Piezoelectric energy harvesting for powering a novel weigh-in-motion system

This paper describes the development and evaluation of a piezoelectric energy harvester (PEH) designed to power a novel system for weighing roadway vehicles in-motion. The PEH consists of four lead zirconate titanate piezoelectric (PZT) stacks connected in parallel. Each stack is made of six PZT elements of alternating polarity. The paper describes the electromechanical characterization of the PZT stacks, the design of the PEH electronic circuit and its power generation potential under realistic traffic conditions. An electromechanical model was fitted to laboratory data that allows relating PZT stacks voltage output to the applied forces, as a function of loading frequency (i.e., vehicle speed). The PEH circuitry consists of a rectifier, a flyback and a step-down converter to reduce voltage output to the 0-3.3 V range. The flyback input thresholds were 100 V and 300 mW. At highway speeds, these thresholds were exceeded for sinusoidal forces with amplitudes higher than 13 kN. Exceeding these thresholds generated over 200 mW of power, which is sufficient for supporting the low-power microprocessors considered. The amplitude of intermittent pulsating forces that can exceed these thresholds were estimated as a function of the rest period between pulses. For a rest period of 60 ms (i.e., typical rest period between tandem truck axles), the estimated amplitude was 33.4 kN. It was shown that this force is exceeded by roughly 35% of the typical truck tires.