Piezoelectric materials for bistable energy harvester: A comparative study

This paper deals with the potential of various lead-free piezoelectric materials for energy harvesting. The performance of these materials is simulated for unimorph bistable piezoelectric energy harvester. The finite element method considering first-order shear deformation theory is used to model the system. The energy harvesting potential of bistable system (Non-linear) is compared with its linear counterpart. The results depict that the mean power density is almost 100% higher in case of bistable system. K_0.5Na_0.5NbO₃-LiSbO₃ (KNN-LS) family exhibited better performance than the conventional lead-based piezoelectric material lead zirconate titanate (PZT). The mean power density of K_0.5Na_0.5NbO₃-LiSbO₃-CaTiO₃ (2 wt.%) is reported to be 65% higher than PZT.     

Enhanced piezoelectric energy harvester performance using magnetic force and thermal energy

One possible approach of improving the performance of energy harvesters is to use energy harvester with an external magnetic force to create a nonlinear coupling system. In this work, we report experimental results of a single piezoelectric cantilever beam (PCB) with tip mass or conventional piezoelectric energy harvester (CPEH), and the effect of applying an external magnetic force. The output voltage and power at optimal resistance was 7.62 V and 0.62 mW, respectively, at the resonance frequency of approximately 11 Hz of a CPEH. Also, the output voltage and average power at optimal resistance was 8.56 V and 0.44 mW, respectively, at resonance frequency of 7 Hz of a PCB with fixed opposing magnet. Furthermore, the output voltage and average power at optimal resistance was 13.31 V and 1.77 mW, respectively, at resonance frequency of 11 Hz of a PCB with opposing magnet attached at a second cantilever. In addition, comparison between the experimental results of all different configurations showed a reasonable enhancement of performance of energy harvester when an external magnetic force added over the main PCB. Finally, the performance of a multisource energy harvester with magnetic, thermal and mechanical sources is also presented in this study. In this case, it is demonstrated that increase in output voltage with temperature gradient under effect of magnetic force; the results of 2^nd and 3^rd model showed 44% and 99% enhancement of its original output voltage value at 1.2 °C and 2.7 °C temperature difference, respectively.     

宽频激励下双稳态压电振动发电机供电能力分析

为了探讨双稳态压电振动发电机在宽频激励下的供电能力问题,建立了宽频激励下双稳态压电振动发电机系统的动力学模型,仿真了双稳态压电振动发电机系统的输出响应特性和不同运动状态的输出电压特性,研究了双稳态压电振动发电机系统运行在高能量轨道上的激励条件,据此优化双稳态压电振动发电机结构参数,并对传感器网络节点的用电需求和双稳态压电振动发电机的供电能力进行分析。仿真和实验结果表明:双稳态压电振动发电机在宽频激励下,其输出平均功率为3.8 m W,能够满足实际振动环境下无线传感器网络节点的用电需求。     

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.     

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。     

复合式动能采集器的多自由度宽频带设计优化

提出了一种多自由度宽频带压电 磁电复合式动能采集器,该动能采集器可以在多方向采集动能,有效地工作于较宽的频带,且可以同时以压电和磁电方式收集动能,大大提高了动能采集效率。介绍了复合式动能采集器的结构;分析和优化了采集器的拾振系统,从理论上验证了采集器的多自由度和宽频带的特性;介绍了磁电换能系统。研究结果表明,采集器在不同的工作频率下出现了两个振动峰值,验证了采集器的宽频带动能采集特性。通过实验测试进一步得出,与压电或磁电换能系统各自的输出性能相比,压电 磁电复合式换能系统的总体输出性能有所提高。     

Experimental study on a wide-band piezoelectric energy harvester with rotating beams vibrating in perpendicular directions

We present here a new design for a wide-band piezoelectric energy harvester. Our system consists of two mutually perpendicular cantilever beams with attached PZT (lead zirconate titanate) patches. Traditional piezoelectric energy harvesters can only generate a single resonance peak and therefore they are limited by a narrow band and low power output. In this paper, by using two piezoelectric cantilever beams aligned in a mutually perpendicular direction, two resonance peaks are observed. Additionally, by adjusting the rotation angle of these beams, the operational frequency bandwidth has been enlarged by 70%–100%. Therefore, our new piezoelectric energy harvester has the potential to harvest energy in a wider frequency range for practical applications with variable frequency sources.     

基于压电材料的变压器振动能量收集装置研究

变压器振动信号在线监测是检测变压器运行状态的重要手段,振动传感器的供能方式制约了振动检测方法的应用。为了实现振动传感器取能,文中设计了一种基于压电材料的变压器振动能量收集装置,利用收集的振动能量为振动传感器供电。首先,根据变压器振动特性,采用多模态取能方式,建立三悬臂式压电取能结构的输出电压与输出功率模型。其次,通过Comsol Multiphysics仿真分析能量收集装置输出功率和外加激励频率的关系。最后,搭建变压器振动能量收集实验平台,测得压电式能量收集装置的实际输出功率为11.547 μW。利用振动能量收集装置为振动传感器供电,可以保障在线监测设备的供电,减少外接电源对设备安全稳定运行的影响。     

基于Halbach阵列的多方向多模态动能采集器设计

为了使振动能量采集器适应外界振动环境的宽频带、方向随机特性,设计了一套基于Halbach永磁阵列的多方向多模态动能采集器。首先,建立了采集器的立方体-球状物理模型并分析了该模型的动力学特性。接着,设计出采集器的基本结构,重点对弹性梁的设计进行了具体分析,再利用有限元软件对设计出的结构进行动力学分析。同时,在结构设计的基础上,提出了基于Halbach永磁阵列的换能结构,将该阵列与一般的顺次永磁阵列进行比较分析。最后,搭建了实验系统平台,测试出采集器在不同输入激励下的输出电压。实验结果表明,采集器在不同激励方向可以达到对应的振动模态,并且均能产生有效的输出电压。因此,该采集器具有多方向多模态采集特性。     

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.

基于涡激振动的PVDF压电风能采集实验研究

为提高PVDF压电薄膜的发电能力,研究了一种基于涡激振动机理的PVDF压电能量采集结构,将风能转换为电能以供微功耗电子产品使用.设计了信号调理电路将压电薄膜的电荷输出转换为电压输出,通过微型风洞实验分别研究了在不同风速下,单片、双片、3片PVDF压电薄膜串联、并联的发电性能.实验结果表明,所选取的PVDF压电薄膜的谐振...     

Fabrication and characterization of flexible piezoelectric composites with natural rubber matrix

Abstract

This work aims to fabricate and characterize flexible piezoelectric composites with natural rubber (NR) matrix. Different amounts of Pb(Mg_1/3Nb_2/3)_0.65Ti_0.35O₃ (PMNT) powders were added in NR matrices. Porosity, tensile strength and percent elongation at break of composites tended to decrease with increasing PMNT content. The dielectric constant of the NR materials was found to be 3.5. It was raised up to 4.2, 5.0, 4.5, 4.8 and 5.1 when 60, 80, 100, 120 and 150 phr PMNT powders were added. However, dielectric loss of NR materials did not change with PMNT additions. Among this composite system, the NR/100PMNT composite showed the best piezoelectric properties, which its output voltage, piezoelectric coefficient (d₃₃) and piezoelectric voltage coefficient (g₃₃) values were equal to 1.61 V, 2.1?×?10^?4 pC/N and 5.4?×?10^?6 V?m/N, respectively. This composition composite is a promising material suitable for further improvement to be used as piezoelectric generators in energy harvesting applications.     

Energy harvesting using piezoelectric materials: Case of random vibrations

A dramatic consumption reduction of integrated circuits related to the development of mobile electronic devices has been reached over the past years, enabling the use of ambient energy instead of batteries. The focus is here on the transformation of ambient mechanical vibrations into electrical energy. This paper compares the performances of a vibration-powered electrical generator using PZT piezoelectric ceramics associated to two different power conditioning circuits. A new approach of the piezoelectric power conversion based on a nonlinear voltage processing is presented and implemented using a particular circuit. Theoretical predictions and experimental results show that the new technique may increase the power harvested by a factor up to 4 compared to the Standard technique. The power optimization problem is in particular examined in the case of broadband, random vibrations.     

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.     

压电振动能量收集的拓频方法及阻抗分析

利用能量收集技术来为装置供电,比有线布网供电和电池供电节约成本,同时便于设备的无线部署和长期运营维护。振动能量作为自然界中最常见的机械能之一,收集振动能量可以促进装置微小型化。现有的振动能量收集技术主要利用了装置与环境振动产生共振,因此能量收集的频率带宽仅在共振频率附近的小范围内,这限制了技术的应用场景。文中基于目前的机械和电气等各种拓展振动能量收集技术,分析了电气方法的频率响应特性。此外,相位可变开关电感电路作为电气拓频方法,比同步开关电感电路具有更宽的振动频率响应,使得在环境振动频率远离共振频率时,整体装置保持高水平的能量收集效率和能力。     

A simple and powerful analytical model for MEMS piezoelectric multimorphs

We have developed an analytical model for use in design and modelling of piezoelectric MEMS devices. The model allows for incorporation of any number of device material layers in a multimorph structure including piezoelectric materials. The resulting lumped circuit model fully incorporates the electro-mechanical coupling effects in the piezoelectric layers as well as electrical or mechanical loading of the device structure. Since the model is analytic, and only requires the specification of well-defined material properties, it allows for fast and interactive modelling of a multitude of MEMS device structures incorporating piezoelectric materials. We will demonstrate the capability of the model by presenting results from fitting the model to impedance measurements performed on cantilever structures. This allows for extraction of device and material parameters that are difficult to obtain by other means, such as the piezoelectric coefficient and the mechanical quality factor.     

Sustainable micro-power circuit for piezoelectric energy harvesting tile

Piezoelectric energy harvesting tiles are used for converting the power of pedestrian footsteps in to electricity and can be used at the micro- and milli-watt level for storage and powering electronics devices. This paper effectively combines the systems and techniques for developing a sustainable circuit with the self-starting and self-power functions to efficiently store energy and drive low power consumption electronic devices from the piezoelectric energy harvester tile. The main part of the system is 80% efficient impedance matching converter with the self-starting and battery-less operation. The presented circuit has an overall efficiency of 63% and can power a wireless sensor node to transmit the information wirelessly.     

海洋波浪压电发电装置的进展

本文对海洋波浪压电发电装置的发展进行了回顾。总结和阐明了各种类型装置的性能,指出共振是获得高效率的直接方法。针对变化的海洋环境,优化装置能够有效地提高效率,增加响应的带宽,使装置在较宽频率变化范围内都能保持高效运作,能够适用于实海况随机变化的波浪条件。作者阐明了现有装置的局限性,提出了一种新颖的波浪压电发电装置,该装置将吸收的波能以冲击荷载形式作用于压电发电振子上,使其在各种来波条件下都发生共振,并且以预先设定的频率输出电能。采用具有独立功能的分离式浮体组合,提高波能吸收效率,保障发电机工作环境平稳。最后提出了波浪压电发电研究中所要注意的一些问题。     

Analysis and design of an integrated RF energy harvester for ultra low-power environments

Radio-frequency (RF) energy harvesting must cope with the limited availability and high variability of the energy source. In this paper, the available RF power in three typical environments (urban, semi-urban, and rural) is investigated. Measurements show that in the surveyed urban and semi-urban environments, an average input power above −22 and −29 dBm, respectively, is available in the [700, 1,000] MHz band. A mathematical model of the interface between the RF rectifier and the DC-DC converter is provided. The analysis demonstrates that the energy can be efficiently transferred to the external accumulator coupling the rectifier with a strobed, input control DC-DC converter. Based on the measurements and the analysis, an RF harvester architecture has been designed in 65 nm Complementary Metal-Oxide Semiconductor (CMOS) technology to operate over the [−40, 85]^oC temperature and the [1.1, 2.5] V battery voltage ranges. The input control strategy adopted for the converter allows the adaptation of the harvester to the available RF power and enables a real maximum power point tracking (MPPT). Post-layout simulation of the harvester, recharging a large capacitor, precharged at 2 V, at 950 MHz of input frequency returned a 33.4% peak efficiency with an input power of 15 μW (−18 dBm). The minimum input power leading to a positive energy balance is −30 dBm with an output voltage of 1.1 V.