Power Generation From Human Motion Through Magnetic Spring System

A magnetic-spring electromagnetic energy harvester which consists of a hollow tube with two magnets fixed to the end and an attracting magnetic stack moving inside it is presented in this paper to harvest energy from human motion. The dynamic model of the electromagnetic generator is derived according to Newton’s law and Ansoft Maxwell software is used to calculate the repulsive force between middle and end magnets. Experimental results under frequency-sweep excitation and constant frequency excitation with different acceleration levels show that the generator has the potential to generate electricity for a broadband frequency range and ability to light up a LED. In the experiments considering human motion, the voltage response caused by the impact between shoes and ground are investigated. Under that condition, the influence of equivalent mass of moving magnetic stack and speeds of motion on the energy harvesting efficiency is analyzed. Results show that larger equivalent mass could obviously improve the performance of the generator and the obtained maximum output power reaches 2.11 mW.