A Bending Mode Galfenol Electric Power Harvester

Iron-Gallium alloys (Galfenol) are promising transducer materials that combine high magnetostriction, desirable mechanical properties, high permeability and a wide operational temperature range. In this study, we present results from a proof-of-concept prototype energy harvester that produces an output voltage proportional to the load-induced bending of the Galfenol element. The device consists of a polycrystalline Galfenol strip bonded to an aluminum cantilever beam which has an effective length of 1.5 in. Two brass pieces containing a permanent magnet are used to mass load each end of the beam and to provide a magnetic bias field through the Galfenol strip. An induction coil around the cantilever beam captures the magnetic flux variation of Galfenol as the beam vibrates. The first bending mode resonant frequency of the device was measured at 223 Hz. The power generated from the prototype subjected to 4-g acceleration at 222 Hz frequency was 16.4 mW(RMS), with corresponding power efficiency for output electrical power per input mechanical power of more than 30%.