Every year, millions of migratory birds cross the North and Baltic Seas, with some of their migration routes passing near wind farms. ‘The impact of these installations on migratory birds had been insufficiently researched,’ says the BWO. As a result, together with several companies in the sector (including EnBW, Iberdrola, Ørsted, RWE, Skyborn Renewables and Vattenfall), it commissioned a study to investigate the actual collision risk at a near-shore wind farm in northern Germany.  

Researchers obtained precise data on birds’ evasive behaviour near the wind farm, analysing over four million bird movements over a period of one and a half years.  

The results were that over 99.8% of diurnal and nocturnal migratory birds avoided the turbines, ‘a significantly larger proportion than previously assumed’, according to the BWO.

Furthermore, contrary to previous assumptions, no correlation was found between migration intensity and collisions. Even during periods of high nocturnal migration activity, very few birds flew through the rotor area, says the study.

Using a combination of a specialised bird radar system and AI-supported camera systems represented ‘a methodological breakthrough’, comments BWO, ‘enabling unprecedented accuracy in recording bird flight movements in the rotor plane’. In addition, researchers searched for ‘collision victims’ (bird carcasses) every five days. ‘This allowed for reliable conclusions to be drawn regarding collision frequency.’

‘The data refute the previous assumption that high migration intensity automatically leads to more collisions,’ continues BWO. ‘Therefore, blanket shutdowns during periods of heavy bird migration do not appear to be a sensible approach.’  

BWO Managing Director Stefan Thimm concludes: ‘With this research, we want to depoliticise the discussion, improve the data basis and make decisions based on facts.’  

Germany’s largest offshore wind farm feeds first electricity to the grid

Meanwhile, the first 15 MW wind turbine at the He Dreiht wind farm offshore Germany transmitted its first electricity to the national grid on 26 November. Further wind turbines will gradually follow suit over the coming weeks. Electrical utility and majority shareholder EnBW has so far installed 27 out of a total of 64 wind turbines, which are all set to be commissioned by summer 2026.

Boasting a total output of 960 MW, producing some 3.6bn kWh a year, He Dreiht will be Germany’s largest offshore wind farm to date. The V236-15 15 MW turbines are being supplied by Vestas.  

A single rotation of the rotor on the 15 MW wind turbine is reported to be enough to supply the equivalent of four households with electricity for a day. At a hub height of 142 metres, the rotor with a diameter of 236 metres sweeps through an area of 43,742 m² per revolution – equivalent to the area of six football fields. By way of comparison, the output of the turbines installed by EnBW in 2010 on the EnBW Baltic 1 wind farm is 2.3 MW, notes the wind operator.

He Dreiht is capable of generating enough electricity to meet the needs of around 1.1 million households, adds EnBW.  

The wind farm is being built about 85 km north-west of Borkum and 110 km west of Heligoland, close to the commissioned Albatros and Hohe See wind projects. Once fully commissioned it will almost double the company’s offshore portfolio from its current 976 MW.

A consortium of Allianz Capital Partners, AIP and Norges Bank Investment Management holds a 49.9% stake in He Dreiht.  

He Dreiht offshore wind farm  

Photo: EnBW/Rolf Otzipka