Abstract
The most conventional configuration for vibration-based piezoelectric energy harvesting is cantilever beams. Researchers are continuously striving to enhance both the power capacity and bandwidth. While conventionally rectangular cantilever beams are used for cantilever energy harvesting, research has shown that rectangular shapes are not the ideal one for maximum power density. A lot of investigation has previously been carried out to optimize beam shapes. However, most of those previous studies cover trapezoidal and triangular beam shapes. This warrants the study of other beam shapes including concave and convex-shaped beams. In this work, concave and convex-shaped cantilever beam energy harvesters were investigated with varying geometric configurations. The output power from each shape was examined by altering the ratio of the beam’s middle width to the base width while keeping the thickness, surface areas, volume, and mass of the beam. The piezoelectric material attached to the beam followed a similar approach to mitigate the impact of PZT on the beam’s power capacity as it serves as the energy conversion medium. Such an approach was required to understand the true influence of concave and convex cantilever shapes on energy harvesting. One-third of the beam surface area was coated with piezoelectric material following the uni-morph setting. The coating of piezoelectric material on the beam was provided at its fixed end to obtain the maximum power out of piezoelectric material. Due to the significant influence of the geometric configuration of the beam on output power, it has been expressed in terms of power density. Furthermore, the resonant frequency of each shape was explored, as the output from the cantilever energy harvester attains its maximum at the resonant frequency of each specific shape. Results of the study revealed that a convex cantilever beam can achieve a superior output power density compared to concave and standard rectangular beams while utilizing an identical volume of beam and piezoelectric material. This holds particularly when the piezoelectric coating is applied near the fixed end. It is worth highlighting that in cases where the piezoelectric layer is near the fixed end, the power output is predominantly influenced by the base width of the beam, with a lower base width corresponding to higher output power density.
