Comparison of Piezoelectric Energy Harvesting Devices for Recharging Batteries

Piezoelectric materials can be used as a means of transforming ambient vibrations into electrical energy that can be stored and used to power other devices. With the recent surge of micro scale devices, piezoelectric power generation can provide a convenient alternative to traditional power sources used to operate certain types of sensors/actuators, telemetry, and MEMS devices. However, the energy produced by these materials is in many cases far too small to directly power an electrical device. Therefore, much of the research into power harvesting has focused on methods of accumulating the energy until a sufficient amount is present, allowing the intended electronics to be powered. In a recent study by Sodano et al. (2004a) the ability to take the energy generated through the vibration of a piezoelectric material was shown to be capable of recharging a discharged nickel metal hydride battery. In the present study, three types of piezoelectric devices will be investigated and experimentally tested to determine each of their abilities to transform ambient vibration into electrical energy and their capability to recharge a discharged battery. The three types of piezoelectric devices tested are; the commonly used monolithic piezoceramic material lead-zirconate-titanate (PZT), the bimorph Quick Pack (QP) actuator and Macro Fiber Composite (MFC). The experimental results estimate the efficiency of the three devices tested and identify the feasibility of their use in real world applications. Various different capacity batteries are recharged using each device, to determine the charge time and maximum capacity battery that can be charged. The results presented in this paper show the potential of piezoelectric materials for use in power harvesting applications, provide a means of choosing the piezoelectric device to be used and estimating the amount of time required for it to recharge a specific capacity battery.