## 1 Introduction  
Recent years have witnessed a significant growth in offshore wind energy production. As compared to other renewable energy sources, it has been developing most rapidly. In Europe, the power accumulated in offshore power plants is now 12.6 GW. In 2016, wind energy production was the target of many energy production industry investors. In Europe, the amount of 27.6 mld. \(\mathbf{\epsilon}\) has been spent on this kind of investments including 18.2 mld. \(\mathbf{\epsilon}\) for offshore wind farms. The number of land investments has dropped by 5% (down to 9.4 mld. \(\mathbf{\epsilon}\)), which is the first drop reported during the last few years. It is expected that by 2030, 7-11% of electric energy in the EU will be produced in offshore wind power plants. It is estimated that by the year 2030, the cumulative capacity installed in European offshore energy power plants will range from 65 to 85 GW [1; 2; 3; 4]. The technical resources available to investors for development of offshore wind energy production in Europe is impressive. An analysis of areas to be used for this kind of investment (with the exception of, for example protected areas such as NATURA 2000--protection area of natural habitats and species specific types within the territory of the European Union, areas used for fishing and sailing or strategic ones) shows that most of them are characterized by a high coefficient of electric energy production (above 10,000 TWh/year/100 km\({}^{2}\)) [2; 5; 6]. A typical wind farm consists of nearly 8000 different elements, whereas, the most important ones are: rotor with blades, gondola, tower and a foundation. Figure 1 shows the technological environment of an offshore wind farm with the most commonly used types of foundations. Monopile is the most popular type of foundation (74% of European offshore installations) due to the low construction costs, simplicity, and the possibility of being used in shallow water (less than 20 m deep). The post is drilled or bounded into the sea bottom. In the beginning, a GBS (gravity-based structure) was used in shallow water (up to 15 m deep); currently it is being adjusted to bigger and bigger depths (nearly 30 m). A large area and the weight of the foundation protect the power plant from the forces of waves and wind. The foundation of bases of the tripod and triple type are fixed on three posts so that they can be used in deeper water. Three ends of the base are set or bounded into the sea bottom to support the central axis of the installation, connecting the axis with a turbine. Whereas the foundation of jacket type consists of a larger structure made of steel bars which are symmetrically sited beyond the main axis of the entire structure (efficiency of materials) [2; 7; 8]. The major differences between construction of a land and an offshore wind farm are caused by the impact of two factors: the sea environment and high installation costs. Nowadays, investment costs involved in construction of an offshore power plant can be even two times higher than for the land power plant. Offshore turbines must be more resistant to corrosion, easy to maintain, and have high storm resistance. Therefore, materials, specialist coat systems, and compartments with filtered and ventilated air need to be used for protection against the effect of salty mist. The anchoring system and the structure of the tower need to take into consideration such factors as: tides and currents,  
Figure 1: Technological environment and methods used for offshore wind farm anchoring. Authors’ own work. height and power of waves, ships, icebergs, increased turbulences, and wind power during storms. The design of an offshore wind farm needs to take into account the environmental and ecological aspects--particularly it needs to focus on avoiding disruption of the water ecosystem in the location site. They cannot be situated within the flyways of birds.