Careful Simulation of New Micromagnets Boost Power-Harvesting Devices for the Internet of Things

Using new magnets and simulating factors including thickness and coil windings, these energy harvesters outperform the competition.

A team of researchers at the University of Toulouse, the French National Center for Scientific Research (CNRS), Georgia Tech, and the Grenoble Alpes University have come up with a potential method for boosting energy harvesters for low-power Internet of Things (IoT) devices — by using new magnets with a specific size and spacing revealed through simulation.

The promise of ubiquitous wireless sensor networks and other broad deployments of the IoT is tempered by one key issue: Powering the devices. While increasing efficiency of the sensors and processors themselves help, boosting their ability to harvest energy from the environment is another approach — and one the research team suggests will pay dividends.

"Using finite element simulations, we report here a complete guideline to optimize a MEMS electromagnetic energy harvester consisting of an in-plane vibrating silicon frame supporting an array of micromagnets that faces a static 2D micro-coil," the team writes in the abstract to a paper, which offers a new design for devices harvesting energy from vibrations. "The dimensioning of the magnet array and the specific design of the coil are addressed, considering patterned 50μm thick NdFeB films with out of plane magnetization."

A key part of the team's work is finding trade-offs between the thickness of the novel high-performance micromagnets and the number of turns in the facing coil: By tweaking the two, along with the spacing between the magnets and the distance between the magnet array and the coil, the team found that they could noticeably boost the power output of the system.

"We are now producing harvesters using the guidelines that we have developed through this study," co-author Lise-Marie Lacroix says, with a view to deploying them in aerospace, automotive, biomedical, and other sectors of the Internet of Things — though there's no word yet as to commercial availability.

For those looking to follow in the researchers' footsteps, meanwhile, there's a clear message: Detailed simulation will be required for peak performance. "The optimization of an EM-VEH [Electro-Magnetic Vibration Energy Harvesting] system requires ad-hoc simulations to fully benefit from the largest potential electromechanical coupling, which depends also on the amplitude of vibration and the distance h between the coil and the magnets. An optimization based only on the stray field profile of the array is clearly not sufficient.

The team's work has been published in The European Physical Journal Special Topics (EPJ ST), with an open-access copy available through Springer.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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