This paper reviews recent developments in energy harvesting technologies for structural health monitoring applications. Many industries have a great deal of interest in obtaining technology that can be used to monitor the health of machinery and structures. In particular, the need for autonomous monitoring of structures has been ever-increasing in recent years. Autonomous SHM systems typically include embedded sensors, data acquisition, wireless communication, and energy harvesting systems. Among all of these components, this paper focuses on the energy harvesting technologies. Since low-power sensors and wireless communications are used in newer SHM systems, a number of researchers have recently investigated techniques to extract energy from the local environment to power these stand-alone systems. Ambient energy sources include vibration, thermal gradients, solar, wind, pressure, etc. If the structure has a rich enough loading, then it may be possible to extract the needed power directly from the structure itself. Harvesting energy using piezoelectric materials by converting applied stress to electricity is most common. Other methods to harvest energy such as electromagnetic, magnetostrictive, or thermoelectric generator are also reviewed. Lastly, an energy harvester with frequency tuning capability is demonstrated.
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