Modeling and parametric studies of magnetic shape memory alloy–based energy harvester

Abstract

This article presents a model to simulate the behavior of a magnetic shape memory alloy while harvesting vibratory energy. In this type of energy harvester, magnetic shape memory alloy element is placed in the air gap of a ferromagnetic core which conducts the magnetic flux. Two apparent coils are wound around a ferromagnetic core: one to produce bias magnetic field by passing a rectified electric current and the other to serve as an energy pickup coil. Applying compressive time-variant strain field to magnetic shape memory alloy element changes its dimensions and magnetic properties as well. Presence of the bias magnetic field returns magnetic shape memory alloy element to its initial state while removing the load. Changes in magnetic properties of magnetic shape memory alloy will change the magnetic flux passing through the pickup coil and will produce an alternative voltage in that coil based on the Faraday’s law of induction consequently. In the modeling strategy, magnetic behavior of magnetic shape memory alloy element during operation is obtained by solving the thermodynamic-based constitutive equation numerically and the energy harvesting process modeled with equivalent magnetic and electric circuits. By varying the system parameters in the model, output voltage and power changes are reported accordingly.