Design and operation of the ISWEC full-scale plant at Pantelleria

The aim of the present poster is the presentation of the ISWEC (developed by Wave for Energy and Politecnico di Torino) technology and the methodologies developed for its design process, the description of the full scale plant in Pantelleria (Italy) and the critical analysis of the experimental operative results. ISWEC (Inertial Sea Wave Energy Converter) is a system using the gyroscopic reaction provided from a spinning flywheel to extract power from sea waves. Its main features consist in the all-enclosed, monolithic layout and the capacity to adapt to different wave conditions by regulating the ISWEC control parameters, such as the gyro speed and the PTO (Power Take Off) control law. The gyroscopic core of ISWEC is a modular scalable unit installed in a sealed hull that protects the mechanic and the electronic systems from the marine environment, thus intrinsically granting high reliability and availability. The design of the device starts from a scatter diagram that describes the source availability in the installation site. Based on the diagram it is possible to pre-design the geometrical and mechanical properties of the device. Then, an in house developed algorithm with a simplified numerical model allows the research of the optimal configuration by means of multi-variables cost functions. The simulations output is the device productivity, along with consideration about structural loads, PTO utilization, floater and inertial properties. Once the preliminary design is achieved, experimental tests are needed for an optimal design of the control. The ISWEC 100 kW plant in Pantelleria consists of a 100 kW machine, with floater dimensions 8 by 15 m and a total displacement of 300 ton, of which 200 ton are sand ballast to tune the device on the site most energetic waves. The device was deployed 800 m from the shore, in a water depth of 30 m, in August 2015. Since then the machine operated in the different sea conditions, while physical quantities such as wave height, period and direction, instantaneous power production and internal parameters were monitored. The campaign provided experimental data used to validate the mathematical models predicting power output, loads on moorings and loads on bearings, thus improving the reliability of the numerical tools for ISWEC design and assessment.