Piezoelectric Vibration Energy Harvester Using Indirect Impact of Springless Proof Mass

This paper presents an impact-based piezoelectric vibration energy harvester using freely movable spherical proof mass and MFC (Macro Fiber Composite) beams as piezoelectric cantilevers. When external vibration is applied, a metal sphere moves freely along the channel and collides with both ends of the cavity, which induces the vibration of parallel-connected MFCs and generates electric power. A proof-of-concept device having the form-factor of a wristwatch has been designed and tested. Moreover, spherical proof mass made of different materials has been tested to analyze the relationship between output power, long-term reliability, and audible noise level during operation. Maximum peak-to-peak open circuit voltage of 41.2V and average power of 908.7 mu W have been obtained in response to a 3g vibration at 17Hz for device with parallel-connected MFC beams.