Improved piezoelectric multifrequency energy harvesting by magnetic coupling

In vibration energy harvesting, for the generators to be efficiently applicable over a range of source frequencies, many methods can be adopted, among which the use of array of converters with different resonance frequencies has been reported as particularly effective. However, for a given excitation frequency only one single converter at a time contributes to the power generation, with a corresponding limitation in the whole generated power density. In this paper, the design and testing of an improved energy harvesting device using dynamic magnetic force technique is presented, which takes advantage of magnetic force and multi-cantilever beams to increase the power output. The motions of the cantilever beams with magnetic coupling and the effects of the distances among the magnets on the output power are investigated for achieving the optimal performances. Experimental results show that the new harvester can get a 55.6% increase in the output power.