Conventional Energy Harvester Research Articles

Effect of geometric non-linearity and tip mass on the frequency bandwidth of a cantilever piezoelectric energy harvester under tip excitation

The research community is investigating a variety of approaches to convert mechanical energies to useful electrical energy in order to fulfil the ever-increasing demand for energy and fulfil the requirements of the various sectors. In this regard, numerous contributions toward increasing the capacity and efficiency of the various energy harvesting techniques have been proposed in recent times; one such promising technology is piezoelectric-based vibration energy harvesting. In the present work, the effect of geometric nonlinearity and tip mass is investigated on the operational frequency range of a cantilever nonlinear piezoelectric energy harvester. The proposed mathematical model is based on an energy-based variational approach. The methodology is formulated for the piezoelectric patched cantilever beam and, eventually solved using an efficient numerical technique . An amplitude incremental iterative algorithm is used to solve the non-linear governing equations of motion for the proposed non-linear broadband harvester along with the experimental validation. Firstly, a parametric study is performed to determine the optimum piezoelectric patch dimensions. Subsequently, the attempt is made to increase the frequency bandwidth for optimum energy harvesting by taking advantage of geometrically non-linear behaviour. Additionally, a tip mass, appropriate for the excitation level, can be added to the harvester design to make it effective for lower excitation frequency. Increased frequency bandwidth for improved energy harvesting capacity with the hardening type nonlinearity and tip mass is meaningfully shown with the help of frequency-amplitude response. Furthermore, to interpret the efficacy of nonlinear harvesters in terms of frequency band-width, power spectral density plots with improved harvesting capability are presented and compared with the conventional linear vibration energy harvester.

Rationally Designed Anti‐Glare Panel Arrays as Highway Wind Energy Harvester

AbstractThe anti‐glare panels along highways can block the dazzling lights of opposing vehicles at night, playing an important role in the highway safety. Inspired by the highway anti‐glare panels, wind energy harvesting triboelectric nanogenerator (AG‐TENG) arrays to properly capture energy from highway moving vehicles is developed. A single AG‐TENG installation module can achieve a high power density of 0.2 Wm−2 at a wind speed of 3 m s−1. This wind speed is too low to drive conventional wind energy harvesting equipment. The performance of the AG‐TENG shows no degradation after 80 h of continuous operation (1 440 000 times). Thus, with the rational consideration and features, the system can generate enough power to drive internet of things (IoT) devices and environmental sensors, as well as offer wireless alarming and radio frequency identification vehicle monitoring. This study provides a promising strategy to properly harvest wind energy on highways using existing infrastructures under the condition of even no natural wind, showing broad application prospects in distributed environmental monitoring, intelligent highways, and the IoT.

Configurable Hybrid Energy Synchronous Extraction Interface With Serial Stack Resonance for Multi-Source Energy Harvesting

Conventional multi-source energy harvesters use the time-division multiplexing (TDM) scheme, where the inductor operates in discontinuous current mode (DCM) and fails to perform well in continuous current mode (CCM). This article presents a single-inductor hybrid energy synchronous extraction circuit with serial stack resonance (SSR) for multi-source energy harvesting. The proposed circuit incorporates a synchronous electric charge extraction (SECE) circuit for ac energy and two buck–boost circuits for dc energy with a single inductor, which can operate either in a TDM mode to harvest energy from different sources separately or in an SSR mode to extract energy from multiple sources synchronously. The proposed harvester is fabricated in a 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS process. It is configured with a photovoltaic (PV) cell, a thermoelectric generator (TEG), and two piezoelectric transducers (PZTs), where the number of PZTs is flexible to meet different application needs.

Super-Aerophilic Biomimetic Cactus for Underwater Dispersed Microbubble Capture, Self-Transport, Coalescence, and Energy Harvesting.

Human ocean activities are inseparable from the supply of energy. The energy contained in the gas-phase components dispersed in seawater is a potential universal energy source for eupelagic or deep-sea equipment. However, the low energy density of bubbles dispersed in water introduces severe challenges to the potential energy harvesting of gas-phase components. Here, a super-aerophilic biomimetic cactus is developed for underwater dispersive microbubble capture and energy harvesting. The bubbles captured by the super-aerophilic biomimetic cactus spines, driven by the surface tension and liquid pressure, undergo automatic transport, coalescence, accumulation, and concentrated release. The formerly unavailable low-density dispersive surface free energy of the bubbles is converted into high-density concentrated gas buoyancy potential energy, thereby providing an energy source for underwater in situ electricity generation. Experiments show a continuous process of microbubble capture by the biomimetic cactus and demonstrate a 22.76-times increase in output power and a 3.56-times enhancement in electrical energy production compared with a conventional bubble energy harvesting device. The output energy density is 3.64 times that of the existing bubble energy generator. This work provides a novel approach for dispersive gas-phase potential energy harvesting in seawater, opening up promising prospects for wide-area in situ energy supply in underwaterenvironments.

Enhancing the Bandwidth and Energy Production of Piezoelectric Energy Harvester Using Novel Multimode Bent Branched Beam Design for Human Motion Application.

In recent years, harvesting energy from ubiquitous ultralow-frequency vibration sources, such as biomechanical motions using piezoelectric materials to power wearable devices and wireless sensors (e.g., personalized assistive tools for monitoring human locomotion and physiological signals), has drawn considerable interest from the renewable energy research community. Conventional linear piezoelectric energy harvesters (PEHs) generally consist of a cantilever beam with a piezoelectric patch and a proof mass, and they are often inefficient in such practical applications due to their narrow operating bandwidth and low voltage generation. Multimodal harvesters with multiple resonances appear to be a viable solution, but most of the previously proposed designs are unsuitable for ultralow-frequency vibration. This study investigated a novel multimode design, which included a bent branched beam harvester (BBBH) to enhance PEHs' bandwidth output voltage and output power for ultralow-frequency applications. The study was conducted using finite element method (FEM) analysis to optimize the geometrical design of the BBBH on the basis of the targeted frequency spectrum of human motion. The selected design was then experimentally studied using a mechanical shaker and human motion as excitation sources. The performance was also compared to the previously proposed V-shaped bent beam harvester (VBH) and conventional cantilever beam harvester (CBH) designs. The results prove that the proposed BBBH could harness considerably higher output voltages and power with lower idle time. Its operating bandwidth was also remarkably widened as it achieved three close resonances in the ultralow-frequency range. It was concluded that the proposed BBBH outperformed the conventional counterparts when used to harvest energy from ultralow-frequency sources, such as human motion.

On analysing vibration energy harvester with auxetic core and magneto-electro-elastic facings

Powering systems without heavy maintenance-intensive batteries is a challenge for various engineering applications. Often, energy in the form of heat, vibration, sound etc., is squandered while operating many machines/structures. A judicious utilisation of these potent energies using energy harvesters (EH) will reduce the degree of dependency on depletable energy sources. Sometimes, EH acts as a parasitic mass and consumes additional space. To address this issue, the current work proposes a lightweight vibration-based bimorph beam (VBBB) EH constituted of multifunctional magneto-electro-elastic (MEE) facesheets and auxetic metamaterial core (AMC). The frequency response functions, which consider series and parallel configurations of the active ME layers, are derived using distributed parameter single-mode formulation to quantify the system’s output response. The overall effect of the negative Poison’s Ratio of the auxetic materials, combined with the material, geometric and parameters such as the number of turns and resistances, is investigated. The advantage of using an auxetic core to enhance the energy harvester’s performance is realised through an improved power output as the thickness of the auxetic core layer rises. The maximum values of the output parameters are witnessed for larger auxetic angles and lower rib–length ratios. Meanwhile, greater values of the geometrical parameters like length-to-thickness ratio and length-to-width ratio result in enhanced power harvested. A comparative study justifies that under similar working conditions, the power output of the auxetic-based energy harvester is almost 1.5 times more than the conventional metal-based energy harvesters. Further, auxetic-based EH reported a 22% weight reduction for the same power output obtained from the conventional metal-based EH. This enables the lightweight construction of low-powered smart systems with enhanced efficiency. It is believed that the results of this article will lead to further studies on utilising multifunctional composites and metamaterials for complex engineering applications.

A hybrid piezoelectric and electrostatic energy harvester for scavenging arterial pulsations

Implantable and wearable biomedical devices suffer from a limited lifespan of on-board batteries which require change causing physical discomfort. In order to overcome this, various energy harvesters have been developed as the human body possesses several types of energy available for scavenging through appropriately designed energy harvesting devices, while the cardiovascular system in particular represents a constant reliable source of mechanical energy from vibration. Most conventional energy harvesters exploit only a single phenomenon, such piezo- or triboelectricity, thus producing reduced power density. As an improvement, hybridisation of energy harvesters intends to negate this drawback by simultaneously scavenging energy by multiple harvesters. In the present work, the reverse electrowetting on dielectric (REWOD) phenomenon is combined with the piezoelectric effect in a proof-of-concept hybrid harvester for scavenging biomechanical energy from arterial or other type pulsations. A mathematical model of the harvester was developed; and, an investigation using computational fluid dynamics simulations was carried out using the COMSOL Multiphysics software. The effect of the materials of piezoelectric film and geometrical features of the harvester on parameters such as the displacement, the frequency of pulsations and the energy produced were studied. An experimental setup that could model the time-varying pressures and displacements caused from arterial pulsations was designed and the characteristics of the produced piezoelectrical energy were analysed. A comparison between experimental and computational data was carried out demonstrating a good agreement. The dependencies between geometrical parameters and electrical output were determined and recommendations on piezoelectric materials and design solutions were provided.

A novel wake-excited magnetically coupled underwater piezoelectric energy harvester

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

Enhancing the power level harvested by rectenna systems based on focusing metasurfaces for ambient environments

Electromagnetic (EM) RF (radio frequency) energy harvesting in dynamic ambient environments is a challenge for conventional energy harvesting systems such as rectennas. The main challenges are the low efficiency of the collector and low ambient power levels, which makes it hard to consider in industrial applications. Several research works have focused on the design of high-efficiency antennas to achieve an efficient and maximum possible level of RF EM energy harvesting. Their main objective is to improve the EM energy harvesting system by overcoming the low efficiency of the collector, which is the main part of the rectenna system. In this work, we propose and investigate a methodology in terms of EM energy harvesting based on the concentration and focusing of EM energy in a small zone where it can be easily collected and transferred indirectly to the rectenna system. It consists of a focusing device and a methodology to associate the latter with existing RF energy harvesting systems. We demonstrate a focusing metasurface design implemented alongside an off-the-shelf rectenna device at 900 MHz, where an enhanced energy harvested power level up to a linear gain of 8 is achieved compared to the case when only the rectenna is used. Numerical results as well as measurements results in an anechoic chamber are shown. Experimental power received levels are given both in the focusing plane and in time for the validation of the concept.

A new energy harvesting scheme for multi-relay cooperative networks

Wireless networks have gone through unprecedented changes in the last decade owing to the rise in the number of users. Radio frequency (RF) energy harvesting (EH) (termed as RF-EH) can be a potential solution to encounter the energy constraints in the next generation wireless devices. In this study, we have proposed a new RF-EH technique from an RF source which was, to the best of our knowledge, not considered useful in any previous works. We have investigated the performance of an RF-EH cooperative multi-relay network by benefiting from the transmitted signal of the best relay (Rb) to the destination. In the most common RF-EH cooperative multiple relaying networks, only the relays harvest energy from the signal of source to power up themselves. However, in the proposed RF-EH technique, both the signals of source and Rb are exploited to harvest energy. In the proposed scheme, each of the relays harvests energy from the transmitted signal by source during phase-1, whereas the relays other than the Rb also harvest energy from the transmitted signal of Rb to destination during phase-2. Additionally, we have investigated our proposed scheme for both time-switching and power-splitting receiver architectures. Finally, from the simulation results, an increase in the system throughput and better outage performance is observed in the proposed scheme as compared to the conventional EH protocol in which EH is performed merely from the signal of source.

Theoretical modelling and experimental investigation on a frequency up-converted nonlinear piezoelectric energy harvester

Ambient vibration energy harvesting has attracted the great attention of numerous researchers to replace the battery power supply strategy of electronic devices. However, the high natural frequency and narrow broadband operation are still significant shortcomings of the conventional vibration energy harvesters to be widely deployed. This paper presents a novel piezoelectric energy harvester (PEH) based on the traditional impact frequency up-converted PEH to achieve lower and broader operating frequency. Nonlinear magnetic force is adopted to regulate the working frequency of PEH. Distributed-parameter modelling and magnetic force simplified modelling are applied in analyzing the piecewise linear dynamic characteristics of the low-frequency driving beam, and the piezoelectric effect is employed for calculating the output voltage of the high-frequency generating beams. Theoretical results comparison between the traditional impact PEH and the proposed novel PEH shows that the introduced nonlinear magnetic force offers a lower initial frequency and broader operating bandwidth. The comparison experimental study achieves a close match to the theoretical results. Under excitation conditions of 3 m/s 2 excitation acceleration, 3 mm impact distance, and 19 mm magnet distance, the initial frequency decreases by about 9.5 Hz, and the operating bandwidth increases from 9 Hz to 16.5 Hz. The maximum power output value of the proposed PEH is 0.491 mW. The novel proposed PEH in this paper provides promising guidance and understanding for energy harvesting in low and broadband environmental vibration. • A novel frequency up-converted nonlinear piezoelectric energy harvester (PEH) is proposed for lower and wider bandwidth energy harvesting. • Developed the theoretical model and analyzed the performance of the device based on averaging method. • The comparison experimental results achieve a close match to the theoretical research that the novel PEH has lower and wider operating frequency than the conventional impact PEH.

On a nonlinear broadband piezoelectric energy harvester with a coupled beam array

A conventional energy harvester usually has narrow operational bandwidth, which makes it difficult to harvest energy with varying frequencies in the actual field. Herein, a nonlinear piezoelectric energy harvester with a coupled beam array is designed to broaden bandwidth and improve energy harvesting performance. The proposed harvester consists of a base, two elastic supports, and four piezoelectric beams with different natural frequencies. Due to the coupling effect caused by the two elastic supports, the four piezoelectric beams have large output voltages not only at their own natural frequencies, but also at the natural frequencies of other beams. Meanwhile, the two elastic supports enable the four piezoelectric beams to become nonlinear beams, which also contributes to operational bandwidth broadening. Next, the equivalent mass-spring-damping model and governing equations of the harvester are obtained, based on the lumped-parameter method. A strong coupling is found to occur when the equivalent stiffness of the elastic support is small. Subsequently, a fabricated prototype and an experiment platform are utilized to measure the energy harvesting performance of the harvester. Under 1 g up-sweep excitation, the average output power of the harvester from 40 Hz to 80 Hz is 144.2 % higher and the bandwidth is 93.3 % wider than those of the non-coupled multi-resonance harvester, which houses four beams separately. Finally, actual applicability of the proposed energy harvester is evaluated by operating a Bluetooth location tracking Internet of Things (IoT) device without a battery. Besides, the fabricated prototype is applied to the vehicle engine where the frequencies of vibration sources change rapidly with time and velocity. The field test argues that the harvester can be used in unstable or varying conditions, where a typical vibration energy harvester may not work efficiently, due to its limited operational bandwidth.

An enhanced galloping-based piezoelectric energy harvester with non-rotational bluff body

This study proposes a bluff body non-rotational galloping-based piezoelectric wind energy harvester (BNRGH) for overall output performance enhancement. The bluff body used in this structure is designed to be available to rotate with respect to the free end of two cantilever beams by the connection of rotatable hinges. A series of performance comparisons are conducted experimentally in a wind tunnel between the proposed structure and the conventional galloping-based piezoelectric energy harvester, which commonly configured with a single beam. The results show that the proposed structure is capable of preventing the variation of the attack angle due to the self-rotation of the bluff body caused by the deflection of a common single beam, thus avoiding the amplitude saturation of the bluff body at a higher wind velocity range. It shows that the output voltage remains a continuous linear increase within elastic deformation range of the cantilever beam even in higher wind velocity range, which is helpful in accomplishing a broad wind range for a significant improvement of the overall performance. Overall, the proposed BNRGH provides a design guidance for a small size galloping-based energy harvester to achieve an excellent output performance, which holds great potential to promote its application in wireless node networks for self-power supply.

Adaptive Capacitor Charging Circuit With Simplified Configuration for Efficient Piezoelectric Energy Harvesting

In this study, we present an adaptive capacitor charging circuit for efficient piezoelectric (PE) energy harvesting (EH), which simplifies the configuration for powering wireless sensor network (WSN) nodes. In the circuit, the PE harvester directly charges the storage capacitor through the rectifier, eliminating the energy loss in the dc–dc converter of conventional EH circuits. An adaptive control circuit is designed to optimize the average charging power. Theoretical analysis shows that the optimal average power of the novel circuit varies from 81.4% to 86.5% of the maximum power of the conventional EH circuit, without considering the power dissipation in the dc–dc converter. Moreover, the power losses of both the proposed and conventional circuits are estimated. When the excitation level is low, the net harvested power of the proposed circuit can be enhanced to as high as 180% of that of the conventional circuit. The experimental results validate that the power transferred to the load is increased by adopting the proposed interface. It is also proved that the circuit is adaptive to different harvesters and excitation conditions. In addition, the area of the proposed circuit is reduced, allowing it to be easily integrated into the WSN nodes.

Performance investigation of a crossing angle adjustable galloping-based energy harvester

In this study, we proposed a crossing angle adjustable galloping-based piezoelectric energy harvester (CAGPEH) configured with a lambda-shaped beam to improve the energetic performance. The proposed structure can overcome the limitation of the installation capability of a conventional galloping energy harvester with a single cantilever beam by varying the crossing angle. This structure can change the crossing angle between primary and secondary beams so that the bluff body always faces the changing wind direction to ensure an efficient harvesting performance. A distributed parameter model was established using Euler-Bernoulli beam theory and Lagrange method, and a series of numerical analyses was performed to uncover the dynamical behaviors of the aero-electromechanical coupled system. The first two modes were considered to obtain a comprehensive understanding of the dynamic behaviors at different crossing angles. We validated the theoretical model through amplitude and output voltage comparisons between numerical and experimental results. The results show that a larger crossing angle and a smaller length proportional factor of the primary and secondary beams help reduce the critical wind velocity. The results show that a significant increase rate of 103% in the overall average output power (OAOP) can be achieved with a crossing angle of 30° and a proportional factor of 0.6. It is expected that the CAGPEH can help develop self-power systems for applications in wireless sensor systems.

Water Droplet‐Based Nanogenerators

AbstractWater is one of the most sustainable resources in the world, offering an abundance of hydro energy. Getting a large amount of electricity through conventional water energy harvesting is expensive, with complex mechanisms and bulky installation systems. In the case of the small amount of energy for some portable electronic devices and sensor systems, water droplet harvesting as a sustainable energy resource has become a forward‐looking step to meet the future demand for green energy. The ultimate demand for green energy in the future requires all the possible sustainable energy sources surrounding human society. The emerging potential of water droplet‐driven energy‐harvesting nanogenerators can meet a significant portion of the green energy demand. In this review, the recent developments in droplets‐driven nanogenerators for effective energy scavenging is summarized. It also includes an extensive discussion about the device structures from the material selection and output performance aspects. This review also gives a brief discussion on the applications of droplet‐based nanogenerators and outlines the future possibilities via the current improvement in designs and fabrication strategies that have been introduced by the field.

Defect-mode-induced energy localization/harvesting of a locally resonant phononic crystal plate: Analysis of line defects

Phononic crystals that are artificially engineered structures have recently been introduced for vibration energy harvesting and sensing applications due to their unique features of band gaps and wave propagation control. Conventional energy harvesters made of phononic crystals are mainly designed for acoustic energy harvesting at a high-frequency vibration source (i.e., kHz levels). In this work, a defect-mode-induced energy harvester is designed for low-frequency excitations in the range of 0–300 ​Hz. The entire system that is a locally resonant phononic crystal (LRPC) plate with line defect patterns is consisted of elastic-wrapped core scatterers periodically embedded in epoxy resin. A two-dimensional (2D) three-component unit cell structure is arranged on the plate and the band gap property is analyzed to optimize the geometric parameters. Defects are then introduced to the LRPC plate with a 7 ​× ​7 point array for analysis. In addition, numerical and experimental studies are conducted to investigate the performance of energy harvesting when attaching a piezoelectric patch on the defect points. The results demonstrate that the proposed LRPC vibration energy harvester having a line defect mode (with continuous or alternate points) shows good performance in energy harvesting, in which a peak power output of 42.72 ​mV can be achieved under 10 ​m/s2 and 252 ​Hz. The performance is almost 6 times more than that of the single-point defect model under the same excitation conditions. The present LRPC-type energy harvester with a line defect mode is more suitable for energy harvesting for low-frequency and broadband conditions.

A rotational vibration energy harvester for near-zero-energy applications in railway environment

The vibration in the railway environment contains a huge amount of available mechanical energy, which can be utilized as a practical power source for low-power independent distributed appliances. This paper proposed a rotational vibration energy harvester (RVEH) based on a linear cam mechanism for near-zero-energy applications in railway environment. The RVEH system mainly consists of a motion conversion mechanism (MCM) and electromagnetic generators. The motion conversion mechanism realizes the motion conversion from vibration to uni-directional rotation based on a linear cam and a one-way rectifier. The electromagnetic generators convert kinetic energy into electrical energy. The test shows that the electric outputs of the proposed RVEH is improved under vibration excitations compared with the conventional vibration energy harvester (VEH, the RVEH without a one-way rectifier). Also, the RVEH has a comparatively long duration of electric outputs after the vibration excitation, suitable for the intermittent vibration excitation input. And the RVEH can operate as a power supply, producing output characteristics of an average output power of 66 mW and a peak output power of 0.15 W, sufficient to power 155 LEDs in series or a thermometer. It is foreseeable that the RVEH is a promising self-powered solution for applications in railway environment.

An ultra-low frequency ball-impacted potential-variable nonlinear energy harvester

Efficient energy harvesting for ultra-low frequency vibrations remains a large challenge. An ultra-low frequency ball-impacted potential-variable nonlinear energy harvester (abbreviated as BPNEH) is proposed in this work to provide a new solution for the challenge. Upon excitation, a horizontal beam, which is magnetically coupled to a vertical one, vibrates back and forth with large amplitudes through ball-impacts, along with a variable potential energy due to the vibration of the coupled vertical one. A prototype of the proposed BPNEH is fabricated to demonstrate the effective contribution of both the ball-impact and the variable potential energy under an ultra-low frequency excitation. Compared to a conventional potential-variable nonlinear energy harvester (abbreviated as PNEH), the RMS voltage of the proposed BPNEH is increased by 78.4 % in 1–8 Hz, along with a sub-peak that appears to the left side of the main peak. This new finding of a double peak phenomenon is further observed and clarified by a theoretical model, where the output voltage of the proposed BPNEH is increased by 209.6 % in 1–10 Hz. In addition, the main factors affecting the sub-peak in the observed double peak phenomenon are also considered and discussed with respect to harvesting more energy. The proposed BPNEH along with the double peak phenomenon is believed to be applicable to ultra-low frequency scenes, especially with large amplitudes, of engineering fields such as wearable devices, structural health monitoring systems, etc.

Optimization for piezoelectric energy harvesters with self-coupled structure: A double kill in bandwidth and power

Vibration energy harvesting is promising to supply power autonomy for many electronic devices. This paper proposes a novel nonlinear piezoelectric energy harvester with a two-degree-of-freedom self-coupled structure. The operating frequency range and the power output of the new harvester is enhanced simultaneously compared with the conventional stopper-based nonlinear energy harvester. The dynamic model of the self-coupled structure is established, and then the bucket hat-like elastic potential energy function of the structure is obtained, which accounts for the superior performance of the harvester. Moreover, an optimization methodology for developing the nonlinear piezoelectric energy harvester was proposed. The conventional and novel energy harvesters were designed, optimized, and fabricated. Experimental results indicate that the maximum output power of the novel energy harvester can be enhanced to 3.54 times of that of the conventional energy harvester with a stopper structure. Besides, the working bandwidth is broadened from 4.7 Hz to 5.2 Hz. It is expected that this work is devoted to the future improvement of vibration energy harvesters in practical applications.