WIND AND WAVE STUDY FOR OFF-SHORE WIND FARM APPLICATIONS

The study focuses on wind-waves-bottom characterization as first step in the feasibility evaluation of an offshore windfarm in the offing of Apulian coast - Italy. Planning offshore windfarm, hydrodynamic and aerodynamic fields, and their interaction, must be investigated. Waves studies and their transformation due to diffraction, shoaling, refraction, etc. are fundamental to predict the effects that sea could have on turbine’s foundation, especially for floating turbine, mooring lines, structural stress and moreover to consider the influence that frequently high waves may have on installation, operation and maintenance. In this study, starting from wind data and a nautical map, a good determination of the wave motion has been obtained. Particularly, three-hours measurements of wind intensity and direction, by on-land anemometer, have been used. Wind data of a period of time of 45 years, from 1951 to 1996, have been statistically processed to extract the most relevant winds with velocity and duration bigger than 10 knots and 6 hours respectively. Using the nautical map of the area under investigation, the sea bottom morphology has been reconstructed to obtain a model of bathymetry. After that, the bathymetric curves have been traced on the map, converted in a depth matrix and then transformed into an interpolated grid point. Subsequently, the assessment of waves propagation has been obtained through both Jonswap Spectrum and SPM method and the results have been compared. Finally, the wave heights and peak periods were calculated with reference to return period of fifty years and used as input in two model: Nearshore Spectral Waves (NSW) model and Parabolic Mild Slope Spectra Waves (PMS) model. In conclusion, this study can represent a useful approach to plan an offshore windfarm.