Constituting abrupt magnetic flux density change for power density improvement in electromagnetic energy harvesting

In this paper, we originally investigate how formulation of abrupt magnetic flux density change influences the electric outputs, e.g. open-circuit voltage, power density and charging rates, of electromagnetic energy harvesters. Electromagnetic energy harvesters are comprised of one magnet array and two sets of coil arrays. In a certain volume, the dimension and number of magnets evidently determines the number of abrupt magnetic flux density change (denoted as beta, beta=0,1,2,3,5,7) and further the output voltage. To study how this correlation affects the performance of the harvester, a configuration is first proposed and by conducting simulation, we infer that the highest voltage is induced by the case where beta=3, namely when the length, height and width of the magnet are the same. This hypothesis is further validated by three series of experimental results: the open-circuit voltage first increases, reaches its peak where beta=3, and falls offsharply as beta increases from 0 to 7; the cubic-magnet array configuration yields the highest power and power density, more than 20 times higher than that of the case without abrupt magnetic flux density change. The instantaneous power reaches as high as 284 mW under resonance at 1 g excitation acceleration with an overall dimension of 4.8cm x3.9cm x2.5cm; The charging-capacitor experimental results confirms this as the cubic magnet case yields the largest charging rate and highest saturation voltage. We mainly attribute this phenomenon to the collective relation of the flux change and magnet volume as beta grows from 0 to 7. This finding reveals the best configuration of magnet arrays that leads to the most desirable performance from electromagnetic energy harvesters.

Automated summary

The study focuses on how abrupt magnetic flux density changes influence the electric outputs of electromagnetic energy harvesters. It is found that the cubic-magnet array configuration yields the best performance in terms of output voltage, power density, and charging rates, demonstrating the importance of magnet volume in optimizing the harvester's performance.