Harvesting Vehicular Kinetic Energy Using Piezoelectric Sensors

Road pavements sustain numerous times of vehicle passage each day. The kinetic energy of vehicle motion can be captured, harvested, and converted into electricity for decentralized roadway lighting and operation of traffic lights. Application of piezoelectric technology is a promising method to harvest mechanical energy of vehicles which otherwise is dissipated as heat. Piezoelectricity refers to the ability of some materials to build up electric charges in response to the applied pressure or strain. The primary objective of this research was to design and build an energy harvester using a piezoelectric sensor network to harvest kinetic energy of vehicular motion and generate electrical current to charge a battery. In particular, the project's goal was to have a proof-of-concept to build a ramp-device consisting of 50 piezoelectric sensors to charge a 3V, 1 milliampere-hour coin cell battery. This device would be charged using a 700 lb motorcycle to induce the pressure onto the sensors to charge the battery. Industry standards to consider included the Institute of Electrical and Electronic Engineers (IEEE) regarding the use of piezoelectric sensors. Another consideration was the US Patent 9,054,511 B2 for an impact-type piezoelectric micro power generator. Design variations included overall shape, size, roadway placement, and internal components to increase vibrations for the piezoelectric sensors to convert to electrical energy. A final design was selected based on a feasibility and merit analysis. During construction of the device, plain carbon steel rod and sheeting were combined using MIG welding to make the frame with 3 doors hinged to the frame to access the inner components. The components consisted of 2 groups of 25 piezoelectric sensors (for a total of 50), on an acrylic backboard and sandwiched between two layers of silicone to protect the sensors from the external vehicular pressure on the external casing. These components were located within the middle compartment in the casing accessible by 2 doors. At the beginning of the project, a linear regulator was used, but this was switched to a buck converter to boost the charging current from the piezoelectric network to the coin cell battery. The effect of the buck converter was to regulate the charging voltage and reduce the charging time of the coin cell battery through a higher charging current. The buck converter and battery were attached to the sensors and located in another compartment inside the frame, accessible by the 3rd door. Mechanical tests performed consisted of testing the durability of the outer frame. Electrical tests performed consisted of connecting the charging circuitry to a function generator as a known input AC voltage source, and then to the piezoelectric sensors. Both types of inputs resulted in the charging of the battery.