Power conditioning for MEMS-based waste vibrational energy harvester

Abstract

Increasing energy needs push industry to build more sustainable and efficient systems. One of the methods to achieve energy efficiency is to feed wasted energy generated by a system itself during operation back to the system. Vibrational energy is one of the most common ambient energy forms in mechanical systems and can be converted into electrical energy with the implementation of piezoelectric energy harvesters. What makes this possible is the piezoelectric effect that some crystals and ceramics with no inversion symmetry show. Piezoelectric materials generate a potential difference when a force is applied and deform under an electric field. Power electronics is used to turn this potential into a usable energy. The amount of power generated by a single piezoelectric energy harvester could be very low, but Microelectromechanical Systems (MEMS) technology makes it possible to have thousands of devices in a very small area. Previously, a MEMS-based piezoelectric harvester for military applications was designed, developed, and tested at NPS. In this thesis, methods to convert the AC voltage output of this device into a DC voltage were investigated to find an efficient method. Because of their higher power needs, multiple devices need to be connected to achieve required power levels for military applications. Microfabrication processes allow for building large number of such devices at the same time. This thesis also studies the possible connections for an array of devices. Connection geometry that will produce the maximum power output for a number of devices is proposed.