Wireless sensors are an emerging technology that has the potential to revolutionize the monitoring of simple and complex physical systems. Prior research has shown that one of the biggest issues with wireless sensors is power management. A wireless sensor is simply not cost effective unless it can maintain long battery life or harvest energy from another source. Piezoelectric materials are viable conversion mechanisms because of their inherent ability to covert vibrations to electrical energy. Currently a wide variety of piezoelectric materials are available and the appropriate choice for sensing, actuating, or harvesting energy depends on their characteristics and properties. This study focuses on evaluating and comparing three different types of piezoelectric materials as energy harvesting devices. The materials utilized consisted on PZT 5A, a single crystal PMN 32%PT, and a PZT 5A composite called Thunder. These materials were subjected to a steady sinusoidal vibration provided by a shaker at different power levels. Gain of the devices was measured at all levels as well as impedance in a range of frequencies was characterized. Results showed that the piezoelectric generator coefficient, g33, predicts the overall power output of the materials as verified by the experiments. These results constitute a baseline for an energy harvesting system that will become the front end of a wireless sensor network.
Comparison of energy harvesting systems for wireless sensor networks