A string-driven rotor for efficient energy harvesting from ultra-low frequency excitations

Abstract

This Letter reports a string-driven rotor for constructing ultralow frequency energy harvesters. Consisting of a disk-shaped rotor with a shaft, an elastic string, and an inelastic string, the proposed rotor structure can convert ultralow frequency vibrations or linear reciprocating motions to high-speed rotation of the rotor without any sophisticated transmission mechanism. On the basis of the string-driven rotor, an electromagnetic energy harvester is designed, and the corresponding theoretical model is established. Both simulation and experiments demonstrate the high output performance of the harvester under a periodic excitation with an amplitude of 5 mm and at a frequency lower than 5 Hz. The harvester also generates 6.5 mW power when driven by hand at a frequency of approximately 4 Hz. This study exhibits the exciting potential of the string-driven rotor for boosting the efficiency of harvesting energy from pervasive ultralow frequency excitations.