Energy harvesting from waves using tandem floaters connected by piezoelectric beams

In this paper, a small-scale floating system capable to extract energy from the waves is presented. The prototype floating structure consists of two box-shaped bodies joined by flexible beams and keeps its position with respect to the seabed via mooring lines. Due to the wave excitation, the platforms experience relative pitch rotations, and the mechanical energy related to this relative motion is then converted in electrical energy using a power take-off system based on piezoelectric beams. A simple experiment is arranged to demonstrate the feasibility of the concept and to obtain data to validate the numerical model. Two floaters are built in plastic materials, linked to each other with commercial PZT piezoelectric harvesters. The regular-wave tests are carried out in a small basin with a plunge wavemaker properly designed to produce a small wave amplitude suitable for the physical model dimension. The experimental data relative to the floater motion is used as input to calculate the tip displacement of the flexible element reproducing the mechanical behavior of the real PZT device. The tip displacement timehistory then serves as input to calculate the voltage output of the connecting piezoelectric device via a numerical model developed with a multiphysics software package