Construction begins for Hollandse Kust Zuid

4C Offshore | Tom Russell
By: 05/07/2021 Vattenfall

Vattenfall, alongside its recently announced partner BASF, has started the construction of its 1.5GW Hollandse Kust Zuid offshore wind farm. The first vessel transporting foundations to the construction site departed today.


The project 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. They are located between 18 and 36 kilometers 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.

Martijn Hagens, CEO Vattenfall Netherlands: “With the construction of the first subsidy-free offshore wind farm in the world we are starting a new chapter, demonstrating that this market is becoming mature. I am extremely proud of the step we’re now taking, bringing Dutch households and our industrial partners another step closer to fossil free living.”


The construction works for Hollandse Kust Zuid start with the installation of monopile foundations. 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.


An installation vessel transports the foundations to their offshore location and positions itself at the exact location. The ship's crane then lifts the monopile into the water and lowers it until it reaches the seabed at a depth of 17 to 28 metres. Once the foundation is in position on the seabed, a hydraulic hammer is used to drive the pile to the desired depth.


“Over the next few months, we will already install dozens of foundations,”said project director Ian Bremner. “During the winter there is a scheduled break, as sea and weather conditions are often too poor to work safely. In the spring of 2022, construction will resume, and we will install the remaining foundations followed by inter array cables and turbines. The first turbines are currently scheduled to be commissioned in the spring of 2022, with all turbines expected online by summer of 2023.”


Last month, Vattenfall and BASF agreed the sale of 49.5% of the offshore wind farm. Closing of the transaction is expected in the fourth quarter of 2021, subject to the approval of the relevant authorities.



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