A design study to harvest electrical energy from walking and running motions

Abstract

This thesis studies two different methods of harvesting electrical energy from everyday activities such as walking and running. It is a design study that aims to create a device which can be attached or incorporated into a shoe, ideally a military boot, so that soldiers can charge back-up batteries for their devices while out in the field. The goal was to create a device that could achieve a peak energy harvesting power output on the order of 0.1 Watts. The original concept for the device involved the use of macro piezoelectric fiber harvesters which harness strain energy from the sole of the shoe as it naturally bends and flexes throughout daily activity. Strain testing indicated the the maximum peak power output that could be expected from these actuators was on the order of 10- 4W to 10- 3 W, and testing of the harvesters themselves yielded peak power values on the order of 10 7W to 10-6W. These low power values turned the design study away from the use of piezoelectrics and a design incorporating a miniature air turbine coupled with an electromagnetic generator was introduced. Initial testing on this proof of concept device yielded peak power values on the order of 10- 4W to 10- 3W with much room for improvement. It was concluded that this sort of device would be more effective for harvesting energy from the shoes, and future iterations of the initial prototype were proposed.