Beam Harvester Research Articles

A four bar mechanism as dynamic magnifier for improved performance of multi–modal piezoelectric harvester beams

A four bar mechanism as dynamic magnifier for improved performance of multi–modal piezoelectric harvester beams

Flexural wave energy harvesting by the topological interface state of a phononic crystal beam

In this study, we design the 3D-printed phononic crystal (PnC) beam with the topological interface state for harvesting the mechanical energy of flexural waves. The PnC beam is formed by arranging periodic grooves on its surface. The PnC beam with either topologically trivial or non-trivial phase can be achieved via changing the distance between the grooves. The topological interface state is then generated by combining two PnCs with distinct topological phases. The existence of the interface state of the PnC beam is verified both numerically and experimentally. To convert the mechanical energy into the electricity, a piezoelectric disc is attached at the interface of the proposed PnC beam. Compared to the reference beam harvester, the measured output power is significantly amplified by the PnC harvester at the frequency corresponding to the interface state. Furthermore, the PnC beam energy harvester based on the topological state exhibits robustness against geometrical disorders.

A rotational piezoelectric energy harvester based on trapezoid beam: Simulation and experiment

Rotational piezoelectric energy harvesters which can directly convert mechanical energy into electrical energy are considered as one of the most attractive harvesters for self-powered rotational wireless monitoring systems. In this paper, a trapezoid piezoelectric cantilever beam is proposed to improve the output of rotational piezoelectric energy harvester. Finite element simulation results indicate that the trapezoid beam harvester can bear higher stress than the rectangle beam harvester near the clamping end and show excellent electrical output properties. The experimental results are consistent with the simulation analysis results, and verify that the rotational piezoelectric energy harvesters are endowed with the characters of up-conversion frequency and ring-down pattern. Experimentally, a prototype trapezoid beam harvester has been fabricated to harvest wind energy, which can generate an average output power density of 0.64 mW/cm2 at the matching impedance of 50 kΩ. Our work has demonstrated that the proposed trapezoid beam harvester is a good potential generator for harvesting flow energies and monitoring conditions of rotating machinery.

Broadband rotary hybrid generator for wide-flow-rate fluid energy harvesting and bubble power generation

The ocean contains copious available natural resources and energy. Ocean in situ power generation technology, directly harvesting energy from ocean fluids, is the crux of solving the problem of power supply for eupelagic or deep-sea exploration equipment. However, the ultralow frequency and wide-flow-rate characteristics of ocean fluids have brought severe challenges to in situ power generation in the ocean. In this paper, we develop a broadband rotary piezoelectric-electromagnetic hybrid generator to effectively harvest the energy of wide-flow-rate and ultralow frequency fluids. By using rotational torque to directly drive deformation of piezoelectric films, the hybrid generator effectively collects extremely low-speed rotational energy (as low as 0.01 Hz), with the efficiency and speed of energy conversion of the piezoelectric component of the generator being respectively 8.2 times and 60 times higher than that of a traditional piezoelectric cantilever beam harvester. The integration of the electromagnetic component further improves the energy harvesting performance of the generator over a wide flow velocity range. Compared with existing energy harvesters, the water-driven power generation per unit flow rate is enhanced by a factor of 75.5. The output power density of the proposed underwater bubble power generation system using the hybrid generator is 287 mW/m3, which is 275 times higher than previous devices. This work provides a viable approach to blue energy exploitation, especially ocean in situ power generation, and opens up many prospects for underwater cable-free power supply to eupelagic or deep-sea equipment.

Experimental and numerical implementation of auxetic substrate for enhancing voltage of piezoelectric sandwich beam harvester

To harvest energy from environment vibration, it is a good way to use piezoelectric material as a generator that converts mechanical strain to electrical charge. This paper aims to develop a numerical model to predict the performance of piezoelectric energy harvester in beam configuration in accordance to experimental test and then study the effect of implementing auxetic substrate. Two beams are manufactured using isotropic and auxetic substrates. Implementing auxetic substrate excites piezo in both in-plane directions leading to generate more charge while equivalent stress remains constant. Modal test and frequency sweep are done for these two types of beams. For updating the model, mechanical and coupling properties of components in beam studied and more effective parameters are selected and participated in optimization. Genetic algorithm is used for optimization and converged after seven generations. The updated model has maximum 1.6% error in natural frequency and 5.6% in voltage. With a fine adjustment of beam dimensions, natural frequencies are set to 50 Hz and performance of two beams are compared. With same amount of piezo material and same stress applied on, a 30% improvement on output voltage is observed.

Vibro-impact energy harvester with optimal kinetic and elastic energies absorption

Many vibrating energy harvesters convert elastic or strain energy to electricity, while the energy of the structure is mainly distributed between potential and kinetic energies. The focus of the present work is on maximizing energy harvesting of the structure through the optimal energy absorption of its mechanical energy. The collision mechanism is used for this purpose. Primary piezoelectric harvester on the main structure and secondary piezoelectric harvester utilizing impact force in the form of harvesting beam used for this purpose. The results show that there is a significant increase in energy absorption and bandwidth. The effect of different geometrical and mechanical parameters on the system's efficiency is investigated. Experimental validation is presented to evaluate the theoretically obtained results. The presented mechanism gives up to 80 times improvement in the harvested power.

Dynamic analysis of a functionally graded piezoelectric energy harvester under magnetic interaction

The aim of this embodiment is to present an analytical analysis of a functionally graded piezoelectric energy harvester consisting of a flexible functionally graded piezoelectric layers carrying magnetic mass at the free end. The magnetic tip mass is in interaction with a permanent magnet which is located at a distance from the top of the tip mass. The oscillation of the harvester happens via excitation of the base. Using Rayleigh’s beam theory and Hamilton’s principle and considering geometric nonlinearity, the coupled electromechanical governing equations have been developed. The nonlinear frequency response of the piezoelectric energy harvester beam has also been studied under base excitation. A parametric study has been carried out to investigate the effect of grading index and magnetic force on responses of both free vibration and induced excitation cases. The results were compared with those obtained using three-dimensional finite element model developed in COMSOL Multiphysics 5.5 commercial software and good agreement has been observed. The results from both the analytical method and simulation confirm that tuning the design parameters of grading index and magnetic gap to the optimal value results in a considerable change in the performance of the energy harvester.

Analytical and experimental investigation of stepped piezoelectric energy harvester

Conventional Piezoelectric Energy Harvesters (CPEH) have been extensively studied for maximizing their electrical output through material selection, geometric and structural optimization, and adoption of efficient interface circuits. In this paper, the performance of Stepped Piezoelectric Energy Harvester (SPEH) under harmonic base excitation is studied analytically, numerically and experimentally. The motivation is to compare the energy harvesting performance of CPEH and SPEHs with the same characteristics (resonant frequency). The results of this study challenge the notion of achieving higher voltage and power output through incorporation of geometric discontinuities such as step sections in the harvester beams. A CPEH consists of substrate material with a patch of piezoelectric material bonded over it and a tip mass at the free end to tune the resonant frequency. A SPEH is designed by introducing a step section near the root of substrate beam to induce higher dynamic strain for maximizing the electrical output. The incorporation of step section reduces the stiffness and consequently, a lower tip mass is used with SPEH to match the resonant frequency to that of CPEH. Moreover, the electromechanical coupling coefficient, forcing function and damping are significantly influenced because of the inclusion of step section, which consequently affects harvester's output. Three different configurations of SPEHs characterized by the same resonant frequency as that of CPEH are designed and analyzed using linear electromechanical model and their performances are compared. The variation of strain on the harvester beams is obtained using finite element analysis. The prototypes of CPEH and SPEHs are fabricated and experimentally tested. It is shown that the power output from SPEHs is lower than the CPEH. When the prototypes with resonant frequencies in the range of 56-56.5 Hz are tested at 1 m/s2, three SPEHs generate power output of 482 μW, 424 μW and 228 μW when compared with 674 μW from CPEH. It is concluded that the advantage of increasing dynamic strain using step section is negated by increase in damping and decrease in forcing function. However, SPEHs show slightly better performance in terms of specific power and thus making them suitable for practical scenarios where the ratio of power to system mass is critical.

System-level finite element analysis of piezoelectric energy harvesters with rectified interface circuits and experimental validation

The finite element method (FEM) has been widely used for numerical studies of piezoelectric energy harvesting (PEH) systems, through commercial finite element (FE) packages or specially developed FE formulations. As a convenient computational tool, FEM can deal with systems of high complexity and has evolved into a multiphasic solution to coupled problems in engineering. However, most of FE packages and formulations are limited to coupled-field simulations of PEH systems connected with a linear circuit. On the other hand, rectified circuits are a critical component in practical applications because electronic devices such as wireless sensor nodes and wearable electronics require a DC power supply. Based on the equivalent impedance analysis, this paper proposes a method to enable a coupled-field study of piezoelectric energy harvesters with the standard AC-DC interface circuit through an equivalent linear circuit. The proposed method enables FE packages and formulations to analyze, design, and optimize PEH harvesters at the system level, by either adding the capability of simulating rectified circuits, or reducing a nonlinear circuit interface simulation into a faster and more stable linear simulation that can be solved more conveniently. This equivalent linear circuit method was applied to a rectangular shaped bimorph beam harvester in ANSYS and validated experimentally. The results also match well with those obtained from a system-level analytical approach. As an application example, a comparison study was performed between the rectangular and triangular energy harvesters using FE packages and the proposed equivalent circuit, given the same natural frequency and material volume. In addition, the implementation of this method with FE formulations is briefly outlined and discussed.

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.

Electromechanical modelling of piezoelectric vibration energy harvester with a novel dynamic magnifier

Abstract In piezoelectric energy harvesting devices, the relative displacement between the two ends of the harvester beam decides the output power from the piezoelectric patch. A novel four bar mechanism with a helical spring is used as a dynamic magnifier to improve the relative displacement and thereby the output power from the harvester. This dynamic magnifier is placed between the base excitation location and the composite harvester beam to form two degrees of freedom (2DOF) piezoelectric energy harvester. Electromechanical coupled analytical equations for the voltage and output power are derived using a lumped electromechanical model. The model is developed assuming linear transverse vibrations of the harvester. A dynamic magnifier is fabricated for the required frequency range and the suitable dimensions of the harvester beam are estimated using commercially available software. Experiments are conducted for base excitation amplitude of 0.05 mm and the performance of the proposed 2DOF harvester is studied for the output voltage and power. The proposed 2DOF harvester has shown 110 % improvement in output power in first mode and 270 % improvement in second mode compared to the conventional single degree of freedom (SDOF) cantilevered harvester for given identical input conditions. The measured frequencies and output power are validated with analytical solutions and are found to be in good agreement. Further, the effect of mass ratio, stiffness ratio and base excitation amplitude on the output voltage and power is investigated using analytical expressions.

Enhancing Performance of a Piezoelectric Energy Harvester System for Concurrent Flutter and Vortex-Induced Vibration

This paper proposes a novel and efficient energy harvester (EH) system, for capturing simultaneously flutter and vortex-induced vibration. There exists a coupling effect between flexible spring energy harvester (FSEH) and cantilever beam energy harvester (CBEH) in aerodynamic response and output characteristic. Many prototypes of the harvester were manufactured to explore the coupling effect in a wind tunnel. The experimental results demonstrate that FSEH is mainly subjected to flutter-induced vibration and CBEH undergoes vortex-induced vibration. Disturbance of FSEH first takes place, a limited oscillation cycle then occurs, and chaos ultimately happens as airflow velocity increase. Root mean square voltages are more than 11 V for FSEH at beyond 10.52 m/s, which shows the better output performance over the existing harvesters. Vibration response and output voltage of various harvesters are mutually enhanced with each other. An enhancing ratio for FSEH-130-25 is up to 69.6% over FSEH-130-0, while the enhancing ratio for CBEH-130-30 is 198.3% compared to CBEH-0-30. Field application testing manifests that discharging time to power the pedometer is almost twice as long as the charging one for FSEH-130-25 at 14.48 m/s. The current research offers a suggestive guidance for promoting future practical application in micro airfoil aircrafts.

Performance of non-uniform functionally graded piezoelectric energy harvester beams

The appearance of functionally graded piezoelectric materials has solved the lamination problem of the conventional piezoelectric structures. Functionally graded piezoelectric materials are the new materials with unexplored capabilities. This article theoretically investigates the effects of non-uniformity on the performance of the functionally graded piezoelectric material cantilever beams subjected to harmonic excitation. The governing equations are derived based on Timoshenko and Euler–Bernoulli beam theories. The finite element method with the application of superconvergent element is employed here for the discretization and the vibration analysis of the system. This model is validated by comparing the numerical results with the experimental results of piezoelectric energy harvesters of conventional shapes available in the open literature. Parametric studies are carried out with respect to the effects of tapering ratios, the degree of non-uniformity, load resistance, and the volume fraction parameter on the electrical output power and the fundamental resonance frequency. It was observed that the application of diverging beams noticeably enhances the power output per mass of piezoelectric element extracted while decreases the natural frequency which is advantageous for scavenging energy from ambient surroundings. The results reveal that there is an optimal value for the non-homogeneous parameter leading to the maximized harvested energy under different operating conditions.

Numerical modelling of micro energy harvesting systems based on piezoelectric composites polarized with interdigitated electrodes

This paper focuses on the numerical modelling of micro-energy harvesting systems(MEHSs) based on piezoelectric composites polarised with interdigitated electrodes (PCPIE). The system response and the harvested energy are numerically assessed using a multilayer piezoelectric shell finite element (FE) with a uniform fibre aligned electric field (UFAEF) in each active layer. Circuit and compatibility equations are included to take into account the presence of the electrical network. A state-space (SS) model is derived and used to evaluate the effect of electrical impedance on damping and natural frequencies, as well as dissipated energy/power. An energy harvester beam with a piezoelectric macro fibre composite (MFC) patch is first modelled with the developed tools. Numerical results are found to be in good agreement with experimental results reported in the literature. Finally, a MEHS consisting of a closed-box beam equipped with PCPIE devices bonded to its skin is analysed. The structural system is subjected to dynamic loading imposing oscillating displacements and deformations compatibles with those expected during service-life. Numerical results show the influence of the electrical impedance on system response, damping, natural frequencies, and electrical power.

Electro-vibration modeling and response of 3D skeletal frame configuration for energy harvesters

3D skeletal frame configuration is introduced as a means for overcoming deficiencies encountered by conventional 1D beam energy harvesters (EHs). A composite finite element model based on 3D beam kinematics is further developed and tailor-made for this purpose. A comprehensive electro-vibration analysis is conducted using a MATLAB code for the 3D skeletal frame EH as an enhanced application of the theory and compared to the corresponding 1D beam harvester. The results obtained by the theory is then validated against numerical responses based on active solid elements. It is shown that the novel 3D skeletal frame configuration offers substantial benefits over the conventional 1D beam including higher strain areas, multi-directionality, and effectively higher extracted power levels. These are actually among the most significant deficiencies by 1D beam topologies. The internal volume of the novel EH along with the surfaces of the tip mass can be utilized for electronic components and circuit boards.

An isotope harvesting beam blocker for the National Superconducting Cyclotron Laboratory

Harvesting isotopes from beam stops and other activated materials at accelerator facilities is a promising source of environmentally, scientifically and socially important radionuclides. At the Facility for Rare Isotope Beams (FRIB), a multitude of short- and long-lived radionuclides will be collected in a synergistic manner by dumping unused beams into a flowing-water beam stop. Ongoing exploratory research at the National Superconducting Cyclotron Laboratory (NSCL) with an analogous beam blocker aims towards obtaining the necessary radiochemical expertise for this endeavor.Herein we present a beam blocker and an isotope harvesting system which allows collection of a wide variety of aqueous and gaseous radionuclides. The water which flows through the beam blocker functions as an isotope production target and concurrently transports the newly formed radionuclides to collection sites. The system includes analytical instruments for online measurements of conductivity, dissolved oxygen, temperature, pressure and for detection of radiolytic products. To limit the levels of radiolytically produced hydrogen peroxide, a stainless-steel based degradation system was designed and implemented. The suitability of the constructed system for the anticipated radionuclide harvesting project was demonstrated by offline tests and under irradiation with 140 MeV/u 48Ca20＋ ions at the NSCL Coupled Cyclotron Facility.

A novel passive mechanism to improve power output in 2DOF piezoelectric vibration energy harvester

Cantilevered piezoelectric vibration energy harvesters are usually operated in the first mode and analysed as single degree of freedom (SDOF) systems. To improve their performance, a two degree of freedom (2DOF) system with a novel dynamic magnifier is developed by combining four bar mechanism and helical spring to act as elastic magnifier. This dynamic magnifier is attached between the base (excitation location) and the fixed end of cantilevered elastic harvester beam. To identify a suitable configuration for the dynamic magnifier, simulations are performed with two different configurations of passive mechanism, viz., 1:2 and 1:1 magnification four bar mechanisms. The natural frequencies of the first two modes obtained with 1:1 magnification four bar mechanism are close, giving good bandwidth and the mechanism is fabricated according to the simulation results. The simulated relative displacements and first two modal frequencies are in good agreement with experiments. There after macro fiber composite (MFC) with copper as substructure is used to fabricate the harvester beam within the required operating frequency range. The improvement in measured output power from 2DOF harvester over SDOF harvester is found to be 110% in the first mode and 270% in the second mode. Further, bandwidth analysis and effect of increase in magnifier mass is also investigated and performance characteristics of proposed 2DOF harvester are compared with the earlier similar harvesters. This kind of harvester with a novel four bar mechanism as a dynamic magnifier has not been reported in literature.

Novel tunable broadband piezoelectric harvesters for ultralow-frequency bridge vibration energy harvesting

With a nonlinear X-shaped structure connected with piezoelectric harvesters through two types of special mounting configurations (horizontal and vertical cases), novel coupled vibration energy harvesting systems are purposely constructed and investigated for exploiting nonlinearity and structural coupling effect in vibration energy harvesting. Different from concentrating on a beam harvester itself in the literature (i.e. the beneficial nonlinearity comes from the beam itself), this study focuses on exploring the nonlinear benefits that the X-shaped structure could provide, together with structural coupling effect. The novelty lies in that the coupled X-structured harvesting systems have both the advantages of the existing simple cantilevered beam harvester (harvesting power only at around the natural frequency of the beam) and the spring-mass system supported beam harvester (harvesting energy only at around the natural frequency of the supporting spring-mass system). With the proposed X-structures, the effective operation bandwidth of traditional cantilever based harvesters can be greatly enlarged and also be extended to an ultralow frequency range. This is a very special feature of the proposed X-structure based harvesting systems compared with conventionally designed cantilevered harvesters or the spring-mass supported cantilevered harvesters. The proposed devices can be regarded as advantageous versions of the cantilever-based configurations for ultralow frequency range. In addition, the X-structured harvesters can achieve very tunable harvesting bandwidth (i.e. tuning the harvesting frequency of the first peak) by adjusting several structural parameters. The experiment tests demonstrate that the proposed harvesting devices hold potentials for traffic-induced bridge vibration energy harvesting, which can be used for powering the sensors for bridge health monitoring.

Promote efficiency of harvesting vibration energy by tailoring potential energy with addition of magnets

Large-amplitude snap-through motion might happen between two equilibria of a buckling inverted piezoelectric beam under vibration excitation, therefore enhancing the energy harvesting performance of system significantly. However, in practical application, owing to the deep potential well of a buckling beam, relatively large excitation amplitude is needed to trigger such snap-through motion. To overcome this limitation, we herein propose an improved inverted beam harvester that comprises an inverted beam with an affixed tip magnet and two additional magnets mounted in the vicinity of the equilibrium positions. By introducing this repulsive magnetic force, the potential energy could be tailored to promote the occurrence of snap-through motion. Numerical simulation is conducted and it is shown that with the proposed design the harvester would be able to realize snap-through motion more easily compared to the original buckling system. This has also been validated by the experiment in which large deflection and voltage output are both observed when snap-through motion is activated under low excitation frequency.

Design and analysis of a hollow triangular piezoelectric cantilever beam harvester for vibration energy collection

The vibration of transportation infrastructure is random and of low frequency. The vibration energy can be collected and converted into electric energy by installing the piezoelectric cantilever beam (PCB) harvesters on the transportation infrastructure. The resonance frequency and the resonance number of the PCB harvesters within the low frequency range play critical roles. This paper presents an analysis of four types of PCB harvesters designed according to the characteristics mentioned above to evaluate the influence of three different shapes (rectangle, trapezoid and triangle) on the power generation capacity of the piezoelectric cantilever beams. The results show that the triangular PCB harvesters are more suitable for the low-frequency vibration environment of transportation infrastructure, and they usually have higher voltage outputs. In order to widen the resonant frequency of the triangular cantilever to better adapt to the random vibration environment of the transportation infrastructure, the performance of a hollow triangular piezoelectric cantilever beam (HTPCB) was also assessed. Through modeling and analysis, the resonant frequency of the HTPCB has a broader low frequency range. In practical applications, deployment of the HTPCB harvesters on transportation infrastructures such as pavements and bridges can collect more energy in the random and low-frequency vibration environment of the transportation infrastructures.