Large Power Amplification in Magneto‐Mechano‐Electric Harvesters through Distributed Forcing

Abstract

Energy harvesting from extremely low frequency magnetic fields using magneto‐mechano‐electric (MME) harvesters enables wireless power transfer for operating Internet of Things (IoT) devices. The MME harvesters are designed to resonate at a fixed frequency by absorbing AC magnetic fields through a composite cantilever comprising of piezoelectric and magnetostrictive materials, and a permanent magnetic tip mass. However, this harvester architecture limits power generation because volume of the magnetic end mass is closely coupled with the resonance frequency of the device structure. Here, a method is demonstrated for maintaining the resonance frequency of the MME harvesters under all operating conditions (e.g., 60 Hz, standard frequency of electricity in many countries) while simultaneously enhancing the output power generation. By distributing the magnetic mass over the beam, the output power of the harvester is significantly enhanced at a constant resonance frequency. The MME harvester with distributed forcing shows 280% improvement in the power generation compared with a traditional architecture. The generated power is shown to be sufficient to power eight different onboard sensors with wireless data transmission integrated on a drone. These results demonstrate the promise of MME energy harvesters for powering wireless communication and IoT sensors.

Recent Progress in Devices Based on Magnetoelectric Composite Thin Films

“…These generators comprise a resonating cantilever structure with high-performance piezoelectric materials fabricated on highly magnetostrictive substrates (Ni, metglas, Galfenol, etc.). More recently, significant improvements in the performance of MME harvesters have been achieved by exploiting their intrinsic parameters, such as adopting high-performance piezoelectric and magnetostrictive materials, modulating the geometric structures, distributing magnetic torque from magnetic mass, and using magnetic flux concentrators [ 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 ]. The power outputs in the range of microwatts to milliwatts were obtained using these MME generators to successfully operate the autonomous Internet-of-Things (IoT) sensors.…”

Significantly Enhanced Power Generation from Extremely Low‐Intensity Magnetic Field via a Clamped‐Clamped Magneto‐Mechano‐Electric Generator

“…[23] Note that a magnetic field with an intensity above 5 Oe was normally used to demonstrate the energy harvesting performance of a typical MME generator previously. [11,12,20,23,24] However, the reference level for general public exposure to time-varying magnetic fields at 50/60 Hz recommended by the World Health Organization (WHO) is 1 Oe, [25] and the magnetic field intensity at a distance of 30 cm from most household appliances is also below the guideline limit. [26] Although a respectable energy output can be obtained by placing a MME generator in close proximity to magnetic sources, the resulting side effects for industrial machines or household appliances will greatly limit the practical applications.…”

“…The current solutions for solving this issue include: i) the amplification of an external magnetic field by adding a magnetic flux concentrator close to the tip mass in a MME cantilever; [12] and ii) the increase of the magnetic mass by optimizing the flexural rigidity of a MME cantilever [26] or by adopting a distributed dual magnetic mass. [11] Figure 1a schematically shows the vibration mode of a typical MME cantilever. The magnetic tip mass has a large deflection and thus contributes most of the kinetic energy of the system.…”

“…[4,5] From the viewpoint of environmental pollution, the elimination of batteries, which are classified as "hazardous wastes," is also of great significance. [6] Among a large number of harvestable energy sources, like vibration, [7,8] radiation, [9,10] and magnetic/electric fields, [11,12] stray magnetic energy generated from power transmission cables, industrial machines, household appliances, etc., is technically favored because of the fixed frequency of 50 or 60 Hz and the ubiquitous distribution. [13][14][15][16] Coil devices based on electromagnetic induction principles are conventionally adopted to capture the ambient but wasted magnetic field energy.…”

High performance of polycrystalline piezoelectric ceramic-based magneto-mechano-electric energy generators

“…In recent years, the Magneto-Mechano-Electric (MME) energy generator has shown excellent potential for low amplitude magnetic field to electrical energy conversion. [12][13][14][15][16][17] The typical MME generator is a cantilever structure comprising a magnetoelectric (ME) composite structure of piezoelectric and magnetostrictive layers and permanent magnets as proof mass [11,12]. The basic factors contributing to the output electrical performance are magnetoelectric (ME) effect, magnetic flexural torque from the magnetic proof mass and their synergetic interaction under externally applied magnetic field [15].…”