Optimal analysis on coil and rotor in a diamagnetically airflow energy harvester

In this paper, the proposed diamagnetic levitation structure was studied to explore its potential in energy harvesting. It is proved that the floating magnet rotor can be levitated stably under the joint action of two highly oriented pyrolytic graphite (HOPG) sheets and the lifting magnet. Simulation calculation was carried out to analyze the influence of different coil radius and wire diameter on peak voltage and average power in scheme A or scheme B, so as to obtain appropriate layout and wire diameter for the coils which was built the experimental platform. Subsequently, the center hole, notch radius and thickness of the floating rotor are analyzed by experiment. And the influence of different parameters on rotation speed of the rotor and peak output voltage of coils is obtained. Through experimental results, it is found that the notch radius of the floating rotor has the greatest influence on the rotation speed of the rotor. Based on the experiment, a new-type rotor was designed, with an outer shell to reduce the notch radius. Compared with the original floating rotor, there was 49.73% increase in voltage, 55.70% increase in rotation speed and 124.50% increase in power according to the experimental results. Test was performed with the optimization, the LED array of Zhengzhou University logo, which was composed of 60 LED lights, was lighting up. According to the oscilloscope measurement, the diamagnetic levitation energy harvester has an output voltage up to 1.294 V and average power of 60.67 mW under gas flow rate of 3000 sccm and nozzle exit velocity of 6.173 m/s. Obviously, the new-type rotor proposed in this paper could significantly increase the energy conversion efficiency, and make the future application of airflow energy harvester a step further.