Showing papers on "Energy harvesting published in 2007"

A review of power harvesting using piezoelectric materials (2003–2006)

Abstract: The field of power harvesting has experienced significant growth over the past few years due to the ever-increasing desire to produce portable and wireless electronics with extended lifespans. 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 limited lifespan, thus necessitating 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 a 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 convert it into usable electrical energy. The concept of power harvesting works towards developing self-powered devices that do not require replaceable power supplies. A number of sources of harvestable ambient energy exist, including waste heat, vibration, electromagnetic waves, wind, flowing water, and solar energy. While each of these sources of energy can be effectively used to power remote sensors, the structural and biological communities have placed an emphasis on scavenging vibrational energy with piezoelectric materials. This article will review recent literature in the field of power harvesting and present the current state of power harvesting in its drive to create completely self-powered devices.

Power management in energy harvesting sensor networks

Abstract: Power management is an important concern in sensor networks, because a tethered energy infrastructure is usually not available and an obvious concern is to use the available battery energy efficiently. However, in some of the sensor networking applications, an additional facility is available to ameliorate the energy problem: harvesting energy from the environment. Certain considerations in using an energy harvesting source are fundamentally different from that in using a battery, because, rather than a limit on the maximum energy, it has a limit on the maximum rate at which the energy can be used. Further, the harvested energy availability typically varies with time in a nondeterministic manner. While a deterministic metric, such as residual battery, suffices to characterize the energy availability in the case of batteries, a more sophisticated characterization may be required for a harvesting source. Another issue that becomes important in networked systems with multiple harvesting nodes is that different nodes may have different harvesting opportunity. In a distributed application, the same end-user performance may be achieved using different workload allocations, and resultant energy consumptions at multiple nodes. In this case, it is important to align the workload allocation with the energy availability at the harvesting nodes. We consider the above issues in power management for energy-harvesting sensor networks. We develop abstractions to characterize the complex time varying nature of such sources with analytically tractable models and use them to address key design issues. We also develop distributed methods to efficiently use harvested energy and test these both in simulation and experimentally on an energy-harvesting sensor network, prototyped for this work.

Advances in energy harvesting using low profile piezoelectric transducers

Abstract: 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.

Energy harvesting from a backpack instrumented with piezoelectric shoulder straps

Abstract: Over the past few decades the use of portable and wearable electronics has grown steadily These devices are becoming increasingly more powerful However, the gains that have been made in the device performance have resulted in the need for significantly higher power to operate the electronics This issue has been further complicated due to the stagnant growth of battery technology over the past decade In order to increase the life of these electronics, researchers have begun investigating methods of generating energy from ambient sources such that the life of the electronics can be prolonged Recent developments in the field have led to the design of a number of mechanisms that can be used to generate electrical energy, from a variety of sources including thermal, solar, strain, inertia, etc Many of these energy sources are available for use with humans, but their use must be carefully considered such that parasitic effects that could disrupt the user's gait or endurance are avoided These issues have arisen from previous attempts to integrate power harvesting mechanisms into a shoe such that the energy released during a heal strike could be harvested This study develops a novel energy harvesting backpack that can generate electrical energy from the differential forces between the wearer and the pack The goal of this system is to make the energy harvesting device transparent to the wearer such that his or her endurance and dexterity is not compromised This will be accomplished by replacing the traditional strap of the backpack with one made of the piezoelectric polymer polyvinylidene fluoride (PVDF) Piezoelectric materials have a structure such that an applied electrical potential results in a mechanical strain Conversely, an applied stress results in the generation of an electrical charge, which makes the material useful for power harvesting applications PVDF is highly flexible and has a high strength, allowing it to effectively act as the load bearing member In order to preserve the performance of the backpack and user, the design of the pack will be held as close to existing systems as possible This paper develops a theoretical model of the piezoelectric strap and uses experimental testing to identify its performance in this application

Self-powered portable electronic device

Abstract: The present invention is directed to devices, systems, and methods having energy harvesting capabilities for self-powering portable electronic devices. The energy harvesting system preferably includes piezoelectric ceramic fibers that harvest mechanical energy to provide electrical energy or power to operate one or more features of the portable electronic device. The piezoelectric ceramic fibers may be in and/or on a structure of a portable electronic device and/or auxiliary devices/structures associated with a portable electronic device. The piezoelectric ceramic fibers allow generation of charge from mechanical inputs seen in everyday use of the portable electronic device and provide for the collection of generated energy. The energy harvesting capabilities also provide for conversion and storage of the harvested energy as electrical energy that may be used for powering one or more features of the portable electronic device. The piezoelectric ceramic fiber energy harvesting system may reduce and/or eliminate the need for external power sources and/or battery power.

Electromagnetic Energy Harvesting Circuit With Feedforward and Feedback DC–DC PWM Boost Converter for Vibration Power Generator System

Abstract: This paper presents an integrated vibration power generator system. The system consists of a mini electromagnetic vibration power generator and a highly efficient energy harvesting circuit implemented on a minute printed circuit board and a 0.35-mum CMOS integrated chip. By introducing a feedback control into the dc-dc pulsewidth modulation (PWM) boost converter with feedforward control, the energy harvesting circuit can adjust the duty ratio of the converter following the variation of the input voltage and the voltage of energy storage element to get high energy conversion efficiency. The energy harvesting circuit rectifies the input ac voltage, steps up the dc output of the rectifier by the dc-dc PWM boost converter with feedforward and feedback control and stores the electric energy into a super capacitor, which can be used as a small electrical power supply for an intelligent micro sensor network

A wireless autonomous device system

Abstract: A method of powering a wireless autonomous device having energy harvesting circuitry, on-board electronic circuitry, and RF transmitter circuitry using an RF transmitting profile that includes a plurality of RF pulses. That same profile may also be used to simultaneously communicate information to the wireless autonomous device in a number of ways, including different encoding schemes. A system including a plurality of wireless autonomous devices that employs the methods is also provided. Further, a method of designing a wireless autonomous device system and/or a wireless autonomous device to be used therein is provided that employs an equivalent circuit for the wireless autonomous device that is in the form of a lumped parameter RLC circuit with an energy source.

Consideration of Impedance Matching Techniques for Efficient Piezoelectric Energy Harvesting

Abstract: This study investigates multiple levels of impedance-matching methods for piezoelectric energy harvesting in order to enhance the conversion of mechanical to electrical energy. First, the transduction rate was improved by using a high piezoelectric voltage constant (g) ceramic material having a magnitude of g33 = 40 times 10-3 V m/N. Second, a transducer structure, cymbal, was optimized and fabricated to match the mechanical impedance of vibration source to that of the piezoelectric transducer. The cymbal transducer was found to exhibit ~40 times higher effective strain coefficient than the piezoelectric ceramics. Third, the electrical impedance matching for the energy harvesting circuit was considered to allow the transfer of generated power to a storage media. It was found that, by using the 10-layer ceramics instead of the single layer, the output current can be increased by 10 times, and the output load can be reduced by 40 times. Furthermore, by using the multilayer ceramics the output power was found to increase by 100%. A direct current (DC)-DC buck converter was fabricated to transfer the accumulated electrical energy in a capacitor to a lower output load. The converter was optimized such that it required less than 5 mW for operation.

On the efficiencies of piezoelectric energy harvesting circuits towards storage device voltages

Abstract: Using piezoelectric elements to harvest energy from ambient vibrations has been of great interest over the past few years. Due to the relatively low power output of piezoelectric materials, energy storage devices are used to accumulate harvested energy for intermittent use. Piezoelectric energy harvesting circuits have two schemes: one-stage and two-stage energy harvesting. A one-stage energy harvesting scheme includes a conventional diode bridge rectifier and an energy storage device. In recent years, two-stage energy harvesting circuits have been explored. While the results shown in previous research and development are promising, there are still some issues that need to be studied. Energy storage devices such as rechargeable batteries and supercapacitors have different cell voltages. Moreover, the storage cells can be connected in series to increase the voltage range. The storage device voltage is an important factor that influences the energy harvesting efficiency. This paper will study the efficiencies of the energy harvesting circuits considering the storage device voltages. For one-stage energy harvesting, expressions are derived to calculate the efficiencies towards different storage device voltages and verified by experiments. For two-stage energy harvesting circuits, theoretical efficiency expressions are derived and verified by PSPICE simulations. These two energy harvesting schemes are also compared. The results show that a one-stage energy harvesting scheme can achieve higher efficiency than the two-stage scheme towards a range of energy storage voltages.

Synchronized switch harvesting applied to self-powered smart systems: Piezoactive microgenerators for autonomous wireless receivers

Abstract: This paper introduces the conceptual architecture of a fully integrated, truly self-powered structural health monitoring (SHM) scheme. The challenge here is to power an array of numerous distributed actuators and sensors as well as wireless data transmission modules without recurring to heavy and costly wiring. Based on microgenerators which directly convert ambient mechanical energy into electrical energy, using the synchronized switch harvesting (SSH) method, the proposed solution allows avoiding the periodic replacement or reloading of batteries. This addresses environmental and economic issues at the same time, knowing that such elements are heavy, polluting and might be installed in rather inaccessible locations. Indeed, especially in airborne structures saving weight and maintenance cost is of priority importance. Previous work showed that such microgenerators provide a stand-alone power source, whose performances meet the requirements of autonomous wireless transmitters (AWTs) that comprise an acoustic Lamb wave's actuator and a radio frequency (RF) emitter (D. Guyomar, Y. Jayet, L. Petit, E. Lefeuvre, T. Monnier, C. Richard, M. Lallart, Synchronized switch harvesting applied to self-powered smart systems: Piezoactive microgenerators for autonomous wireless transmitters, Sens Actuators A: Phys. 138 (1) (2007) 151–160, doi:10.1016/j.sna.2007.04.009 ). Following this work, the present contribution presents a further step towards the integration of the SHM technique. It shows the ability of our microgenerators to provide enough energy to give logical autonomy to each self-powered sensing node, named autonomous wireless receiver (AWR), and thus to provide some local (decentralized) pre-processing ability to the SHM system. A preliminary design of the device using off-the-shelf electronics and surface mounted piezoelectric patches will be presented. Since the existence of a positive energy balance between the harvesting capabilities of the SSH technique and the energy requirements of the proposed device will be proved, the system formed by the combination of the AWR with the previously developed AWT, is a proof of concept of truly self-powered smart systems for damage detection in simple structures, setting apart application-specific optimization or miniaturization concerns that will be addressed in future works.

System for energy harvesting and/or generation, storage, and delivery

Abstract: A device and method for harvesting, generating, storing, and delivering energy to a load, particularly for remote or inaccessible applications. The device preferably comprises one or more energy sources, at least one supercapacitor, at least one rechargeable battery, and a controller. The charging of the energy storage devices and the delivery of power to the load is preferably dynamically varied to maximize efficiency. A low power consumption charge pump circuit is preferably employed to collect power from low power energy sources while also enabling the delivery of higher voltage power to the load. The charging voltage is preferably programmable, enabling one device to be used for a wide range of specific applications.

Adaptive power management in energy harvesting systems

Abstract: Recently, there has been a substantial interest in the design of systems that receive their energy from regenerative sources such as solar cells. In contrast to approaches that attempt to minimize the power consumption we are concerned with adapting parameters of the application such that a maximal utility is obtained while respecting the limited and time-varying amount of available energy. Instead of solving the optimization problem on-line which may be prohibitively complex in terms of running time and energy consumption, we propose a parameterized specification and the computation of a corresponding optimal on-line controller. The efficiency of the new approach is demonstrated by experimental results and measurements on a sensor node.

Energy harvesting using piezoelectric materials: Case of random vibrations

Abstract: 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.

A Review of Commercial Energy Harvesters for Autonomous Sensors

Abstract: Current commercial autonomous sensors are mainly powered by primary batteries. Batteries need to be replaced and hence can become the largest and most expensive part of the system. On the other hand, our environment is full of waste and unused energy such as that coming from the sun or mechanical vibrations. As a result, commercial energy harvesters are increasingly available to power autonomous sensors. This work presents and analyses commercial energy harvesters currently available. First, environmental energy sources are classified and described. Then, energy harvesting principles are described and some guidelines are given to calculate the maximum power consumption allowed and the energy storage capacity required for the autonomous sensor. Finally, commercial energy harvesters are evaluated to determine their capability to power a commercial autonomous sensor in some given circumstances.

Optimal Utilization of Distribution Networks for Energy Harvesting

Abstract: The introduction of distributed generation (DG) is leading to a fundamental change in how distribution networks are utilized and viewed. Distribution networks are now used as a means to connect geographically dispersed energy sources to the electricity system, thereby converting what were originally energy delivery networks, to networks used both for the delivery and harvesting of energy. This paper presents a methodology which maximizes the amount of energy that may be reaped from a given area, while taking account of the available energy resources, connection costs, losses, frequency of constraint breaches, and other technical constraints. The optimal energy allocation is determined for a sample section of network, illustrating the implementation of the methodology and the scope for non firm access to the distribution network

Recharging Batteries using Energy Harvested from Thermal Gradients

Abstract: With the recent advances in wireless technology and low power electronics the idea of capturing the ambient energy surrounding a system and using it to provide electrical power to devices that do n

Energy scavenging for wireless sensor networks

Abstract: Conventional condition monitoring of electrical machinery is conducted by measuring signals such as currents and vibrations outside the motor. Wireless sensors now provide a means of accessing and measuring useful signals inside the motor where the phenomena responsible for failure occur. These sensors are capable of not merely sensing, but also processing, storage and eventually communication. Since all these activities require power that is supplied conventionally by batteries, the useful life of the sensor node is limited by the life of the battery. This paper describes the design of an energy scavenger capable of collecting energy from the fringing field in a three-phase induction motor. The field in the magnetic filed is converted to electrical energy for use in intelligent wireless sensor nodes. The alternating magnetic field in a three phase induction motor is first measured by the hall-effect sensors. A coil wound on a ferrite core harvests the leaked energy. The experimental results are compared to the theoretical calculations of induced voltage. The paper describes results from tests conducted with a prototype coil that is used to power wireless sensor nodes in a motor running at full speed.

Low Frequency Pulsed Resonant Converter for Energy Harvesting

Abstract: A pulsed-resonant ac-dc converter and an integrated circuit (IC) controller have been designed, fabricated, and tested for harvesting energy from low-voltage (1.2V), low-power (1-100muW) energy transducers with output frequency in the 10-Hz-1-kHz range. Simulations using foundry models suggest that the silicon loss could be as low as 0.6muW, and the efficiency could reach 70%. With the IC experimentally packaged, the measured efficiency is between 50% and 70%, depending on the size and the loss in the resonant inductor

An active energy harvesting scheme with an electroactive polymer

Abstract: We investigate the energy harvesting with an electrostrictive polymer, possessing high electromechanical response and elastic energy density, which make it possible to generate high electric energy density and attractive for the active energy harvesting scheme. It is shown that combining the active energy harvesting scheme and high electromechanical response of the polymer yields a harvested electric energy density of ∼40mJ∕cm3 with a 10% efficiency.

Energy harvesting with piezoelectric drum transducer

Abstract: Piezoelectric materials can convert ambient vibrations into electrical energy. In this letter, the capability of harvesting the electrical energy from mechanical vibrations in a dynamic environment through a piezoelectric drum transducer has been investigated. Under a prestress of 0.15N and a cyclic stress of 0.7N, a power of 11mW was generated at the resonance frequency of the transducer (590Hz) across an 18kΩ resistor. It is found that the energy from the transducer increases while the resonance frequency of the transducer decreases when the prestress increases. The results demonstrate the potential of the drum transducer in energy harvesting.

Optimization of a piezoelectric unimorph for shock and impact energy harvesting

Abstract: Piezoelectric bending structures can be designed to act as an electrical generator for converting ambient mechanical energy into useful electrical energy. The produced electrical energy is stored or dissipated into an electrical load. Most of the analyses on piezoelectric generators proposed in the literature are limited to a steady-state approach to the problem. These analyses fail to give clear insights when the dynamical behaviour of the piezoelectric bender is governed by its transient characteristics, for example in the case of a shock or impact excitation, and we analyse such a situation in this paper. It is first pointed out that the rate of transfer of energy towards the electrical load is optimized by maximizing the figure of merit of the structure and by choosing an appropriate value of the load. According to this consideration, a method to design piezoelectric benders for impact or shock energy harvesting in terms of their geometry and material properties is then proposed.

Analysis of Piezoelectric Materials for Energy Harvesting Devices under High-g Vibrations

Abstract: We analyzed the miniaturized energy harvesting devices (each volume within 0.3 cm3) fabricated by using three types of piezoelectric materials such as lead zirconium titanate (PZT) ceramic, macro fiber composite (MFC) and poly(vinylidene fluoride) (PVDF) polymer to investigate the capability of converting mechanical vibration into electricity under larger vibration amplitudes or accelerations conditions (≥1g, gravitational acceleration). All prototypes based on a bimorph cantilever structure with a proof mass were aimed to operate at a vibration frequency of 100 Hz. PZT-based device was optimized and fabricated by considering the resonant frequency, the output power density, and the maximum operating acceleration or safety factor. PVDF- and MFC-prototypes were designed to have same resonant frequency as well as same volume of the piezoelectric materials as the PZT prototype. All three devices were measured to determine if they could generate enough power density to provide electric energy to power a wireless sensor or a microelectromechanical systems (MEMS) device without device failure.

Integrated Power Harvesting System Including a MEMS Generator and a Power Management Circuit

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 realised as a system on a package (SoP) with all components fabricated entirely using the microfabrication techniques. 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 the proposed system of 5 mm3 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 two months.

P3F-5 An Ultrasonic Through-Wall Communication System with Power Harvesting

Abstract: Electromagnetic "wireless" techniques are ineffective for communicating through a solid steel barrier due to the shielding effect of the metal. Although holes can be made in the barrier to allow wires to pass through, they are often undesirable because they can reduce the integrity of the barrier. In contrast, ultrasound propagates readily through steel and can be used to convey information without degrading the barrier. Since it may be inconvenient to periodically access the sensor side of the barrier, it is also desirable to make the sensor/communication system operate for an indefinite period without servicing. Power harvesting can be used to derive electric power for the circuits from the ultrasonic power applied at the other side of the barrier, making batteries unnecessary. This paper describes an ultrasonic communication system with power harvesting using two ultrasonic transducers and continuous-wave ultrasound techniques. Experimental results are presented, which were obtained using a 5.7 cm thick steel block with 2.54 cm piezoelectric transducers at 1 MHz. The data shows reliable communication at rates of up to 55 kbps and power delivery of over 0.25 W.

Human Body Energy Harvesting Thermogenerator for Sensing Applications

Abstract: A low temperature thermal energy harvesting system to supply power to wireless sensing modules is introduced. The thermoelectric generator module (TEG) makes use of the temperature gradient between the human body (the heat source) and the ambient to deliver a low voltage output that is up-converted by means of a power management circuit. This regulated power source is able to reliably supply a wireless communication module that transmits the collected temperature, current and voltage measurements.

Energy harvesting by means of thermo-mechanical device utilizing bistable ferromagnets

Abstract: An inventive energy harvesting apparatus may include a ferromagnetic material and/or a shape memory alloys to convert thermal energy to mechanical energy to electrical energy. The apparatus is subjected to a thermal gradient to cause beams to bend thus creating stress/strain in a piezoelectric material, or creating magnetic flux in a magnetic path. The charges created in this process can be transferred to electrical batteries.

Remote control with energy harvesting

Abstract: A remote control includes energy harvesting that provides power in addition to a battery. The energy harvesting and the battery may be switchably used to power transmit operations, receive operation, and/or display operations. The remote control may be used as part of an automotive vehicle remote keyless entry system in which vehicle status is displayed by the remote control.

Energy harvesting by magnetostrictive material (MsM) for powering wireless sensors in SHM

Abstract: A new class of vibrational energy harvester based on Magnetostrictive material (MsM) Metglas 2605SC is deigned, developed, and tested in building practical energy harvesting wireless sensor networks. Compared to piezoelectric material, Metglas 2605SC offers advantages including ultra-high energy conversion efficiency, high power density, longer life cycles without depolarization issue, and flexibility to operate in strong ambient vibrations. To enhance the energy conversion efficiency and shrink the size of the harvester, Metglas is annealed in the direction normal to the axial strain direction without the need of electromagnet for applying bias (static) magnetic field. To seamlessly integrate with a newly developed wireless sensor at NC State 1 , a prototype design for the MsM harvester is proposed. An analytical model is developed for the harvesting using an equivalent electromechanical circuit. The model resulting in achievable output performances of the harvester powering a resistive load and charging a capacitive energy storage device, respectively, is quantitatively derived. An energy harvesting module, which powers a wireless sensor, stores excess energy in an ultracapacitor is designed on a printed circuit board (PCB) with dimension 25mm x 35mm. The main functionalities of the circuit include a voltage quadrupler, a 3F ultracapacitor, and a smart regulator. The output DC voltage from the PCB can be adjusted within 2.0~5.5V. In experiments, the maximum output power and power density on the resistor can reach 200 mW and 900 mW/cm 3 , respectively. For a working prototype, the average power and power density during charging the ultracapacitor can achieve 576 mW and 606 mW/cm 3 respectively, which are much higher than those of most piezo-based harvesters.