A multi-frequency electromagnetic vibration energy harvester based on ferrofluid

Abstract

A multi-frequency planar electromagnetic generator is proposed to harvest energy from low-frequency vibrations efficiently in a wide frequency range. The vibration energy harvester is composed of two single-degree-of-freedom resonant systems with different natural frequencies. Two permanent magnets are used as single-degree-of-freedom spring mass to respond to external vibrations, and controlled by another permanent magnet with magnetic attraction. In addition, ferrofluid adsorbed on the poles of two moving permanent magnets can reduce the damping significantly to improve the utilization of low-frequency micro vibrations. Experiments show that, during human walking and jogging, the fabricated generator can obtain 1.3718 mW and 1.4227 mW output power, respectively.