A rotational energy harvester with a semi-flexible one-way clutch for capturing low-frequency vibration energy

Renewable vibration energy is widely distributed in our living environment, but the low-frequency and irregular features impede its efficient exploitation and practical applications. To solve this issue, this paper proposes an innovative semi-flexible one-way clutch (OWC) and an OWC-based rotational energy harvester (OWC-REH) to achieve high and useable electric power out of low-frequency (<5 Hz) vibrations. The OWC consists of a pendulum equipped with a flexible thruster and a rotor designed with zigzag-shaped bulges on its surface. Through the interaction between the thruster and the bulges, the conversion of the bi-directional pendulum swing to the uni-directional rotor rotation can be realized. When excited by vibrations with an amplitude of 12 mm, the rotor achieves a fast speed of 240 rpm and the OWC-REH can generate high output power of 4.3 mW at 2.4 Hz. The energy conversion efficiency of the OWC-REH reaches a high value of 36.2%. When the OWC-REH is fastened to human limbs, the harvested energy from human motions can maintain the normal operation of portable electronic devices. This study proposes a promising strategy for utilizing the pervasive low-frequency vibrations as the sustainable energy for low-power electronics.