piezoelectric - vibrations

Converting Mechanical Vibrations into Electrical Energy Electrical engineer Rajeevan Amirtharajah and his students at the University of California, Davis, have demonstrated a novel device for harvesting mechanical energy. The device consists of a small disk made of piezoelectric material (material that generates electric potential in response to mechanical stress) scribed with multiple electrodes. External vibrations induce special vibrational shapes, or modes, within the disk, which generate multiple voltages with unique phase relationships. Their research has focused on developing integrated circuits that combine the generated voltages with greater than 98 percent efficiency into a single power supply, effectively harvesting energy from the environment. Previous work in such devices has focused on one-dimensional systems such as cantilever beams; this work has demonstrated improved energy harvesting efficiency by using two-dimensional systems such as disks combined with efficient power conversion electronics. Sensors that harvest energy from their environment transcend the current limitations of traditional battery-powered sensors. Battery-powered wireless sensor networks (such as those used in infrastructure monitoring, health care, national security, and space exploration) are limited in individual sensor size, operating lifetime and maintenance cost by the finite energy capacity of batteries. The combination of new energy harvesting devices, highly efficient energy conversion electronics, and energy scalable integrated circuits offers great promise. If realized, it could extend the operating life of wireless sensors, reduce the maintenance cost and environmental impact of battery replacement, and enable entirely new applications such as long-lived centimeter-scale biomedical implants.