Design of a Wave Energy Converter A case of application: ISWEC

Wave energy is one of the most promising renewable energy sources of the last few decades. Wave power has been investigated in Europe since the Seventies. In 1974 Prof. Stephen Salter proposed one of the first Wave Energy Converters (WEC), called Duck, at the University of Edinburgh. In the past four decades, hundreds of Wave Energy Converters have been proposed and studied, but so far a final architecture to harvest wave power has not been identified. Many engineering problems are still to be solved, like survivability, durability and effective power capture in a variable wave climate. ISWEC (Inertial Sea Wave Energy Converter) is a system that exploits the gyroscopic reactions provided from a spinning flywheel for the wave power conversion similarly to what the gyroscopic stabilizer do to reduce the roll motion of a boat. The flywheel works inside a sealed floating body in order to be protected from the outer environment and to grant reliable and durable operation conditions. Such a body is retained by means of two slack mooring lines connected to a deadweight lying on the seabed. The wave action induces the body pitching oscillation that may be damped to obtain the power transfer from the waves to the body. Furthermore an action torque is provided from the PTO on the gyroscope aiming at the energy conversion, while a reaction torque is given from the gyroscope to the hull. In such a way the power transfer from the floater to the PTO is obtained. The aim of the current thesis is to introduce the ISWEC as a possible technology for the wave power conversion. The mathematical model of the device and its validation by means of the experimental tests is here presented and its application for the full scale ISWEC prototype design porocess is shown. Finally an optimal control strategy has been proposed as a possible alternative to the basic linear control technique.