Energy Scavenging for Wireless Sensor Nodes with a Focus on Vibration to Electricity Conversion by Shadrach

Energy Scavenging for Wireless Sensor Nodes with a Focus on Vibration to Electricity Conversion by Shadrach Joseph Roundy Doctor of Philosophy in Mechanical Engineering University of California, Berkeley Professor Paul K. Wright, Chair The vast reduction in size and power consumption of CMOS circuitry has led to a large research effort based around the vision of ubiquitous networks of wireless communication nodes. As the networks, which are usually designed to run on batteries, increase in number and the devices decrease in size, the replacement of depleted batteries is not practical. Methods of scavenging ambient power for use by low power wireless electronic devices have been explored in an effort to make the wireless nodes and resulting wireless sensor networks indefinitely self-contained. After a broad survey of potential energy scavenging methods, the conversion of ambient vibrations to electricity was chosen as a method for further research. Converters based on both piezoelectric and electrostatic (capacitive) coupling were pursued. Both types of converters were carefully modeled. Designs were optimized based on the models developed within in total size constraint of 1 cm. Test results from the piezoelectric converters demonstrate power densities of about 200 μW/cm from input vibrations of 2.25 m/s at 120 Hz. Furthermore, test results matched simulated outputs very closely thus verifying the validity of the model as a basis for design. One of