This paper presents the results of a theoretical and experimental study aiming to develop a stress-based roadway energy harvesting system. It describes two prototypes using piezoelectric elements. Prototype I consisted of 4, 8, and 16 8-mm-diameter cylindrical piezoelectric elements sandwiched between two copper plates. Prototype II consisted of a stack of 11 50-mm-diameter piezoelectric elements connected in parallel by alternating their polarities. Basic piezoelectric theory suggests that the relationship between power output and stress is nonlinear. Finite-element (FE) analysis shows a dependency of the power output of a cylindrical piezoelectric unit on loading frequency. The experimental evaluation included testing the prototypes in a universal testing machine under controlled temperature conditions. In addition, Prototype II was subjected to repetitive loads using an asphalt pavement analyzer without observing any loss in power output. Three-dimensional dynamic FE simulations were performed to determine the optimum installation depth of an energy harvesting module in an asphalt concrete pavement structure. Assuming moderate traffic levels and installation in the right-wheel path only, the energy output estimated per Prototypes I and II was 360 and 171 W-h annually. This technology shows promise in powering self-standing data acquisition systems or light-emitting diode (LED) lights in rural areas where there are no electrical power lines roadside.

This paper presents a preview of an ongoing study to develop an energy harvesting system based on piezoelectric elements embedded into the pavements structure. The system development involved designing and testing a number of prototypes in the laboratory under controlled stress conditions. In addition, it involved numerical modeling of the stress distribution in the power generation module and economic analysis of the value of the electric power generated, under a given traffic composition scenario. The results available to date suggest that this technology shows promise in powering LED traffic lights and wireless sensors embedded into pavement structures

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.