Electromechanical Energy Conversion Efficiency Research Articles

Design and performance of a novel magnetically induced penta-stable piezoelectric energy harvester

The magnetically induced multi-stable piezoelectric vibration energy harvesters have garnered significant attention due to their strong nonlinear characteristics, wide operating bandwidths, and high electromechanical energy conversion efficiency. However, a traditional penta-stable design typically requires four rectangular external magnets. The excessive number of structural parameters amplify complexities in system optimization, dynamic analysis, and prototype installation, impeding harvester manufacturing and application. This study presents a novel penta-stable harvester design that utilizes interaction forces among a rectangular magnet and two annular magnets, resulting in a simplified system requiring only two external magnets. This design approach streamlines system design, dynamic analysis, and prototype installation, providing a fresh perspective on magnetic penta-stable vibration energy harvester design. The magnetizing current method is employed to accurately determine the system’s magnetic field and magnetic force. Stability analysis indicates that the multi-stability of the harvester is influenced by both the vertical magnetic force and equivalent linear elastic force, which can be effectively controlled by adjusting the system’s components. Dynamic simulations conducted under Gaussian white noise excitation confirm the penta-stable behavior of the system, and the dynamic responses verify that a shallower potential well depth contributes to the system’s ability to attain a higher output voltage. Experimental validations closely align with simulation results, providing strong evidence for the accuracy of the study’s findings. Furthermore, a practical application experiment demonstrates the harvester’s capability to power a hygrothermograph, highlighting its potential for real-world energy harvesting applications.

Induction Motors Technical Condition In-Service Testing Methods

The article describes methods for in-service diagnostics of the technical condition of induction motors, which are the most widely used type of electromechanical systems. By now, a large number of various studies on this matter have been published. It is stated that the accomplished studies implement an "external" approach to solving the problem, which consists in deriving a diagnostic conclusion based on an analysis of changes in the electric motor external characteristics in one of its operation modes. In addition, these studies are based on two-dimensional models of the classical theory of electrical machines, which does not allow them to adequately reflect situations of multidimensional distribution of electromagnetic quantities in a vector space. These circumstances generated the need to develop more advanced diagnostic methods, called topological ones. Topological diagnostics methods are theoretically substantiated based on the ideas about the IM multidimensional vector space. It is shown that the parametric properties of the vector space and first of all of its working area, have a key influence on the electromechanical energy conversion efficiency. Two methods for testing different areas of the vector space are outlined. In the first case, the space working area is tested for parametric uniformity and operational stability. The results of three experiments provide unbiased and sufficient information about the degree of its homogeneity, about the changes that have occurred during the operation, and about their rates. The testing makes it possible to draw well-grounded conclusions about the electric motor active part technical condition and the degree of its criticality. In the second case, the vector space phase coordinates are tested for parametric uniformity and operational stability. The results presented testify that the proposed testing scheme is sensitive to phase parameter deviations. This is facilitated by the differential principle of its construction. The signal in a short-circuited phase, which appears in the case of a parametric phase imbalance, serves as its clear indicator. The presented mathematical modeling data confirm the efficiency of the proposed testing methods.

Design and Analysis of Mechanical Characteristics of EAP Flexible Drivers

Electroactive polymer(EAP) is a “smart material” with high energy density, high electromechanical energy conversion efficiency, simple structure, good adaptability to the working environment, etc. It can be made into various shapes to realize flexible drivers. At present, the common EAP actuator is mainly composed of EAP film wound on a spring, and the output performance of this type of actuator is related to the spring stiffness, film prestretching rate, voltage, and other factors. Its working process is actually an electromechanical coupling process. In this paper, two types of cylindrical actuators are designed and tested. The electromechanical coupling mathematical model is constructed to simulate the driver. According to the experimental and simulation results, the relationship between the output displacement and elongation strain of EAP actuator and voltage, spring stiffness, and tensile rate is analyzed. It provides a reference and basis for the design of similar actuators.

Enhanced piezoelectricity in lead-free halide perovskite nanocomposite for self-powered wireless electronics

Lately, lead-free flexible piezoelectric nanogenerators (PENGs) have drawn much attention because of the threat posed by lead (Pb)-based piezoelectric materials to the environment. Here, we reported an organic-inorganic hybrid perovskites (OIHP) PENG, which is a combination of lead-free formamidinium tin (Sn) halide perovskite (CH(NH2)2SnBr3 (FASnBr3)) nanoparticles (NPs) and polydimethylsiloxane (PDMS) polymer matrix. By using piezoelectric force microscopy (PFM) measurements, we unveil the excellent piezoelectric properties of the FASnBr3 NPs with a high piezoelectric charge coefficient (d33) of ~ 50 pm/V. Due to the outstanding flexibility and uniform distribution properties, the device demonstrated a maximum piezoelectric peak to peak output voltage of 94.5 Vp-p, peak to peak current of 19.1 μAp-p, and output power density of 18.95 μW/cm2 with a tiny force of 4.2 N; these characteristics substantially outperform a number of the state-of-the-art halide perovskite based PENGs (Table S1). Given their high electromechanical energy conversion efficiency, the electrical energy produced from the PENGs was used to power a Bluetooth-capable system on chip (SoC) to build an entirely self-powered radio frequency (RF) communication system. For the first time, we established a self-powered RF wireless communication between nanogenerator and smart electronic devices which is solely based on a lead-free PENG. It is anticipated that the fabricated FASnBr3 @PDMS nanocomposite PENG not only possesses outstanding performance and reliability but also serves as a stepping-stone towards achieving self-powered Internet of Things (IoT) devices built using environment-friendly perovskite piezoelectric materials.

High performance of polycrystalline piezoelectric ceramic-based magneto-mechano-electric energy generators

ABSTRACT The cantilever-structured magneto-mechano-electric (MME) energy generator with smaller volume exhibits excellent magnetic energy conversion performance than electro-magnetic current induction type energy harvesters. An anisotropic single crystal is an ideal piezoelectric constituent of a high-performance MME generator owing to its superior electromechanical properties and high electromechanical energy conversion efficiency. However, the complicated synthesis and high cost of piezoelectric single crystals limit the wide deployment of the MME generator. Alternatively, the implementation of the polycrystalline ceramic piezoelectric can largely reduce the device fabrication cost. In this work, the PMN-PZT single crystal fiber composites (SFC) were replaced by high-performance polycrystalline ceramic (MnO2-doped 25PMN-PZT) fiber composites (PCFC) for MME generator. The magnetoelectric response and harvested electrical power of SFC- and PCFC-based MME generators were measured. Interestingly, the electrical output power of the PCFC-based MME generator at 10 Oe magnetic field tuned at 60 Hz was found to be ~90% of that of its SFC-based counterpart, in addition to the superior thermal stability. The presented MME energy generator has excellent potential for applications as low cost and efficient power source for wireless sensor networks deployable to the internet of things (IoTs), low power consumption electronic devices, etc., by harvesting the stray magnetic energy.

An overview of electricity powered vehicles: Lithium-ion battery energy storage density and energy conversion efficiency

Electricity powered vehicles/Electric vehicles using renewable energy are becoming more and more popular, since they have become an effective way to solve energy shortage, and environmental pollution. Battery electric vehicles with zero emission characteristics are being developed on a large scale. With the scale of electric vehicles, electric vehicles with controllable load and vehicle-to-grid functions can optimize the use of renewable energy in the grid. This puts forward the higher request to the battery performance. The energy density of the batteries and renewable energy conversion efficiency have greatly also affected the application of electric vehicles. This paper presents an overview of the research for improving lithium-ion battery energy storage density, safety, and renewable energy conversion efficiency. It is discussed that is the application of the integration technology, new power semiconductors and multi-speed transmissions in improving the electromechanical energy conversion efficiency, and the issues and challenges of increasing battery energy density. In order to improve the safety, it is analyzed how to improve the estimation accuracy and temperature control performance of the battery management system. As the demand for fast charging and renewable energy of electric vehicles increases, the latest developments and technical challenges of on-board rapid charging technology are introduced. • We present an overview on energy storage density and energy conversion efficiency of electricity powered vehicles. • Methods to increase the energy storage density of electricity powered vehicles are proposed. • Efficient inverter and multi-speed transmission improving renewable energy conversion efficiency are discussed. • The integration improves the energy efficiency of electricity powered vehicles. • Integrated fast charging and coordinated charging for renewable energy are discussed.

Polyvinylidene Fluoride-Added Ceramic Powder Composite Near-Field Electrospinned Piezoelectric Fiber-Based Low-Frequency Dynamic Sensors.

In this study, near-field electrospinning (NFES) is used to fabricate BaxSr1–xTiO3 (BST)/poly(vinylidene fluoride) (PVDF) piezoelectric fiber composites with excellent mechanical properties and chemical properties. BST ceramic powder is blended with PVDF solution uniformly to prepare a solution of appropriate conductance. The parameter for BST/PVDF fiber processing is based on PVDF fibers. Scanning electron microscopy, differential scanning calorimetry, microtensile testing, Fourier transform infrared spectroscopy, and electricity test of the blends of BST/PVDF fibers are incorporated. Mechanical properties of the fibers are then measured by microtensile testing. Effects of distinct ratios of Ba/Sr and the content of Ba0.7Sr0.3TiO3 ceramic powder on BST/PVDF piezoelectric fibers are discussed. Finally, BST/PVDF piezoelectric fiber composites are patterned on a poly(ethylene terephthalate) (PET)-based structure with an interdigital electrode as a BST/PVDF flexible energy harvester to capture ambient energy. The results show that the BST ceramic powder is ∼58–93 nm, and the diameters of piezoelectric fiber composites are ∼6.8–13.7 μm. The tensile strength of piezoelectric fiber composites is ∼74.92 MPa, and the Young’s coefficient tensile strength is ∼3.74 GPa. Mechanical properties are 2–3 times higher than those of pure PVDF piezoelectric fibers. The maximum open-circuit voltage and closed-loop current of BST/PVDF fibers reached ∼1025 mV and ∼391 nA, respectively. The electromechanical energy conversion efficiency of the BST/PVDF energy harvester is found to be 1–2 times higher than that of the PVDF energy harvester. It is confirmed and validated that the addition of BST ceramic powder could effectively increase the piezoelectric constant of PVDF piezoelectric fibers.

Tunability of band gaps and energy harvesting based on the point defect in a magneto-elastic acoustic metamaterial plate

The present study investigated the intelligent control of both band gaps (BGs) and energy harvesting based on the point defect of magneto-elastic acoustic metamaterial and piezoelectric effect. The numerical results obtained by the finite element method indicate that band structures and frequency range of acoustic energy harvesting can be modulated significantly by an applied magnetic field, which leads to broadband BGs and promotes the electromechanical energy conversion efficiency. Consequently, the proposed structure can provide new avenues for designing of both tunable acoustic insulator and a broad-distributed energy harvester in engineering fields.

Research on Driving Circuit Improvement of Coilgun

Theoretically, the energy conversion efficiency of the synchronous induction coil launcher (SICL) can reach 100%, but at present, the test data show that the highest current is only a little higher than 20%, which shows that the efficiency of the coil launcher has a lot of room for improvement. In this paper, three improved schemes are proposed for the topology of the traditional crowbar circuit based on the pulse capacitor to improve the electromechanical energy conversion efficiency of the electromagnetic coil launcher. They are main circuit breaking, crowbar break-off circuit, and crowbar circuit with inductor, respectively. In order to verify the feasibility of the above three methods, a five-stage coil launcher was simulated and analyzed. Then, based on the model, three improved circuits were calculated and analyzed by the finite-element simulation software. The results show that all of the three methods can improve the efficiency of energy conversion to a certain extent. Both the first and second methods have limited effect on increasing efficiency. In addition, they need to add some expensive equipment such as circuit breaker. So, they are not recommended. The third way of increasing an inductor in the crowbar circuit could increase the muzzle velocity and efficiency obviously. The muzzle velocity increased from 30.6 to 35 m/s. The effect of armature capture is reduced which is worthy of recommendation.

Maximum Torque-per-Amp Control for Traction IM Drives: Theory and Experimental Results

A novel maximum torque per Ampere (MTPA) controller for the induction motor (IM) drives is presented. It is shown to be highly suited to applications that do not demand an extremely fast dynamic response, for example, electric vehicle drives. The proposed MTPA field oriented controller guarantees asymptotic torque (speed) tracking of smooth reference trajectories and maximizes the torque per Ampere ratio when the developed torque is constant or slow varying. An output-feedback linearizing concept is employed for the design of torque and flux subsystems to compensate for the torque-dependent flux variations required to satisfy the MTPA condition. As a first step, a linear approximation of the IM magnetic system is considered. Then, based on a standard saturated IM model, the nonlinear MTPA relationship for the rotor flux are derived as a function of the desired torque, and a modified torque–flux controller for the saturated machine is developed. The static and dynamic flux reference calculation methods to achieve simultaneously an asymptotic field orientation, a torque–flux decoupling, and an MTPA optimization in a steady state, is proposed. The method guarantees a singularity free operation and can be used as means to improve stator current transients. Experimental tests prove the accuracy of the control over a full torque range and show successful compensation of the magnetizing inductance variations caused by saturation. The proposed MTPA control algorithm also demonstrates a decoupling of the torque (speed) and flux dynamics to ensure asymptotic torque tracking. In addition, a higher torque per Ampere ratio is achieved together with an improved efficiency of electromechanical energy conversion.

High-efficiency control of brushless doubly-fed machines for wind turbines and pump drives

The paper is concerned with vector control of a promising brushless doubly-fed reluctance machine (BDFRM) technology for generator and drive systems with limited adjustable speed ranges such as wind turbines or pump-alike installations. The BDFRM has been receiving increasing attention because of the low capital and operation and maintenance costs afforded by the partially-rated power electronics and the high reliability of brushless construction, while offering performance competitive to its well-known slip-ring counterpart, a doubly-fed induction machine. The comprehensive comparative studies have evaluated the performance of two robust control algorithms by computer simulations and experimentally on a custom-made BDFRM under the maximum torque per inverter ampere conditions for improved efficiency of electro-mechanical energy conversion.

Enhanced Electromechanical Response of Ionic Polymer Actuators by Improving Mechanical Coupling between Ions and Polymer Matrix

Poly[(vinylidene difluoride)-co-(chlorotrifluoroethylene)] (P(VDF–CTFE)) and P(VDF–CTFE)/poly(methyl methacrylate) (PMMA) cross-linked blends were exploited as ionic electroactive polymer (i-EAP) actuators with electrolyte ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [C2mim][TfO] for the first time. Compared to the traditional i-EAPs that are based on Nafion or Aquivion (Hyflon) ionomers, i-EAP actuators made with P(VDF–CTFE) and P(VDF–CTFE)/PMMA polymers exhibited remarkably enhanced actuation strain and significantly reduced electrical capacitance. The increase in the strain–charge ratio e/C indicates that this improvement is a direct result of improved elastic coupling between the [C2mim][TfO] electrolyte and the polymer matrix. As a result, an order-of-magnitude improvement in electromechanical energy conversion efficiency is achieved for both P(VDF–CTFE) and P(VDF–CTFE)/PMMA polymer-based actuators, which makes them promising polymer matrices for i-EAP actuators.

Serial Communication and Temperature Monitoring of MSMA Actuator Based on DS18B20

The magnetically controlled shape memory alloy (MSMA) is a new type of intelligent materials, which has large strain and high efficiency of electromechanical energy conversion, however, temperature has great influence to it. The DS18B20 digital thermometer provides 9-bit to 12-bit Celsius temperature measurements, which has an operating temperature range of -55 Degrees Celsius to +125 Degrees Celsius and is accurate to ±0.5 Degrees Celsius, Therefore it’s used to monitor the temperature of MSMA actuator in this paper. Serial communication is very important in our daily life; the paper mainly introduces hardware and software design for it and serial communication between pc and c51 based on matlab, meanwhile, drawing temperature curve by existing functions of matlab.

Theory of dielectric elastomers

In response to a stimulus, a soft material deforms, and the deformation provides a function. We call such a material a soft active material (SAM). This review focuses on one class of soft active materials: dielectric elastomers. When a membrane of a dielectric elastomer is subject to a voltage through its thickness, the membrane reduces thickness and expands area, possibly straining over 100%. The dielectric elastomers are being developed as transducers for broad applications, including soft robots, adaptive optics, Braille displays, and electric generators. This paper reviews the theory of dielectric elastomers, developed within continuum mechanics and thermodynamics, and motivated by molecular pictures and empirical observations. The theory couples large deformation and electric potential, and describes nonlinear and nonequilibrium behavior, such as electromechanical instability and viscoelasticity. The theory enables the finite element method to simulate transducers of realistic configurations, predicts the efficiency of electromechanical energy conversion, and suggests alternative routes to achieve giant voltage-induced deformation. It is hoped that the theory will aid in the creation of materials and devices.

Study on a Piezohydraulic Motor for Maximal Energy Efficiency

A piezohydraulic linear motor driven by a piezostack diaphragm pump is presented and studied. The diaphragm of pump chamber consists of a membrane and rigid disk, instead of a single piston or membrane. An analytical model is established to evaluate piezohydraulic motor performance in terms of velocity, pushing force, mechanical energy conversion efficiency (MEE), and electromechanical energy conversion efficiency (EMEE). The involved effect factors of motor performance are radius ratio (rigid-disk radius to chamber radius), area ratio (pump-chamber area to cylinder-piston area), force ratio (external load to blocked force of piezostack), and step ratio (cylinder-piston stroke to free displacement of piezostack). Analytical results show that there are optimal structural parameters (radius ratio and area ratio) for property parameters (force ratio, step ratio, MEE, and EMEE) to obtain maximal values. Considering the achievable peak MEE and EMEE, the design method was introduced for different purpose of applications. A piezohydraulic motor was fabricated and tested to examine the influence of radius ratio on performance of the piezohydraulic motor. The experimental results show that both the motor velocity and driving force can be enhanced with optimizing radius ratio.

Electromechanical coupling coefficient k31eff for arbitrary aspect ratio resonators made of [001] and [011] poled (1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 single crystals

The dependence of k31eff on the aspect ratio G=l(1)l(2) has been calculated for resonators made of [001] poled 0.67Pb(Mg(13)Nb(23))O(3)-0.33PbTiO(3) (PMN-0.33PT) and [011] poled 0.71Pb(Mg(13)Nb(23))O(3)-0.29PbTiO(3) (PMN-0.29PT). Based on the derived unified formula, the lateral electromechanical energy conversion efficiency mid R:k31effmid R:2 decreases with G for [001] poled PMN-0.33PT but increases with G for [011] poled PMN-0.29PT.

Electromechanical energy converters of micromechanic devices on the basis of ferroelectric films

The peculiarities of flexible metallic film electrostatic rolling on the ferroelectric film surface are studied. The efficiency of electromechanical energy conversion is shown to be significantly higher on executing of the process mentioned, that on application of reversed piezoelectric effect.

Dynamic Power and Energy Capabilities of Commercially-Available Electro-Active Induced-Strain Actuators

A method has been developed to predict the apparent material constants, the input and output power and energy, and the electro-mechanical energy conversion efficiency of electro-active induced-strain actuators under full-stroke, quasi-linear dynamic operation. The effect of the piezo-electric counter electro-motive force on the apparent input admittance is included. The non-symmetric expansion-retraction behavior of the electro-active material under full-stroke dynamic operation is symmetrized using a bias-voltage component and a superposed dynamic voltage amplitude that produce, in the actuator, a static position and a dynamic stroke amplitude, respectively. It is shown that the presence of the bias-voltage operation increases significantly the reactive power amplitude, and a simple formula for estimating this increase is provided. Reaction power values up to three times larger than those for unbiased operation were found. The secant linearization method and vendor data were used to evaluate the full-stroke piezoelectric strain coefficient, d, elastic compliance, s, electrical permittivity, ∈, and electro-mechanical coupling coefficient, x, of the electro-active actuator. Consistency with the basic active-material values was checked, and correction of the actuator full-stroke electro-mechanical coupling coefficient was applied, when required. Maximum power and energy delivery under optimal dynamic conditions (dynamic stiffness match) was studied, and the dynamic energy output capability of several commercially-available actuators were computed. Output energy densities per unit volume, mass, and cost were also calculated. The best electro-mechanical conversion efficiency, which was shown to take place at stiffness ratios slightly different from the dynamic stiffness match, was also computed.

Pulse Mode Operation for Piezoelectric Ceramic Actuator

Multilayer piezoelectric ceramic actuators were driven in large amplitude pulse modes by a new charge-discharge circuit with a series inductor. About 56% of the supplied electrical energy was recovered for the mechanically unloaded actuator. About 21% was lost as heat at the actuator. The maximum electro-mechanical energy conversion efficiency for the mechanically loaded actuator was 36%.