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

• Published in: International journal of mechanical sciences 2021-05, Vol.198, p.106363, Article 106363
• Main Authors: Li, Zhongjie, Liu, Yong, Yin, Peilun, Peng, Yan, Luo, Jun, Xie, Shaorong, Pu, Huayan
• Format: Article
• Language: English
• Subjects: Abrupt magnetic flux density change; Electromagnetic energy harvesting; Magnet array configuration; Power density improvement
• ISSN: 0020-7403; 1879-2162
• DOI: 10.1016/j.ijmecsci.2021.106363

•Forming abrupt magnetic flux density change for electromagnetic energy harvesters.•Studying how the formation affects the power density of the harvesters.•Revealing that the cubic-magnet configuration leads to the best yields.•Proving that alternating polarities enhance power outputs by up to over 20 times. 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 β, β=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 β=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 β=3, and falls off sharply as β 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 × 3.9cm × 2.5cm; 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 β 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. [Display omitted]