Energy Harvesting Characteristics Research Articles

A comprehensive numerical study on flow-induced vibrations with various groove structures: Suppression or enhancing energy scavenging

This paper focuses on the enhancement or suppression effect of flow-induced vibration (FIV) caused by symmetrically installed groove structures with different shapes under high Reynolds numbers. The fluid flow field is simulated using the non-constant two-dimensional Reynolds-averaged Navier-Stokes (2D-RANS) equation and the SST k-ω turbulence model. A cylinder attached to four different groove shapes (square, triangular, semicircular, and two quarter-circle splices) is simulated for each shape of the groove with five mounting angles. The oscillatory amplitude, frequency response, displacement time history curve, vortex shedding mode, and energy harvesting characteristics are analyzed for each working condition at 2 < U* < 14 and 2.02 × 104 <Re < 1.44 × 105. The results show that the cylinder with different groove shapes and installation angles have different dynamic responses. The oscillatory amplitude of the square groove bluff body with α = 30°, 60°, and 150° is basically enhanced compared to the smooth cylinder, and the working bandwidth is increased as well. For the square groove placed at α = 60°, the oscillatory amplitude increases by 100% compared to the smooth cylinder, and the working bandwidth of the square groove at α = 90° is reduced by 50%. For the square groove body with α = 120°, the amplitude is enhanced, but the working bandwidth is reduced. The working bandwidth of the triangular groove is widened at all five angles, with the α = 60° groove being optimal, widening by 75%. Except for the triangular groove with α = 90°, the amplitude is improved to some extent compared with the smooth cylinder. The working bandwidths of the semicircular grooves are widened, and the improvement effect of α = 150° is the smallest of the five angles. For the two quarter-circle splices grooves, the grooves arranged at α = 30°, 90°, 120°, and 150° have a decrease in amplitude when U* = 6, and more pronounced at 90° and 120°. Two quarter-circle spliced groove cylinders with α = 120° have the best amplitude enhancement effect.

Correlation Assessment Between Power Generation by Indoor Photovoltaic Energy Harvesting and Storage Characteristics

Correlation Assessment Between Power Generation by Indoor Photovoltaic Energy Harvesting and Storage Characteristics

Multi-solution phenomena and nonlinear characteristics of tristable galloping energy harvesters with magnetic coupling nonlinearity

Different from linear energy harvesters, nonlinear energy harvesters have multi-solution phenomena and nonlinear characteristics, some of which are beneficial for high-performance energy harvesting. This paper employs the incremental harmonic balance method to deduce the semi-analytical solutions of bistable and tristable nonlinear galloping energy harvesters. The traditional harmonic balance method is used to select the initial values for the incremental harmonic balance method, and the two points tracing algorithm is used to track each solution curve. The stabilities of the semi-analytical solutions are determined by the Floquet theory. The multi-solution phenomena and nonlinear characteristics of tristable galloping energy harvesters and bistable galloping energy harvesters are revealed. The root-mean-square voltage and response frequency of the bistable galloping energy harvester have three non-zero solutions and only one is stable. Those of the tristable galloping energy harvester have nine non-zero solutions (two of which are stable) and the tristable galloping energy harvester has two cut-in wind speeds. Subsequently, cases with different nonlinear stiffness coefficients are studied. Overall, this paper provides a framework for the theoretical analysis of nonlinear flow-induced vibration energy harvesters.

Modeling of a Porous Piezoelectric Nano Energy Harvester Based on Timoshenko-Beam Theory

Collecting electric power from the vibration of piezoelectric beams is practical and has been widely used for decades. This paper investigates a porous piezoelectric cantilever Timoshenko-beam energy harvester at nanoscale. The aim is to propose an optimized Timoshenko beam in order to gain more power with the same working conditions. For this purpose, the width of the beam is assumed to be exponentially changing and pores are also introduced into the beam to relieve the inherent brittleness of piezoelectric materials. Based on Timoshenko beam theory and porous piezoelectric elasticity, the uncoupled motion equations of the porous piezoelectric nanoTimoshenko beam are deduced. The analytical solutions to the output voltage and power density are obtained. According to the numerical calculation, it can be concluded that the electrical output can be improved by increasing the section parameter. Moreover, the surface effects and pore properties on the energy harvesting characteristics are discussed. In addition, when there is a concentrated mass at the free end of the beam, the displacements and output power are studied.

Synergistic analysis of wake effect of two cylinders on energy harvesting characteristics of piezoelectric flag

In this study, the effect of asymmetric wake flow regime of two side-by-side cylindrical bluff bodies on power output is experimentally examined by using a piezoelectric flag. Different synchronization modes of the flag with wake flow are observed. It is demonstrated that the streamwise gap between the flag and cylinders (Gx), and the center-to-center gap between cylinders have a significant impact on the flag's dynamical behavior that results in a fluctuation in the power output of the piezoelectric flag. The levels of output power are analyzed by varying the Gx and the cross-stream or lateral gap (N/d) between the two cylinders. N/d values from 1.0 to 2.0 for different values of Gx (2.0 ≤ Gx ≤ 4.0) are experimentally tested. The comparison of the flapping response at each point is made to ascertain the impact of the harvester's dynamic behavior on the output energy. The power generated at each point is recorded for all cases and a comparative analysis is made to find the optimal configuration. Limited research is conducted in the past to enhance the energy output by using the bluff body with the improved wake dynamics. Hence, two cylinders are employed in a uniform flow and crosswise gap between cylinders is varied to change the characteristics of the wake region. The cylinder arrangement with N/d = 1.0, shows continuous oscillations and higher output power persisting for 2.0 ≤ Gx ≤ 4.0. The monotonic rise in power output is observed till Gx = 4.0. The stated configurations with N/d = 1.0 gives a significant advantage over a single-cylinder-based energy harvester as a kinetic source of fluid energy harvester from the flowing fluid. The output power became almost doubled with an increase of 95% approximately using side-by-side arrangement.

Energy-Harvesting Characteristics of a Dual-Mode Magnetic Suspension for Vehicles: Analysis and Experimental Verification

The advantages of the proposed dual-mode magnetic suspension are it having a high level of safety and a compact structure compared with the previous studies. However, the structure parameters can affect the energy harvesting of the suspension system. Therefore, this paper aims to analyze the energy-harvesting characteristics of the proposed dual-mode magnetic suspension. Firstly, the structure and working principle of the proposed suspension are introduced. Then, the influences of the various parameters for the actuator on the energy regeneration characteristics are analyzed by the finite element method, such as the magnetic ring, the fixed plug thickness, the heat dissipation, and the air gap, and the actuator parameters are defined by the orthogonal analysis method. Furthermore, the numerical results of the energy harvesting are calculated. Finally, the vibration experimental setup is manufactured, and the simulation analysis is verified by the experiment. The results demonstrate that the excitation amplitude is 3.1 mm, the frequency is 18 Hz, and the maximum induced EMF is 8.8 V. Additionally, compared with passive suspension, the energy harvesting of the proposed suspension has been verified in the laboratory, which lays the foundation for the design and analysis of the dual-mode magnetic suspension in a real vehicle.

Enhanced piezoelectric response in BTO NWs-PVDF composite through tuning of polar phase content

We have fabricated a flexible, environment friendly piezoelectric nanogenerator (PENG) based on the ferroelectric Polyvinylidene fluoride (PVDF) composite incorporated with Barium titanate (BaTiO3) nanowires (NWs) of piezoelectric coefficient d 33 = 308 pm V−1. The single-layered PENG can deliver output power density of 10 μW cm−2 and an output voltage of 2 V with a nominal mechanical load of 1 kPa. BaTiO3 (BTO) NWs of different concentrations were incorporated into PVDF to tune the polar phase content, internal resistance, and optimize the output power. We show that there exists a critical value of BTO NWs loading of 15 wt%, beyond which the piezoelectric energy harvesting characteristics of the PVDF nanocomposites decrease. The oxygen vacancies present in the BTO NWs surface attract the fluorine ions of PVDF chain and favour the formation of β phase. The enhanced value of dielectric constant and dielectric loss of BTO-PVDF samples in the low frequency region suggest strong interfacial polarization in the composite system. The fabricated PENG can charge a super-capacitor up to 4 V within 35 s. The origin of the high power output from the BTO (15 wt%)-PVDF composite is attributed to the combined effect of enhanced polar phase content, strong interfacial polarization, and reduced internal resistance. This study provides an effective pathway in enhancing the performance of BTO-PVDF based piezoelectric energy harvesters.

Harvesting airflow energy from circular cylinder wake via a thin polyvinylidene fluoride film

To improve the characteristics of airflow energy harvesting, this paper presents a new piezoelectric wind energy harvester (PWEH), in which a polyvinylidene fluoride (PVDF) film was directly located in the wake of the circular cylinder. Four important parameters were independently varied for detailed experimental investigations: wind speed, spacing ratio for the distance between the center of the circular cylinder and the tip of the PVDF film to the circular cylinder diameter, diameter of the circular cylinder, and load resistance. The results indicated that the designed PWEH performed optimally with the occurrence of resonance, maintaining a relatively high output when significantly exceeding the resonance wind speed. The PVDF film inhibited the vortex shedding of the circular cylinder, which weakened with increasing spacing ratio. The optimum value of the spacing ratio should be approximately 2.5, which yields an effective coupling between the vortex and structure. The diameter of the circular cylinder played an important role in determining the output power. The match between the load resistance and PWEH also contributed to the high-level performance. Moreover, with an increase in the diameter of the circular cylinder, the increasing blockage ratio unexpectedly enhanced the vortex shedding frequency and decreased the theoretical resonance wind speed, which provided a new orientation for improving the performance of such PWEHs.

Electrical Response of Ba&lt;sub&gt;0.7&lt;/sub&gt;Ca&lt;sub&gt;0.3&lt;/sub&gt;TiO&lt;sub&gt;3&lt;/sub&gt;-BaZr&lt;sub&gt;0.2&lt;/sub&gt;Ti&lt;sub&gt;0.8&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Solid Solution

The structure, microstructure, Fourier transformed infrared spectra, dielectric, and impact generated energy harvesting characteristics of x(Ba0.7Ca0.3)TiO3–(1-x)Ba (Zr0.2Ti0.8)O3; x = 0, 0.5, and 1.0 synthesized using solid-state reaction method are discussed in this work. The X-ray diffraction (XRD) process was used to examine the forming of a single-phase compound. The Rietveld refinements of XRD data were used in FullProf software to determine crystal symmetry, lattice parameters, and space groups. A scanning electron microscope was taken into use to examine the surface morphology of all of the samples. The samples' phase transition temperature was observed to lie between-10°C and 87°C, shifting toward the higher temperature side as x increased. In the case of x = 0.5, two-phase transitions were discovered at 22°C and 70°C. The value of impact generated output voltage and electrical energy increases as applied mechanical energy increases. The findings of this study point to the possibility of using 0.5(Ba0.7Ca0.3)TiO3–0.5Ba (Zr0.2Ti0.8)O3 ceramic for energy harvesting and sensing purposes.

Performance improvement of a control valve with energy harvesting

Providing a continuous and stable power supply to monitoring equipment in intelligent pipe network systems far from the grid is a complex and urgent problem. Ball valves are widely used in various fluid delivery systems, by adding an energy harvesting characteristic to the spool of the ball valve, a new type of ball valve with a Savonius impeller is proposed, which not only has the fluid regulation characteristics of traditional valves, but also harvests energy in the fluid. Based on CFD simulation software, the matching characteristics of valve and impeller are studied by using slip mesh technology, the energy harvesting performance of valves under different openings is analysed, and the influence of the parameter change of the overlap ratio and blade arc angle of impeller on the energy harvesting characteristics of valves is also studied. The results show that the energy harvesting performance of the valve is the best at 25% opening, the energy harvesting performance is the best at the overlap ratio Rs = 0 and Rs = 0.15, and the energy harvesting performance is better in the range of blade arc angle θ = 80°–180°.

Power characteristics of vibration-based piezoelectric energy harvesters: the effect of piezoelectric material nonlinearity

Piezoelectric energy harvesting has received tremendous interests in the past two decades as a viable solution to self-powered electronics and devices. Recently, significant emphasis has been given to nonlinear energy harvesters driven by the desire for broadband, high-performance energy harvesting. Numerous efforts have been devoted to the understanding and modeling of the electromechanical coupling and the effect of nonlinearities introduced by mechanical and electrical aspects of the system. However, very few works in the literature considered the effect of piezoelectric material nonlinearity on the system power performance. Nevertheless, it has been found that piezoelectric nonlinearity is significant even at low to moderate excitation level. This paper is motivated to study the power behavior of piezoelectric energy harvesters with piezoelectric nonlinearity, most importantly, the power limit and electromechanical coupling. For this purpose, an approximate model is developed from the nonlinear model in the literature to derive the closed-form expressions of important power characteristics. Analytical analysis shows that the effect of piezoelectric material nonlinearity results in a nonlinear damping term and a nonlinear stiffness term in the approximate model. The approximate solutions of optimal load resistance, maximum power, power limit, and critical electromechanical coupling are obtained and validated by numerical simulations first. The induced nonlinear damping reduces the power limit of the system compared to its linear counterpart. Interestingly, a harvester that exhibits strong electromechanical coupling under small excitation could become weakly coupled under large excitation. The analytical analysis and numerical results are validated by experiments.

Simple analytical models and analysis of bistable vibration energy harvesters

In order to scavenge the energy of ambient vibrations, bistable vibration energy harvesters constitute a promising solution due to their large frequency bandwidth. Because of their complex dynamics, simple models that easily explain and predict the behavior of such harvesters are missing from the literature. To tackle this issue, this paper derives simple analytical closed-form models of the characteristics of bistable energy harvesters (e.g. power-frequency response, displacement response, cut-off frequency of the interwell motion) by mean of truncated harmonic balance methods. Measurements on a bistable piezoelectric energy harvester illustrate that the proposed analytical models allow the prediction of the mechanical displacement and harvested power, with a relative error below 10%. From these models, the influences of various parameters such as the inertial mass, the acceleration amplitude, the electromechanical coupling, and the resistive load, are derived, analyzed and discussed. The proposed models and analysis give an intuitive understanding of the dynamics of bistable vibration energy harvesters, and can be exploited for their design and optimization.

A novel seesaw-like piezoelectric energy harvester for low frequency vibration

This paper presents a novel seesaw-like piezoelectric energy harvester which has rotating motions to enhance the harvesting performance at low frequency vibrations. Firstly, the designing of the harvester with the specific structure was accomplished, and then the finite element analysis was conducted to simulate its dynamic characteristics. Finally, the prototype of the harvester was fabricated whose power generating behaviors were experimentally investigated. The influence of key structural parameters on the energy harvesting performance was evaluated by a combination of simulation and experiment. The effect of the inertia difference on the energy harvester characteristics was studied innovatively. The results indicated that the energy harvester reached the second-order resonance at a low frequency due to the adoption of the rotating shaft. And the piezoelectric material was involved in a significant strain due to the inertia difference between both ends of the beam. The efficiency of the harvester is relevant to the system moment of inertia and the excitation acceleration. The second-order resonant frequency of the harvester is as low as 19.18 Hz. When the excitation acceleration is 2.94 m/s2, the maximum output voltage and power of the harvester are 49.15 V and 4.03 mW respectively, which demonstrates the superior harvesting performance of the structure. This work can provide a novel method for designing efficient ambient energy harvesters supplying for low-power electronic devices.

Energy harvesting characteristics of a flapping wing with the oscillating aspirators in uniform flows and shear flows

In this study, we install oscillating aspirators on the upper and lower wing surfaces of the airfoil to intensify energy harvesting characteristics of a flapping wing. At the Reynolds number of 1100, an unsteady laminar 2-D numerical simulation has been used to understand the characteristics of flapping wings’ energy harvesting in uniform flows and shear flows. We focus on the adaptability between the oscillating aspirators and the motion of flapping wings, and demonstrate how the oscillating aspirators and its environmental adaptability can help improve energy harvesting efficiency. Under the same working conditions, the energy collection efficiency of flapping wings in shear flows is not as good as that in uniform flows. The results show that when the oscillating aspirator works on lower wing surface at 0.0T–0.5T and works on the upper wing surface at 0.5T–1.0T, the energy collection efficiency reach the highest. The flow field analysis shows that the oscillating aspirator can increase the pressure gap of airfoil’s both sides and makes the vortex closer to the airfoil. The oscillating aspirator can improve the lift force and torque of flapping wings in both uniform flows and linear shear flows.

Piezoelectric properties and related parameters of novel 1–2–2 composites based on single crystals of the PZN–xPT type

High-performance 1–2–2 composites based on domain-engineered relaxor-ferroelectric single crystals are analyzed, which demonstrate strong electromechanical coupling and large energy-harvesting characteristics. The role of the single-crystal rods and laminar polymer matrix is highlighted. A large anisotropy of the piezoelectric charge coefficients d 3j* and electromechanical coupling factors k 3j* is observed in specific volume-fraction ranges, with proposed dependence diagrams. The effective parameters of composites with parallelepiped-shaped rods are compared to similar parameters for composites based on cylindrical rods, with good agreement between parameters. These novel composites can be used in piezoelectric sensors, actuators, transducers, and energy-harvesting devices.

A Versatile Model for Describing Energy Harvesting Characteristics of Composite-Laminated Piezoelectric Cantilever Patches.

Vibration-based energy harvesters consisting of a laminated piezoelectric cantilever have recently attracted attention for their potential applications. Current studies have mostly focused on the harvesting capacity of piezoelectric harvesters under various conditions, and have given less attention to the electromechanical characteristics that are, in fact, crucial to a deeper understanding of the intrinsic mechanism of piezoelectric harvesting. In addition, the current related models have mostly been suitable for harvesting systems with very specific parameters and have not been applicable if the parameters were vague or unknown. Drawing on the available background information, in this study, we conduct research on a vibration-based cantilever beam of composite-laminated piezoelectric patches through an experimental study of its characteristics as well as a modeling study of energy harvesting. In the experimental study, we set out to investigate the harvesting capacity of the system, as well as the electromechanical (voltage/current-strain and power-strain relationships) characteristics of the cantilever harvester. In addition, we summarize some pivotal rules with regard to several design variables, which provide configuration design suggestions for maximizing energy conversion of this type of harvesting system. In the modeling study, we propose a coupled electromechanical model with a set of updated parameters by using an optimization program. The preceding experimental data are used to verify the superiority of the model for accurately predicting the amount of harvested energy, while effectively imitating the characteristics of a cantilever harvesters. The model also has merit since it is suitable for diversified harvesters with vague or even unknown parameters, which cannot be dealt with by using traditional modeling methods. Overall, the experimental study provides information on a comprehensive way to enhance the harvesting capacity of piezoelectric cantilever transducers, and the modeling study provides a wide scope of applications for cantilever harvesters even if precise information is lacking.

Multiferroic and energy harvesting characteristics of P(VDF-TrFE)-CuFe2O4 flexible films

Ferroelectric polymer-based multiferroics are very promising candidates for a wide variety of applications. To realize such a composite material with remarkable multiferroic behavior, we have developed CuFe 2 O 4 nanoparticles loaded poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) films by a solvent casting approach. Different weight percentages (2, 4, 8 and 16) of CuFe 2 O 4 nanoparticles were achieved in the P(VDF-TrFE) matrix. Remarkable improvement in the multiferroic behavior has been observed with the addition of the magnetic nanoparticle. Through this approach, by adjusting the filler content we could vary the magnetoelectric coupling coefficient from 6.12 to 26.31 mVcm −1 Oe −1 . The piezoelectric energy harvesting performances of the prepared multiferroic materials were also studied. The energy harvesting devices based on the developed materials were produced output voltages between 3 and −3 V during repeated pressure imparting. • CuFe 2 O 4 nanoparticles loaded P(VDF-TrFE) films were developed by a solvent casting approach. • Dielectric, magnetic and magnetoelectric properties of the composites were enhanced with CuFe 2 O 4 nanoparticles loading. • The highest ME coefficient of 26.31 mVcm −1 Oe −1 was noticed for the composite film with 16 wt% of CuFe 2 O 4 nanoparticles. • Developed PEHDs produced output voltages between 3 and −3 V during repeated pressure imparting.

A hybrid sensor for motor tics recognition based on piezoelectric and triboelectric design and fabrication

With the gradual development of various artificial electronic skins and smart patches and other wearable electronic products, the collection of biomechanical energy to achieve self-powered sensing is critical to achieving the efficient function and sustainability of the system. In this work, a study of a novel hybrid sensor fabricated based on the piezoelectric and triboelectric design for motor tics recognition will be presented. A plant bionic and flexible hybrid self-powered sensor (PBHS) for motor tics recognition is reported. By combining bionic polydimethylsiloxane (PDMS) triboelectric nanogenerator and a layered stacked porous polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) nanofiber piezoelectric nanogenerator in mixing through near-field electrospinning (NFES) process on the flexible printed circuit board (FPCB) substrate, this enables the sensor which is a layer-by-layer stacked porous PVDF-TrFE nanofiber (LPPN) mainly composed of about 2500 piezoelectric polymers as a height of 2.2 mm thin wall to enhance energy harvesting characteristics. Compared with the original PVDF-TrFE nanogenerator, the voltage output performance is nearly reached to 5 V as a ~200% improvement. Furthermore, a self-powered tics recognition system has been developed through deep learning to provide doctors to observe the status of patients with motor tics of Tourette syndrome. By using the deep learning model of long short-term memory (LSTM) of a type of recurrent neural network (RNN), the overall sequences hybrid signal recognition rate for tic recognition has been achieved to 88.1%.

Investigation on the interphase effects on the energy harvesting characteristics of three phase magneto-electro-elastic cantilever beam

In this work the influence of the interphase region in a three-phase magneto-electro-elastic composite material on the energy harvesting characteristics of a vibration based cantilever beam is studied analytically. The three-phase composite made of Barium Titanate/Terfenol-D/Cobalt Ferrite with different interphase regions have been considered for the evaluation. The mathematical expressions for the coupled governing equations are derived through a lumped parameter model in conjunction with Gauss's Law, Newton's Law and Faraday's Law. The generated electric and magnetic potential are harvested through the surface electrodes and a wound coil. The numerical results suggest that the interphase volume fraction and composition adversely affect the coupled material properties, which in turn significantly alters the output response of the energy harvester. Also, the lower values of resistance and number of turns of coil have a predominant effect on the energy harvester's performance. The results of this work demonstrate the significance of the interphase region and its effects on the coupled energy harvesting behavior in multifunctional composite materials.

Vibration-Based Energy Harvesting Characteristics of Functionally Graded Magneto-Electro-Elastic Beam Structures Using Lumped Parameter Model

Vibration-Based Energy Harvesting Characteristics of Functionally Graded Magneto-Electro-Elastic Beam Structures Using Lumped Parameter Model