Design Of Rotary Piezoelectric Generator With Broad Work Bandwidth Driven By Gentle Breeze

With the portable electric devices and the wireless sensors applied widely, it attracts lots of attentions that the renewable energy resources are utilized to provide electric power for the devices in real time. As the vibrational energy is pollution-free and rich in the environment, it's suitable for supplying energy to the devices. However, the power equipment driven by wind, which is an important way inducing vibration, mainly include the generators using high-frequency vibrational power or generating power with the high speed wind. To utilize the low-frequency vibrational energy caused by gentle breeze, a rotary piezoelectric generator with broad work bandwidth driven by gentle breeze was designed. The generator was mainly composed of three parts:the wind transmission part, the piezoelectric power generation part and the buffering part. When wind blew to the generator, the piezoelectric cantilevers vibrated, which was forced by the non-contact force generated by the mechanical structure of the wind transmission part, and according to the piezoelectric effect, the vibrational energy would be converted into electric power. In the structure of the generator, a buffering part to increase frequency was added to broaden the work bandwidth of the generator and protect the piezoelectric cantilever. The main work of this paper are as follows:Firstly, the overall structure of the generator was designed with a vertical axis, which is simple and easy to rotate. And an impeller of the shape S was applied for the wind transmission part, while the piezoelectric cantilever was used in the piezoelectric power generation part. The buffering part was used to increase the working bandwidth and there were two types of structure designed for the buffering part:the bump stop and the circular arc.Secondly, the formulas of the the wind transmission part were collected and derived. Then, the sizes and the output power of the wind transmission part could be computed by the formulas. What's more, the linear relation between the revolving speed and wind speed could be derived as well.Thirdly, the theoretical models of the piezoelectric power generation part and the buffering part were established and the simulation analysis were performed. When the buffering part was a bump stop, there were two methods presented to analyze the collision between the piezoelectric cantilever and the bump stop. Comparing the simulation results, it was found that both of the two methods were in accord with the output performance of the cantilever, but the former one was complicated and more accurate and the latter one was clear and simpler. When the buffering part was circular arc, the output performance of the piezoelectric cantilever was derived and analyzed. Comparing the different buffering parts, the simulation results indicated that the piezoelectric cantilever will generate more power with the circular arc in the same experimental situation, but there were more limitations of the circular arc and it increased the installation difficulty.Lastly, to improve the output performance of the piezoelectric generator and verify that the bump stop could broaden the working bandwidth, the experimental plat was set up based on the structure characteristic of the piezoelectric power generation part and the buffering part. Then, the impact of the bump stop on the output performance of the piezoelectric generator was tested and several important parameters such as the number and the distance of the magnets, the position of the bump stop are optimized. The test and optimization results indicated that, when there were four magnets mounted on the driving wheel and the distance between the magnets mounted on the driving wheel and the piezoelectric cantilever was 10 mm?15 mm, the piezoelectric generator performed best and in the same time, the bump stop was at the position with the the vertical and the horizontal distances are 7 mm and 0.8?1.2 mm respectively.The experimental results proved that the buffering part could broaden the working bandwidth of the generator with an increase of 9.1 times from 5.38 m/s?6.38 m/s to 2.92 m/s 13.0 m/s, and the optimal matched resistance decreased from 350 k? to 1 k?. The optimization results provided important reference for the design of the piezoelectric generator.