Technology

Foundation

For the Princess Amalia Wind Farm, a monopile foundation was selected. A monopile is a 320-ton steel tube with a diameter of approximately 4 metres and a length of approximately 50 metres. If the weather conditions allow it, three monopiles and three transition pieces will be loaded onto the Jumping Jack and dragged to sea. The Jumping Jack is a type of jack-up rig or self-elevating platform that fixes itself on the sea-floor using four feet and is then able to fully lift itself from the water. This is how a stable working island of 100 by 30 metres is created, from which the installation activities can take place.

The Jumping Jack has a lifting capacity of 1,200 tons and is used to drive the foundations into the sea-floor. At the start of this process, the monopile is discharged horizontally and placed vertically on the sea-floor. A special gripper ensures that the monopile is levelly positioned before it can be driven into the ground. Each monopile is driven 30 metres into the ground in approximately 2 hours.

A “J-tube” is then fitted around the monopile, leading the cables from the wind turbine to the sea-floor. The last section of the foundation is the transition piece. This forms the connection between the monopile and the tower. The transition piece is fixed to the monopile using a cement-like substance called ‘grout’.