## 1 Introduction  
It is now universally recognized that global warming and related climate changes are caused by anthropogenic emissions of climate-altering gases into the atmosphere. In order to contain the increase in global temperatures to below 1.5 \({}^{\circ}\)C, compared to pre-industrial levels, incisive measures must be quickly adopted. Following the Paris Agreement (COP21, 2015), many countries have committed to reducing emissions and various initiatives are already in place to encourage the so-called decarbonization of the various sectors. Approximately one-third of emissions is generated by electricity production, where decarbonization is strictly related to the increasingly massive energy production from renewable sources. The European Commission is one of the main players in this transition, setting ambitious and binding renewable targets for its member states. At the European level, a target of 20% and 32% renewable energy on gross final consumption was set at 2020 (Directive 2009/28/EC) and at 2030 (Directive REDII), respectively, and then was broken down into specific targets for each member state. One of the most widespread renewables installed in Europe at the end of 2019 was wind power [1], with a significant growth rate, because Europe still holds technological leadership in the wind energy sector. Wind installation transition from land to sea is due to several different factors: the land sites suitable for sustainable exploitation of wind from economic, environmental, and social resourcesare gradually decreasing. Offshore wind resources are generally higher and less turbulent than onshore ones. Visual impact, as long as you move far enough from the coast, is reduced; it is possible to revitalize the offshore industrial sector and the ports, currently in decline in many European regions, and to create jobs in the frame of a \"blue\" and \"green\" economy. One of the challenges related to offshore wind installation is the higher cost compared to land-based ones, which, until a few years ago, was not completely compensated by the higher energy production. In recent years, costs significantly reduced because of technological research in the sector and of a scale economy. In 2019, the average electricity cost from offshore wind plants winning the auctions in Europe was in the order of 50 \(\upxi\)/MWh, competitive with the land-based one [2]. Another challenge concerns the turbine foundations. Offshore wind turbines are installed on foundations where technology is borrowed from the oil and gas sector. As far as fixed foundations are concerned, the solutions are mature: monopiles are used, up to 30 m water depth, while jackets or tripods are used from 30 to 50-60 m water depth. Over 60 m water depth: floating platforms are the suitable technology; however, floating wind turbines are currently at the demonstration stage. There is still no consensus about the buoyancy design (single-column, semi-submerged, tension leg platform), the material (steel or concrete), and a number of other features. The two most advanced systems are Hywind, a ballasted monocolumn produced by Equinor (former SINTEF), and Windfloat, the semi-submersible platform produced by Principle Power. These are the only two solutions that reached the array level demonstration phase at present [3; 4; 5]. Concerning Europe, at the end of 2019, 183 GW of onshore wind power capacity and 22 GW of offshore wind power capacity were installed [6]--almost all in the North Sea. Offshore wind capacity growth in 2019 was equal to 3.6 GW [2]. The European Community expects to install 450 GW of offshore wind by 2050 [7]. Concerning Italy, the wind power capacity installed at the end of 2019 was equal to 10.5 GW, all onshore, mainly distributed in the major islands and in the southern regions, where the wind resource is higher. In 2019, the percentage of wind production on the total energy demand was 6.3% [8].