Modeling and optimization of a Wave Energy Converter using ANSYS AQWA

In the framework of renewable energy, Wave Power represents a highly promising resource for the production of green energy as it is characterized by very high power density values. Moreover, Marine Energy is currently still an open field, even though the amount of research investments and patents in this field has been rising in the past 40 years. Real waves are not monochromatic and are in fact a classical example of stochastic phenomena. As such, real waves are highly complex and can be studied by means of statistical frequency domain analysis. Devices able to transform this kind of energy in a more usable form, i.e. electricity, are called WECs (Wave Energy Converters). In 2009 Politecnico di Torino started studying and designing ISWEC (Inertial Sea Wave Energy Converter) to be deployed in Pantelleria Island, one of the most powerful sites in Italy. The core of the system is a one degree of freedom gyroscope enclosed in a sealed floating hull: the spinning motion of the flywheel, combined with the motion of the floating hull, produces a gyroscopic torque that can be exploited by means of a generator called PTO (Power Take Off). The gyroscope motion unloads an inertial reaction on the hull that combined with the waves, allows power absorption. The geometry of the hull and the hydrodynamic description of the system are key factors in designing such a device. The team in Politecnico di Torino chose ANSYS AQWA to tackle the hydrodynamic subproblem. The software capability that allows for the calculation of the hydrodynamic of the floating system, was fundamental in determining the most suitable geometry of ISWEC hull. The article presents and explains the results obtained using the software for the following tasks. As a first step, a parametric analysis comparing numerous geometries was carried out with AQWA-LINE. Furthermore, it was possible to use ANSYS AQWA as the core software for dynamic simulation of the whole system, implementing the gyroscope model and the dynamic interaction between the spinning gyroscope and the floating hull by means of a DLL developed in Fortran environment.