Inductive Energy Harvester Research Articles

Optimization Design of an Inductive Energy Harvesting Device for Wireless Power Supply System Overhead High-Voltage Power Lines

Overhead high voltage power line (HVPL) online monitoring equipment is playing an increasingly important role in smart grids, but the power supply is an obstacle to such systems’ stable and safe operation, so in this work a hybrid wireless power supply system, integrated with inductive energy harvesting and wireless power transmitting, is proposed. The energy harvesting device extracts energy from the HVPL and transfers that from the power line to monitoring equipment on transmission towers by transmitting and receiving coils, which are in a magnetically coupled resonant configuration. In this paper, the optimization design of online energy harvesting devices is analyzed emphatically by taking both HVPL insulation distance and wireless power supply efficiency into account. It is found that essential parameters contributing to more extracted energy include large core inner radius, core radial thickness, core height and small core gap within the threshold constraints. In addition, there is an optimal secondary coil turn that can maximize extracted energy when other parameters remain fixed. A simple and flexible control strategy is then introduced to limit power fluctuations caused by current variations. The optimization methods are finally verified experimentally.

Energy Harvesting from the Stray Electromagnetic Field around the Electrical Power Cable for Smart Grid Applications.

For wireless sensor node (WSN) applications, this paper presents the harvesting of energy from the stray electromagnetic field around an electrical power line. Inductive and capacitive types of electrodynamic energy harvesters are developed and reported. For the produced energy harvesters, solid core and split-core designs are adopted. The inductive energy harvester comprises a copper wound coil which is produced on a mild steel core. However, the capacitive prototypes comprise parallel, annular discs separated by Teflon spacers. Moreover, for the inductive energy harvesters' wound coil and core, the parametric analysis is also performed. A Teflon housing is incorporated to protect the energy harvester prototypes from the harsh environmental conditions. Among the inductive energy harvesters, prototype-5 has performed better than the other harvesters and produces a maximum rms voltage of 908 mV at the current level of 155 A in the power line. However, at the same current flow, the capacitive energy harvesters produce a maximum rms voltage of 180 mV. The alternating output of the prototype-5 is rectified, and a super capacitor (1 F, 5.5 V) and rechargeable battery (Nickel-Cadmium, 3.8 V) are charged with it. Moreover, with the utilization of a prototype-5, a self-powered wireless temperature sensing and monitoring system for an electrical transformer is also developed and successfully implemented.

Electromagnetic induction energy harvester for high-speed railroad applications

The objective was the development of an energy harvester for the hot-box detector of the HEMU-430 project high-speed train in Korea. In this study, we attempt the development of energy harvesters that incorporate a monitoring system in the train wheel bearing. We verified the use of electromagnetic induction as an effective method for harvesting energy from low-frequency vibration through the environmental test. We applied mechanical, electromagnetic, and electrical modeling processes to maximize the relative motion between core parts, and the optimization should be done using a mass spring damping model. We analyzed the wheel vibration sources at speeds between 300 and 400 km/h, fabricated a prototype of the energy harvester, and used a reinforced material for the practical application. Based on analyses of the static and fatigue properties of different materials, we decided the proper material as Invar 42. We also secured the structural stability by FEM. Our onboard measurement revealed that the generation characteristics of a narrow band resonance module capable of operating at a specific resonance frequency could be verified. The results of environmental tests confirmed that the Invar 42 cantilever beam–type electromagnetic induction energy harvester could be used as a model of a highly durable system.

Investigation of Pendulum Structures for Rotational Energy Harvesting from Human Motion

Energy Harvesting from human motion as a means of powering body-worn devices has been in the focus of research groups for several years now. This work presents a rotational inductive energy harvester that can generate a sufficient amount of energy during normal walking to power small electronic systems. Three pendulum structures and their geometrical parameters are investigated in detail through a system model and system simulations. Based on these results a prototype device is fabricated. The masses and angles between pendulum arms can be changed for the experiments. The device is tested under real-world conditions and generates an average power of up to 23.39 mW across a resistance equal to the coil resistance of the optimal pendulum configuration. A regulated power output of the total system including power management of 3.3 mW is achieved.

Energy harvesting from human motion: exploiting swing and shock excitations

Modern compact and low power sensors and systems are leading towards increasingly integrated wearable systems. One key bottleneck of this technology is the power supply. The use of energy harvesting techniques offers a way of supplying sensor systems without the need for batteries and maintenance. In this work we present the development and characterization of two inductive energy harvesters which exploit different characteristics of the human gait. A multi-coil topology harvester is presented which uses the swing motion of the foot. The second device is a shock-type harvester which is excited into resonance upon heel strike. Both devices were modeled and designed with the key constraint of device height in mind, in order to facilitate the integration into the shoe sole. The devices were characterized under different motion speeds and with two test subjects on a treadmill. An average power output of up to 0.84 mW is achieved with the swing harvester. With a total device volume including the housing of 21 cm3 a power density of 40 μW cm−3 results. The shock harvester generates an average power output of up to 4.13 mW. The power density amounts to 86 μW cm−3 for the total device volume of 48 cm3. Difficulties and potential improvements are discussed briefly.

Inductive Energy Harvesting for Rotating Sensor Platforms

An inductive energy harvesting concept for structures rotating in proximity to a stationary body is proposed. The performance of such devices is studied analytically and numerically, and an experimental proof of concept is presented, demonstrating energy output density of 1 mW/cm3 from a typical geometry and rotation scale. The proposed approach may be suitable for powering retrofitted wireless sensors on engine bodies and also on rotating parts where complex stator-rotor wiring solutions would otherwise be required.

Inductive energy harvesting from variable frequency and amplitude aircraft power lines

This paper presents a non-contact method of harvesting energy from an aircraft power line that has an AC current of variable amplitude and a frequency range of 360-800 Hz. The current and frequency characteristics of the aircraft power line are dependent on the rotation speed of the electrical generators and will therefore change during a flight. The harvester consists of an inductive coil with a ferrite core, which is interfaced to a rectifier, step-down regulator and supercapacitor. A prototype system was constructed to demonstrate reliable output voltage regulation across a supercapacitor that will supply a peak power of 100 mW under duty cycled load conditions. The system could fully charge a 40 mF supercapacitor to 3.3 V in 78 s from a power line current of 1.5 Arms at 650 Hz.

Research Activities in the Field of Electromagnetic Energy Harvesting Micro Systems

Introduction The use of energy from the ambient shows a great possibility to reduce energy consumption. One point is energy harvesting, which means to obtain electrical energy from available sources like solar, thermal or vibrational energy [1]. Therefore the development of new forms for converting energy is in the focus of researchers. In the field of microsystems the use of vibrational energy seems to be the best convertible energy form. This paper gives a review about the state of the art in the field of electromagnetic energy harvesting systems and especially the research activities at the IMPT Concepts for electromagnetic harvesting systems There are three general technical applications for the design of an inductive micro energy harvester system [2]. If a rotational excitation can be used the concept of a dynamo is the best way for energy conversion. For a linear excitation of a mass-spring system, a relative movement between a coil and a hard magnet induces a voltage caused by the change of the magnetic field detected by the coil. The third alternative is the use of an imbalanced pendulum to combine the two possibilities above Example for thin-film device One approach is to use the principle of an integrated hallbach array in a linear energy harvester [3]. This array has a special arrangement of permanent magnets (Fig. 1) that doubles the magnetic field on one side while cancelling the field to near zero on the other side. Two thin-film coils are located next to the hallbach array and the movement induces a voltage in the coils.Fig. 1: Operation of the electromagnetic energy harvester [3] Investigated Principles at IMPT For the integration of energy harvesting devices into smart systems it will be necessary to minimize the volume of such an application. Furthermore the use of an adjustment to avoid the resonant frequency dependencies is important. This device consists of four independent thin-film coil systems [4]. Each consists of a double layered spiral coil with 15 windings in each layer. The total height of this coil is approx. 30µm without the substrate. For inducing a voltage a rotational flying wheel is chosen. On this wheel four permanent magnets with a saturation flux density of 1.3 T are placed to induce a change of the magnetic field. The induced voltage depends on the distance between the coils and the permanent magnets. In our case the distance is about 750 µm. The reason for this air gap is that the electrical contacts are realized by wire bonding. The calculation of the systems predicts a voltage of 2.1 mV for a revolution of 1,000 rpm. The measurement shows an induced voltage of about 2.0 mV and therefore verifies the calculations.The demonstrator was fabricated using an acrylic glass tube with an outer diameter of 11 mm and an inner diameter of 9 mm [5]. The screw thread for the mounting of the springs was fabricated using stainless steel. A groove was milled into the acrylic glass corpus. The 100 windings of the coil were wound around the corpus into the groove. One great challenge was the connection between the springs and the permanent magnet. In a first approach we tried to bring a drill hole into the small permanent magnet but the material of the sintered magnet was to brittle and the magnet broke. For the connection of these parts glue was used. The resonance frequency of the system is about 42 Hz and the system produces a maximum induced voltage output of about 2 V. Conclusion The review shows a lot of possibilities to use the inductive principle to convert mechanical energy into electrical energy.

Fokker–Planck equation analysis of randomly excited nonlinear energy harvester

The probability structure of the response and energy harvested from a nonlinear oscillator subjected to white noise excitation is investigated by solution of the corresponding Fokker–Planck (FP) equation. The nonlinear oscillator is the classical double well potential Duffing oscillator corresponding to the first mode vibration of a cantilever beam suspended between permanent magnets and with bonded piezoelectric patches for purposes of energy harvesting. The FP equation of the coupled electromechanical system of equations is derived. The finite element method is used to solve the FP equation giving the joint probability density functions of the response as well as the voltage generated from the piezoelectric patches. The FE method is also applied to the nonlinear inductive energy harvester of Daqaq and the results are compared. The mean square response and voltage are obtained for different white noise intensities. The effects of the system parameters on the mean square voltage are studied. It is observed that the energy harvested can be enhanced by suitable choice of the excitation intensity and the parameters. The results of the FP approach agree very well with Monte Carlo Simulation (MCS) results.

Design, fabrication and characterization of an inductive human motion energy harvester for application in shoes

The concept of energy harvesting has been in the focus of research for more than two decades now and with the continuous device miniaturization and reduction in power consumption of the electronics it has become a viable power source for mobile systems. The increasing desire for mobility and longevity in terms of battery life has eventually led to wearable systems, i.e. electronic circuits with their power supply which are being integrated into textiles and everyday life. This paper reports the development of a cylindrical inductive energy harvesting device which exploits the accelerations available in the plane of the foot during walking. The modeling and characterization of the system is based upon real-world acceleration data recorded during treadmill runs. Although a wider range of test subjects would be required to increase the statistical relevance of the measured data, it is concluded that the energy provided by this system is sufficient to power low energy circuits at comparatively slow walking velocities. Additionally, the obtained knowledge can be used to develop a smaller, parallelized system.

Interface circuit using SMFE technique for an inductive kinetic generator operating as a frequency-up converter

This paper presents a novel interface circuit for an inductive kinetic energy harvester, which is designed based on the SMFE (Synchronized Magnetic Flux Extraction) technique. The generator is designed to fit into a shoe sole to power a telemetric device. It operates as a frequency-up converter and possesses a small output series resistance, allowing the SMFE scheme to be applied as an energy harvesting enhancement technique. A prototype has been implemented and simulated using discrete components in order to demonstrate the SMFE concept and compare it with typical standard interfaces used (Full Bridge and Voltage doubler rectifiers). Compared to the standard schemes, the SMFE method is able to extract a considerably higher amount of energy for a wide range of output voltages. Assuming one walking step per second, the complete system could provide 18.8 mW output power using the SMFE interface, compared to 8 mW with the full bridge and 12.3 mW using the voltage doubler.

Electromagnetic energy harvester for monitoring wind turbine blades

ABSTRACTThe long composite blades on large wind turbines experience tremendous stresses while in operation. There is an interest in implementing structural health monitoring (SHM) systems inside wind turbine blades to alert maintenance teams of damage before serious component failure occurs. This paper proposes using an energy harvesting device inside the blade of a horizontal axis wind turbine to power a SHM system. The harvester is a linear induction energy harvester placed radially along the length of the blade. The rotation of the blade causes a magnet to slide along a tube as the blade axis changes relative to the direction of gravity. The magnet induces a voltage in a coil around the tube, and this voltage powers the SHM system. This paper begins by discussing motivation for this project. Next, a harvester model is developed, which encompasses the mechanics of the magnet, the interaction between the magnet and the coil, and the current in the electrical circuit. A free fall test verifies the electromechanical coupling model, and a rotating test examines the power output of a prototype harvester. Copyright © 2013 John Wiley & Sons, Ltd.