Evaluation of coupled piezoelectric and electromagnetic technique for vibration energy harvesting

Vibration energy harvesting is an attractive technique for potential powering of wireless sensors and other low power micro devices. In order for the device to have maximum power output, it is necessary to match electrical and mechanical damping. In this work a coupled piezoelectric and electromagnetic energy harvesting device is evaluated for its efficiency and compared with optimized standalone piezoelectric and electromagnetic techniques. A piezoelectric cantilever beam with a cylindrical magnet as its tip mass and a resonance frequency of 19 Hz is used, with a coil winding vertically aligned with the magnet such that the magnetic tip would pass through the coil. The total power output from the coupled energy harvesting technique is monitored which produced a power output of similar to 340 mu W compared to 301 mu W from an optimized standalone piezoelectric energy harvesting and 120 mu W from an standalone electromagnetic energy harvesting device. The total damping in the system is determined to be 0.054 compared to 0.046 and 0.04 for piezoelectric and electromagnetic techniques.