Design and development of a novel bi-directional piezoelectric energy harvester

In this paper, a novel bi-directional piezoelectric energy harvester which can harvest vibration energy bi-directionally is introduced and investigated theoretically and experimentally. The proposed harvester is composed of two sub-systems: a main beam to generate electricity and a spring–mass oscillator to trigger the vibration of the main beam from an additional direction by using magnets to couple the two sub-systems. The theoretical model is built on the basis of the Euler–Bernoulli beam theory and the magnetic charge model. A prototype is fabricated to test the performance of the harvester experimentally. Linear upward and downward frequency sweeps are used to obtain the frequency responses. The experimental results show good agreement with the theoretical model under frequency sweeps. A comparison with a beam–beam bi-directional piezoelectric energy harvester is also performed experimentally. Although both bi-directional piezoelectric energy harvesters exhibit the capability of harvesting vibration energy in two orthogonal directions, the beam–spring energy harvester shows a more consistent performance in both directions as regards the bandwidth and amplitude of the frequency responses. (paper)