Power Harvesting Through Magnetostrictive Devices: A Linear Model

Energy harvesting, sometimes referred to as “power scavenging” or “energy extraction”, can be defined as “converting ambient energies such as vibration, temperature, light, RF energy, etc. to usable electrical energy by using energy conversion materials or structures, and subsequent storage of the electrical energy for powering electric devices”. There has been a significant increase in the research on vibration-based energy harvesting in recent years. In this contest magnetostrictive devices are considered a promising technology. The Villari effect, also known as the inverse magnetomechanical effect, is the change in magnetization that a magnetostrictive material undergoes when subjected to an applied uniaxial stress. This effect pertains to the transduction of energy from the elastic to the magnetic state and is inverse of Joule magnetostriction. Furthermore, the Villari effect exhibits many of the attributes of the direct magnetostrictive effect since its physical origin lies in magnetoelastic coupling. Transducers utilizing the Villari effect consist of a coil wound on a core of magnetostrictive material. In this paper, a linear magnetomechanical coupling model is developed to analytically calculate the potential electrical power such transducers can generate when subjected to applied harmonic mechanical vibration. Theoretical results are confirmed by experimental tests on two different magnetostrictive devices.