Offshore contractor Allseas has completed the installation of the topsides of the Hollandse Kust Zuid (HKZ) Alpha wind-farm platform in the North Sea, located 20 kilometres the coast of the Netherlands.

The giant offshore vessel Pioneering Spirit carried out the installation by positioning the Alpha topside on the substructure jacket, the offshore contractor said on Tuesday.

The transformer station is one of the two topsides for the HKZ offshore grid, which will connect the offshore wind-farm area with the Dutch onshore high-voltage grid at Maasvlakte, Allseas said.

Edward Heerema, the chief executive of the Switzerland-headquartered Allseas said: “Pioneering Spirit has made a name for itself in recent years with record-breaking lifts for the oil and gas industry.

“The successful installation of the Alpha topside demonstrates the versatility of the vessel and our added value in the energy transition.”

Marco Kuijpers, TenneT 's director of large offshore projects said that “with the installation of the Alpha topside, the offshore grid that TenneT is building in the North Sea is starting to take shape”.

“Hollandse Kust (zuid) Alpha is the first connection of an offshore wind farm to the [high-voltage substation at Maasvlakte], with a capacity of 700 megawatts,” he noted.

Petrofac is the main engineering, procurement, construction and installation contractor for the HKZ Alpha offshore wind-farm project.

Significant milestone

Petrofac Group chief executive Sami Iskander said that “the safe installation of the Alpha topside is a significant milestone in the delivery,” of the key energy transition project.

The Beta topside — also with a capacity of 700 MW — is expected to follow in the first quarter of next year, Allseas noted.

The fabrication of two High Voltage Alternating Current (HVAC) transformer stations Alpha and Beta was carried out at the Drydocks World yard in Dubai.

Swedish power utility Vattenfall is building Hollandse Kust Zuid, together with partner BASF.

The wind farm will be located approximately 18 kilometres off the coast of The Hague and Zandvoort.

When fully operational, Hollandse Kust Zuid is billed to be the largest offshore wind farm in the world. The 140 turbines have a combined installed capacity of 1.5 gigawatts.

The Dutch government assigned TenneT as its offshore grid operator, subject to the latter's energy agreement with Vattenfall.

TenneT will install 1.4 GW of offshore grid connections for the Hollandse Kust Zuid site, and provide for additional flexible transport capacity. All plots will be developed by Vattenfall.

Offshore wind debut

Allseas earlier this year made its debut in the offshore wind sector by using the Pioneering Spirit to install a high-voltage converter platform for the Saint-Nazaire offshore wind-farm development in the Bay of Biscay, offshore France.

Saint-Nazaire, also known as Parc du Banc de Guerande, is the first commercial-scale wind farm in French waters.

Wind-farm focus

Several leading offshore transport and installation players with roots in the oil and gas industry are expanding their presence in the lucrative wind-farm market, as the energy transition gathers pace.

Oslo-listed Subsea 7, Malaysia’s Sapura Energy, Vietnam’s PTSC and Italy’s Saipem are among those bidding for work on global offshore wind farm jobs as they look to widen their portfolios and boost their order books, drawing synergies from their existing capabilities in the oil and gas sector.