Design Optimization and Economic Analysis of an Offshore Wind Farm: the Pantelleria Case Study

In recent years Europe has seen a great development of renewable energy, in a perspective of reducing polluting emissions and transitioning to cleaner forms of energy, as established by the European Green New Deal. Among the most promising, wind energy has come to cover almost 15% of European electricity needs and is constantly growing. However, if on one side the onshore sites characterized by great wind potential and availability are already occupied by existing wind farms, the same cannot be said for offshore sites. The immense offshore wind potential, characterized by winds with higher availability and productivity than onshore ones, would allow to cover energy needs at ever higher odds and would not lead to further exploitation of the soil. Today, the main offshore wind farms consist of fixed structures, located in the North Sea and the Baltic Sea, i.e. shallow seas that lend themselves well to monopile or jackets structures. In order to extend wind farms to deeper seas, such as Atlantic Ocean and Mediterranean Sea, floating structures have been introduced from some years. These systems consist of a platform supporting the wind turbine, connected to the seabed through moorings and anchors. Furthermore, in order to transfer the energy produced to the coast, it is required an electrical system, consisting of electrical substations, array marine cables and export cables. However, the lack of standardization of these structures, the considerable size that requires large quantities of steel or concrete, the difficulty of construction and the need to employ large ships entail very high investment and maintenance costs and have partly slowed down the development of such technologies. The LCOE, although a cost reduction is expected in the coming years partly due to the development of new technologies and partly to industrial innovations, is much higher when compared to fossil fuels or other renewable sources. The aim of this thesis is to present the floating structures currently widespread, such as spar-buoy, semi-submersible and tension leg platform, to describe their main features, as well as advantages and disadvantages. Later, a hydrostatic tool, which allows for five different concepts to analyse the main hydrostatic parameters, such as metacentric height, hydrostatic stiffnesses and maximum static pitch angle, will be illustrated. This tool, implemented through Matlab’s genetic algorithm, allows to optimize the main dimensions of each platform, in order to minimize the overall cost of steel or concrete necessary for construction, while ensuring the stability and buoyancy constraints imposed by the actual Standards. Subsequently, the case study of a floating wind farm located near the island of Pantelleria will be introduced. The system, that involves the use of platforms optimized by genetic algorithm, consists of two turbines for an installed power of 10 MW. The composition of the Capital Expenditure, the Operational Expenditure and a sensitivity analysis will be described, in order to evaluate the Levelized Cost Of Energy and the main parameters that influence it, such as Capacity Factor and Wacc. Finally, it will be performed the scaling of two types of optimized platforms, in order to obtain two models that will be used to verify experimentally the stability of such structures.