Magnetic energy harvesting with magnetoelectrics: an emerging technology for self-powered autonomous systems

The deployment of wireless sensor networks (WSNs) for the internet of things (IoT) and remote monitoring devices has made tremendous progress in the last few years. At the same time, energy harvesters are also being developed to satisfy the power requirement of WSNs and other low power consumption electronics, to increase the device operating time and overcome the limitations of conventional electric power supplies, including batteries. Among various resources for energy harvesting, the magnetic noise produced by power transmission infrastructures and associated mechanical vibrations are ubiquitous energy sources that could be converted into electricity by high efficiency energy conversion materials or devices. Electromagnetic energy conversion systems that operate on the principle of Faraday's induction law can provide sufficient power from strong magnetic fields. However, under weak magnetic fields with low frequency such as 50/60 Hz, the power generated from an electromagnetic device is disappointingly small. Alternative energy harvesting technologies with high power density and small device volume/dimensions are obviously necessary for WSNs of IoT. In this review article, the current status and prospects of an emerging magnetic energy harvesting technology, the so-called magneto-mechano-electric (MME) generators, are reviewed. MME generators utilize the magnetoelectric (ME) coupling in composites of piezoelectric and magnetostrictive materials and interaction between the proof magnet mass and magnetic field. Since the piezoelectric phase in the composite also responds to mechanical vibration directly, an ME-based energy harvester can harness energy from both mechanical vibrations and magnetic fields simultaneously. This combination is expected to enhance the total power output and conversion efficiency. The MME generator can be a ubiquitous power source for WSNs, low power electronic devices, and wireless charging systems by harvesting energy from the tiny magnetic fields present as parasitic magnetic noise in an ambient environment.