Harvesting energy from twisting vibration of a rotor suspended by a piece of string

This letter reports a twisting-vibration based energy harvesting method to generate electricity from ultra-low frequency excitations. Different from the conventional rotational energy harvesters (REHs) that normally use a shaft or bearing structure to support the rotor, the proposed method turns to a piece of string to suspend and drive the rotor. To demonstrate the operational principle and feasibility of this method, we designed a harvester prototype based on the electromagnetic transduction and established the corresponding dynamic model. Both theoretical results and experimental tests exhibit the favorable performance of this method in energy harvesting, which enables the design of REHs with a simpler structure. Moreover, the inherent frequency up-conversion feature makes the proposed method well suited for operating in the natural environment that abounds with ultra-low frequency excitation sources. (letter)