Michael D’Agati ‘18

Developing better ways to power portable electronic or wireless sensor systems has become more desirable in our increasingly mobile world. Multiple projects have proposed harvesting mechanical stresses from the human body to power these devices, but many of them use piezoelectric materials, which create current in a circuit due to changes in pressures on the material. Many small piezoelectric projects can only produce tiny amounts of power that often have to be amplified. Now, there’s a new alternative: harvesting electromagnetic energy created by human motion.

Instead of using piezoelectric methods, Dr. Wei Wang of Xi’an Jiaotong University in Xi’an, China and his team developed a simulation and computer model to test the feasibility of converting mechanical energy from the human body to electromagnetic energy using magnetic springs. To test the feasibility of using an electromagnetic harvester, they used Ansoft Maxwell software to model the device and determine the best way to conduct magnetic stacking – taking mechanical energy from the human body and converting it to electromagnetic energy by using freely moving magnets, which can create a current in wires looped around those magnets. Based on modeling and theoretical analyses, the device could generate electricity in a broadband frequency range, which is good for changing human motion speed. A physical prototype was also developed for testing on a human leg. The results showed that larger equivalent mass and longer movement length for the moving magnetic stack could enhance the performance of the energy harvesting device, especially for running. In an experiment, participants were asked to walk or run at the speed of 4-9 km/h with the device attached to their leg. The results showed that a maximum average output power of 10.66 mW was obtained with a total weight of the person equaling 218.7 g and a swing motion of the leg at a speed of about 8 km/h.

Another, although rather unconventional, method of harvesting human mechanical motional energy was developed in this project. This simulation also showed the best way in which to stack the magnets. This proof of concept project showed that this unique method for harvesting human mechanical energy is promising for powering electronic devices as an alternative to piezoelectric methods.

References:

1. Wang, et al., Magnetic-spring based energy harvesting from human motions: design, modeling and experiments. Energy Conversion and Management 132, 189-197 (2017). doi: 10.1016/j.enconman.2016.11.026.
2. Image retrieved from: https://pixabay.com/p-1526374/?no_redirect.