Multi-directional electromagnetic vibration energy harvester using circular Halbach array

In this paper, a multi-directional electromagnetic vibration energy harvester (EVEH) using the circular Halbach array (HA) is presented based on the Faraday’s law of electromagnetic induction. The circular HA is a specific arrangement of permanent magnets which could concentrate the magnetic field inside the circular array by a certain rule, while reduce the magnetic field outside the circular array to almost zero at the same time. The HA could break through the limitation of the related published vibration energy harvesters that could work in only one single direction. Thus, it could optimize the collecting efficiency. The experimental results show that the presented harvester could generate considerable electric output power in all vibrating directions. An optimal output power is 9.32 mW at a resonant frequency of 15.40 Hz with an acceleration of 0.5 g (with g=9.8 m/s2) across a 700-turn coil in the vibrating direction of 90°, which is 1.53 times than the minimum optimal one in the direction of 45°. The EVEH using the circular HA could work in all directions and generate considerable electric output power, which validates the feasibility of the EVEH that works in all directions and is beneficial for improving the practical application.