Numerical and experimental performance study of magnetic levitation energy harvester with magnetic liquid for low-power-device’s energy storage

Abstract

Energy harvesting is an emerging technology that uses ambient vibrations to generate electricity. The harvesting energy from vibrating environments can be stored by batteries to supply low-power devices. This paper presents a new structure of magnetic levitation energy harvester (MLEH) for low-power-device’s energy storage, which uses magnetic liquid to improve energy conversion efficiency and broaden bandwidth. Its working principle, structure and analysis model are introduced in detail. Specifically, the mathematical model of the energy harvester system is established by harmonic balance method. The nonlinear stiffness of the magnetic spring and damping characteristics of the system are analyzed by experiments. In addition, four prototype energy harvesters are designed for different magnet distances and magnet numbers. Finally, the experimental results are compared with the numerical results of dynamic simulation to verify the accuracy of the proposed model. Performance improvements of the energy harvester with magnetic liquid are evaluated by defining bandwidth growth rate and normalized power density. The experimental results show that when the wire diameter in the coil is 0.44 mm, the peak power of the energy harvester with magnetic liquid is 1.64 times greater than that of the energy harvester without magnetic liquid, the normalized power density can reach 183.39 μW⋅cm−3⋅g−2, and the bandwidth is widened by 65%.