An arc-shaped electromagnetic energy harvester for ultra-low frequency vibrations and swing motions

This letter presents a bi-directional electromagnetic energy harvester (EMEH) that consists of a spherical magnet encapsulated in an arc-shaped tube and two sets of coils wrapped around the tube. Two springs are affixed at the two ends of the tube to reduce the impact-induced energy dissipation and recycle the kinetic energy of the magnet. Experimental studies reveal that the arc-shaped EMEH is capable of capturing energy from ultra-low frequency vibrations that come from two orthogonal directions. Moreover, under the swing motion, the magnet is driven by its geopotential energy to move along the inner surface of the tube and then induce the coils to generate electrical power. Experimental measurements with the arc-shaped EMEH attached on human limbs show that the proposed design could perform simultaneous energy extraction from the vibration and swing motion even though they come from different directions, demonstrating the superior adaptability to the diverse excitations that are abundant in our living environment.