Wind turbine installation in the North Sea

On assignment for Norwind, NGI participated in the installation of offshore windmills in the German sector in the North Sea. NGI also  verified the installation of the foundation piles of the wind turbines.

Alpha Ventus is the first offshore wind farm project in Germany, located 4 km from the shore West of Borkum reef. The farm includes 12 wind turbines. The reasons for the remote location of the park are the favourable wind conditions and the already existing marine park closer to shore. After completion, Alpha Ventus will produce power sufficient to service 50 000 dwellings.

NGI was contracted by Norwind to measure the exact pile top positions after piling 30 metres below the sea surface. These measurements are very important as the jacket structure for the wind turbine is to be directly inserted onto the piles, and the jacket-pile fit must be within very tight tolerances.

NGI also did the monitoring and control of the final pile driving, ensuring that the piles were level, and with the correct inclination. The operational criteria were critical because the levels of the piles are determinant for the verticality and efficiency of the wind turbines. The piles were installed within centimeter precision, which was absolutely within the acceptance criteria .

On each location, four foundation piles were installed, two- metres in diameter and 30-40 m into the seabed. The installation took longer time than anticipated, due to both difficult weather conditions and the stringent requirements on tolerance.

The wind turbine project Alpha Ventus in the North Sea.