## 2 Literature Review
### Wind Energy
#### 2.1.2 Offshore Wind Energy in the World  
The offshore wind sector has grown exponentially since 1991, when the world's first offshore wind farm was built off the coast of the city of Vindeby, Denmark [22]. This park consisted of 11 offshore wind turbines, with a unit capacity of 450 kilowatts (kW), making a total installed capacity of 4.95 megawatts (MW) [13]. Between 1991 and 2001, several experimental projects were carried out, with the construction of several offshore wind farms operating in the EU (Table 1). The different models of wind turbines and different types of foundations were tested. Wind turbines of 450 to 600 kW of nominal capacity were used for these projects, with distances up to 7 km from the coast and depths up to 10 m [12]. In 2002, one of the largest offshore wind farms so far was built in the North Sea, located at Horns Rev, Denmark. This park consisted of 80 Vestas wind turbines, producing an installed capacity of 160 MW. The construction of Horns Rev I was a very important step in the establishment of the offshore wind industry, given that it was the first park to make use of many technologies, which have since become standard in the offshore wind industry. Since 2007, offshore wind energy has been growing vigorously, with a progressive increase in the size and power of equipment, as well as in increasing the distance from the coast and the use of higher depths, contributing to a total of more than 30 wind farms offshore in the EU in 2008 [18]. At the beginning of 2011, 1247 wind turbines were operative, corresponding to 49 wind farms, in nine European countries [23]. In 2012, offshore wind energy gained importance and experienced growth worldwide, marked by a 10% representation of this type of energy produced in Europe. This year, it contributed about 4100 MW worldwide, where about 1/3 were produced in Europe, especially in the United Kingdom, Germany, Italy, Spain, Sweden, and France [24]. The year 2017 was the most relevant year for this sector for various reasons, including the development of the project for the first offshore wind island, which significantly increased the total installed capacity in Europe. Additionally, new economic regulations were introduced, which encouraged investment by countries such as Germany and the Netherlands. This year was also marked by the expansion of offshore wind energy in northern Europe, later extending to Asia, North America, and other countries [16]. At the end of 2017, this type of energy was already installed in the ocean waters of eleven European countries, with approximately 84% (15,780 MW) of all offshore wind farms in the world. Of the remaining 16%, a large part was in China, followed by Vietnam, Japan, South Korea, and the USA [16]. By the end of 2018, 17 countries (11 in Europe, 5 in Asia, and 1 in North America) had offshore wind capacity. The United Kingdom maintained its leadership at full capacity (8 GW), followed by Germany (6.4 GW), China (4.4 GW), Denmark (1.3 GW), and Belgium (1.2 GW) [25]. In 2019, this type of renewable energy had a 24% share in new installations in Europe, with a record 3627 MW of new capacity connected to the grid. About half of the installations were in the United Kingdom, with an installed capacity of 1764 MW, and the rest in Germany (1111 MW), Denmark (374 MW), Belgium (370 MW), and Portugal (8 MW) [25]. Currently, more than 100 offshore wind farms are active in Europe [26], including the Hornsea One offshore wind farm, located in the North Sea, in the United Kingdom, with a capacity of 1218 MW [25; 27].