With the three-legged foundations (Tripods) the wind turbines are firmly anchored to the seabed. The steel constructions weigh up to 900 tonnes and are up to 50 metres high. The so-called piles are "nailed" to the seabed with 30 to 40 metres long steel pipes with a diameter of around 3 metres. In the so-called prepiling process the steel tubes, which are weighing up to 100 tonnes, were first placed exactly at the corresponding points on the seabed by means of a ramming template and each pile was driven in with up to 3,000 hammer blows. Then the tripods were exactly placed on the steel nails. In total, around 48,000 tonnes of steel were used for the foundation of the wind farm, consisting of 40 tripods and 120 steel nails.

Bubble curtain

In order to protect the marine mammals, in the Trianel Borkum wind farm the bubble curtains were used industrially for the first time during the pile driving to anchor the tripods. A perforated tube is placed around the construction site in a ring and filled with compressed air. The evasive air bubbles create a curtain in the water that minimizes the noise generated during construction. The Trianel Borkum wind farm is the first offshore wind farm which complied with the limit set by the authorities and thereby implemented the protection of marine mammals.

40 wind turbines

The first expansion stage of the wind farm consists of 40 AREVA M5000 wind turbines with a total capacity of 200 MW. Each wind turbine has a capacity of 5,000 kW. The wind turbines with a total height of 148 metres from the waterline to the blade tip consist of a gondola, the rotor star and the tower. At a height of 90 metres above sea level the approximately 200 tonnes heavy gondola houses the transmission, the rotor bearing and the generator, the main technical systems for energy conversion. The rotor star has a total diameter of 116 metres and thus covers an area of about one and a half football fields. During the rotation of the rotor the energy of the wind is first converted into mechanical energy and then into electrical energy in the generator. The wind turbines are designed for wind speeds of up to 25 m/s which corresponds to wind force 10. At full power the rotors rotate at a top blade speed of around 320 km/h about 15 times a minute on their own axis.

Trianel converter platform

The park-internal converter platform is the "socket" of the wind farm. On two decks 20 metres above sea level the transformer platform houses the transformers to transform the generated electricity. Two large transformers convert the produced power from the 33 kV voltage level to the 155 kV voltages required for transfer to the grid connection. Both Trianel wind farms Borkum I and II share the transformer platform.

Power connection (TENNET)

The converter platform DolWin alpha with a capacity of 800 MW is the heart of the offshore grid connection DolWin 1 of the network operator TenneT. With a height of 42 metres and a floor area of around 2,600 m² it is one of the largest constructions in the North Sea. The installation weight of the platform is around 9,300 tonnes. Here, the three-phase current produced in the Trianel Borkum wind farm is converted into direct current and then transported to shore via a 75-kilometres submarine cable. The wind power reaches the converter station Dörpen West via another 90-kilometres-long land route.

Converter station Dörper West

At the converter station Dörper West in Emsland the direct current from the grid connection in the North Sea is converted back into three-phase current and finally fed into the transmission grid.