The jacket for TenneT’s Hollandse Kust West Beta transformer platform has been successfully placed on the seabed off the North Holland coast.
The ready-made topside will be installed next year.
Wind farm operator RWE/OranjeWind can then connect the wind farm, which will be built at sea in a few years, to this “socket at sea”.
The jacket was sailed on a floating pontoon from the port of Vlissingen to its final destination about 53 kilometres off the coast of Egmond aan Zee.
The steel structure, 49 metres high and weighing more than 2,100 tonnes, was lifted from the floating pontoon by the lifting vessel Sleipnir (Heerema Marine Contractors) last weekend and placed on the seabed.
The jacket is firmly anchored at the four corner points using piles driven more than 50 metres into the seabed.
These piles are placed in large tubes of 10 metres that are welded to the feet of the chassis.
By filling the space between the piles and the pipes with cement (grout) you create a connection that ensures that the platform can withstand even the heaviest storm on the North Sea.
Prior to installation, the soil conditions on site were carefully examined and TenneT carefully checked whether there were any explosives from the Second World War.
A large bed of stones was then poured for a solid and level foundation. The stones also ensure that the soil under the jacket is not washed away by seawater currents.
With regular maintenance, the construction has a minimum lifespan of up to 40 years, TenneT said.
From the beach at Velsen, contractor NBOS (Boskalis / Orient Cable) is currently installing the sea cables that will connect the socket to the electricity grid in 2025.
These cables (220 kilovolts) are laid at a safe depth and connected to the land cables behind the dunes.
Through this connection, the electricity ultimately ends up in the high-voltage grid at the correct voltage (380 kilovolts) via the transformer station in Wijk aan Zee.
TenneT’s socket is intended for the wind farm that RWE/OranjeWind will have built at sea in the coming years.
The jacket (undercarriage) and the topside (superstructure) are built by the contractor combination Equans/Smulders.
The grid operator will soon bring the green energy ashore at Velsen via the 700MW grid connection, TenneT added.