Hollandse Kust Zuid construction behind schedule

4C Offshore | Tom Russell
By: 24/12/2021 Vattenfall

Vattenfall has provided an update on the construction of its Hollandse Kust Zuid wind farm, which started in the summer off the Dutch coast. The project fell short of its foundation installation target for 2021 but project director Ian Bremner maintains that the construction schedule is flexible enough to allow the project to recover its progress next year.


The first construction campaign saw the installation of the first few dozens of monopiles – the foundations on top of which the turbines are later installed. These foundations and secondary steel components are shipped from foundation manufacturer Sif’s yard on the Maasvlakte by the installation vessel Seaway Strashnov. This ship has a crane that lifts the monopile into the water and lowers the foundations, until it reaches the seabed at a depth of 17-28 metres. Once the foundation is in position on the seabed, a hydraulic impact hammer is used to drive the pile to the final penetration depth. During this first installation campaign, 34 of the total 140 monopiles were installed.


Ian Bremner returned as project director for Vattenfall’s flagship offshore wind project after having already worked on HKZ back in 2018. Ian looks back at the first construction campaign, and provides a peek into next year’s activities. Ian Bremner briefly served as project director on HKZ in 2018, before moving to Vattenfall’s Danish offshore wind farm
Kriegers Flak. When the construction of Danish Kriegers Flak (DKF) was nearly finished, and construction of Hollandse Kust Zuid was set to start, he transferred back to HKZ.

Commenting on his return, Bremner said: “Even though I already knew many people from the core team, there were lots of new faces as well. Stepping into the project at this crucial time right before construction started, I had to make sure that we knew exactly what to expect from each other. This is very difficult in the midst of the pandemic, with everybody working remotely. That said, it was made easier by the fact that the team was already operating in a steady state related to Covid restrictions and very used to that virtual environment. Nevertheless, it remains a challenge not being able to have that invaluable face time with the team."

“We had a challenging start, due to some unexpected technical difficulties on the foundation installation vessel”,
Ian explains. “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.


"However, there is flexibility in the start date of the second foundation installation campaign, and that allows the project to recover the installation shortfall from the first campaign. This means that the early challenges do not materially impact the overall schedule. 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.”


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.


Bremner added: “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. 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.”

“This has been a rollercoaster of a year for me, moving straight from Kriegers Flak, which was nearly finished, to HKZ, which was just at the beginning of the construction process. But delivering the world’s biggest offshore project is something that energizes me every day. The whole team and all of the contractors involved are highly motivated for this project to succeed. Cooperation has been really good at all levels. Of course, we all faced challenges and we have been able to overcome all of them. My primary focus for next year is that we continue to execute the project without incident. Health, Safety and Environmental performance is my top principle, and I will never deviate from it or compromise my position for any short term project gain. I am also energized to travel and have more opportunities to meet my team face to face. This is important to build trust and resilience– a necessity for the high stakes second campaign.”


The Hollandse Kust Zuid wind farm zone consists of two sites,
Hollandse Kust Zuid 1&2 and Hollandse Kust Zuid 3&4, and is being developed by Vattenfall which secured the rights to the projects with subsidy free bids in March 2018 and July 2019. In July, BASF and Vattenfall announced the signing of a contract for the sale of 49.5% of interest in the site to BASF.

The wind farms are located between 18 and 36 kilometres off the Dutch coast, between the Hague and Zandvoort. They will be fitted with 140 units of Siemens Gamesa 11 MW, SG 11.0-200 DD offshore turbines. Once the wind farm is operational, the 140 wind turbines will produce more than 6 TWh of green electricity annually.


Offshore construction of the wind farm will start in July 2021. Once fully operational, the wind farm will be the largest offshore wind farm in the world with 140 wind turbines and a total installed capacity of 1.5 GW. The Hollandse Kust Zuid wind farm will also be one of the first offshore wind farms in the world which does not receive any price subsidies for the power produced. The project is expected to become fully operational in 2023.

Earlier this month, Allianz Capital Partners, on behalf of Allianz Insurance Companies (Allianz), announced it has signed an agreement to purchase a 25.2% stake in the Hollandse Kust Zuid wind farm from BASF.
As agreed in a long-term fixed-price corporate power purchasing agreement BASF will receive most of the power originating from the overall 49.5% share of Allianz and BASF in HKZ.

For more information on offshore wind farms worldwide, click here.