Electromagnetic vibration energy harvesting with high power density using a magnet array
Electromagnetic vibration energy harvesters have been widely used to convert the vibration energy into electricity.
However, one of the main challenges of using electromagnetic vibration energy harvesters is that they are usually in very
large size with low power density. In this paper, a new type of electromagnetic vibration energy harvester with
remarkably high power density is developed. By putting the strong rare-earth magnets in alternating directions and using
high-magnetic-conductive casing, magnetic flux density up to 0.9T are obtained. This configuration also has a small
current loop with less electrical reluctance, which further increases the high power density when the coil is designed to
follow the current loop. The prototype, the size of which is 142x140x86 mm 3 ,
can provided up to 727Ns/m damping
coefficient, which means 428 kNs/m 4 damping density when it is shunt with 70Ω external resistive load which is set to
the same as the internal resistor of the harvester to achieve maximum power. The corresponding power density is 725
μW/cm 3 at 15HZ harmonic force excitation of 2.54mm peak-to-peak amplitude. When shot-circuited, 1091Ns/m
damping coefficient and 638 kNs/m 4 damping density is achieved. The effectiveness of this novel vibration energy
harvester is shown both by FEA and experiments. The eddy current damper is also discussed in this paper for
comparison. The proposed configuration of the magnet array can also be extended for both micro-scale and large-scale
energy harvesting applications, such as vibration energy harvesting from tall buildings, long bridges and railways.