A Study on Energy Harvesting by Amorphous Strips

Magnetostrictive materials can play an important role in the realization of energy harvesters, a topic of growing scientific and industrial interest, because of their high-specific energy. Important applications are reported in the literature regarding Fe-Ga and rare-earth based harvester cores, but these materials are not suitable for exploiting low-energy vibrations. In this paper, we discuss the properties and behavior of a harvester based on a magnetostrictive amorphous core. It is made of a bundle of suitably strained (preloaded) Fe-based amorphous strips directly subjected to axial vibration. Using five 20 μm thick strips of width 10 mm and length 60 mm, the harvester can generate 18 μW under a vibration-generated sinusoidal stress of 2.3 MPa at 300 Hz. Such a power is equivalent to a ~3 μW/cm³ power density. We discuss the role of the physical and geometrical parameters on the performance of the harvester and provide a modeling approach successfully validating the device performance.