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A piezoelectric alternative magnetic field energy harvester with permanent magnet bias

In this paper, an electromechanical energy harvester with resonant frequency of 55.5Hz and ability of scavenging the AC current energy by magnetic field coupling is designed and characterized. The energy harvester consists of a piezoelectric cantilever and a permanent magnet bias. An iron mass is mounted on the free end of the cantilever with the permanent magnet set proximity to it. This structure greatly simplifies the fabrication and installation of the energy harvester. The device is placed close to a wire carrying AC current to couple its alternative magnetic field. The alternative magnetic force on iron mass is enhanced due to the static magnetic field from the permanent magnet. Thus the piezoelectric cantilever is deflected and generates an output power. Experiment results show that the open circuit output voltage reaches 0.66V with respect to an alternative magnetic field produced by a 40-turn coil with 10mA AC current. The tested maximum output power is 0.4μW with optimal impedance of 500kOhms.