A new piezoelectric energy harvesting design concept: multimodal energy harvesting skin

This paper presents an advanced design concept for a piezoelectric energy harvesting (EH), referred to as multimodal EH skin. This EH design facilitates the use of multimodal vibration and enhances power harvesting efficiency. The multimodal EH skin is an extension of our previous work, EH skin, which was an innovative design paradigm for a piezoelectric energy harvester: a vibrating skin structure and an additional thin piezoelectric layer in one device. A computational (finite element) model of the multilayered assembly - the vibrating skin structure and piezoelectric layer - is constructed and the optimal topology and/or shape of the piezoelectric layer is found for maximum power generation from multiple vibration modes. A design rationale for the multimodal EH skin was proposed: designing a piezoelectric material distribution and external resistors. In the material design step, the piezoelectric material is segmented by inflection lines from multiple vibration modes of interests to minimize voltage cancellation. The inflection lines are detected using the voltage phase. In the external resistor design step, the resistor values are found for each segment to maximize power output. The presented design concept, which can be applied to any engineering system with multimodal harmonic-vibrating skins, was applied to two case studies: an aircraft skin and a power transformer panel. The excellent performance of multimodal EH skin was demonstrated, showing larger power generation than EH skin without segmentation or unimodal EH skin.     

Electromagnetic energy harvester for harvesting acoustic energy

This paper reports a suspended coil, electromagnetic acoustic energy harvester (AEH) for extracting acoustical energy. The developed AEH comprises Helmholtz resonator (HR), a wound coil bonded to a flexible membrane and a permanent magnet placed in a magnet holder. The harvester’s performance is analyzed under different sound pressure levels (SPLs) both in laboratory and in real environment. In laboratory, when connected to 50 Ω load resistance and subjected to an SPL of 100 dB, the AEH generated a peak load voltage of 198.7 mV at the resonant frequency of 319 Hz. When working under the optimum load resistance, the AEH generated an optimum load power of 789.65 µW. In real environment, the developed AEH produced a maximum voltage of 25 mV when exposed to the acoustic noise of a motorcycle and generated an optimum voltage of 60 mV when it is placed in the surroundings of a domestic electrical generator.     

Pyroelectric nanogenerators for harvesting thermoelectric energy

Harvesting thermoelectric energy mainly relies on the Seebeck effect that utilizes a temperature difference between two ends of the device for driving the diffusion of charge carriers. However, in an environment that the temperature is spatially uniform without a gradient, the pyroelectric effect has to be the choice, which is based on the spontaneous polarization in certain anisotropic solids due to a time-dependent temperature variation. Using this effect, we experimentally demonstrate the first application of pyroelectric ZnO nanowire arrays for converting heat energy into electricity. The coupling of the pyroelectric and semiconducting properties in ZnO creates a polarization electric field and charge separation along the ZnO nanowire as a result of the time-dependent change in temperature. The fabricated nanogenerator has a good stability, and the characteristic coefficient of heat flow conversion into electricity is estimated to be ～0.05-0.08 Vm(2)/W. Our study has the potential of using pyroelectric nanowires to convert wasted energy into electricity for powering nanodevices.     

Cyclic energy harvesting from pyroelectric materials

A method of continuously harvesting energy from pyroelectric materials is demonstrated using an innovative cyclic heating scheme. In traditional pyroelectric energy harvesting methods, static heating sources are used, and most of the available energy has to be harvested at once. A cyclic heating system is developed such that the temperature varies between hot and cold regions. Although the energy harvested during each period of the heating cycle is small, the accumulated total energy over time may exceed traditional methods. Three materials are studied: a commonly available soft lead zirconate titanate (PZT), a pre-stressed PZT composite, and single-crystal PMN-30PT. Radiation heating and natural cooling are used such that, at smaller cyclic frequencies, the temporal rate of change in temperature is large enough to produce high power densities. The maximum power density of 8.64 μW/cm3 is generated with a PMN-30PT single crystal at an angular velocity of 0.64 rad/s with a rate of 8.5°C/s. The pre-stressed PZT composite generated a power density of 6.31 μW/cm(3), which is 40% larger than the density of 4.48 μW/cm3 obtained from standard PZT.     

Double synchronized switch harvesting (DSSH): a new energy harvesting scheme for efficient energy extraction

This paper presents a new technique for optimized energy harvesting using piezoelectric microgenerators called double synchronized switch harvesting (DSSH). This technique consists of a nonlinear treatment of the output voltage of the piezoelectric element. It also integrates an intermediate switching stage that ensures an optimal harvested power whatever the load connected to the microgenerator. Theoretical developments are presented considering either constant vibration magnitude, constant driving force, or independent extraction. Then experimental measurements are carried out to validate the theoretical predictions. This technique exhibits a constant output power for a wide range of load connected to the microgenerator. In addition, the extracted power obtained using such a technique allows a gain up to 500% in terms of maximal power output compared with the standard energy harvesting method. It is also shown that such a technique allows a fine-tuning of the trade-off between vibration damping and energy harvesting.     

用于振动能量收集的MEMS压电悬臂梁

本文介绍了一种MEMS悬臂梁器件,将环境中的振动机械能转化为电能.该悬臂梁的主体材料为单晶硅,其上覆盖一层用Sol-Gel法制备的PZT压电材料,利用压电材料的正压电效应实现机电能量的转换.论文给出了悬臂梁式振动能量收集器的一个简单理论模型.器件采用(110)硅基片,有利于通过湿法腐蚀制备质量块.质量块可以用来降低器件的谐振频率,并提高输出电功率.尺寸参数为3600μm×270 μm的器件样品的测试结果表明,在其谐振频率1673Hz,振幅为11nm的振动条件下,该器件的最大输出功率大于1nW,即0.11 μW/cm2.     

Polymer-based nanopiezoelectric generators for energy harvesting applications

Abstract

Energy harvesting from ambient vibrations originating from sources such as moving parts of machines, fluid flow and even body movement, has enormous potential for small power applications, such as wireless sensors, flexible, portable and wearable electronics, and bio-medical implants, to name a few. Nanoscale piezoelectric energy harvesters, also known as nanogenerators (NGs), can directly convert small scale ambient vibrations into electrical energy. Scavenging power from ubiquitous vibrations in this way offers an attractive route to provide power to small devices, which would otherwise require direct or indirect connection to electrical power infrastructure. Ceramics such as lead zirconium titanate and semiconductors such as zinc oxide are the most widely used piezoelectric energy harvesting materials. This review focuses on a different class of piezoelectric materials, namely, ferroelectric polymers, such as polyvinlyidene fluoride (PVDF) and its copolymers. These are potentially superior energy harvesting materials as they are flexible, robust, lightweight, easy and cheap to fabricate, as well as being lead free and biocompatible. We review some of the theoretical and experimental aspects of piezoelectric energy recovery using Polymer-based NGs with a novel emphasis on coupling to mechanical resonance, which is relevant for efficient energy harvesting from typically low frequency (<1 kHz) ambient vibrations. The realisation of highly efficient and low cost piezoelectric polymer NGs with reliable energy harvesting performance could lead to wide ranging energy solutions for the next generation of autonomous electronic and wireless devices.     

Investigation of electrostrictive polymers for energy harvesting

The recent development of electrostrictive polymers has generated new opportunities for high-strain actuators. At the current time, the investigation of using electrostrictive polymer for energy harvesting, or mechanical to electrical energy conversion, is beginning to show its potential for this application. In this paper we discuss the mechanical and electrical boundary conditions for maximizing the energy harvesting density and mechanical-to-electrical coupling of electrostrictive materials. Mathematical models for different energy harvesting approaches were developed under quasistatic assumptions. Energy harvesting densities then are determined for representative electrostrictive material properties using these models. Comparison with a magnetic-based energy harvesting system suggests that electrostrictive energy harvesting systems are preferable for "small" energy harvesting applications with low-frequency excitation.     

Catalytic-free growth of VACNTs for energy harvesting

Abstract

The present study introduces a process to grow micro-honeycomb (µ-HC) vertically aligned carbon nanotubes (VACNTs) using thermal chemical vapor deposition technique. Methane is used as a source of carbon and hydrogen gas as a reducing agent. Where, the fabricated µ-HC structure reported in literature involves complex synthesis process and requires a catalyst layer, the novelty of the process used here lies in the fact that no catalyst layer is used for the growth of CNT network, rather copper foil is used as a substrate. The in-situ cracking of CNTs due to water treatment leads to the formation of µ-HC CNT network, which is confirmed by Raman spectroscopy. Further scanning electron microscopy analysis shows that the length of developed µ-HC CNT is ～5?µm. Hexagonal µ-HC network shows more than 94% absorption in UV-Vis-NIR wavelength region. The designed process provides high-yield with a low-cost synthesis of vertically aligned CNTs having 3?D microarchitecture. The fabricated CNT network can be used as an electrode for supercapacitor, as an active layer in a photovoltaic cell and most of the energy harvesting devices.     

Laser-machined piezoelectric cantilevers for mechanical energy harvesting

In this study, we report results on a piezoelectric- material-based mechanical energy-harvesting device that was fabricated by combining laser machining with microelectronics packaging technology. It was found that the laser-machining process did not have significant effect on the electrical properties of piezoelectric material. The fabricated device was tested in the low-frequency regime of 50 to 1000 Hz at constant force of 8 g (where g = 9.8 m/s(2)). The device was found to generate continuous power of 1.13 microW at 870 Hz across a 288.5 kOmega load with a power density of 301.3 microW/cm(3).     

Liquid-FEP-based U-tube triboelectric nanogenerator for harvesting water-wave energy

Harvesting ambient mechanical energy is a key technology for realizing self-powered electronics. With advantages of stability and durability, a liquid–solid-based triboelectric nanogenerator (TENG) has recently drawn much attention. However, the impacts of liquid properties on the TENG performance and the related working principle are still unclear. We assembled herein a U-tube TENG based on the liquid–solid mode and applied 11 liquids to study the effects of liquid properties on the TENG output performance. The results confirmed that the key factors influencing the output are polarity, dielectric constant, and affinity to fluorinated ethylene propylene (FEP). Among the 11 liquids, the pure water-based U-tube TENG exhibited the best output with an open-circuit voltage (V_oc) of 81.7 V and a short-circuit current (I_sc) of 0.26 μA for the shaking mode (0.5 Hz), which can further increase to 93.0 V and 0.48 μA, respectively, for the horizontal shifting mode (1.25 Hz). The U-tube TENG can be utilized as a self-powered concentration sensor (component concentration or metalion concentration) for an aqueous solution with an accuracy higher than 92%. Finally, an upgraded sandwich-like water-FEP U-tube TENG was applied to harvest water-wave energy, showing a high output with V_oc of 350 V, I_sc of 1.75 μA, and power density of 2.04 W/m³. We successfully lighted up 60 LEDs and powered a temperature–humidity meter. Given its high output performance, the water-FEP U-tube TENG is a very promising approach for harvesting water-wave energy for self-powered electronics.

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Nonlinear pyroelectric energy harvesting from relaxor single crystals

Energy harvesting from temperature variations in a Pb(Zn_1/3Nb_2/3)_0.955Ti_0.045O₃ single crystal was studied and evaluated using the Ericsson thermodynamic cycle. The efficiency of this cycle related to Carnot cycle is 100 times higher than direct pyroelectric energy harvesting, and it can be as high as 5.5% for a 10degC temperature variation and 2 kV/mm electric field. The amount of harvested energy for a 60degC temperature variation and 2 kV/mm electric field is 242.7 mJmiddotcm^-3. The influence of ferroelectric phase transitions on the energy harvesting performance is discussed and illustrated with experimental results.     

Optimizing energy harvesting parameters using response surface methodology

Energy harvesting is a process in which energy that would otherwise be wasted is stored and then used to power a system. Due to their unique properties piezoelectric materials are ideal for energy harvesting applications. In this study a pre-stressed piezoelectric composite was pressure loaded dynamically to harvest energy. The objective of this study was to optimize, using piezoelectric diaphragms, relevant parameters that have an effect on the energy harvesting process. Parameters considered were temperature, pressure, resistance and frequency. Response surface methodology was used to develop models to identify optimal parameter ranges and also to predict power conversion capabilities for specific parameter levels. Power densities of approximately 24.27 muW/mm³ were measured at optimal conditions. The model identified an optimal temperature of 12degC and a pressure of 240 kPa, which are in agreement with experimental results.     

Advanced pyroelectric materials for energy harvesting and sensing applications

Heat energy is among the most wasted energy in the environment which is available in an ample quantity. So, developing new technology for harvesting and detecting wasted thermal energy to produce electrical energy which may be used as reliable energy sources for ultra-low power devices like nanogenerators and self-powered sensor applications. In this approach, pyroelectric energy harvesting technology has gained a huge attraction for application in power generation and sensing systems. Currently, a class of pyroelectric and piezoelectric materials has drawn enormous attraction because of its pyroelectric effect caused by spontaneous polarization and successful thermal energy harvesting for producing electrical energy for application in many sensor networks. This review makes a comprehensive summary of the significance and physical application of pyroelectric materials including single crystal, inorganic films, ceramics, organic materials, polymers, and composites as energy harvesting devices for scavenging thermal energy from surrounding for sensing devices. Finally, the perspective for next-generation self-powered sensor technologies is described.     

Cymbal压电发电换能器有限元分析

通过建立Cymbal压电发电换能器的机电耦合有限元分析模型,计算分析了换能器结构参数对输出电压和谐振频率的影响以及外接负载对Cymbal换能器输出电压和输出功率的影响。研究表明,为了降低换能器的工作频率和提高换能器的输出电压,应增大换能器的空腔底部直径和减小换能器的空腔高度;在选择金属端冒和压电陶瓷厚度等参数时,应综合考虑换能器系统的刚度和外界振动源的频率特性和加速度特性;在任意一个频率点上,Cymbal换能器均存在一个最佳的外接负载,使得换能器的输出功率最大,而这个最佳的负载阻抗就等于Cymbal换能器在这个工作频率点上的输出阻抗。文中还提出并分析了基于外加预应力的多振子级联方式Cymbal压电发电换能器系统的结构。     

Inlay-inspired meta-piezoelectric plates for the low-frequency vibration energy harvesting

Journal of Materials Science: Materials in Electronics - Different novel auxetic geometries are proposed applicable for the low-frequency vibration energy harvesting. The geometrical idea...     

Flexible nanocrystal-coated glass fibers for high-performance thermoelectric energy harvesting

Recent efforts on the development of nanostructured thermoelectric materials from nanowires (Boukai, A. I.; et al. Nature 2008, 451, (7175), 168-171; Hochbaum, A. I.; et al. Nature 2008, 451, (7175), 163-167) and nanocrystals (Kim, W.; et al. Phys. Rev. Lett. 2006, 96, (4), 045901; Poudel, B.; et al. Science 2008, 320, (5876), 634-638; Scheele, M.; et al. Adv. Funct. Mater. 2009, 19, (21), 3476-3483; Wang, R. Y.; et al. Nano Lett. 2008, 8, (8), 2283-2288) show the comparable or superior performance to the bulk crystals possessing the same chemical compositions because of the dramatically reduced thermal conductivity due to phonon scattering at nanoscale surface and interface. Up to date, the majority of the thermoelectric devices made from these inorganic nanostructures are fabricated into rigid configuration. The explorations of truly flexible composite-based flexible thermoelectric devices (See, K. C.; et al. Nano Lett. 2010, 10, (11), 4664-4667) have thus far achieved much less progress, which in principle could significantly benefit the conversion of waste heat into electricity or the solid-state cooling by applying the devices to any kind of objects with any kind of shapes. Here we report an example using a scalable solution-phase deposition method to coat thermoelectric nanocrystals onto the surface of flexible glass fibers. Our investigation of the thermoelectric properties yields high performance comparable to the state of the art from the bulk crystals and proof-of-concept demonstration also suggests the potential of wrapping the thermoelectric fibers on the industrial pipes to improve the energy efficiency.     

基于压电效应的时均流能量收集研究进展

基于压电技术的时均流能量收集是一种新型的环境能量收集形式,具有结构简单、成本低廉、无污染、无电磁干扰和使用寿命长的特点。按照不同的时均流能量收集原理分类介绍了最新研究进展,对各种装置之间的性能做了比较,其中采用时均流激声发动机驱动压电换能器的方法能够实现更高的能量转化效率。     

压电俘能技术研究现状综述

摘要：随着微电子、无线网络和MEMS等低耗能产品的应用日益广泛,以化学电池为其主要供能方式存在着诸多弊端,而压电俘能器具有结构简单、不发热、无电磁干扰、无污染和易于实现机构的微小化、集成化等诸多优点,且能满足此类低耗能产品的供能需求而备受关注。综述了压电俘能技术的国内外研究现状。围绕提高压电俘能效率,从压电振子构成形式、能量存储电路和能量存储元件等方面进行了系统的介绍,并对压电俘能技术的发展方向进行了预测。压电俘能技术可应用于导弹引信,海啸预警、桥梁安全监测、石油输油管道监测等重要领域的安全检测装置的自供能系统中,同时也可为无线网络、嵌入式系统和MEMS等低耗能产品的实现无线供能,展现出了压电俘能技术的良好应用前景。     

"Quantum coaxial cables" for solar energy harvesting

Type II core-shell nanowires based on III-V and II-VI semiconductors are designed to provide the highly desirable but not readily available feature--efficient charge separation--and concurrently address the different material challenges specific for a few key renewable energy applications: including hydrogen generation via photoelectrochemical water splitting, dye-sensitized solar cells, and conventional solar cells. They also open up new avenues for studying novel physics and material sciences in reduced dimensionality of very unusual quasi-one-dimensional systems. A first-principles density function theory within the local density approximation (LDA) is used for the electronic structure calculation and a valence-force-field method for the structural relaxation, and empirical corrections to the LDA errors are applied.