Materials, structures and power interfaces for efficient piezoelectric energy harvesting

The possibility of recycling ambient energies with miniature electrical generators instead of using batteries with limited lifespan has stimulated important research efforts over the past years. Integration of such miniature generators is mainly envisioned into low power autonomous systems, for various industrial or domestic applications. This paper focuses on the use of piezoelectric materials for generating electrical energy from ambient mechanical vibrations. A review of the piezoelectric materials and the electromechanical structures which have been proposed in this field is first presented. Electrical circuits with one-stage, two-stage and three-stage interfaces which have been developed for optimizing the electrical power flow from piezoelectric devices to energy storage elements are then compared to a novel technique for controlling the energy converted by piezoelectric materials. This novel approach is derived from Ericsson thermodynamic cycle. A solution for practical implementation is proposed, theoretical predictions and experimental results are compared and discussed.     

Power output estimation and experimental validation for piezoelectric energy harvesting systems

Many modern devices especially for ubiquitous computing or wireless sensor networks need a long life energy source. Batteries or accumulators are often an insufficient solution. Low frequency vibrations can be found in the most technical facilities or even in the human movements. Even while these vibrations are neither wanted nor used in the most times, they enable us to generate electrical energy. Piezoelectric flexural transducers are a promising choice for utilizing the vibrations for energy harvesting. There are two major influences on the amount of generated energy. First there is the frequency behavior of the piezoelectric transducers, for optimal power output the transducer should be driven in resonance. Second, the energy output is highly dependent on the electrical load of the connected application. Both circumstances, working frequency and electrical load, typically are boundary conditions for the development of the generator. Therefore, it is necessary to handpick the type of piezoelectric elements. To meet the requirements of development engineers, a model based design method for energy harvesting systems is needed. As a first step towards such a method, this work proposes a model for the estimations of the power output of piezoelectric flexural transducers. For the validation of this model an experiment is described in detail. The results of the model and the experiments are compared.     

Energy harvesting MEMS device based on thin film piezoelectric cantilevers

A thin film lead zirconate titanate Pb(Zr,Ti)O₃ (PZT), energy harvesting MEMS device is developed to enable self-supportive sensors for in-service integrity monitoring of large social and environmental infrastructures at remote locations. It is designed to resonate at specific frequencies of an external vibrational energy source, thereby creating electrical energy via the piezoelectric effect. Our cantilever device has a PZT/SiN_x bimorph structure with a proof mass added to the end. The Pt/Ti top electrode is patterned into an interdigitated shape on top of the sol-gel-spin coated PZT thin film in order to employ the d ₃₃ mode. The base-shaking experiment at the first resonant frequency of the cantilever (170 × 260 μm) generates 1 μW of continuous electrical power to a 5.2 MΩ resistive load at 2.4 V DC. The effect of proof mass, beam shape and damping on the power generating performance are modeled to provide a design guideline for maximum power harvesting from environmentally available low frequency vibrations. A spiral cantilever is designed to achieve compactness, low resonant frequency and minimum damping coefficient, simultaneously.     

Numerical and experimental study of bistable piezoelectric energy harvester

Piezoelectric energy harvesting from mechanical vibrations is a reliable technology to charge low power electronic equipment. It has been reported in the literature that low frequency broadband vibrations cannot be harvested effectively using linear piezoelectric energy harvester (PEH). In this paper a bistable nonlinear PEH with two distinct energy wells generated using repulsive magnetic interactions between a cantilever magnetic proof mass and an external magnet is considered. It has been modeled using finite element method and validated with experimental results. Experimental results verify that, for our study, distance between magnetic proof mass and external magnet of 1.32 T flux density should be less than or equal to 8.5?mm for maintaining bistability. This distance also affects to the resonance frequency of harvester. Maximum efficiency of the harvester has been noticed at 8.5mm. Further it has been shown experimentally that the bistable nonlinear piezoelectric energy harvester takes almost half of the time taken by its linear counterpart to charge a 20 mAh battery.     

MODELING AND SIMULATION OF PIEZOELECTRIC MEMS ENERGY HARVESTING DEVICE

ABSTRACT

Piezoelectric MEMS power generator is used to harvest energy from the ambient vibrations in the environment. This paper proposes a structure design of MEMS power generator for low-frequency applications, which is based on bulk MEMS technology and (110) Si wafer. The structure consists of a silicon cantilever with a piezoelectric layer attached. The cantilever is modeled as an Euler-Bernoulli beam with a lumped mass beneath the tip of the cantilever, and then analytical modeling and simulations are carried out using MATLAB. Simulation results show that a tradeoff between the geometric parameters and the proof mass should be made for a high output power of the device. To increase the output power, the length of piezoelectric layer can be optimized, which is not necessarily equal to that of cantilever. Simulation results point out ways to perform the optimization of MEMS power generator. The analytical modeling and simulations are also helpful for the design of macro-scale power generator.     

中小型异步电动机振动频率计算

防止定子共振对制造安静电机是必须的.因而若有一个有效的方法能在电机设计阶段就能预测定子固有频率,特别是低阶固有频率,是至关重要的.由于叠层对定子振动的影响和定子齿环振动耦合,定子低阶振动模态具有平面模态特性.利用此特性本文用能量法和拉格朗日方程预测定子低阶固有频率,并用实验对理论预测进行验证,获得理论预测与实验结果很好的一致性.     

Designing a piezoelectric energy harvesting system for the superconductor Maglev

In order to convert the lateral vibration of the superconductor Maglev bogie system into usable energy, an energy harvesting system was designed and optimized by applying steel balls for piezoelectric material to effectively convert mechanical energy into electrical energy. Experiments were conducted to investigate the effect of the vibration displacement (0.2, 0.4, 0.6, 0.8, 1.0 mm), vibration frequency (2, 4, 6, 8, 10 Hz) and vibration direction (x-axis and y-axis) for each different size of steel ball (12.7, 15.8, 17.0, or 20.0 mm). The following experimental results were found, first, as the vibration displacement increased, the average power output also increased. The total weight of the balls affected the results at higher vibration displacements. Second, as the vibration frequency increased, larger balls tended to have a jump point in average power output, with a general trend of increasing average power output. Finally, the x-axis direction effect had more distinct differences for individual ball weight dependences due to the mobility factor of the balls, considering calculated total weight and total area percent. After the optimum condition was found, the wireless sensor was connected and the experimental data suggested the possibility of applying piezoelectric materials to exploit the ambient and random vibrations of a superconductor Maglev bogie system.     

压电振动能量收集系统中二极管整流电路的RC等效模型分析

为了方便分析压电振动能量收集系统的电气特性,基于等效前后压电能量收集系统输出功率相同的原则,提出了将整流器和滤波电容等效为RC电路的方法。分别分析了全波整流、倍压整流电路的电学特性,推导了RC等效电路中等效电阻和电容的计算表达式,并仿真分析了负载等效前后的功率变化曲线。分析结果表明,整流器和滤波电容等效为RC电路的方法是可行的。     

Hot Circuits Can Be Expensive

The higher rated operating temperatures of the insulated power conductors presently available have been of considerable assistance to circuit designers confronted with high ambient temperatures and space limitations. However, the temptation exists to utilize these temperature capabilities to obtain the maximum ampacity with the minimum conductor size in circuits where no unusual ambient temperatures or space constraints are encountered. In response to the escalating cost of electrical energy and the fact that the excessive heating of electrical circuits does represent an avoidable waste, the basic economics of insulated conductor loading is reviewed.     

天然气发动机燃烧性能模拟分析

运用AVL-BOOST软件分别建立天然气发动机和汽油机的燃烧模型,确定了两种燃料发动机的低热值和空燃比等参数后,进行了模拟分析。模拟结果表明,在同样的压缩比情况下,天然气发动机的动力性低于汽油机;天然气发动机的扭矩略低于汽油机,汽油机的加速性能和爬坡性能更好;天然气发动机的压力升高率低于汽油机,天然气发动机运转时噪声低,舒适性好;天然气发动机的放热率低于汽油机,天然气发动机的指示热效率比汽油机高,所以天然气发动机更经济;天然气发动机尾气中的CO、NOx和HC均低于汽油机,天然气发动机对环境的污染小。     

面向电力设备检测与诊断的压电材料及器件

随着中国智能电网建设不断推进及电网规模的扩大,以压电材料为核心的传感器和能量采集器在电力系统在线监测、故障检修、无线传感器网络等方面扮演着越来越重要的角色。从电力检测和传感器自取能出发,回顾近年来基于压电效应的电压电场传感器、声检测和环境能量采集装置的研究进展并介绍了压电陶瓷、压电驻极体、压电复合材料等传统和新兴的压电材料。在现有研究基础上,指出在智能电力系统建设中各类压电器件所面临的挑战,包括频率匹配、环境适应性和集成化等,需要新的微纳加工技术、探索压电效应与其他物理效应耦合、设计新型压电材料和能量收集电路来助力新型压电器件的实际应用。     

Advances in energy harvesting using low profile piezoelectric transducers

The vast reduction in the size and power consumption of sensors and CMOS circuitry has led to a focused research effort on the on-board power sources which can replace the batteries. The concern with batteries has been that they must always be charged before use. Similarly, the sensors and data acquisition components in distributed networks require centralized energy sources for their operation. In some applications such as sensors for structural health monitoring in remote locations, geographically inaccessible temperature or humidity sensors, the battery charging or replacement operations can be tedious and expensive. Logically, the emphasis in such cases has been on developing the on-site generators that can transform any available form of energy at the location into electrical energy. Piezoelectric energy harvesting has emerged as one of the prime methods for transforming mechanical energy into electric energy. This review article provides a comprehensive coverage of the recent developments in the area of piezoelectric energy harvesting using low profile transducers and provides the results for various energy harvesting prototype devices. A brief discussion is also presented on the selection of the piezoelectric materials for on and off resonance applications. Analytical models reported in literature to describe the efficiency and power magnitude of the energy harvesting process are analyzed.

压电式振动能量采集电源管理电路分析

压电式振动能量采集的应用十分广泛,在许多能量采集装置中都采用压电元件实现能量转换。分析了振动能量采集装置中压电元件采集的能量输出管理电路,包括标准能量采集电路、DC-DC变换的优化标准能量采集电路、同步电荷提取电路、电感同步开关采集电路和双同步开关采集电路等五种电源管理电路的原理,比较了它们的能量采集输出效率,指出了各种电源管理电路的特点和适用条件。     

压电式振动能量采集接口电路的研究进展

压电式振动能量采集技术是一种将环境中的振动能量转换为电能并为微电子系统供电的技术。文章介绍了压电式振动能量采集接口电路的研究现状,对标准能量采集电路、同步电荷提取电路、同步开关电感电路、无电感整流等接口电路的工作原理进行了介绍,详细研究了当前国内外研究人员对这些接口电路的改进,对这些改进的接口电路的特点、优势、效率、能耗、实用性等都做了分析。并对压电式振动能量采集接口电路向宽频化、集成化发展方向做了分析。     

Improvement in output power of vibration generators based on piezoelectric elements by using internal capacitor cancel control rectifier

Recently, energy harvesting has attracted increasing attention. The present study focuses on vibration generators based on piezoelectric elements by proposing an internal capacitor cancel control (ICCC) rectifier to improve the output power. The proposed rectifier cancels the internal capacitor to improve the output power while retaining the maximum output power. Accordingly, this paper experimentally demonstrates the improvement in output power by using the ICCC rectifier compared to conventional circuits and the previous proposed circuit.     

Development and testing of an energy saving tool – Suitability analysis with case study

The increasing demand for electrical energy, the depletion of fossil fuel based resources and environmental constraints have made it mandatory for the efficient use of electrical energy, energy saving applications and implementing an energy management program. In this paper, a user-friendly tool for tracking and analyzing the electric bills, suggesting the best electricity tariff, controlling the active and reactive power rates, increasing energy efficiency, allowing the consumer to compare the alternatives and avoiding any penalties is presented step by step. The proposed energy saving tool will also help the electrical and more particularly power engineers and consumers in industrial sector to reduce electricity consumption while maintaining the quality of service. The developed tool is applied and tested to determine the optimal design of electrical power system in a university hospital. Test results reveal the performance of the developed tool for an optimization of commercial and industrial plants under different scenarios of power consumption and load demand. The program is written in the Delphi programming environment XE3 to provide enhanced flexibility and runs on Windows.     

用于自供能传感器的环境能量源研究

采集环境中的能量,实现传感器的自供电,可解决无线传感器携带电池能量有限的问题。自供能传感器能否从环境中获得充足的能量,与环境中的能量源密切相关。介绍了环境中常见能量源转换成电能的原理,并描述了这些能量源的特点、研究现状以及各自的优缺点,同时给出了不同能量源的适用范围,可作为自供能传感器采集环境能量时的参考。     

Instantaneous value control of current vector of energy transfer circuit with inductor converter bridges between superconducting magnets

Energy transfer circuits of inductor converter circuits (ICB), used for power supplies for superconducting magnets, are studied. Analytical solutions of steady-state characteristics of ICB energy transfer circuits are analyzed. On the basis of these solutions, a discussion is presented regarding a new control method of ICB transfer circuit to reduce a voltage ripple across a load superconducting magnet. This paper will propose a new control for line-commutated converters of ICB energy transfer circuit for quick changes in a transfer angle and a transfer frequency for the voltage ripple reduction control. Speeding-up of the proposed controls is also discussed. Validity of the proposed controls is confirmed by computer simulations.     

高功率因数可调光荧光灯电子镇流器

提出了一种简单易行的晶闸管控制荧光灯调光方法。给出了新型电子镇流器的电路结构,重点讨论了提高其功率因数、功率变换及可变调光的工作机理。该新型电子镇流器通过在调光器中引入电源电压信号处理装置,使电源进线由原来单纯传递电能,转变为包含控制信号,在原有接线方式的基础上实现了亮度可调。样机实验表明,该电子镇流器具有一定的应用价值。     

Power Systems in Close Proximity to Pipelines

In recent years, a trend has developed toward building energy corridors which better utilize land resources. Due to the adverse environmental impacts of building electrical power lines by utility companies and the installation of pipelines by the petrochemical industry, many governmental entities are requiring that electric power lines and underground pipelines use the same transmission (energy) corridor. The energy corridor, by design, is used to minimize the land requirements for transmitting energy?whether by electrical transmission lines or through pipelines. The energy corridor does not necessarily minimize the lengths of transmission lines but, conversely, may require longer lines to utilize the land resources better by paralleling transmission systems. The electric power companies have utilized this practice in the past with electrical corridors and are being pressured to make every effort to parallel electric lines in the future on these same corridors. The effect of paralleling electric circuits has been long understood by the electrical engineer. Induced currents and voltages occur between the electrical circuits and may cause relaying, communications, and safety problems. Proper engineering has led to solutions to most of these problems. A problem has developed with the addition of pipelines to the electrical corridors or, conversely, electrical lines to the pipeline corridors. The problem is that the pipeline has become part of the electrical circuit due to electrostatic and electromagnetic coupling. This coupling may cause induced currents and voltages to exist on the pipeline. The pipeline is addressed as an electrical circuit.