Offshore floating wind turbines for Mediterranean sites: preliminary analysis of different concepts

An analysis of different floating platform concepts in site conditions typical of the Mediterranean Sea is presented. A tension leg platform, a spar buoy, and a barge support substructures were investigated. In all the three cases, the National Renewable Energy Laboratory 5-MW machine was considered as wind turbine. This turbine model was also used to carry out a performance comparison between the selected offshore site and an adjacent onshore site, in order to estimate the advantages of the offshore solution in terms of annual energy production. The comparison among the different floating platform concepts considers the loads on the turbine induced by different wind and wave conditions. The simulations were performed using the fully coupled time domain aero-hydroservo- elastic simulation tool FAST, made available by National Renewable Energy Laboratory. The wind and waves data used in the simulation, provided by the UTMEA-CLIM laboratory of ENEA, are typical for Mediterranean Sea conditions. The simulation results are reported and discussed. They represent a first contribution in helping to resolve basic design trade-offs among different floating platform concepts candidate for offshore wind energy deployment in Mediterranean Sea.