Efficient energy conversion circuits for hi-way road traffic energy harvesting using piezoelectric devices
Piezoelectric materials are being explored in this research to harvest mechanical deformations and vibrations on highway pavement produced by passenger and cargo vehicles, converting the mechanical energy to electric energy. Optimal Converter with high efficiency and reliability are required to capture the charges and store the energy in the form of hybrid capacitors or batteries in order to provide sensors and communication systems with sustained source of energy. A number of converter circuits have been designed, simulated, and tested. An EVI (Energy Voltage Current) converter with a conversion efficiency of 85% and better is proposed, constructed, and tested (to have achieved 86-92 % conversion efficiency). The DC energy harvested from the converter is used to charge the battery or hybrid capacitors based on their charging and storage characteristics for a better efficiency. The piezoelectric devices utilized in these tests are lead zirconium titanate (PZT) ceramics in various forms including modified PZT ceramic rods (PZT-5A), thin layer unimorph composite (Thunder X7R), embedded PZT rods 1:3 composite, and various stacked and composite-stacked samples. All these piezoelectric materials greatly depend on load matching to harvest maximum electric power. In addition to voltage regulation, the EVI converter also plays a vital role in optimizing load for various PZT devices to achieve maximum power efficiency. Custom designed signal-amplified shaker, MTS electrodynamic testing system (Acumen III), and universal testing machine (UTM 25) are used for testing these piezoelectric samples and transducers to evaluate the range of voltage regulation, the effectiveness in load optimization, and the power optimization efficiency of the converter circuit. The novel design of the EVI converter is reported in this thesis and the testing results indicate that it can be utilized not only as an AC-DC converter but also as a DC-DC converter. The EVI converter developed in this work is highly promising to be adopted in the piezoelectric highway energy harvesting modules.