Designing and Analyzing of a Piezoelectric Energy Harvester with Tunable Natural Frequency for WSN Application

This paper presents a new approach for a Piezoelectric Energy Harvester (PEH) with actuation piezoelectric layer to shift system natural frequency. Beams are consisted of Si and AlN piezoelectric based on MEMS technology and piezoelectric is deposited on Fixed-Fixed beams with mass loading that produces more stress points and generates more power in comparison to other cantilever beam PEHs. This PEH with ability of shifting system natural frequency is designed in the size of 0.25 cm2 using optimum available space. In addition to piezoelectric generating layers, piezoelectric layers for actuation purpose is added on both sides of the beams for possibility of reducing system natural frequency to less than 10 Hz. Accomplished simulation also confirms theoretical calculation done by Partial Differential Equation (PDE) method for a Fixed-Fixed beam with mass loading in the center to estimate natural frequency of the system and generated voltage from piezoelectric effect. Natural frequency of the system in the designed structure without piezoelectric actuation voltage is about 127 Hz that with 1 g acceleration generated ±3.35 volts and 45 µW electrical powers which can be used in wireless sensor network and biosensing applications.