PENDEXE: A novel energy harvesting concept for low frequency human waistline

We report a novel concept of harvesting energy from low frequency and low force human gait movement from a device attached at the waistline. Due to the rather low characteristic frequencies of the human gait it is difficult to harvest energy piezoelectrically from such movement. The concept reported here uses a pendulum to exploit kinetic energy available from walking and jogging and later converting it into electrical energy by using compliant piezoelectric unimorphs. The pendulum with a fundamental frequency of approximately 2 Hz is directed to excite the piezoelectric unimorphs at their natural frequency of 50 Hz by a mechanical frequency up-conversion technique. The maximum power output is nearly 300 μW. The concept, fabrication of novel rotor-pendulum based harvesting unit and experimentation are discussed in detail.