Horns Rev Offshore Wind Farm

When the world's then-largest offshore wind farm was constructed at Horns Rev in 2002, it was MT Højgaard who installed the foundations for the wind turbines.

Horns Rev Offshore Wind Farm lies 14-20 kilometres out in the North Sea, west of Blåvandshuk, Denmark. The wind and weather conditions in these waters were a major factor in the project when we installed the 80 wind turbine foundations in water depths of between 6 and 14 metres.

The difficult climatic conditions at Horns Rev made it essential that the planning of the project was meticulous, and that it was carried out in one continuous operation within a single season.

Monopile foundations driven into the seabed

The installation of the foundations was based on the monopile principle, where a single pile is driven vertically into the seabed. The monopile foundations consisted of a steel pipe weighing 125-155 tons, with a diameter of 4 metres and a wall thickness of 30-54 millimetres. The monopiles were driven into the seabed to a depth of between 22 and 24,5 metres, using a hydraulic hammer.

Top section and erosion protection

The foundation is completed with a cylindrical 80-100 ton top section, equipped with a flange onto which the turbine tower is secured, and where the internal and external platforms and a landing stage for access to the tower are established. To protect the monopile foundation against erosion, a protective gravel blanket is placed around the pile.

Installation of pile foundations from specialised vessels

The installation of the pile foundations was undertaken using specialised vessels equipped for the purpose and able to handle all stages of the installation process.