Enhanced Swing Electromagnetic Energy Harvesting From Human Motion

Energy harvesting from human motion has received considerable interests for its promising potential to provide an autonomous energy supply for low-power devices. In order to improve comfort and wearability during human motion, this paper presents a Halbach array enhanced electromagnetic energy harvester with swing pendulum to maximally exploit the limb swing excitations. A theoretical model of magnetic arrays is established based on the magnetic charge method. The dynamic equations are derived by the Lagrange equation to predict the output voltage of proposed harvester. The magnetic fields of Halbach array and conventional array are compared under different magnets angles. Moreover, the experimental voltage under harmonic excitations are measured to verify the accuracy of the proposed model, and quantify the enhanced energy harvesting performance by Halbach array. Additionally, the generated average power increases with an increase of walking or running speed. The average power of the proposed device is approximately 0.38 mW at a running speed of 8 km/h when attached to the lower-limb. Consequently, the corresponding mass power density is 23 uW/g during human motion. The power density of proposed harvester can be higher after further optimization, and its applications may expand to smart watch, wristband or even cell phone. (C) 2021 Elsevier Ltd. All rights reserved.