Application of sub-optimal control techniques to a gyroscopic Wave Energy Converter

One of the critical points in wave power exploitation is that the energy source is highly unpredictable and Wave Energy Converters have to be opportunely tuned in order to reach high conversion efficiency. In this paper the control problems of the ISWEC (Inertial Sea Wave Energy Converter) are stated and a control scheme based on the sub-optimal stochastic control logic is presented. ISWEC is able to harvest sea waves energy exploiting the inertial effects of a flywheel. The interaction between the pitching motion of its floater and the spinning flywheel provides a reaction torque which can be exploited to drive an electrical PTO. The optimal control logic results in tuning the floater dynamics to the incoming waves in order to maximize the power transfer from the waves to the floater. In ISWEC the hull dynamics is governed and controlled by the gyroscopic torque. The control scheme here presented has been tested using real waves records acquired at the deployment location in Pantelleria Island, which is one of the most energetic sites of the Mediterranean Sea.