Sleipnir Lowers Hollandse Kust West Beta Topside Into Place

May 22, 2025, by Adnan Memija

Heerema Marine Contractors’ crane vessel, Sleipnir, has installed the topside for TenneT’s Hollandse Kust West Beta substation platform in the Netherlands.

The installation of the Hollandse Kust West Beta topside took place on 21 May, some 50 kilometres off the coast of Egmond aan Zee.

From this autumn, the seventh 700 MW grid connection will also be ready for commissioning, according to the Dutch/German transmission system operator (TSO) TenneT.

The topside left the Port of Antwerp on 17 May on a floating pontoon. It was then towed to Dutch waters and transported by sea to its final destination.

Equans, Smulders Load Out Hollandse Kust West Beta Substation Topside

Grid Connection

This marks the completion of the third and final 700 MW platform built by the Smulders-Equans joint venture for its client TenneT Netherlands.

“In total, this is the seventh and, for the time being, last connection for an offshore wind farm that TenneT is developing via this 700 MW standard. Meanwhile, TenneT has started the new 2 gigawatt grid connection concept in both the Netherlands and Germany, with which we will connect wind farms to the high-voltage grid from 2028,” said Marco Kuijpers, Director of Large Projects Offshore at TenneT.

The jacket foundation for Hollandse Kust West Beta was installed at the site by Sleipnir in May 2024. The same year, Boskalis and Orient Cable, working as consortium partners, laid the two export cables that will transport renewable energy from the OranjeWind offshore wind farm to the mainland.

“Inside the large steel platform, among other things, there are two power transformers that raise the voltage level from 66,000 volts to 220,000 volts for efficient transmission of the power to land. There is also over 130 kilometres of cable in the topside to connect all the systems,” said Robert Koens, Project Manager at TenneT.

RWE, in a joint venture with TotalEnergies, won the right to build and operate an offshore wind farm in the Hollandse Kust West (HKW) VII site in the Dutch tender in 2022.

Located approximately 53 kilometres off the coast of IJmuiden, the OranjeWind offshore wind farm will feature 53 Vestas V236-15.0 MW turbines. The project will have an installed capacity of 795 MW and a grid connection capacity of 760 MW. The additional 35 MW is reserved to optimise connection efficiency, even when production is lower.