Offshore construction Hollandse Kust Zuid wind farm progressing well: “It is a great feeling that all our ideas are now put into practice”

The offshore construction on the Hollandse Kust Zuid wind farm officially started on the 5th of July. Since then, the first series of monopiles have successfully been installed, with dozens more to go this summer. Malte Röder, together with his team, has been preparing the installation process for the past year as Hollandse Kust Zuid’s foundation installation manager.

Over the next two years, Hollandse Kust Zuid – the world’s first subsidy-free offshore wind farm – will be built off the Dutch coast. The fossil-free energy generated by the wind farm will benefit both households, businesses and industrial partners. As installation manager, Malte and his team make sure that the foundation installation work is well prepared and executed in a safe manner. Malte: “We always try to identify who’s best suited to perform a certain task and work collaboratively towards the same goal.”

Special designs

Malte started working on Hollandse Kust Zuid in the summer of 2020. “We started with the design for the installation tools and methodology and together with Seaway 7 we worked towards a suitable concept for the installation of our foundations.” To guarantee efficient use of materials such as steel, each foundation is designed specifically for the location where it will be installed. The heaviest and largest monopile weighs 955 tons and is 75 metres long, while the lightest and shortest foundation still weighs 735 tons and is 62 metres long. The monopiles will be installed in water depths varying from 17 to 28 metres.


While smaller parts for Hollandse Kust Zuid are stored in IJmuiden and shipped from there, the 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.

Malte: “We will install as many foundations as possible this summer. At the end of summer, we have to take a scheduled break, because weather conditions on the North sea will be too rough to work. During this break we work to improve and optimize our work procedures to ensure that the remaining monopiles will be installed as smoothly as possible next year.”

Lessons learned

The first series of foundations and secondary steel components have now been installed and have already provided some valuable lessons for the rest of the installation campaign. ”One of the lessons we took from this first series of installations is that a couple of bolts and nuts did not work quite as they should. These kind of practicalities are now popping up, because previously we mostly focused on the big parts fitting together. With the construction being far away from shore, you do not just bring new bolts to the construction site. We also have to make sure that other type of bolts have the same lifespan as the rest of the foundation. Plus, everything is so big that you cannot just buy parts in the store.”

“We have also made some improvements already to the preparation of the workplaces. Construction technicians need to have their equipment right next to them, so that they do not need to search for the right tools. It is details like this that you come across when you actually go into construction.” Overall, Malte is very happy with the progress and the collaboration between Vattenfall, Sif and Seaway. “It is great to see all our ideas now put into practice, and work with so many great people who are all very excited about this ground-breaking project.”  

Photos: Vattenfall

Follow Vattenfall

About Vattenfall

Vattenfall generates and supplies electricity, heating, cooling and gas as well as offering customers a variety of sustainable solutions. Vattenfall want to achieve fossil-free energy generation within one generation. This Swedish energy company is investing heavily in wind energy to achieve this aim. We are working towards a sustainable world, for now and in the future.