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Showing papers on "Energy harvesting published in 2008"


Journal ArticleDOI
03 Sep 2008
TL;DR: The principles and state-of-art in motion-driven miniature energy harvesters are reviewed and trends, suitable applications, and possible future developments are discussed.
Abstract: Energy harvesting generators are attractive as inexhaustible replacements for batteries in low-power wireless electronic devices and have received increasing research interest in recent years. Ambient motion is one of the main sources of energy for harvesting, and a wide range of motion-powered energy harvesters have been proposed or demonstrated, particularly at the microscale. This paper reviews the principles and state-of-art in motion-driven miniature energy harvesters and discusses trends, suitable applications, and possible future developments.

1,781 citations


Journal ArticleDOI
14 Feb 2008-Nature
TL;DR: This work establishes a methodology for scavenging light-wind energy and body-movement energy using fabrics and presents a simple, low-cost approach that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres.
Abstract: Nanodevices don't use much energy, and if the little they do need can be scavenged from vibrations associated with foot steps, heart beats, noises and air flow, a whole range of applications in personal electronics, sensing and defence technologies opens up. Energy gathering of that type requires a technology that works at low frequency range (below 10 Hz), ideally based on soft, flexible materials. A group working at Georgia Institute of Technology has now come up with a system that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing their associated nanowires together, mechanical energy is converted into electricity via a coupled piezoelectric-semiconductor process. This work shows a potential method for creating fabrics which scavenge energy from light winds and body movement. A self-powering nanosystem that harvests its operating energy from the environment is an attractive proposition for sensing, personal electronics and defence technologies1. This is in principle feasible for nanodevices owing to their extremely low power consumption2,3,4,5. Solar, thermal and mechanical (wind, friction, body movement) energies are common and may be scavenged from the environment, but the type of energy source to be chosen has to be decided on the basis of specific applications. Military sensing/surveillance node placement, for example, may involve difficult-to-reach locations, may need to be hidden, and may be in environments that are dusty, rainy, dark and/or in deep forest. In a moving vehicle or aeroplane, harvesting energy from a rotating tyre or wind blowing on the body is a possible choice to power wireless devices implanted in the surface of the vehicle. Nanowire nanogenerators built on hard substrates were demonstrated for harvesting local mechanical energy produced by high-frequency ultrasonic waves6,7. To harvest the energy from vibration or disturbance originating from footsteps, heartbeats, ambient noise and air flow, it is important to explore innovative technologies that work at low frequencies (such as <10 Hz) and that are based on flexible soft materials. Here we present a simple, low-cost approach that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing the nanowires rooted on them with respect to each other, mechanical energy is converted into electricity owing to a coupled piezoelectric–semiconductor process8,9. This work establishes a methodology for scavenging light-wind energy and body-movement energy using fabrics.

1,473 citations


BookDOI
TL;DR: Energy Harvesting Technologies as mentioned in this paper provides a cohesive overview of the fundamentals and current developments in the field of energy harvesting, as well as theory and design rules required for fabrication of efficient electronics, and recent findings in thermoelectric energy harvesting systems.
Abstract: Energy Harvesting Technologies provides a cohesive overview of the fundamentals and current developments in the field of energy harvesting. In a well-organized structure, this volume discusses basic principles for the design and fabrication of bulk and MEMS based vibration energy systems, theory and design rules required for fabrication of efficient electronics, in addition to recent findings in thermoelectric energy harvesting systems. Combining leading research from both academia and industry onto a single platform, Energy Harvesting Technologies serves as an important reference for researchers and engineers involved with power sources, sensor networks and smart materials.

1,372 citations


Journal ArticleDOI
TL;DR: In this article, the authors provide an overview of strategies for powering MEMS via non-regenerative and regenerative power supplies, along with recent advancements, and discuss future trends and applications for piezoelectric energy harvesting technology.
Abstract: Power consumption is forecast by the International Technology Roadmap of Semiconductors (ITRS) to pose long-term technical challenges for the semiconductor industry. The purpose of this paper is threefold: (1) to provide an overview of strategies for powering MEMS via non-regenerative and regenerative power supplies; (2) to review the fundamentals of piezoelectric energy harvesting, along with recent advancements, and (3) to discuss future trends and applications for piezoelectric energy harvesting technology. The paper concludes with a discussion of research needs that are critical for the enhancement of piezoelectric energy harvesting devices.

1,151 citations


Journal ArticleDOI
TL;DR: In this article, the design and testing of a resonance frequency tunable energy harvesting device using a magnetic force technique is presented, which enabled resonance tuning to ±20% of the untuned resonant frequency.
Abstract: Vibration energy harvesting is an attractive technique for potential powering of wireless sensors and low power devices. While the technique can be employed to harvest energy from vibrations and vibrating structures, a general requirement independent of the energy transfer mechanism is that the vibration energy harvesting device operate in resonance at the excitation frequency. Most energy harvesting devices developed to date are single resonance frequency based, and while recent efforts have been made to broaden the frequency range of energy harvesting devices, what is lacking is a robust tunable energy harvesting technique. In this paper, the design and testing of a resonance frequency tunable energy harvesting device using a magnetic force technique is presented. This technique enabled resonance tuning to ±20% of the untuned resonant frequency. In particular, this magnetic-based approach enables either an increase or decrease in the tuned resonant frequency. A piezoelectric cantilever beam with a natural frequency of 26 Hz is used as the energy harvesting cantilever, which is successfully tuned over a frequency range of 22‐32 Hz to enable a continuous power output 240‐280 μW over the entire frequency range tested. A theoretical model using variable damping is presented, whose results agree closely with the experimental results. The magnetic force applied for resonance frequency tuning and its effect on damping and load resistance have been experimentally determined. (Some figures in this article are in colour only in the electronic version)

651 citations


Journal ArticleDOI
TL;DR: In this article, an electromagnetic-based generator is presented for supplying generating power from human body motion and has application in providing energy for body worn sensors or electronics devices, and the experimental results show that the prototype could generate 300μW to 2.5mW power from Human Body Motion during walking and slow running.
Abstract: This paper presents an electromagnetic based generator which is suitable for supplying generating power from human body motion and has application in providing energy for body worn sensors or electronics devices. A prototype generator has been built and tested both by a shaker at resonance condition and also by human body motion during walking and slow running. The experimental results will show that the prototype could generate 300 μW to 2.5 mW power from human body motion. The measured results are analyzed and compared with the theoretical model.

547 citations


Proceedings ArticleDOI
03 Apr 2008
TL;DR: This paper serves as a survey for identifying the sources of energy harvesting based on various technical papers available in the public domain.
Abstract: Historically, batteries have been the source of energy for most mobile, embedded and remote system applications. Now, with ubiquitous computing requirements in the fields of embedded systems, wireless sensor networks and low- power electronics such as MEMS devices, an alternative source of energy is required. Also with the limited capacity of finite power sources and the need for supplying energy for a lifetime of a system, there is a requirement for self- powered devices. The process of extracting energy from the surrounding environment is termed as energy harvesting. Energy harvesting, which originated from the windmill and water wheel, is widely being considered as a low- maintenance solution for a wide variety of applications. There are various forms of energy that can be scavenged, like thermal, mechanical, solar, acoustic, wind, and wave. This paper serves as a survey for identifying the sources of energy harvesting based on various technical papers available in the public domain.

496 citations


Journal ArticleDOI
TL;DR: In this paper, the authors provide corrections and necessary clarifications for researchers from different engineering disciplines interested in electromechanical modeling of piezoelectric energy harvesters, including electrical, mechanical and materials engineers.
Abstract: The idea of vibration-to-electric energy conversion for powering small electronic components by using the ambient vibration energy has been investigated by researchers from different disciplines in the last decade. Among the possible transduction mechanisms, piezoelectric transduction has received the most attention for converting ambient vibrations to useful electrical energy. In the last five years, there have been a considerable number of publications using various models for the electromechanical behavior of piezoelectric energy harvester beams. The models used in the literature range from elementary single-degree-of-freedom (SDOF) models to approximate distributed parameter models as well as analytical distributed parameter solution attempts. Because of the diverse nature of researchers working in energy harvesting (including electrical, mechanical and materials engineers), several oversimplified and incorrect physical assumptions have been propagated in the literature. Issues of the correct formulation for piezoelectric coupling, correct physical modeling, use of low fidelity models, incorrect base motion modeling, and the use of static expressions in a fundamentally dynamic problem are discussed and clarified here. These common indiscretions, which have been repeated in the existing piezoelectric energy harvesting literature, are addressed and clarified with improved models, and examples are provided. This paper aims to provide corrections and necessary clarifications for researchers from different engineering disciplines interested in electromechanical modeling of piezoelectric energy harvesters.

456 citations


Journal ArticleDOI
TL;DR: A power generator array based on thick-film piezoelectric cantilevers is investigated to improve frequency flexibility and power output and is promising to support networks of ultra-low-power, peer-to-peer, wireless nodes.

455 citations


Journal ArticleDOI
TL;DR: This paper proposes a low-power maximum power point tracker (MPPT) circuit specifically designed for wireless sensor nodes, i.e., a power transferring circuit for optimally conveying solar energy into rechargeable batteries even in not optimal weather conditions.
Abstract: The success of wireless sensor networks and their pervasive use is somehow constrained by energy supply which, generally provided by batteries, is a finite resource. Energy harvesting mechanisms must hence be taken into account to grant a long time operational life, with solar energy being the most interesting one in outdoor deployments due to its relatively high power density. In this paper we propose a low-power maximum power point tracker (MPPT) circuit specifically designed for wireless sensor nodes (hence effective, flexible, low cost and power-aware), i.e., a power transferring circuit for optimally conveying solar energy into rechargeable batteries even in not optimal weather conditions. High efficiency is granted by an ad hoc adaptive algorithm which, by keeping the MPPT electronics in its optimal working point, maximizes energy transfer from the solar cell to the batteries. The suggested implementation is particularly effective in critical weather conditions where traditional solutions do not work and is characterized by a flexible enough design for immediately hosting, in a plug in fashion, different solar panels and battery typologies.

441 citations


Journal ArticleDOI
TL;DR: In this article, a new class of vibration energy harvester based on magnetostrictive material (MsM), Metglas 2605SC, is designed, developed and tested.
Abstract: A new class of vibration energy harvester based on magnetostrictive material (MsM), Metglas 2605SC, is designed, developed and tested. It contains two submodules: an MsM harvesting device and an energy harvesting circuit. Compared to piezoelectric materials, the Metglas 2605SC offers advantages including higher energy conversion efficiency, longer life cycles, lack of depolarization and higher flexibility to survive in strong ambient vibrations. To enhance the energy conversion efficiency and alleviate the need of a bias magnetic field, Metglas ribbons are transversely annealed by a strong magnetic field along their width direction. To analyze the MsM harvesting device a generalized electromechanical circuit model is derived from Hamilton’s principle in conjunction with the normal mode superposition method based on Euler‐Bernoulli beam theory. The MsM harvesting device is equivalent to an electromechanical gyrator in series with an inductor. In addition, the proposed model can be readily extended to a more practical case of a cantilever beam element with a tip mass. The energy harvesting circuit, which interfaces with a wireless sensor and accumulates the harvested energy into an ultracapacitor, is designed on a printed circuit board (PCB) with plane dimension 25 mm × 35 mm. It mainly consists of a voltage quadrupler, a 3 F ultracapacitor and a smart regulator. The output DC voltage from the PCB can be adjusted within 2.0‐5.5 V. In experiments, the maximum output power and power density on the resistor can reach 200 μW and 900 μ Wc m −3 , respectively, at a low frequency of 58 Hz. For a working prototype under a vibration with resonance frequency of 1.1 kHz and peak acceleration of 8.06 m s −2 (0.82 g), the average power and power density during charging the ultracapacitor can achieve 576 μ Wa nd 606 μ Wc m −3 , respectively, which compete favorably with piezoelectric vibration energy harvesters. (Some figures in this article are in colour only in the electronic version)

Journal ArticleDOI
TL;DR: In this article, a multifrequency mechanoelectrical piezoelectric converter intended for powering autonomous sensors from background vibrations is presented, which is composed of multiple bimorph cantilevers with different natural frequencies, whose rectified outputs are fed to a single storage capacitor.
Abstract: A multifrequency mechanoelectrical piezoelectric converter intended for powering autonomous sensors from background vibrations is presented. The converter is composed of multiple bimorph cantilevers with different natural frequencies, whose rectified outputs are fed to a single storage capacitor. The structure of the converter, description of the operation, and measurement data on the performances are reported. Experimental results show the possibility of using the converter with input vibrations across a wideband frequency spectrum, improving the effectiveness of the overall energy conversion over the case of a single converter. The converter was used to supply power to a battery-less sensor module that intermittently reads the signal from a passive sensor and sends the measurement information via RF transmission, in this way forming an autonomous sensor system with improved measure-and-transmit rate.

Journal ArticleDOI
TL;DR: In this article, an electromagnetic (EM) vibration-to-electrical power generator for wireless sensors, which can scavenge energy from low-frequency external vibrations, is presented. But the proposed generator cannot generate enough energy for proper operation.
Abstract: This paper presents an electromagnetic (EM) vibration-to-electrical power generator for wireless sensors, which can scavenge energy from low-frequency external vibrations. For most wireless applications, the ambient vibration is generally at very low frequencies (1-100 Hz), and traditional scavenging techniques cannot generate enough energy for proper operation. The reported generator up-converts low-frequency environmental vibrations to a higher frequency through a mechanical frequency up-converter using a magnet, and hence provides more efficient energy conversion at low frequencies. Power is generated by means of EM induction using a magnet and coils on top of resonating cantilever beams. The proposed approach has been demonstrated using a macroscale version, which provides 170 nW maximum power and 6 mV maximum voltage. For the microelectromechanical systems (MEMS) version, the expected maximum power and maximum voltage from a single cantilever is 3.97 muW and 76 mV, respectively, in vacuum. Power level can be increased further by using series-connected cantilevers without increasing the overall generator area, which is 4 mm2. This system provides more than an order of magnitude better energy conversion for 10-100 Hz ambient vibration range, compared to a conventional large mass/coil system.

Journal ArticleDOI
TL;DR: This paper reviews the characteristics and energy requirements of typical sensor network nodes, assesses a range of potential ambient energy sources, and outlines the characteristics of a wide range of energy conversion devices, and proposed method to compare these diverse sources and conversion mechanisms in terms of their normalised power density.
Abstract: Wireless sensor networks (WSNs) offer an attractive solution to many environmental, security, and process monitoring problems. However, one barrier to their fuller adoption is the need to supply electrical power over extended periods of time without the need for dedicated wiring. Energy harvesting provides a potential solution to this problem in many applications. This paper reviews the characteristics and energy requirements of typical sensor network nodes, assesses a range of potential ambient energy sources, and outlines the characteristics of a wide range of energy conversion devices. It then proposes a method to compare these diverse sources and conversion mechanisms in terms of their normalised power density.

Journal ArticleDOI
TL;DR: A review of three types of energy harvesting with focus on devices at or below the cm3 scale is presented in this paper, where the harvesting technologies discussed are based on the conversion of temperature gradients, mechanical vibrations, and radiofrequency waves.
Abstract: As sensors for a wide array of applications continue to shrink and become integrated, increasing attention has been focused on creating autonomous devices with long-lasting power supplies. To achieve this, energy will have to be harvested from the sensors’ environment. An energy harvesting device can power the sensor either directly or in conjunction with a battery. Presented herein is a review of three types of energy harvesting with focus on devices at or below the cm3 scale. The harvesting technologies discussed are based on the conversion of temperature gradients, mechanical vibrations, and radiofrequency waves. Operation principles, current state of the art, and materials issues are presented. In addition, requirements and recent developments in power conditioning for such devices are discussed. Future challenges specific to miniaturization are outlined from both the materials and device perspectives.

Journal ArticleDOI
TL;DR: Numerical results show that the OFB of the piezoelectric energy harvesting devices can be tailored by the connection patterns (i.e., in series and in parallel) among PBs.
Abstract: This paper presents a novel approach for designing broadband piezoelectric harvesters by integrating multiple piezoelectric bimorphs (PBs) with different aspect ratios into a system. The effect of 2 connecting patterns among PBs, in series and in parallel, on improving energy harvesting performance is discussed. It is found for multifrequency spectra ambient vibrations: 1) the operating frequency band (OFB) of a harvesting structure can be widened by connecting multiple PBs with different aspect ratios in series; 2) the OFB of a harvesting structure can be shifted to the dominant frequency domain of the ambient vibrations by increasing or decreasing the number of PBs in parallel. Numerical results show that the OFB of the piezoelectric energy harvesting devices can be tailored by the connection patterns (i.e., in series and in parallel) among PBs.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a model that takes into account the losses of discrete components such as diodes or transistors, and a new architecture for the SSHI energy harvesting circuit that limits such losses in the harvesting process.
Abstract: Harvesting energy from environmental sources has been of particular interest these last few years. Microgenerators that can power electronic systems are a solution for the conception of autonomous, wireless devices. They allow the removal of bulky and costly wiring, as well as complex maintenance and environmental issues for battery-powered systems. In particular, using piezoelectric generators for converting vibrational energy to electrical energy is an intensively investigated field. In this domain, it has been shown that the harvested energy can be greatly improved by the use of an original non-linear treatment of the piezoelectric voltage called SSHI (Synchronized Switch Harvesting on Inductor), which consists in intermittently switching the piezoelectric element on a resonant electrical network for a very short time. However, the integration of miniaturized microgenerators with low voltage output (e.g. MEMS microgenerators) has not been widely studied. In the case of low voltage output, the losses introduced by voltage gaps of discrete components such as diodes or transistors can no longer be neglected. Therefore the purpose of this paper is to propose a model that takes into account such losses as well as a new architecture for the SSHI energy harvesting circuit that limits such losses in the harvesting process. While most of the study uses an externally powered microcontroller for the non-linear treatment, this circuit is fully self-powered, thus providing an enhanced autonomous microgenerator. In particular this circuit aims at limiting the effect of non-linear components with a voltage gap such as diodes. It is shown both theoretically and experimentally that the harvested power can be significantly increased using such a circuit. In particular, experimental measurements performed on a cantilever beam show that the circuit allows a 160% increase of the harvested power compared to a standard energy harvesting circuit, while the classical implementation of the SSHI shows an increase of only 100% of the output power in the classical case.

Journal ArticleDOI
TL;DR: In this article, an approach and associated circuitry for harvesting near maximum output power from electromagnetic waves in the RF/microwave region of the spectrum with variable incident power densities in the range of tens of muW/cm2 is presented.
Abstract: This paper presents an approach and associated circuitry for harvesting near maximum output power from electromagnetic waves in the RF/microwave region of the spectrum with variable incident power densities in the range of tens of muW/cm2. It is shown that open loop resistor emulation at the input port of a power converter is a suitable solution for tracking the peak power point of a low-power rectifying antenna source over a wide range of incident RF power densities. A boost converter with a simple low-power control approach for resistor emulation is presented. A hardware design example with detailed efficiency analysis is given using commercially available discrete circuitry. Experimental results are presented for a system harvesting 420 muW to 8 muW from a 6 cm times 6 cm rectifying antenna with incident RF power ranging from 70 muW/cm2 to 30 muW/cm2, respectively. The results demonstrate that resistor emulation is a simple and practical approach to energy harvesting with variable low-power radiative RF sources.

Journal ArticleDOI
15 May 2008-Talanta
TL;DR: Key research challenges to be addressed to deliver future, remote, wireless, chemo-biosensing systems include the development of low cost, low-power sensors, miniaturised fluidic transport systems, anti-bio-fouling sensor surfaces, sensor calibration, reliable and robust system packaging, as well as associated energy delivery systems and energy budget management.

Journal ArticleDOI
TL;DR: The development and implementation of an energy aware autonomous wireless condition monitoring sensor system (ACMS) powered by ambient vibrations that has been successfully demonstrated on an industrial air compressor and an office air conditioning unit, continuously monitoring vibration levels and thereby simulating a typical condition monitoring application.
Abstract: This paper reports the development and implementation of an energy aware autonomous wireless condition monitoring sensor system (ACMS) powered by ambient vibrations. An electromagnetic (EM) generator has been designed to harvest sufficient energy to power a radio-frequency (RF) linked accelerometer-based sensor system. The ACMS is energy aware and will adjust the measurement/transmit duty cycle according to the available energy; this is typically every 3 s at 0.6 m s?2 rms acceleration and can be as low as 0.2 m s?2 rms with a duty cycle around 12 min. The EM generator has a volume of only 150 mm3 producing an average power of 58 ?W at 0.6m s?2 rms acceleration at a frequency of 52 Hz. In addition, a voltage multiplier circuit is shown to increase the electrical damping compared to a purely resistive load; this allows for an average power of 120 ?W to be generated at 1.7 m s?2 rms acceleration. The ACMS has been successfully demonstrated on an industrial air compressor and an office air conditioning unit, continuously monitoring vibration levels and thereby simulating a typical condition monitoring application

Journal ArticleDOI
TL;DR: In this article, an ambient energy scavenging system for powering wireless sensor nodes using a MEMS generator and an ASIC power management circuit has been presented, which is created as a System on a Package with all components fabricated entirely using microfabrication techniques.
Abstract: This paper presents a novel ambient energy scavenging system for powering wireless sensor nodes. It uses a MEMS generator and an ASIC power management circuit. The system is created as a System on a Package with all components fabricated entirely using microfabrication techniques. Its performance is compared with standard approaches using a resistive load or discrete Schottky diodes. The electromechanical transduction is performed using the piezoelectric effect of aluminium nitride thin films. The reported experimental results prove the possibility of exploiting very low amplitude signals delivered by the generator for charging a storage capacitor. It is also shown that a system of 5 mm 3 can endlessly power a simple wireless sensor node; while a lithium polymer thin film battery of the same volume can do so only for less than 2 months.

Journal ArticleDOI
TL;DR: Practical implementation key points of pyroelectric energy harvesting are presented showing that the different thermodynamic cycles are feasible and potentially effective, even compared to thermoelectric devices.
Abstract: In the framework of microgenerators, we present in this paper the key points for energy harvesting from temperature using ferroelectric materials. Thermoelectric devices profit from temperature spatial gradients, whereas ferroelectric materials require temporal fluctuation of temperature, thus leading to different applications targets. Ferroelectric materials may harvest perfectly the available thermal energy whatever the materials properties (limited by Carnot conversion efficiency) whereas thermoelectric material's efficiency is limited by materials properties (ZT figure of merit). However, it is shown that the necessary electric fields for Carnot cycles are far beyond the breakdown limit of bulk ferroelectric materials. Thin films may be an excellent solution for rising up to ultra-high electric fields and outstanding efficiency. Different thermodynamic cycles are presented in the paper: principles, advantages, and drawbacks. Using the Carnot cycle, the harvested energy would be independent of materials properties. However, using more realistic cycles, the energy conversion effectiveness remains dependent on the materials properties as discussed in the paper. A particular coupling factor is defined to quantify and check the effectiveness of pyroelectric energy harvesting. It is defined similarly to an electromechanical coupling factor as k2 = p2thetas0/(epsivthetas 33 CE), where p, thetas0, epsivthetas 33, Ce are pyroelectric coefficient, maximum working temperature, dielectric permittivity, and specific heat, respectively. The importance of the electrothermal coupling factor is shown and discussed as an energy harvesting figure of merit. It gives the effectiveness of all techniques of energy harvesting (except the Carnot cycle). It is finally shown that we could reach very high efficiency using lang111rang0.75Pb(Mg1/3Nb2/3)-0.25PbTiO3 single crystals and synchronized switch harvesting on inductor (almost 50% of Carnot efficiency). Finally, practical implementation key points of pyroelectric energy harvesting are presented showing that the different thermodynamic cycles are feasible and potentially effective, even compared to thermoelectric devices.

Journal ArticleDOI
TL;DR: In this article, the authors developed a novel energy harvesting backpack that can generate electrical energy from the differential forces between the wearer and the pack by replacing the strap buckle with a mechanically amplified piezoelectric stack actuator.

Journal ArticleDOI
TL;DR: In this paper, the authors describe an efficient charging method for a supercapacitor-operated, solar-powered wireless sensor node called Everlast, which enables the system to operate for an estimated lifetime of 20 years without any maintenance.
Abstract: This paper describes an efficient charging method for a supercapacitor-operated, solar-powered wireless sensor node called Everlast. Unlike traditional wireless sensors that store energy in batteries, Everlast's use of supercapacitors enables the system to operate for an estimated lifetime of 20 years without any maintenance. The novelty of this system lies in the feed-forward, pulse frequency modulated converter and open-circuit solar voltage method for maximum power point tracking (MPPT), enabling the solar cell to efficiently charge the supercapacitor and power the node. Experimental results show that by its low-complexity MPPT, Everlast can achieve over 89% conversion efficiency with lower power overhead than the state-of-the-art by two orders of magnitude, while enabling charging a supercapacitor up to 400% faster than direct charging. This makes Everlast particularly applicable to miniature-scale, high-impedance energy harvesting systems.

Journal ArticleDOI
TL;DR: A theoretical model of a piezoelectric based energy harvesting system that is simple to apply yet provides an accurate prediction of the power generated around a single mode of vibration is described.
Abstract: The process of acquiring the energy surrounding a system and converting it into usable electrical energy is termed power harvesting. In the last few years, the field of power harvesting has experienced significant growth due to the ever increasing desire to produce portable and wireless electronics with extended life. Current portable and wireless devices must be designed to include electrochemical batteries as the power source. The use of batteries can be troublesome due to their finite energy supply, which necessitates their periodic replacement. In the case of wireless sensors that are to be placed in remote locations, the sensor must be easily accessible or of disposable nature to allow the device to function over extended periods of time. Energy scavenging devices are designed to capture the ambient energy surrounding the electronics and covert it into usable electrical energy. The concept of power harvesting works towards developing self-powered devices that do not require replaceable power supplies. The development of energy harvesting systems is greatly facilitated by an accurate model to assist in the design of the system. This paper will describe a theoretical model of a piezoelectric based energy harvesting system that is simple to apply yet provides an accurate prediction of the power generated around a single mode of vibration. Furthermore, this model will allow optimization of system parameters to be studied such that maximal performance can be achieved. Using this model an expression for the optimal resistance and a parameter describing the energy harvesting efficiency will be presented and evaluated through numerical simulations. The second part of this paper will present an experimental validation of the model and optimal parameters.

Journal ArticleDOI
TL;DR: An autonomous power generator unit including two micropower sources and their management IC has been fabricated, using a RF power receiver and a 1 V miniature thermogenerator to manage and store the harvested energy in a 30 above-IC deposited microbattery.
Abstract: An autonomous power generator unit including two micropower sources and their management IC has been fabricated: a RF power receiver and a 1 V miniature thermogenerator combined with a micropower DC/DC up-converter are combined with a 78% efficiency manager and charger, and a 5 nW discharge monitor to manage and store the harvested energy in a 30 above-IC deposited microbattery.

Journal ArticleDOI
TL;DR: It is shown that such a technique allows a fine-tuning of the trade-off between vibration damping and energy harvesting, and the extracted power obtained allows a gain up to 500% in terms of maximal power output compared with the standard energy harvesting method.
Abstract: 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.

Journal ArticleDOI
L.M. Swallow1, Jikui Luo1, Elias Siores1, I. Patel1, D. Dodds1 
TL;DR: In this paper, a micropower generator using microcomposite based piezoelectric materials for energy reclamation in glove structures is presented, where the fibres are laid within a single laminate structure with copper interdigitated electrodes assembled on both sides.
Abstract: Rapid technological advances in nanotechnology, microelectronic sensors and systems are becoming increasingly miniaturized to the point where embedded wearable applications are beginning to emerge. A restriction to the widespread application of these microsystems is the power supply of relatively sizable dimensions, weight, and limited lifespan. Emerging micropower sources exploit self-powered generators utilizing the intrinsic energy conversion characteristics of smart materials. 'Energy harvesting' describes the process by which energy is extracted from the environment, converted and stored. Piezoelectric materials have been used to convert mechanical into electrical energy through their inherent piezoelectric effect. This paper focuses on the development of a micropower generator using microcomposite based piezoelectric materials for energy reclamation in glove structures. Devices consist of piezoelectric fibres, 90–250 µm in diameter, aligned in a unidirectional manner and incorporated into a composite structure. The fibres are laid within a single laminate structure with copper interdigitated electrodes assembled on both sides, forming a thin film device. Performances of devices with different fibre diameters and material thicknesses are investigated. Experiments are outlined that detail the performance characteristics of such piezoelectric fibre laminates. Results presented show voltage outputs up to 6 V which is considered enough for potential applications in powering wearable microsystems.

Journal ArticleDOI
08 Dec 2008-Sensors
TL;DR: The state-of-the art technology in the field of both energy storage and energy harvesting for sensor nodes, including batteries, capacitors, fuel cells, heat engines and betavoltaic systems are reviewed.
Abstract: Reduction in size and power consumption of consumer electronics has opened up many opportunities for low power wireless sensor networks. One of the major challenges is in supporting battery operated devices as the number of nodes in a network grows. The two main alternatives are to utilize higher energy density sources of stored energy, or to generate power at the node from local forms of energy. This paper reviews the state-of-the art technology in the field of both energy storage and energy harvesting for sensor nodes. The options discussed for energy storage include batteries, capacitors, fuel cells, heat engines and betavoltaic systems. The field of energy harvesting is discussed with reference to photovoltaics, temperature gradients, fluid flow, pressure variations and vibration harvesting.

Patent
02 Jun 2008
TL;DR: An implantable, rechargeable medical system comprised of an implanted device, a power storage device connected to the implantable device, and a charging device operatively connected to an electrical storage device is described in this article.
Abstract: An implantable, rechargeable medical system comprised of an implanted device, a power storage device connected to the implantable device, and a charging device operatively connected to the electrical storage device. The charging device can be thermoelectric and have components for transferring thermal energy from an intracranial heat accumulator to an extra-cranial heat sink, for generating an electrical current from the thermal energy transfer, for charging the electrical storage device using the electrical current, for measuring power generation, usage and reserve levels, for measuring temperatures of the intracranial and extra-cranial components, for physically disrupting heat transfer and charging operations, and for generating signals relevant to the status of temperature and electricity transfer in relation to energy generation criteria. The system may also have long-range and short range wireless power harvesting capability as well as movement, and photovoltaic charging capability. Components may be dual purpose, being used for receiving wireless energy as well as for accomplishing other operations such as sensing or stimulating. Specialized accessories assist with providing enhanced wireless power charging.