First Installation Campaign at Largest Offshore Wind Farm Under Construction Falls Short

34 out of the 140 monopile foundations were installed at the 1.5 GW Hollandse Kust Zuid wind farm offshore the Netherlands in the first installation campaign, falling short of the target set for 2021, Vattenfall said.

Illustration; Seaway Strashnov installing monopiles at Hollandse Kust Zuid: Photo source: Vattenfall (archive)

The first offshore construction phase at the subsidy-free wind farm started in early July.

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The monopile foundations without transition pieces were transported from Sif’s yard on the Maasvlakte and installed at the site by the heavy-lift vessel Seaway Strashnov.

Seaway Strashnov installing monopile foundations at Hollandse Kust Zuid
Source: Vattenfall

”We had a challenging start, due to some unexpected technical difficulties on the foundation installation vessel,” HKZ project director Ian Bremner said.

”However, once those were resolved and we were up and running, things went really well, and the pace of installation was meeting our expectations. Unfortunately, further technical difficulties interrupted the momentum and we never quite recovered the earlier performance. The delays pushed the works further and further into adverse weather periods to the point where it was no longer viable to continue. This translated into us falling short of our foundation installation target for 2021.”

Bremmer added that the flexibility in the start date of the second campaign will allow the project to recover the shortfall from the 2021 campaign.

”This means that the early challenges do not materially impact the overall schedule,” Bremner said.

”In fact, this first campaign has provided us with lots of opportunity to learn key lessons that we can use to plan and optimize the second campaign, which is a lot more time critical. We are confident that foundation installation performance will improve next year.”

2022 Campaign

The second campaign should start at the beginning of March, with the installation of the remaining 106 monopiles.

Next spring, the first cables and turbines will also be installed. The turbine strings will need to be connected to the offshore substations ready for energization and delivery of first power. The team is using the coming winter period to prepare for this new phase, Vattenfall said.

”We are performing a great deal of programme analysis and detailed planning to be 100 percent prepared for these first connections to the substations and delivery of power to the grid,” Bremner said.

”We have to manage some very complex interfaces between cable and turbine installation and commissioning. There are so many activities taking place involving so many teams and contractors, and all activities are highly interconnected. We are turning every stone to make sure the planning is perfect and that we have all of our risks in clear view and mitigated.”

Hollandse Kust Zuid is being constructed at the site located between 18 and 36 kilometres from the Dutch coast, not far from The Hague and Zandvoort.

Vattenfall, who won the development rights for Hollandse Kust Zuid’s four sites in two Dutch tenders, is building the project together with its partner BASF, who recently bought a 49.5 per cent stake in the project.

The wind farm will feature Siemens Gamesa 11 MW wind turbines scheduled to be fully commissioned in 2023.

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Once completed, HKZ will be the largest operating offshore wind farm in the world.