the amplitude of fish-tailing is larger than a preset threshold. The dual-modal FWPNG device shows the potential application in self-powered biotags for animal behavioral studies and ocean explorations.

3D spirally coiled piezoelectric nanogenerator for large impact energy harvesting

Piezoelectric nanogenerator is an emerging technology that can convert irregular discrete mechanical energy in the environment into electricity, which provides a long-term continuous power supply solution for mobile distributed electronics. However, it is still difficult to effectively harvest the large impact mechanical energy. Here, we developed a new kind of three-dimensional spirally coiled piezoelectric nanogenerator (SC-PENG), which can effectively convert irregular axial impact forces into uniform radial pressures, and achieve large-scale impact mechanical energy harvesting (corresponding pressures range from 80 kPa to 6.32 MPa). Especially, under a large impact pressure of 3.05 MPa, the output current, voltage and the equivalent transfer charge density of SC-PENG is up to 196 μA, 36 V and 2550 μC m−2 respectively, which break the record of PENG among previous studies. The volume of the piezoelectric film and the corresponding volume charge density are 0.224 cm−3 and 580 nC cm−3, respectively. Moreover, factors such as particle connectivity and modulus of the piezoelectric film are explored in detail, which can further improve the electromechanical conversion capability of PENG. This work not only achieves high electrical output of PENG, but also paves an efficient strategy for large impact mechanical energy harvesting towards practical application.

Analysis and experiment of auxetic centrifugal softening impact energy harvesting from ultra-low-frequency rotational excitations

The ubiquitous ultra-low-frequency rotational motions have become a kind of potential source for energy harvesting. Despite this, achieving high energy output at ultra-low rotational frequencies via simple energy harvesting structures appears to be a significant challenge. Therefore, this paper proposes an auxetic centrifugal softening impact energy harvester (ASIEH) to break through this bottleneck. The ASIEH consists of a centrifugal softening driving beam that impacts two rigid auxetic piezoelectric beams to generate electric energy during rotation. The modeling and simulation of the ASIEH and the plain centrifugal softening impact energy harvester (PSIEH) indicate that the high stress distribution and the simultaneous operation of d31 and d32 modes of the auxetic energy harvester can improve the energy output. Under the centrifugal effect, the driving beam experiences the vibration, impact and trapping modes subsequently, among which the impact mode produces the highest energy output. Experiments are conducted to validate the model and show that the peak power of the ASIEH (0.673 mW) can be increased by 200.45% compared with that of the PSIEH (0.224 mW) at 3.5 Hz. Parametric studies indicate that no matter how the impact distance and rotational radius are varied, the peak power and bandwidth of the ASIEH are higher than those of the PSIEH. Owing to the combination of both the centrifugal effect and the auxetic structure, the proposed ASIEH exhibits the great potential in ultra-low-frequency rotational energy harvesting with both high power density (41.23 μW/g) and high output power.

Impact energy harvesting and storage through duct airflow using magnetostrictive clad films

The Internet of Things (IoT) requires power supplies without recharging. We conceived the idea of generating electricity from the impact of magnetostrictive materials against a propeller. This study evaluated the energy harvesting performance and energy storage capabilities of Fe–Co alloy and Ni clad (Fe–Co/Ni) films that directly strike propellers rotated by the wind in a duct airflow. The 0.08- and 0.2-mm-thick Fe–Co/Ni films generated powers of 28.1 and 89.4 µW, respectively. Moreover, the 0.08-mm-thick Fe–Co/No film generated power lower than that generated by the 0.2-mm-thick Fe–Co/Ni film. However, at a wind speed of 1.5 m/s, the 0.08-mm-thick Fe–Co/Ni film generated power, whereas the 0.2-mm-thick Fe–Co/Ni film stopped the rotation of propellers and did not generate any power. Furthermore, the Fe–Co/Ni film was successfully charged in a capacitor, and the stored voltages were 108.3 mV for the 0.08-mm-thick Fe–Co/Ni films for 30 min and 337.3 mV for the 0.2-mm-thick Fe–Co/Ni films for 1 h. It is also worth noting that no damage occurred to the surfaces of the Fe–Co/Ni films.

Fast optimize arm wearable piezoelectric energy harvesters via artificial neural network

• Using artificial neural networks to optimize piezoelectric devices allows skipping the construction of physical models. • The ball impact energy harvesting device is more suitable for human energy harvesting. • Considering different optimization algorithms can effectively improve the predictive power of artificial neural networks. • It is necessary to adjust the initial learning rate of the algorithm. Converting actions of human’s body into electrical energy via wearable energy harvesters is an exciting area. This study presents a ball impact piezoelectric energy converter consisting of two circular ceramic piezoelectric sheets to obtain energy from arm swing. 2264 sets of data were measured to train the artificial neural network (ANN) modes. The performance of ANN optimized by three different algorithms (Nadam, Adamax, and Adadelta) was compared and discussed. Treadmill experiments verified and confirmed the prediction results from ANN, an effective voltage of 11.3 V was demonstrated at a running speed of 9 km/h. Our results show that ANN can speed up the optimizing process for designing better energy harvesters.

Enhanced Low-Velocity Impact Resistance of Helicoidal Composites by Fused Filament Fabrication (FFF).

Bioinspired composites, capable of tailoring mechanical properties by the strategy of making full use of their advantages and bypassing their drawbacks, are vital for numerous engineering applications such as lightweight ultrahigh-strength, enhanced toughness, improved low-/high- velocity impact resistance, wave filtering, and energy harvesting. Helicoidal composites are examples of them. However, how to optimize the geometric structure to maximize the low-velocity impact resistance of helicoidal composites has been ignored, which is vital to the lightweight and high strength for aerospace, defense, ship, bridge, dam, vessel, and textile industries. Here, we combined experiments and numerical simulations to report the dynamic response of helicoidal composites subjected under low-velocity impact (0–10 m/s). Our helicoidal structures, inspired by the Stomatopod Dactyl club, are fabricated using polylactic acid (PLA) by FFF in a single-phase way. The helicoidal strategy aims to exploit, to a maximum extent, the axial tensile strength of filaments and simultaneously make up the shortage of inter-filament contact strength. We demonstrate experimentally that the low-velocity impact resistance has been enhanced efficiently as the helicoidal angle varies, and that the 15° helicoidal plate is better than others, which has also been confirmed by the numerical simulations. The findings reported here provide a new routine to design composites systems with enhanced impact resistance, offering a method to improve impact performance and expand the application of 3D printing.

Electromechanical characterization and kinetic energy harvesting of piezoelectric nanocomposites reinforced with glass fibers

Piezoelectric composites are a significant research field because of their excellent mechanical flexibility and sufficient stress-induced voltage. Furthermore, due to the widespread use of the Internet of Things (IoT) in recent years, small-sized piezoelectric composites have attracted a lot of attention. Also, there is an urgent need to develop evaluation methods for these composites. This paper evaluates the piezoelectric and mechanical properties of potassium sodium niobate (KNN)-epoxy and KNN-glass fiber-reinforced polymer (GFRP) composites using a modified small punch (MSP) and nanoindentation tests in addition to d33 measurements. An analytical solution for the piezoelectric composite thin plate under bending was obtained for the determination of the bending properties. Due to the glass fiber inclusion, the bending strength increased by about four times, and Young's modulus in the length direction increased by approximately two times (more than that of the KNN-epoxy); however, in the thickness direction, Young's modulus decreased by less than half. An impact energy harvesting test was then performed on the KNN-epoxy and KNN-GFRP composites. As a result, the output voltage of KNN-GFRP was larger than that of KNN-epoxy. Also, the output voltage was about 2.4 V with a compressive stress of 0.2 MPa, although the presence of the glass fibers decreased the piezoelectric constants. Finally, damped flexural vibration energy harvesting test was carried out on the KNN-epoxy and KNN-GFRP composites. The KNN-epoxy was broken during the test, however KNN-GFRP composite with a load resistance of 10 MΩ generated 35 nJ of energy. Overall, through this work, we succeeded in developing piezoelectric energy harvesting composite materials that can withstand impact and bending vibration using glass fibers and also established a method for evaluating the electromechanical properties with small test specimen.

Rolling Spherical Triboelectric Nanogenerators (RS-TENG) under Low-Frequency Ocean Wave Action

Triboelectric nanogenerators (TENG), which convert mechanical energy (such as ocean waves) from the surrounding environment into electrical energy, have been identified as a green energy alternative for addressing the environmental issues resulting from the use of traditional energy resources. In this experimental design, we propose rolling spherical triboelectric nanogenerators (RS-TENG) for collecting energy from low-frequency ocean wave action. Copper and aluminum were used to create a spherical frame which functions as the electrode. In addition, different sizes of spherical dielectric (SD1, SD2, SD3, and SD4) were developed in order to compare the dielectric effect on output performance. This design places several electrodes on each side of the spherical structure such that the dielectric layers are able to move with the slightest oscillation and generate electrical energy. The performance of the RS-TENG was experimentally investigated, with the results indicating that the spherical dielectrics significantly impact energy harvesting performance. On the other hand, the triboelectric materials (i.e., copper and aluminum) play a less important role. The copper RS-TENG with the largest spherical dielectrics is the most efficient structure, with a maximum output of 12.75 V in open-circuit and a peak power of approximately 455 nW.

Assessment of Impact Energy Harvesting in Composite Beams with Piezoelectric Transducers.

Piezoelectric energy harvesting (PEH) is studied in the case of a low-velocity impact of a rigid mass on a composite beam. A methodology is outlined, encompassing modelling of the open-circuit impact response in a finite element (FE) package, formulation of a lumped parameter (LP) model for the piezoelectric transducer connected with the harvesting circuit, and experimental verification of the impact using a custom portable configuration with impactor motion control. The subcircuit capacitor charging effect, the impactor mass and velocity on the harvesting subcircuit response, and the obtained output power are quantified. The results indicate that the current methodology can be used as a design tool for the structure and the harvesting circuit to achieve power output from composite beams with piezoelectric patches under impact conditions.

Exploring mechanical assonance for impact energy harvesting using acoustic metamaterials

Acoustic metamaterials are engineered to possess unique dynamic properties that are not commonly found in nature. It has been demonstrated that customizing the characteristics of their local features can help optimize their dynamic performance under specific loading conditions. Drawing inspiration from the literary device called “assonance,” the term “mechanical assonance” may be ascribed to the dynamic phenomenon realized by sequencing oscillators with tuned responses within a waveguide to engineer a prescribed wave transformation across it. In this context, assonance provides a framework to utilize resonant local features within a host structure or material and interactive mechanisms thereof as building blocks to create enriched functionalities for acoustic metamaterials. Using a discrete element representation for an acoustic metamaterial barrier (AMB), a numerical study is conducted to ascertain parametric dependence for assonant mechanisms related to resonator frequencies, their sequencing, and host material stiffness. Normalized metrics are extracted to estimate transmitted pulse mitigation under impact-type loading. It is found that resonator sets with octave spacing having the number of resonators of a specific frequency proportional to that frequency’s amplitude in the input spectrum is desirable for lower transmissibility. Further, sequencing the lowest frequency resonator set closest to the incident-side gives better performance. Engineering a high degree of impedance mismatch between host material sections is also preferable. The energy sequestered by the local resonators can be harvested utilizing the resonator’s mass as the multifunctional kernel for a linear electromagnetic generator. A multiphysical model is developed to predict the harvested electric voltage and power from the AMB and validated using proof-of-concept experiments. Finally, various coil placement and voltage rectification schemes are also studied using simulations to ascertain preferable design configurations.

Poly(Vinylidene Fluoride) Nanofiber Array Films with High Strength for Effective Impact Energy Harvesting

Absorbing high mechanical impact energy and converting it into electrical energy is challenging due to the low efficiency and strength of the existing piezoelectric generators. Here, a new type of piezoelectric nanogenerator is reported that is a sandwich structure composed of upper and lower electrodes and a poly(vinylidene fluoride) (PVDF) nanofiber array film. The PVDF nanofiber array films with dense vertical alignment characteristics are successfully fabricated by a combination of electrospinning and cutting methods. Each nanofiber in the nanofiber array film becomes an independent nanogenerator with an equivalent piezoelectric response which greatly enhances the charges collection and energy conversion efficiency of the nanogenerator. The maximum instantaneous power density of 26.3 μW cm−2 can be reached under the impact of the 9.1 g ball falling freely from a height of 20 cm. The nanofiber array structure endows the piezoelectric nanogenerator with high mechanical strength in the normal direction of the surface and excellent stability. Furthermore, the power output of two parallel‐connected nanogenerators (1.5 × 1.5 cm2 each) can light up 12 LEDs without storage devices. The unique properties of the piezoelectric nanogenerator offer great potential for high mechanical impact energy harvesting and effective conversion.

Piezoelectric Impact Energy Harvester Based on the Composite Spherical Particle Chain for Self-Powered Sensors.

In this study, a novel piezoelectric energy harvester (PEH) based on the array composite spherical particle chain was constructed and explored in detail through simulation and experimental verification. The power test of the PEH based on array composite particle chains in the self-powered system was realized. Firstly, the model of PEH based on the composite spherical particle chain was constructed to theoretically realize the collection, transformation, and storage of impact energy, and the advantages of a composite particle chain in the field of piezoelectric energy harvesting were verified. Secondly, an experimental system was established to test the performance of the PEH, including the stability of the system under a continuous impact load, the power adjustment under different resistances, and the influence of the number of particle chains on the energy harvesting efficiency. Finally, a self-powered supply system was established with the PEH composed of three composite particle chains to realize the power supply of the microelectronic components. This paper presents a method of collecting impact energy based on particle chain structure, and lays an experimental foundation for the application of a composite particle chain in the field of piezoelectric energy harvesting.

Nonlinear multi-mode electromagnetic insole energy harvester for human-powered body monitoring sensors: Design, modeling, and characterization

The current research in wearable electronics is trending towards miniaturization, portability, integration, and sustainability, with the harvesting of biomechanical energy seen as a promising route to improve the sustainability of these wearable electronics. Efforts have been made to prolong operational life of these harvesters, to overcome energy dissipation, lowering resonant frequency, attaining multi-resonant states as well as widening frequency bandwidth of these biomechanical energy harvesters. Herein, an electromagnetic insole energy harvester (EMIEH), capable of efficiently harvesting low-frequency biomechanical energy, has been designed, fabricated and experimentally tested. The core component in the device is the vibrating circular spiral spring, holding two magnets as the driving force on the central platform of the circular spiral spring, and just in-line with the upper and lower wound coils. It has been shown that the harvester exhibits higher sensitivity to low-frequency external vibrations than conventional cantilever-based designs, and hence allows low impact energy harvesting such as harvesting energy from walking, running and jogging. The experimentally-tested four resonant frequencies occurred at 8.9 Hz, 28 Hz, 50 Hz, and 51 Hz. At the first resonant frequency of 8.9 Hz under base acceleration of 0.6 g, the lower electromagnetic generator can deliver a peak power of 664.36 µW and an RMS voltage of 170 mV to a matching load resistance of 43.5 Ω. The upper electromagnetic generator can contribute an RMS voltage of 85 mV, corresponding to the peak power of 175 µW across 41 Ω under the same experimental condition. Finally, the harvester has been integrated into the shoe and it is able to charge a 100 µF capacitor up to 1 Volt for about 8 minutes foot movement. The result has remarkable significance in the development of wireless body monitoring sensors applications.

Study on a collecting structure for impact energy and its dynamic characteristics

The impact energy harvesting technology is studied in this paper, a piezoelectric harvesting structure with additional resonant structure including spring mass components is proposed, and the system dynamics model of the structure is studied. The influence of the structural parameters of spring mass block on the system output voltage is studied by using the model. The research results have certain application value for impact energy harvesting.

Design and analysis of a broadband three-beam impact piezoelectric energy harvester for low-frequency rotational motion

This paper proposes a three-beam impact energy harvester (TIEH) to enhance the energy harveting efficiency for low-frequency rotational motion. The design includes three beams, including the excitation beam, the harvesting beam and the protection beam. The excitation is generated by the impact of the excitation beam and the harvesting beam, and the harvesting beam breaks through the resonance state limitation to obtain more excellent performance in the low-frequency band. Through the design of centrifugal force, the soften or harden effect can be obtained to adapt to different application scenarios. In this paper, the TIEH electromechanical coupling model is established, and the concept of design factor is proposed for the centrifugal force scheme to simplify the design and analysis. The tested TIEH can obtain 52.1 μW at 4.2 Hz with 1.9 Hz bandwidth over 2 V. The Soften TIEH has a 23.0% power increase and 15.8% bandwidth reduction and the Harden TIEH has a 11.9% power reduction and 52.6% bandwidth increase. The results show that the TIEH has the characteristics of low frequency band, wide frequency band, and parameter insensitivity, and has the potential to be applied to a low-frequency rotational structure with limited volume.

A centrifugal softening impact energy harvester with the bistability using flextensional transducers for low rotational speeds

This paper presents a centrifugal softening impact energy harvester with the bistability using flextensional transducers. The bistability is firstly demonstrated to further enhance the advantages of the centrifugal softening effect in improving the impact energy output at low rotational speeds. In the harvester, two flextensional transducers are impacted by a centrifugal softening driving beam, which is experiencing the magnetic repulsive force at the same time. The flextensional transducers are adopted for their high electromechanical coupling coefficient and robustness under the large impact force. A theoretical model is built and validated by experiments. Experimental results show that the bistable harvester can generate higher energy output than the non-linear monostable and linear harvesters at the rotational speed ranging from 60 rpm to 360 rpm and a certain clearance of 1.07 mm. Its maximum instantaneous power and RMS voltage at 60 rpm are respectively increased by 323.1% and 184.3% compared with the non-linear monostable one, and 899.9% and 304.2% compared with the linear one. Such significant improvement cannot be achieved by changing the clearance in the linear harvester while it can be achieved by adding the bistability. Therefore, our proposed method facilitates the effective energy harvesting from widely-distributed low-speed rotations.

Wave impact energy harvesting through water-dielectric triboelectrification with single-electrode triboelectric nanogenerators for battery-less systems

This paper evaluates the effect of water-dielectric interfaces for wave impact energy harvesting at low frequencies (0.7 Hz–3 Hz) on the output performance of Water-Dielectric Single Electrode Mode Triboelectric Nanogenerators (WDSE-TENG). The triboelectric effect is generated between water (with a net positive charge) and a hydrophobic dielectric layer (with a net negative charge). Different WDSE-TENG configurations were tested using distinct hydrophobic materials. The water-fluorinated ethylene propylene (FEP) combination resulted in the best output performance. On the contrary, an output performance reduction by a factor of 3.53 was measured with seawater-dielectric interfaces. This can be compensated by increasing the contact area, with the best performance obtained using silicone rubber compound (Acetoxy, Elastomer) utilizing a WDSE-TENG with two-dielectric layer configuration. Employing seawater as a triboelectric material, the highest electrical output power and power density of 79.18 mW and 0.344 mW/cm2 was generated with a grid of WDSE-TENG, comprising five devices connected in parallel. The output voltage, current, transferred charge, stored energy and energy conversion efficiency (ECE) values of the grid of connected WDSE-TENG devices were compared against a single device. Such energy harvesters were able to power an ultrasonic range sensor and a one-way wireless transmitter for motion detection, distance measurement, and monitoring weather conditions. The stored energy and generated power were ~5.96 mJ and ~5.18 mW, respectively. Furthermore, the integration of the grid of WDSE-TENG with a power management control circuit (PMCC) is able to increase the output power and hence offer the potential to power up electronic devices with power consumption requirements between 1 mW and 100 mW. The results demonstrate that the grid of WDSE-TENG offers an innovative energy harvesting approach using water as a triboelectric material. The device can be used as an energy source for smart battery-less wireless sensing systems at water-structure interfaces in aquaculture (e.g. for fish detection or water level measurement) and weather condition monitoring.

Comprehensive theoretical and experimental investigation of the rotational impact energy harvester with the centrifugal softening effect

Rotation-based energy harvesting has attracted considerable interest in recent years. This paper presents a comprehensive theoretical model to analyze a rotational impact energy harvester using the centrifugal softening effect. The harvester is composed of a centrifugal-softening driving beam that impacts two rigid piezoelectric beams to generate electrical energy through the gravity excitation. The theoretical model is derived based on Hamilton’s principle and Hertzian contact theory. An impact force model is used to overcome the limitation of the previous piecewise linear model, which cannot reflect the influence of the deformations of the driving and generating beams on the impact force and the energy output. Furthermore, an analytical impact force model is originally proposed for such a harvester based on Lee’s method to understand the impact mechanism. The proposed analytical model is validated through comparison with Runge–Kutta method. Both numerical and experimental results show that the centrifugal softening effect can amplify the relative motion between the driving and generating beams and increase the impact force, thus improving output power at low rotational frequencies. The maximum output power is increased by 135.5% at 11.5 Hz for the impact gap of 0.75 mm. In addition, with the large impact stiffness, the impact force can successfully prevent the inverted driving beam from continuously deflecting and suffering the static divergence. Based on the validated theoretical model, parametric studies are conducted to further investigate the effects of the impact stiffness and the centrifugal softening coefficient.

Grid of hybrid nanogenerators for improving ocean wave impact energy harvesting self-powered applications

This paper describes an alternative approach for improving the output power performance for coastal wave impact energy harvesting systems, located at water-structure interfaces. This is achieved by simultaneously coupling the triboelectric and piezoelectric effects, exhibited in some materials. The use of finite element modelling, and experimental electrical characterization, enables the integration of hybrid devices into a breaking water wave generator tank. This provides a mechanism for simulating actual ocean wave conditions at low frequencies (0.7 Hz–3 Hz). Enhancements in the output performance by a factor of 2.24 and 3.21, relative to those obtained from using single triboelectric and piezoelectric nanogenerators, were achieved. This is demonstrated by evaluating the output current, voltage, transferred charge, and charging performance from a grid of up to four hybrid devices connected to capacitors of different capacitance values. Such hybrid devices were capable of powering a one-way wireless transmitter with a generated output power between 340.85 μW and 2.57 mW and sent a signal to a receiver at different distances from 2 m to 8 m. The research shows that such an integrated device can provide a promising mechanism for developing high-performance energy harvesting mechanisms for ocean wave impact to drive self-powered systems having an average power consumption of 1–100 mW. Further, it is estimated that through the construction of large water-hybrid nanogenerator-structure interfaces, output powers of approximately 21.61 W can be generated for powering networks of self-powered sensing systems in smart large-scale applications.