The topside for TenneT’s Dutch offshore platform Hollandse Kust (west Alpha) is set to leave Belgium’s Port of Antwerp for its final destination 50km off the coast of Egmond aan Zee.
Measuring 47 metres long, 35 metres wide and 25 metres high, the large steel box weighing over 3600 tonnes is ready to be placed on the jacket at sea after being successfully placed on a floating pontoon.
This foundation was been firmly anchored to the seabed last year. Almost two years after the first steel cut, this is the second topside built for TenneT by the Equans/Smulders combination.
“First, the floating pontoon is towed to the port of IJmuiden,” said construction manager on behalf of TenneT Matthijs Knollenburg.
“As soon as all weather conditions give the green light for the installation on the jacket, the pontoon will sail to its final destination at sea.
“At that time, the crane vessel Thialf of Heerema Marine Contractors is also on its way from the Norwegian port of Stavanger to that location.”
As soon as the two vessels meet at sea, the pontoon moors against the Thialf.
“The topside is then ‘loosened’, after which the crane vessel lifts the construction into the air,” said Knollenburg.
“Once the pontoon has been towed away, the Thialf will sail for another 500 metres towards the jacket. So-called cones are attached to the jacket.
You can compare this with inverted ice cream cones with which you can lower the topside exactly in the right place without too much measuring.”
After installation, a hotel barge is placed next to the platform so the Equans team can start the welding work to fix the topside. Earlier this year, the two sea cables, with which the green electricity from the wind farm will soon come ashore, were installed by Jan de Nul Group.
The ‘socket at sea’ will be ready for commissioning before the end of this year.
In 2025, Ecowende (a joint venture of Shell and Eneco) will place the 54 wind turbines in the offshore wind farm and connect them to TenneT’s ‘socket’. With an installed capacity of approximately 760MW, Ecowende can green approximately 3% of the current Dutch electricity demand.
The wind farm is scheduled to be commissioned in 2026.