A Magnetically Coupled Electromagnetic Energy Harvester with Low Operating Frequency for Human Body Kinetic Energy.

Xiang Li,Leian Zhang,Chongqiu Yang,Rujun Song,Huirong Zhang,Jinpeng Meng

doi:10.3390/mi12111300

Abstract

In this paper, a magnetically coupled electromagnetic energy harvester (MCEEH) is proposed for harvesting human body kinetic energy. The proposed MCEEH mainly consists of a pair of spring-connected magnets, coils, and a free-moving magnet. Specifically, the interaction force between the magnets is repulsive. The main feature of this structure is the use of a magnetic-spring structure to weaken the hardening response caused by the repulsive force. The magnetic coupling method enables the energy harvester system to harvest energy efficiently at low frequency. The MCEEH is experimentally investigated for improving energy harvesting efficiency. Under harmonic excitation with an acceleration of 0.5 g, the MCEEH reaches resonance frequency at 8.8 Hz and the maximum output power of the three coils are 5.2 mW, 2.8 mW, and 2.5 mW, respectively. In the case of hand-shaking excitation, the generator can obtain the maximum voltage of 0.6 V under the excitation acceleration of 0.2 g and the excitation frequency of 3.4 Hz. Additionally, a maximum instantaneous power can be obtained of about 26 mW from the human body’s kinetic energy.

Highlights

Saha et al [24] designed an electromagnetic energy harvester (EMEH), which was composed of magnets fixed at the ends of the cylinder, a magnet suspended in the middle of the cylinder by the repulsive force, and a coil wound on the outer surface of the cylinder
The main feature of this structure is the use of a magnetic-spring structure to weaken the hardening response caused by the repulsive force
The output performance of the energy harvester device was investigated by changing the excitation frequency, excitation acceleration, and diagram of the magnetically coupled electromagnetic energy harvester

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Micromachines 2021, 12, 1300 designed an electromagnetic energy harvester that could generate higher output power at a lower frequency. Foisal et al [28] proposed two kinds of electromagnetic multi-frequency converter array models and used the magnetic spring technique to harvest energy from low-frequency vibrations. Further studies by Fan presented a two-degree-of-freedom (2-DOF) electromagnetic energy harvester (EMEH) Both experiments and simulation verification results showed that the energy harvester can increase the output power and expand the working bandwidth. We propose a magnetically coupled electromagnetic energy harvester (MCEEH) to harvest vibration energy at low-frequency. The main feature of this structure is the use of a magnetic-spring structure to weaken the hardening response caused by the repulsive force This MCEEH has the advantages of adjustable working frequency and high low-frequency energy harvest efficiency. The experimental results show that the MCEEH can be used to power various microelectronic products, e.g., wrist watches, sensors, hearing aids, etc

Physical Model and Experimental Method

Electrical Output under Hand-Shaking Excitation

Conclusions