A Novel Semicircular Annular Piezoelectric Energy Harvester

In order to broaden the frequency band of the piezoelectric energy harvester (PEH) and improve the power density, a nested semicircular annular PEH is proposed in this work. The design of the nested structure not only broadens the frequency band but also reduces the structure volume, thus enhancing the power density. Moreover, the design of the two-beam array ensures the continuity of the frequency band. A two-degree-of-freedom (2-DOF) lumped parametric model is established to analyze its frequency response and output performance. The effect of the proof masses on the resonant frequency is investigated, and two series-rectification approaches are proposed. The measured results show that the resonant frequency can be modulated by adjusting the weight of the proof masses. At 0.1 g acceleration and 116.5 Hz frequency, the PEH with heights of 10 and 7 mm for Mass 1 and 2, respectively, exhibits an output voltage of 46.4 V, the maximum output power is up to 1.36 mW, and the normalized power density (NPD) of
$79.4 ~\mu \text{W}\cdot \text{g}\,\,^{-{2}}\cdot $
mm
$^{-{3}}$
. The rectified-then-series PEH array has a high dc voltage output in the frequency range of 85–128 Hz with a broadband of 43 Hz, and connecting the power management circuit can make the acceleration sensor operate properly. The simple structure, wide operating band, and high-power density of this PEH can be adapted to vibration environments with more different frequencies to supply power for low-power chips and sensors.