Performance of Galfenol Energy Harvester at High Temperature

Recently, the development of energy harvesting devices has received considerable interest as a means of powering nodes in a wireless sensor network. Additionally, the ability to operate in a high temperature environment is a desired feature especially in the case of wireless sensor networks used in a power plant where elevated temperatures are normal. Vibration based energy harvesting is one method of scavenging energy from the environment. Traditional approaches for vibration based energy harvesting have focused primarily on piezoelectric and electromagnetic approaches. There are, however, limitations associated with high temperature applications. Iron-Gallium alloys (Galfenol) are highly magnetostrictive with magnetically induced strains as high as 400 ppm in single crystals and 280 ppm in highly textured polycrystals. Galfenol is machineable, weldable, and has tensile strength of approximately 500 MPa. These unique properties foreshadow the material’s use in conventional transducers operating in severe environments. An investigation into the magnetostriction performance at temperatures up to 225°C found magnetostriction degraded relative to that at room temperature by close to 25%. From those measurements, two important advantages of Galfenol were found. First, even though the performance degraded at 225°C, the original performance is recovered when the temperature comes back to room temperature. The second advantage is that the performance at 225°C was stable. Based on these results, it was determined that Galfenol could be utilized at temperatures of at least 225 °C. In this paper, a series of tests are conducted in a thermal chamber to evaluate the Galfenol energy harvester performances from temperatures ranging from room temperature to 200°C. A linear coupled model for a Galfenol energy harvester is developed based on fundamental properties of a tuned mass beam system. A non-linear version of the model is developed and compared to experimental evaluations. A comparison with experimental evaluations provides good correlation with results. It is shown that the Galfenol energy harvester can provide consistent power from room temperature to 200°C.