# Energy Productivity Potential of Offshore Wind in Poland and Cooperation with Onshore Wind Farm
## 1 Introduction  
In recent years, wind energy has become one of the cheapest sources of electricity in terms of Levelised Cost of Electricity [1, 2]. Installed cost reduction of technology as well as technology development is being observed nowadays. This, together with implemented support systems for renewable energy development, has resulted in significant increases in the installed capacity of renewable sources, including wind energy, in Poland and in other countries [3]. The increasing share of electricity generated from these sources has influenced the electricity market and prices in this market. Electricity generated from today's RESs has an impact on the stabilization of electricity prices in the wholesale market [4, 5, 6]. In Poland, during days when the value of energy generation from onshore wind turbines is close to or above half of the installed capacity--about 8 GW from onshore wind installed already--the market price of the power exchange is significantly lower than on other days [7]. This is also apparent when the value of the share of wind-generated energy exceeds 20% of the daily energy production [4]. At the same time, this technology only contributes to a certain extent to ensuring that the power demand of the electricity system is met. In addition, wind energy production is unpredictable due to weather conditions, but it is nevertheless possible to make estimates on a different time scale in terms of its quantity. For years, wind power has ranked highest in terms of volume of energy generation among renewable energy sources. In terms of installed capacity, it was only in 2021 that the installed capacity of photovoltaics globally exceeded the installed capacity of wind turbines [8]. Figure 1 presents the cumulative installed capacity in the period of 2011-2021 for wind energy and PV [1]. In 2021, for the first time, solar PV (875 GWp) reached a higher installed capacity worldwide than wind turbines (837 GW) [11]. In Europe, the installed capacity of wind technologies is still higher (236 GW) than in photovoltaic sources (193 GW). In addition, Poland's PV reached a higher installed capacity than that of wind turbines due to implemented dedicated support programs [12; 13]. Energy generation from onshore wind in Poland is characterized by high temporal variability; as an example, hourly data from the day with the highest energy production in the first half of 2022 (21 February) and the lowest one (6 March) were selected (Figure 2). In the first interval, hourly energy production was higher than 6000 MWh, and in the second period, hourly energy production for the first half of the day did not exceed 100 MWh. At that time, the total installed wind power capacity in the Polish electricity system was about 7.8 GW--onshore and offshore had not been installed until now (data as of February 2023). However, capacity utilization from wind turbines differs depending on wind conditions and is limited in Poland onshore (even for seaside areas). One of the possibilities for providing more available capacity and obtaining a higher capacity factor for wind power is the use of offshore wind turbines. This is also the main focus of research for this thesis, including the selection of a methodology for comparing wind sources as well as their complementarity and in terms of overlapping capacity in the electricity system. In terms of wind energy production, geographical diversification of production is possible [15], and in this respect, offshore wind is a potential extension of this generation's units--i.e., onshore and offshore diversification of energy production ensues [16]. As is well known, the energy production of wind turbines depends mainly on the wind speed in the area where the wind turbine is located. The assessment of wind energy potential is one of the first necessary steps in the implementation of wind turbine investments. Wind is a highly variable, dynamic element of climate, both spatially and temporally. Figure 1: Wind turbine and photovoltaic capacity in world and Europe [9; 10].