Development and Evaluation of Piezoelectric Prototypes for Roadway Energy Harvesting

This paper describes the development of several piezoelectric prototypes capable of harvesting energy from the action of traffic on roadways. It provides a brief overview of piezoelectric theory to show that the relationship between the power generated and the applied stress has a quadratic form. The amount of energy available for harvesting is explored through finite element simulations of the strain energy in pavements under moving tire loads. The prototypes developed involve various configurations of cylindrical and prismatic piezoelectric elements. Exploratory analysis shows that it is desirable to alternate the polarity of stacked piezoelectric elements and connect them in parallel to avoid generating unmanageably high voltages. The prototypes are tested in uniaxial compression under sinusoidal loading at a frequency of 10 Hz. Curves are fitted to the electrical power versus stress laboratory data. For a single pass of a 44.48-kN truck tire load, the electrical power generated is estimated to be between 1.0 and 1.8 W. A number of traffic scenarios are considered for translating this power output into energy. The estimated annualized cost of the harvesters and the amount of electric energy produced per year is used to compute the levelized cost of energy (LCOE) for this technology. For the most promising harvester the LCOE is between $\$19/\mathrm{kWh}$ and $\$4.8/\mathrm{kWh}$, depending on traffic level.