Design, manufacturing and testing of dielectric elastomer generators for wave energy conversion.

Ocean wave energy is a widely abundant and highly concentrated form of renewable energy. Recently, it has been suggested that a special class of multifunctional materials, known as Dielectric Elastomers (DEs), could be employed to deploy Power Take-Off (PTO) systems for Wave Energy Converters (WECs). This thesis deals with novel designs, manufacturing and experimental validation of WECs with Dielectric Elastomer Generator (DEG) PTO. First, an analysis and design of two concepts has been done, i.e., 1) Oscillating Water Column (OWC) with inflatable diaphragm DE PTO; 2) pressure differential WEC with submerged diaphragm DEG in direct contact with water. Design procedures for full-scale WECs are provided. Wave tank experiments on an OWC prototype with scale in the order of 1:30 have been accomplished. The device hydrodynamics has been optimized to guarantee tuning within a prescribed range of wave frequencies. A DEG that integrates most of the functionalities of the real device has been employed in the tests, and electrical power generation from waves has been successfully achieved. Moreover a design and field test of a set of membranes has been done at The Natural Ocean Engineering Laboratory (NOEL). A single module of the DAB (Dual Active Bridge) has been built and tested. By properly controlling the electric activation of the DE PTO, capacitance variations can be exploited to convert mechanical energy from the waves into electric energy. Finally, manufacturing of membranes and electrodes has been addressed, obtaining excellent results in the 3D printing of carbon-based electrodes on silicone membranes.