Floating offshore wind turbine for Mediterranean Sea: a comparative analysis of class I and class III wind turbines and preliminary assessment of the supply chain impact in Italy

Achieving Europe's 2030 target of 42.5% energy consumption from Renewable Energy System is crucial to reduce Green House Gases and energy dependence on volatile markets. The European Commission highlights the importance of offshore wind energy, especially floating technologies to expand wind farm areas. The European market is dominated by Class I fixed-bottom wind turbines suited for northern Europe's wind conditions, while Class III turbines for lower wind speeds are developed exclusively in Asia. This study aims to optimize power output through the development of a new offshore wind turbine with IEC-class III characteristics, optimal for the Mediterranean Sea, to improve wind resource utilization and open a new turbine production market, highlighting positive supply chain impacts. An in-house MATLAB-based tool was developed to compute technical potential and Levelized Cost Of Energy, by simulating two wind turbine classes, to compare the actual offshore reference wind turbine with a new optimal model. A floating wind farm configuration based on 10x10 wind turbines was considered with a semi-submersible platform and different turbines spacing to provide an optimal configuration. The Class III wind turbines were modelled based on the IEA 15MW wind turbine, through a preliminary analysis to select the rotor diameter, then simulating the power curve and main characteristics in more detail through WISDEM software. Wind data was gathered from CERRA and a detailed Maritime Spatial Planning was done to compute the eligible area, based on EMODnet, including shipping densities, military zones, bathymetric constraints, and protected areas. An accurate productivity methodology was developed, including wake losses according to Jensen's model and electrical losses due to internal connection and transmission to the onshore substation, for which two transmission modes (High Voltage Alternative Current or High Voltage Direct Current) were analysed. A detailed cost model was implemented, with a particular detail for the dimension of blade, platform and tower. To conclude, a preliminary impact assessment was carried out by considering the advantages of the development of an Italian steel production line, quantifying the job creation that would result from the manufacturing of the “Mediterranean wind turbine”. The optimal configuration achieved a mean increase of 7-8% of technical potential with respect the Class I reference, selecting Class III turbine as the optimal technology in about 90% of the eligible area. Despite the higher costs from upsizing the rotor, it yields a 7% reduction in LCOE for the largest turbine. Among the main findings, wind turbines with Class III characteristics result in productivity increases for the Mediterranean area that offset the cost increase and leads to a reduction in LCOE. Another significant result supporting the development of the supply chain is the number of jobs that would be created by reaching the Italian target of 2030, with a total of 1196 workers employed in three years, between steel and blade production. It is inferred that the development of such turbines and the consequent development of a supply chain, in addition to bringing positive impacts in terms of jobs and a increase in production on local companies, is necessary for an optimization of the resource for areas such as the Mediterranean, with the possibility of extending its use to areas characterized by limited winds, which today are not yet exploited.