The 1.5GW Hollandse Kust Zuid (HKZ) offshore wind farm project is under construction in an area that is divided into four parcels in the North Sea, approximately 18km off the coast of the Netherlands.

Being developed by Swedish energy company Vattenfall, the HKZ is the first non-subsidised wind farm project in the Netherlands. The company will supply the electricity generated at the wind farm to its customers in the Netherlands.

The Netherlands Government awarded the tender for the construction and operation of the first two parcels of the wind farm (Zone Sites I and II) to Chinook CV, a subsidiary of Vattenfall, in March 2018. The initial preparatory works for the parcels began in March 2019. The company won the tender for the remaining two parcels (Zone Sites III and IV) in July 2019.

The wind farm is expected to be commissioned by mid-summer 2023. The electricity generated by the farm will be sufficient to power up to three million households in the Netherlands. The project is in line with the Dutch Government’s target to produce 3.5GW of new offshore wind energy by the end of 2023.

The final investment decision on the wind farm was taken by Vattenfall in June 2020. Vattenfall agreed to sell a 49.5% stake in the offshore wind farm to BASF, a German chemicals company, for a consideration of €300m ($353m) in June 2021. The deal is subject to approval from relevant authorities and is expected to close in the fourth quarter of 2021.

BASF’s total commitment for the project amounts to €1.6bn ($1.88bn) including the funding for the wind farm’s construction. The deal is part of BASF’s aim to reduce its greenhouse gas emissions by 25% by 2030 and achieve net-zero emissions by 2050.

The construction of the wind farm began in July 2021, with the first vessel transporting the monopile foundations to be installed at the construction site. Each foundation, weighing between 735t (62m) and 955t (75m), will be installed at water depths between 17m and 28m.

Hollandse Kust Zuid wind farm location

The HKZ wind farm sites are located in the Hollandse Kust (zuid) Wind Farm Zone (HKZWFZ), which extends across an area of 235.8km².

The HKZWFZ is situated to the west of the Netherlands, off the coast of the Zuid-Holland (South Holland) and Noord-Holland (North Holland) provinces, in water depths between 18m and 27m.

It contains the operational Luchterduinen Wind Farm in its northeastern side and is enclosed by the coastline and main shipping routes of IJmuiden and Rotterdam. The northern side of the HKZWFZ is bordered by a sand extraction area, while anchorage areas are situated towards the northern and southern parts of the zone.

Conditions that favour the site include suitable seabed and water depth, ideal weather conditions and proximity to the port of Ijmuiden, which is the maintenance hub for the HKZ wind farm.

Details of the Hollandse Kust Zuid wind farm

The zone sites I and II of the HKZ wind farm, each with a capacity of 350MW, will cover an area of approximately 115km², while the zone sites III and IV will span approximately 110km² with a capacity of 750MW in total.

Approximately 140 wind turbine monopile foundations will be erected and 66kV inner array grid cables laid, totalling a length of 315km, using heavy lift, cable-laying and support vessels in 2021 and 2022.

The wind farm zone contains several active, inactive, existing, and planned cables and pipelines. The maintenance and operational activities of the wind farm will be controlled from the port of Ijmuiden.

Wind turbine details

The HKZ wind farm will be equipped with approximately 140 units of the new SG 10.0-193 DD offshore wind turbine, featuring IntegralBlade manufacturing and direct-drive technologies.

The wind turbines have a rated power of 10MW and can generate 11MW of power. The length of the rotor blades is 94m, while the diameter of the three-blade rotor of the wind turbine is 193m with a 29,300m² of swept area. The wind turbine is estimated to improve annual energy production by 30%.

The direct-drive wind turbines are lightweight and smaller in dimension with a lesser number of rating and wear-prone components. A permanent magnet generator, which requires no excitation power, is used in the turbine to improve efficiency. All these design elements reduce the installation, operation and maintenance costs of the turbines.

The installation of the turbines is planned for 2022.

Power supply details

The HKZ wind farm will contain two offshore transformer platforms, HKZ Alpha and HKZ Beta, each with AC connections of 700MW capacity.

Each platform will contain two 220kV AC export cables. Electricity generated from the turbines will be transferred to the platforms through 66kV infield cables. The electricity will be stepped up to 220kV at the platforms and transported through export cables to the existing onshore 380kV Maasvlakte high-voltage substation.

Four 550m-long pipeline sections will be drilled by controlled horizontal directional drilling under the seawall south of the Maasgeul channel. The pipelines will safely connect both platforms to the Maasvlakte substation with cables. The electricity will move to the south ring of the TenneT-operated Randstad 380kV line and then to the national high-voltage network for distribution. The HKZ Alpha high-voltage substation will be installed using Sleipnir, a semi-submersible crane vessel, and will enter service in 2021. HKZ Beta is expected to become operational in 2022.

PPA supporting Hollandse Kust Zuid wind farm

In March 2021, Air Liquide, a French industrial gas producer, entered a 15-year power purchase agreement (PPA) to off-take 100GWh of clean energy generated by the wind farm to power its factories in the Netherlands.

BASF will also acquire the electricity generated by the project, as per its ownership share, through a long-term PPA to support the production of chemicals at its sites across Europe, especially the Antwerp Verbund facility in Belgium, which is the biggest plant in the country.

Contractors involved in Hollandse Kust Zuid wind farm project

TenneT signed a contract with Vattenfall to provide offshore grid connection for the third and fourth sites of the wind farm in April 2020. The agreement for the first two parcels was signed in 2019.

Vattenfall selected Seaway 7 for the transportation and installation of 76 monopile foundations and infield cables for sites I and II in April 2019. Subsea 7 was contracted for the transportation and installation of monopile foundations and cables in April 2020.

Sif Group was contracted to supply the monopile foundations, while Siemens Gamesa is responsible for providing the wind turbines. Swire Blue Ocean was selected to install the turbines using Pacific Osprey, the flagship wind farm installation vessel.

The Van Oord-Hellenic Cables consortium received a contract from TenneT for the delivery and installation of sea and land cables for the Alpha platform. LMR Drilling was subcontracted for horizontal directional drilling for the installation of the cables and platform.

Petrofac won a contract for offshore grid connections. The company subcontracted Heerema Marine Contractors to transport and install the HKZ Alpha high-voltage alternating current (HVAC) platform.

Prysmian Powerlink and Twentsche Kabelfabriek is responsible for the manufacture and supply of the inter-array cable systems for connecting the turbines to the two offshore high-voltage stations.

Windcat Workboats was contracted to provide a hydrogen-powered boat for maintenance activities. Drydocks World is building the HKZ platforms Alpha and Beta.

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