Piezoelectric Conversion Research Articles

Energy harvesting using a dynamic weighing system based on piezoelectric materials

Road transport is one of the main energy-consuming sectors. Therefore, the concept discussed in this article is of great interest since it aims to transform this sector into a producer of clean and renewable energy by using piezoelectric conversion. The work carried out in this article concerns the study of the electrical power density recovered by a miniaturized dynamic weighing system using piezoelectric sensors inserted into the road surface and by varying the speed and the weight of the vehicle. The system studied in this article therefore offers the possibility of measuring and then controlling the load of a moving vehicle using the vibrations generated during its passage and then converting them into electricity by direct piezoelectric effect. A mathematical model representing the relationship between the weight of the vehicle and the voltage peaks generated by the passage of the latter over the piezoelectric sensors has been developed. This model was implemented on the Matlab software, which made it possible to carry out, based on several experimental tests, a study of the variation of the coefficients of proportionality according to the weight of the vehicle and its rolling speed. The power density collected by this application at different speeds and masses was then calculated. According to the tests carried out, the recovered power density is approximately 36.06 W/m3 for a travel speed of 0.52 m/s and a vehicle weight equal to 1150 g.

Electromechanical conversion efficiency of GaN NWs: critical influence of the NW stiffness, the Schottky nano-contact and the surface charge effects.

The piezoelectric nanowires (NWs) are considered as promising nanomaterials to develop high-efficient piezoelectric generators. Establishing the relationship between their characteristics and their piezoelectric conversion properties is now essential to further improve the devices. However, due to their nanoscale dimensions, the NWs are characterized by new properties that are challenging to investigate. Here, we use an advanced nano-characterization tool derived from AFM to quantify the piezo-conversion properties of NWs axially compressed with a well-controlled applied force. This unique technique allows to establish the direct relation between the output signal generation and the NW stiffness and to quantify the electromechanical coupling coefficient of GaN NWs, which can reach up to 43.4%. We highlight that this coefficient is affected by the formation of the Schottky nano-contact harvesting the piezo-generated energy, and is extremely sensitive to the surface charge effects, strongly pronounced in sub-100 nm wide GaN NWs. These results constitute a new building block in the improvement of NW-based nanogenerator devices.

An investigation on an absorber working through piezoelectric conversion mechanism

AbstractA novel absorber, which is equivalent to a spring and a damper, is developed and the corresponding equivalent formulae of stiffness coefficient and damping coefficient are derived. The key component of the absorber is the circular array of multi‐section U‐shaped piezoelectric coupled beams (MUPCBs) which can alleviate harmful vibration of various devices by converting the vibration energy into electrical energy. As an example, the absorber is used in a quarter vehicle suspension system, and its properties of energy harvesting and vibration attenuation are studied using the computational model of dual‐mass iteration method. The dual‐mass model includes two sprung masses (body mass and wheel mass) which are linked by the absorber. The effects of some important factors, such as the piezoelectric coupling section (PCS) length, the PCS substrate thickness, the force arm length of the MUPCB, the speed of vehicle and the class of road surface on the root mean square (RMS) of the output power, are discussed. The research results show that half of the amplitude of the harmful vibration can be attenuated and a power up to 254.3 W can be realized by the absorber made of MUPCBs in the quarter vehicle suspension computational case. This research provides a feasible piezoelectric absorber suitable for various devices by transferring the vibration energy into electricity to attenuate the harmful vibration and achieve the energy recycling application.

Application of Smart Materials in the Actuation System of a Gas Injector.

This paper presents the results of research related to the selection of materials for passive and active components of a three-layer piezoelectric cantilever converter. The transducer is intended for use in a low-pressure gas-phase injector executive system. To ensure the functionality of the injector, its flow characteristics and the effective range of valve opening had to be determined. Therefore, a spatial model of the complete injector was developed, and the necessary flow analyses were performed using computational fluid dynamics (CFD) in Ansys Fluent environment. The opening and closing of the injector valve are controlled by a piezoelectric transducer. Thus, its static electromechanical characteristics were found in analytical form. On this basis, the energy demand of the converter, required to obtain the desired valve opening, was determined. Assuming a constant transducer geometry, 40 variants of material combinations were considered. In the performed analyses, it was assumed that the passive elements of the actuator are made of typical materials used in micro-electromechanical systems (MEMSs) (copper, nickel, silicon alloys and aluminum alloys). As for the active components of the converter, it was assumed that they could be made of polymeric or ceramic piezoelectric materials. On the basis of the performed tests, it was found that the energy demand is most influenced by the relative stiffness of the transducer materials (Young’s modulus ratio) and the piezoelectric constant of the active component (d31). Moreover, it was found that among the tested material combinations, the transducer made of silicon oxide and PTZ5H (soft piezoelectric ceramics) had the lowest energy consumption.

Hydrocavitation Piezoelectric Ocean Wave Energy Harvesting

Abstract The possibility to convert the ocean wave energy into electrical energy by piezoelectric layers has excited the imagination of ocean wave energy conversion designers for decades owing to its relative robustness (no mechanical parts are needed), the capability to cover large areas, and its relatively low cost. Unfortunately, the very poor efficiency featured by piezoelectric layers in the application of ocean waves has prevented its application even as an energy harvester. Here, the possibility to induce hydrocavitation and then working with higher local pressures for substantial efficiency enhancement is discussed. Utilizing a simplified geometrical and physical model and the linear and potential theory, a first theoretical estimation for the energy enhancement driven by hydrocavitation was calculated. It was found that the power could be enhanced several orders of magnitude which, although still rather low, however, the enhanced electric outputs can be used now as energy harvesters. Additional R&D is encouraged in order to explore the possibilities to harness hydrocavitation to enhance piezoelectric converters.

A low-frequency rotational electromagnetic energy harvester using a magnetic plucking mechanism

Energy harvesting from rotational motion, such as vehicle tires and rotational devices, remains a challenge because of the difficulty of balancing the harvesting frequency range and the power-generation density and efficiency. Traditional energy harvesters using the mechanism of magnetic plucking and piezoelectric conversion cannot overcome the inherent disadvantages of the output power and the strictness of the application conditions. In this study, a low-frequency rotational electromagnetic energy harvester using a nonlinear magnetic plucking configuration is proposed. Using the novel structure to pluck a cylindroid generating magnet in each rotational motion, the resetting effect provides a new way to stabilize the output voltage and improve the energy harvesting performance. Two design factors for controlling the resetting effect were studied theoretically and experimentally. The finite element method based on the Maxwell stress tensor not only helps in understanding the magnetic field density distribution in the energy harvesting process but also reveals the resetting mechanism. Simulating a vehicle tire with a diameter of 0.6 m rotating at a speed of approximately 20 km/h, it was experimentally validated that the maximum average output power across all the rotating frequencies (0.5–5.0 Hz) reached 13.13 mW under certain excitation conditions in the experiment, which is increased by 215.9% compared with the harvester without the resetting effect. The great performance under different application conditions demonstrated that the proposed electromagnetic energy harvester has a great potential in energy harvesting from low-frequency rotational motions.

Micro windmill piezoelectric energy harvester based on vortex-induced vibration in tunnel

A micro windmill piezoelectric energy harvester is proposed to explore the wind energy translation based on vortex-induced vibration(VIV). The novel power takeoff is composed of a wind turbine with three blades, an air blast blower, an ancillary wind tunnel, and a circular PVDF piezoelectric converter. The air blower improves the airflow speed in the wind tunnel. A bluff body is fixed in the flow field to induce vortex and excite the circular PVDF piezoelectric film vibration. Theory and experiments are conducted to investigate the energy translation. Based on the blade element momentum method(BEM), the theoretical model of the air blast blower is derived. The calculation results show that the axial fan blasts the air into the wind tunnel, and the airflow speeds range from 1.37 m/s to 18.78 m/s. Furthermore, the theoretical model of the VIV is developed to decorated the airflow aerodynamic characteristics around the bluff body. The vortex-induced high-frequency resonance consequently improves the piezoelectric energy harvesting efficiency and promotes the excitation force amplitudes. Correspondingly, the output electric power on the piezoelectric plate is numerically investigated based on the theoretical model and experiment. The optimal output power matches the load resistance and the wind velocity on the bluff body. The maximal output power arrived at 8.97 μW on the external load resistance of 650 KΩ with a wind velocity of 19 m/s. Furthermore, experimental results validate the theoretical dynamic model and show that a windmill piezoelectric energy harvester based on vortex-induced vibration (VIV-WPEH) can increase the output power over either range of the low natural airflow speed and the optimizing bluff body individually.

Piezoelectric ceramic for energy harvesting from ambient vibration

Direct piezoelectric conversion is very popular in generating power from mechanical stress. There is continuous progress in power harvesting from mechanical vibration. In this article, experimental tests on a piezoelectric circular plate, to evaluate the electric power produced by the piezoelectric conversion at low acceleration over a wide range of ambient vibration frequency, are presented. The experimental analysis is presented and discussed. The results demonstrate the potentiality of using low-cost piezoelectric diaphragms to harvest energy from ambient vibration. Under low acceleration (5.36 m/s2), the vibration frequency was varied in the range of 10– 200 Hz and the generated power was measured. Under a very small dynamic force (less than 0.06 N), the output power of 1.5 mW was obtained with an 8.5 mm drum harvester across a load resistance of 17.8 kΩ at a frequency of 173 Hz.

A study of a new hybrid vibration energy harvester based on broadband-multimode

To improve the energy conversion efficiency and working frequency bandwidth of a single frequency piezoelectric vibration energy harvester, a new type of hybrid vibration energy harvester is developed which is combined with the mechanism of piezoelectric and electromagnetic energy conversion. The system comprises of a PZT cantilever beam, an elastic suspended magnetic mass, a magnet block attached to the end of the cantilever beam and a resonator. The addition of resonator can not only increase the mode, but also adjust the frequency of harvester flexibly. Nonlinear magnetic force of magnet block not only broadens the frequency band and improves the output performance of the system, but also changes the resonant frequency to make the harvester have better adjustable performance. On this basis, an improved electromechanical coupled analytical model of continuum is proposed which can be solved by the Runge-Kutta algorithm and the influence of different factors (the mass and spring stiffness of the resonator, as well as the electromechanical coupling coefficient, electromagnetic coupling coefficient, magnet mass and magnetic flux) on the output are analyzed. According to the prototype of the vibration energy harvester developed, an experimental system was built. The performance of the independent and hybrid energy harvesters is evaluated by experimental and analytical methods. The peak output voltage of the piezoelectric part was about 4 times that of the electromagnetic part. The peak output current of the electromagnetic part is about 30 times that of the piezoelectric part. The study results show that the proposed new hybrid vibration energy harvester can achieve a wider frequency range and multimodal vibration energy harvesting. In addition, the bandwidth and power of the harvester can be dynamically adjusted by changing the resonator or electromechanical coupling coefficient, and the bandwidth of the harvester can also be adjusted by changing the quality and characteristics of the magnet.

Определение координат отражателей в плоскости, перпендикулярной сварному соединению по эхосигналам, измеренным преобразователями по схеме TOFD

The TOFD method, which is widely used in ultrasonic flaw detection, makes it possible to distinguish a crack from a volume reflector by the phase of the echo signals and to determine its height with high accuracy. However, the TOFD method without scanning the piezoelectric transducers across the weld joint does not allow to determine the displacement of the reflector from the center of the welded joint, which is very important when evaluating the results of the control. The scanning devices used for this purpose have a complex design, their price is higher than that of one-dimensional scanning devices, and, most importantly, the control time increases significantly. If the echo signals reflected from the bottom of the object of control are used, taking into account the change in the wave type, then a combined image of the reflector can be obtained from a set of partial images recovered by the digital focusing antenna (DFA) method. If we use the echo signals measured in the combined mode for each piezoelectric converter, we can estimate the displacement of the reflector across the welded joint with an accuracy of ±1.5 mm. Numerical and model experiments have confirmed the efficiency of the proposed approach.

RETRACTED: Design of a piezoelectric energy conversion based wind generator

This manuscript presents a new experimental wind generator based on piezoelectric energy conversion for low power applications. The aim is to demonstrate an alternative renewable energy generation method for low power applications. The generator has four blades of a propeller equipped with a total of twenty-four (24) thin film piezoelectric transducers (TFPTs). The output voltage is generated using a newly developed circuit topology. The generator was tested at three wind speeds 10 m/s, 14 m/s and 18 m/s, with a maximum output voltage of 10.2 V being produced at a wind speed of 18 m/s. Results show that this generator has promise to be suitable for low power batteryless applications, for example wireless sensor nodes (WSN).

Novel dam-like effect based on piezoelectric energy conversion for drug sustained release of drug-loaded TiO2 @ BaTiO3 coaxial nanotube coating

Nanotube coatings on titanium surfaces have favorable biocompatibility and structures and are widely used in local drug delivery. However, when a drug freely diffuses out of a nanotube, it leads to an explosive release, making the duration of action extremely short. In this study, a high concentration of vancomycin hydrochloride region similar to a dam was formed on a nanotube coating surface by exploiting the attraction of the electric charge generated by the energy conversion of the piezoelectric effect to vancomycin hydrochloride. The “dam” not only reduces the diffusion rate of vancomycin hydrochloride inside the nanotube into the dam and the diffusion rate of the dam to the outside but also forms a high concentration of vancomycin hydrochloride action region. The free diffusion rate of vancomycin hydrochloride loaded on the TiO2 @ BaTiO3 coaxial nanotubes was reduced by the piezoelectric effect, and the cumulative release of vancomycin hydrochloride for 7 days is reduced by 54.8%. The polarized vancomycin-containing coaxial nanotube coating has a long-lasting antibacterial effect on Staphylococcus aureus. The TiO2 @ BaTiO3 coaxial nanotubes loaded with vancomycin hydrochloride coating with piezoelectric properties has potential application value in controlled drug delivery.

Performance Evaluation of a Vortex Induced Piezoelectric Energy Converter (VIPEC) with CFD Approach

A novel vortex induced piezoelectric energy converter (VIPEC) was present in this paper to harvest flow kinetic energy from the ambient environment through a piezoelectric beam. The converter consists of a circular cylinder, a pivoted beam attached to the tail of the cylinder and several piezoelectric patches. Vortex induced pressure difference acts on the beam and drives the beam to squeeze piezo patches to convert fluid dynamic energy into electric energy. Transition Shear Stress Transport (SST) combined with Scale Adaptive Simulation (SAS) model was employed to predict the turbulent flow and flow separation around the cylinder with various beam lengths at high Reynolds number of 8 × 104 based on the computational fluid dynamics (CFD) approach. The accuracy of SST-SAS model was investigated through verification and validation studies. The output voltage equation was derived from the piezoelectric constitutive equation. It was revealed that the beam length influences the flow wake pattern, the separation angle and shedding frequency greatly through changing the adverse pressure gradient around the cylinder. The wake pattern becomes symmetrical about the beam when the beam length is longer than a critical value. The length of the beam has little influence on the separation angle. When the beam length is about 1.3 times the diameter of the cylinder, the shedding frequency and output voltage achieves its maximum, and the separation angle is minimal. Maximal output voltage reaches 20 mV.

Frequency Up-Conversion Hybrid Energy Harvester Combining Piezoelectric and Electromagnetic Transduction Mechanisms

A hybrid energy harvester with frequency up-conversion structures is proposed. The harvester achieves a high power output by utilizing both piezoelectric and electromagnetic transduction mechanisms. The harvester comprises a flexible substrate and two (internal and external) cantilevers. The internal and external cantilevers used for piezoelectric and electromagnetic conversion, respectively, are arranged such that the piezoelectric internal cantilever can vibrate with a large displacement to produce high output power. We use a frequency up-conversion method to convert the bending of the harvester into the vibration of the structure so that the harvester can generate energy even from the mechanical motion with an extremely low frequency. Two harvester configurations are investigated to validate the effect of the relative positions of the coil and magnet on the output voltage of the harvester. The maximum power output of the hybrid harvester is 7.38 mW, with outputs of 1.35 and 6.03 mW for piezoelectric and electromagnetic conversion, respectively.

Magnetic Field Energy Harvesting with a Lead-Free Piezoelectric High Energy Conversion Material

This article presents a high-performance lead-free piezoelectric energy harvester (LPEH) system for magnetic field. It based on a Ba0.85Ca0.15Ti0.90Zr0.10O3 + CuO 0.3 wt% (BCTZC0.3) composite was fabricated by sintering at 1450 °C. The BCTZC0.3 composite, which has an enhanced high energy conversion constant (d33×g33), shows improved piezoelectric power-generation performance when compared with conventional piezoelectric energy harvesters. The BCTZC0.3-based LPEH produces instantaneous maximum power of 8.2 mW and an energy density of 107.9 mW/cm3 in a weak magnetic field of 250 μT. This system can be used to charge a capacitor and operate a wireless sensor network (WSN) system to provide temperature sensing and radio-frequency (RF) transmission in a 250 μT magnetic field. The proposed LPEH is a promising green-energy device for potentially self-powering WSN systems when applied.

Theoretical study on a novel piezoelectric ocean wave energy harvester driven by oscillating water column

ABSTRACT The wireless sensors offer the possibility of highly accurate salinity, temperature, or pollution detection for the ocean. Therefore, a novel self-powered piezoelectric wave energy harvester with a long service life was developed to replace the batteries in the sensors. A Pb(Zr,Ti)O3(PZT-5A) piezoelectric converter was applied to displace the traditional air turbine in this paper. The wave crest enters the chamber and compresses the entrapped air with oscillating water column (OWC). The outlet of piezoelectric patch deforms and output electric power when it is forced by the fluctuating air pressure. Based on the velocity potential and Green’s function method, theoretical analyses were conducted in the assumption of an incompressible fluid. A numerical OWC aerodynamic model was developed to verify the theoretical calculation based on the Reynolds-Averaged Navier-Stokes equations solver and Computational Fluid Dynamics (CFD) commercial software. The fluctuating air pressure was obtained in the chamber by numerical simulation. The pressure rose to 65 Pa when the ocean wave entered the air chamber with a daft of 0.3 m and a period of 1.8 s. Resultly, the piezoelectric harvester generates electric energy of J. This electric energy was used to evaluate the efficiency piezoelectric wave energy conversion system. Theoretical calculation results were consistent with that of the numerical simulation very well. This work testified their validity for the novel wave energy harvesting system.

Trypan blue stained KAP crystal: A comparative study on morphological, structural, optical, di-/piezo-electric and mechanical properties

Single crystals of pure and trypan blue (TB; C34H28N6O14S4) stained (0.01 mol%) potassium hydrogen phthalate (KAP; C8H5KO4) were grown by slow evaporation solution method. Experimentally obtained crystal habit of KAP matched well with the theoretical morphology predicted using BFDH laws. Eight planes ({111} & {111¯}) out of total fourteen planes got selectively coloured by TB dye molecules. Affinity of TB dye towards specific growth sectors can help various scientists to understand the selective nature of dye molecules and thereby will help in proposing novel tailor-made stained photonic crystals. UV–Vis-NIR spectra for TB stained KAP crystals displayed a strong absorption peak at 563 nm, which was blue shifted for TB dye in KAP matrix relative to neutral aqueous solution of TB dye. This shift in the absorption maxima towards lower wavelength confirms the successful colour insertion into selective growth sectors of stained KAP crystals. The effect of TB staining on various optical parameters namely optical conductivity, optical band gap, refractive index and extinction coefficient of host KAP matrix was studied. The structural conformation and the recognition of different functional groups present in as grown KAP crystals were approved by powder XRD and FTIR studies, respectively. Dielectric constant increased and dielectric loss decreased as a result of TB dye staining in KAP material. The piezoelectric conversion efficiency got increased from 1.22 pC/N for un-dyed KAP single crystal to 1.53 pC/N for TB stained KAP single crystals. In Vickers micro-hardness studies, TB stained KAP crystals displayed better mechanical strength.

Influence of the ultrasonic vibration amplitude on the melt pool dynamics and the weld shape of laser beam welded EN AW-6082 utilizing a new excitation system for laser beam welding

Laser beam welding is a commonly used technology for joining similar and dissimilar materials. In order to improve the mechanical properties of the weld, the introduction of ultrasonic vibration into the weld zone has been proposed [5]. The ultrasonic system consists of an electronic control, a power supply, a piezoelectric converter and a sonotrode, which introduces the vibration into the weld zone. Its proper design is of great importance for the process performance. Furthermore, the effects of ultrasound in a melt pool need to be understood to evaluate and optimize the process parameters. In addition, it is important to find out the limits of ultrasonic excitation with respect to a maximum vibration amplitude. Therefore, firstly different methods of ultrasonic excitation are investigated and compared with respect to their performance. A system which is based on using longitudinal vibrations turns out to be the best alternative. Secondly, the system design is described in detail to understand the boundary conditions of the excitation and finally, simulations about the influence of ultrasonic vibrations are done by using a simplified model. The system is used to perform experiments, which aim at detecting the maximum vibration amplitude doing bead on plate welds of EN AW-6082 aluminum alloy. The experiments reveal a significant change of the weld shape with increasing ultrasonic amplitude, which matches the simulative findings. If the amplitudes are small, there is a marginal effect on the weld shape. If the amplitudes are high, melt is ejected and the weld shape is disturbed. In the present case, amplitudes over 4 µm were found to disturb the weld shape.

Methods of transferring two-dimensional materials

The advent of two-dimensional (2D) materials, a family of materials with atomic thickness and van der Waals (vdWs) interlayer interactions, offers a new opportunity for developing electronics and optoelectronics. For example, semiconducting 2D materials are promising candidates for extending the Moore's Law. Typical 2D materials, such as graphene, hexagonal boron nitride (h-BN), black phosphorus (BP), transition metal dichalcogenides (TMDs), and their heterostrcutures present unique properties, arousing worldwide interest. In this review the current progress of the state-of-the-art transfer methods for 2D materials and their heterostructures is summarized. The reported dry and wet transfer methods, with hydrophilic or hydrophobic polymer film assistance, are commonly used for physical stacking to prepare atomically sharp vdWs heterostructure with clear interfaces. Compared with the bottom-up synthesis of 2D heterostructures using molecular beam epitaxy (MBE) or chemical vapor deposition (CVD), the construction of 2D heterostructures by transfer methods can be implemented into a curved or uneven substrate which is suitable for pressure sensing, piezoelectric conversion as well as other physical properties’ research. Moreover, the transfer of 2D materials with inert gas protected or in vacuum operation can protect moisture-sensitive and oxygen-sensitive 2D materials from degerating and also yield interfaces with no impurities. The efficient and non-destructive large-area transfer technology provides a powerful technical guarantee for constructing the 2D heterostructures and exploring the intrinsic physical and chemical characteristics of materials. Further development of transfer technology can greatly facilitate the applications of 2D materials in high-temperature superconductors, topological insulators, low-energy devices, spin-valley polarization, twistronics, memristors, and other fields.

Fixed-Frequency Control of Piezoelectric Resonator DC-DC Converters for Spurious Mode Avoidance

Piezoelectric resonators have shown promise as efficient, power-dense energy storage element alternatives to continue the miniaturization of DC-DC converters. However, practical piezoelectric resonators diverge from their ideal behavior due to spurious modes that cause high loss regions throughout their operating frequency range. Typically, control of piezoelectric resonator DC-DC converters is constrained to unidirectional power flow each resonant cycle for maximum efficiency operation. However, output power depends on the frequency with such control, which means the converter cannot operate at loads corresponding to spurious mode frequencies. This paper presents a fixed-frequency control mode utilizing the high-quality factor of piezoelectric resonators to avoid spurious modes. The fixed-frequency control enables efficient operation spanning the converters full load range, demonstrated through a prototype DC-DC converter with a custom fabricated lithium niobate resonator. At a conversion ratio of 60 V to 30 V, spurious modes limit the converters operating range from 33 W to 51 W using unidirectional power-constrained control, yet the fixed-frequency control extends operation from 33 W to 2 W.