Questions and answers about offshore wind farms

Offshore wind is one of the fastest growing sectors of renewable energy (RES) in Europe, using offshore wind energy.

The first offshore wind farm was created in Denmark in the early 1990s. Currently, 12 European countries have installations (turbines) in various sea basins. The market leader is the United Kingdom, where the installed capacity has exceeded 8 GW, and existing plans provide for reaching 30 GW by 2030. The next positions are occupied by Germany, Denmark, Belgium and the Netherlands.

PGE Baltica plans to build three offshore wind farms in the Polish part of the Baltic Sea (Baltica 3 and 2 by 2030, Baltica 1 – after 2030). Their total maximum capacity will be up to 3.5 GW.

Offshore wind farms are built mainly in the north of Europe due to favourable wind conditions – the density of wind energy in Europe is the most advantageous in the North Sea and the Baltic Sea.

The Baltic Sea is an attractive location for offshore wind farms, also due to the relatively shallow waters, lower wave height and smaller tides than in the North Sea. The Baltic Sea was the first location of the offshore wind farm – Vindeby in Denmark with a capacity of 5 MW.

Turbines can reach a height of up to 250 m from sea level – it is higher than the Palace of Culture and Science in Warsaw! The rotor blade can have up to 110 m. Technologies used in offshore wind farms are constantly developing. Parameters of turbines and infrastructure needed for their installation and maintenance are still improving.

Turbines start working at a wind speed of 3m/s, or “light breeze”. Except that this speed is measured at the height of the turbine hub, where it blows strongly than at the base in case of offshore turbines at a height of about 130 m above the water surface.  When there is a “light breeze” at 130 m, it usually blows even less at the surface. In practice, very rare (about 5% of the time per year) are the cases when an offshore wind farm does not generate energy at all.

Then turbines stop. Obviously, when they do not produce energy, all safety systems are still powered, such as navigation lighting, communication, etc. In addition, even in completely windless weather, a wind farm can provide services for the transmission network operator, consisting of the so-called reactive power compensation – very important from the point of view of the stability of the power system operation.

Over 80% of Poles believe that energy from offshore wind farms has a positive impact on the fight against climate change. Nearly 2/3 of Poles indicated offshore wind energy as the preferred way to power their home. Over 3/4 of Poles believe that offshore wind energy is a good or best way to generate energy from a social point of view – this is the result of a public opinion survey commissioned by the Polish Wind Energy Association, published in an IMF report from May 2019. To sum up, offshore energy is the society's most acceptable technology for generating electricity.

Source: PWEA report “The future of offshore wind energy in Poland”, May 2019, pages 8-9