Interoperable magneto-mechano-electric harvester with dual magnets for household appliance power cords

Abstract

Magneto-mechano-electric (MME) harvesters, which convert stray magnetic fields into reusable electricity, have attracted significant attention as power sources for Internet of Things (IoT) devices in wireless sensor networks. However, their limited output power has typically restricted their operation to controlled laboratory settings, such as Helmholtz coils that generate uniform magnetic fields. This study introduces a novel MME harvester featuring a piezoelectric cantilever with a dual-magnet structure. The tip-end magnet attaches to a current-carrying power cord, while the middle magnet interacts with an electromagnetic induction Cu coil. By optimizing key parameters—including the cantilever length, magnet weight, and the distance between the Cu coil and inner magnets—the harvester achieves a root mean square (RMS) power density of 0.264 mW/cm³ near a power cord carrying 7.12 A_RMS when operating household appliances such as a hair dryer. To further enhance energy harvesting efficiency, the power cord was reconfigured into a double-circular arrangement to concentrate the stray magnetic field. This modification increased the harvester’s output power by 861.74 % compared to the conventional linear configuration, enabling the successful operation of a multifunctional IoT sensor with a power consumption of 4.09 mW. These findings underscore the potential of the proposed MME harvester as a practical energy source for self-powered IoT sensor systems.