Magneto-Mechano-Electric Harvester for AC Circular Magnetic Field

Magneto-mechano-electric (MME) harvesters utilize magnetic force between a permanent magnet and an ambient AC stray field to generate mechanical vibrations. These vibrations are subsequently converted into electrical energy through piezoelectric materials. We investigated energy harvesting in a circular magnetic field using an MME energy harvester with magnets positioned at the ends of a circular piezoelectric plate. The ambient AC stray field induces vibrations in the magnets, which in turn generate AC electric voltage through the vibrational bending of the plate. The magnetization configuration of the magnets determines the vibration symmetry of the piezoelectric plate. Parallel and anti-parallel magnetizations of the magnets induce the anti-symmetric and symmetric bending of the plate, respectively. It was found that symmetric bending of the plates induced higher voltage than anti-symmetry bending due to the uniform voltage output across the curved area of the piezoelectric substrate. Detailed analysis of the structural and magnetic configurations was performed using 3D finite element method (FEM) simulations, providing effective design insights and a deeper understanding of the harvester’s performance in a circular field. The energy harvester in this study generated an output power of 1.88 mW, which can be converted into 24.7 mW/cm³, with an AC circular field of 5.39 Oe. To enhance the generating power, magnetic flux concentrator (MFC) was added to the harvester. The output power increased by 23% with the MFC positioned horizontally, and by 11% with MFC positioned vertically. The enhancement with MFC in vertical position was not expected and is discussed in detail.

The results in this study were achieved using accessible and cost-effective materials, underscoring the need for further research on the structural design of MME harvesters in environments with various types of ambient magnetic fields.