The jacket is 50 metres long, 34 metres wide and 44 metres high and is anchored to the seabed by six piles, each weighing 162.5 tonnes. The 57.7 metre long piles were drilled 46.5 metres into the seabed. The jacket was then attached to the piles. Together, this forms the foundation for one of the two transformer stations for the wind farm Hollandse Kust (zuid). The transformer platforms will have a capacity of 700MW each. The first jacket for the Hollande Kust (zuid) wind farm has been installed in the North Sea in September last year. The wind farm is developed by Vattenfall, in co-ownership with BASF.
The superstructure (or topside), the transformer station itself, will be lifted onto the first jacket at the end of this year. The topside of the second jacket is expected to follow early next year. Once the topsides have been lifted onto the jacket, the last systems will be connected, tested and put into operation. The cables of the wind turbines will then be connected and the wind farm is expected to be fully operational in 2023.
The installation of the second jacket is an important milestone for TenneT. "The past year has been characterised by uncertainty and challenges due to the COVID pandemic. Not only for TenneT, but also for our contractors and suppliers. Nevertheless, together we succeeded in achieving this performance. We can be proud of that," said Marco Kuijpers, TenneT's Director Offshore Projects.
Hollandse Kust (zuid)
The grid connection for Hollandse Kust (zuid) is located 22 kilometres off the coast of the Dutch province of South Holland. It consists of two transformer platforms at sea, each with two 220kV alternating current cables. The sustainably generated electricity is transported to land via these cables. TenneT has built a new onshore transformer station there and is expanding the high-voltage 'Maasvlakte 380kV' substation. From this high-voltage substation, offshore wind energy will be fed into TenneT's Randstad 380kV South ring. The wind energy goes to the electricity consumers in the country via the national high-voltage grid.
Connecting offshore wind energy up to 2023
TenneT is realising 3.5GW of offshore grid connections for wind farms at sea until 2023. With the completion of Borssele Alpha and Beta, the first 1,4GW has been realised in 2020. This will be followed by Hollandse Kust (zuid) Alpha and Beta and Hollandse Kust (Noord). For these wind farms, TenneT uses the same type of 700MW transformer platform five times, located close to a wind farm, and the same type of 220kV cable connection to the coast. This standardisation enables TenneT to build these projects more efficiently, faster and more affordable.
Programme Net at Sea 2024-2030
According to the follow-up "Wind at Sea Roadmap", a further 6.1GW of offshore wind farms will be developed between 2024 and 2030. This concerns the wind farms in the wind energy areas Hollandse Kust (west) and Ten Noorden van de Waddeneilanden, TenneT is again using three standardised 700MW platforms (2.1GW) for the first two areas. For the efficient connection of the wind energy areas further out in the North Sea, such as IJmuiden Ver (4GW), other techniques are needed based on direct current instead of alternating current. At least two offshore connections of 2GW each will be developed for IJmuiden Ver. In addition, a third 2GW connection is being studied for IJmuiden Ver, in parallel with the other IJmuiden Ver projects.
Offshore grid connections Germany
In the German part of the North Sea, TenneT alone exceeded the German government's 2020 target already a year in advance and operates today 7.1GW. Until 2030 TenneT's offshore grid connection capacity in Germany will be increased to approximately 17GW.