Luca Cavallaro

Potential wave energy production by different wave energy converters around Sicily

The performance of several Wave Energy Converter devices is evaluated at three sites located on the west side of Sicily. To select the most energetic site, the average potential wave energy along the coasts of Sicily is evaluated by adopting a third-generation spectral wave propagation model using as boundary conditions the European Centre for Medium-Range Weather Forecasts operational archive wave and wind data. The most energetic sites are on the western side of Sicily. In the three hotspots identified, the mean energy flux is within the range of 5.33–7.52 kW/m. The analysis shows that all considered devices have a low capacity factor in their original configurations (2.19%–5.12%). The main causes of the poor results in terms of energy production are related to the fact that such devices are optimized for high-energy waves. A resizing of the devices on the basis of the local wave climate showed that a capacity factor that exceeds 30% could be obtained.

Feasibility of an Offshore Wind Farm in the Gulf of Gela Marine and Structural Issues

Some of the marine and structural issues related to the installation of an offshore wind farm three miles away from the shoreline of Gela (Italy) are discussed. In particular, the characterization of the maritime climate has been carried out by considering the winds, the waves, the mean water level variations and the current regime. The results of such an analysis have been used in order to determine the environmental loads on the foundation structure. A gravity based structural type has been proposed as foundation of the wind turbines and the design of a foundation prototype has been carried out by trying to implement the most updated international standards to the Sicilian case. An original automatic optimization procedure has been developed in order to determine the dimensions of the design foundation, which satisfied the prescribed static verifications and provided the lowest costs. The scour process at the basis of the foundation and the wave run-up on the structure have been also taken into account. Finally, problems related to the laying and the maintenance of electrical connection cables are also discussed.

Experiments on Surface Waves Interacting with Flexible Aquatic Vegetation

Surface wave interaction with aquatic vegetation appears to play a key role in coastal hydro-morpho-dynamics. As an example, the presence of a dense meadow at intermediate water depth is usually associated with a stable and resilient shore. Wave-meadow interactions are investigated here by means of physical modelling, with a focus on wave height distribution and hydrodynamics. The central part of a wave flume is covered by flexible artificial seagrass, composed of polyethylene leaves. This vegetation is tested in both near emergent and submerged conditions. The wave height reduction is evaluated by means of a drag coefficient defined from linear wave theory, which contains all the unknowns of the adopted methodology. The behaviour of such a coefficient is investigated as a function of a wave related Reynolds number. The influence of the flexibility of the leaves is also considered, together with a wave frequency parameter. The results show a complex behaviour with three different trends for near rigid, intermediate or highly flexible leaves. Amplitudes of the orbital velocities are investigated and show a fairly good match with the linear wave theory. On the contrary, the mean velocity along the water column appears to be modified by the seagrass for submerged leaves.