Electro-mechanical characterization of a piezoelectric energy harvester

Energy harvesting consists of capturing untapped ambient energy of various forms, such as mechanical, thermal or solar, and converting it into electrical energy. A significant unexploited source of mechanical energy is from vehicle movement on roadways. This paper presents the development of a piezoelectric energy harvester (PEH) capable of converting mechanical energy from roadways into electricity and uses an electro-mechanical model for characterizing it. The PEH consists of a stack of piezoelectric (PZT) elements connected in parallel. Its electro-mechanical properties were characterized by subjecting it to dynamic loads with peaks ranging from 1.1 to 11 kN and loading frequencies ranging from 2.5 to 62 Hz. The model constants were estimated by fitting a model to experimental data through an error minimization routine. This model is capable of converting load input (N) to voltage output (V) and vice-versa. Its quality of fit was successfully tested in the laboratory using different load amplitudes and frequencies. For an external resistance of 500 k Omega and sinusoidal loads with peaks of 1.1 and 11 kN applied at 66 Hz, the maximum voltage output of one of the PZT stacks was 95 V and 1190 V and the corresponding root mean square power output was 9 mW and 1400 mW, respectively. This model provides the background for the development of a self-powered axle load sensing system for roadway vehicles.