Moonfish

Cable installation offshore wind farms Hollandse Kust (noord) and (west Alpha), the Netherlands

In 2050, all energy consumed in the Netherlands will come from sustainable sources, such as wind power. To bring this sustainably generated wind energy on land, network operator TenneT builds transformer platforms offshore. From these ‘power sockets at sea’, submarine power cables and cable connectors bring the electricity on land.

To connect the Dutch offshore wind farms Hollandse Kust (noord) and (west Alpha) with the electric grid on the mainland, TenneT called on the consortium Jan De Nul Group and LS Cable & System. Jan De Nul Group was responsible for the transport, installation and protection of the electricity cables. LS Cable & System took care of cable design and production, as well as connection and testing of circuits.

Both wind farms were connected to a transformer platform by two 220 kV high voltage cables. In total, four cables, with a total length of 210 km, establish the connection with the Dutch electric grid near Beverwijk, just north of the port of IJmuiden. With a production capacity of 1.4 GW, these wind farms supply 1.4 million households for a whole year with green power.

4
cables
210 km
Total length of the four cables
17,000 tonnes
Total weight of the four cables
1.4 GW
Production capacity
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To ensure the success of this challenging project, Jan De Nul deployed a multifunctional fleet of in-house cable installation equipment.

Our cable-laying vessels Isaac Newton and Connector brought the 210 km cables in three trips from South Korea to Wijk aan Zee and installed them on the seabed. This was first levelled by our amphibious crane Starfish and our trailing suction hopper dredger Alexander von Humboldt.

Technical leaflet Isaac Newton Technical leaflet Connector Technical leaflet Starfish

Meanwhile, our foundations expert subsidiary, Soetaert, installed four cofferdams on the beach. Thanks to these cofferdams, we were able to bury the cables seven metres down in the sand and, from there, pull them through the dunes via ducts installed by directional drilling to the onshore transition joint.   

After this beach pull-in, it was our cable trenching machine Moonfish’s turn. The Moonfish buried the cables from the beach 3 kilometres into the sea, at a depth of about 6 to 8 metres below the seabed. The long sword of the Moonfish is fitted with powerful waterjets. The Moonfish uses these to make a deep trench in the seabed, in which the cable is laid at the same time up to an 8-metre depth. The trench is backfilled immediately. As a result, the cables are properly protected against possible future coastal erosion.

Jan De Nul designed and built this innovative machine entirely and specifically for the Hollandse Kust (noord) and (west Alpha) project.

Technical leaflet Moonfish

Moonfish in numbers

250 tonnes
Weight of the Moonfish
11 metres
Height of the Moonfish
8 metres
Depth at which the cables are dug in

Would you like to learn more about our Moonfish?

The teams of our colleagues Dries Poelman (Works Manager) and Arne Baeyens (Project Engineer) worked closely together for 1.5 year to make this machine. In the video below, they present the Moonfish.  

Read more in our newsletter FOCUS!

Once our cable-laying vessels connected the cable with the Hollandse Kust (noord) and (west Alpha) offshore platforms, the submarine vehicle UTV1200 took over from the Moonfish. This machine buried the cables from 3 kilometres off the coast to the offshore transformer stations, respectively 22.5 and 55 km off the Dutch coast.

Finally, our multi-purpose vessel Adhémar de Saint-Venant installed cable protection systems and rocks on the crossing points between different existing cables and pipelines.

Technical leaflet UTV1200 Technical leaflet Adhémar de Saint-Venant
“The Hollandse Kust (North) and (West Alpha) project was truly a pioneering project for Jan De Nul, as we became the first contractor in the cable industry, able to bury cables at depths of up to 8 m under the seabed in the nearshore and inter-tidal area. Moreover, we deployed an enormous amount of work, ingenuity, knowledge and strong cooperation between all stakeholders and managed to achieve this project safely and on time.”

Ward Mertens (Project Manager Hollandse Kust (noord) and (west Alpha))

Photo gallery

We're looking for new talent!

Jan De Nul offers specific offshore services to support the energy transition. These services range from installing monopiles, foundations and wind turbine generators for offshore wind farms to installing, burying and protecting cables, umbilicals and subsea pipelines.

For its challenging offshore activities, Jan De Nul is looking for talent to help construct the energy transition.

Do you want to construct the energy transition? Check out our vacancies!