Modelling and field testing of a breakwater-integrated U-OWC wave energy converter with dielectric elastomer generator

This paper introduces a theoretical and experimental study of a wave energy converter (WEC) that combines the two innovative concepts of U-oscillating water column (U-OWC) and dielectric elastomer generator (DEG) power take-off (PTO). The U-OWC is a type of oscillating water column that features a U-shaped duct that is introduced to tune its dynamics to a certain wave period without active means of phase-control. The DEG is a compliant polymeric generator that makes it possible to convert mechanical energy into electrical energy by exploiting the large deformations of elastomeric membranes. A lumped-parameter mathematical model of the proposed WEC has been set-up and a small-scale model/prototype has been preliminary tested in a benign real-sea environment. During experiments, relevant experimental data have been collected and used for assessing the reliability of the modelling approach. Beside the model validation, specific experiments have been conducted to test a simple but yet effective load shedding system based on the progressive opening of an air valve. Finally, a preliminary design of a full-scale U-OWC equipped with DEG-PTO has been studied through wave-to-wire analysis. The obtained numerical results show an overall performance that is comparable with that of more conventional, expensive and complex PTO technologies.