Offshore wind farm
The 1.5GW Hollandse Kust Zuid (HKZ) offshore wind farm project will be developed in four parcels in the North Sea, approximately 18km off the coast of the Netherlands.
Owned by Swedish energy company Vattenfall, the HKZ is the first non-subsidised wind farm project 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 the 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 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 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 the 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 the proximity to the port of Ijmuiden, which is the maintenance hub for the HKZ wind farm.
The zone sites I and II of the HKZ wind farm, each with 350MW capacity, will cover approximately 115km² area, while the zone sites III and IV will span approximately 110km² with 750MW capacity in total.
Approximately 140 wind turbine monopile foundations will be erected and 66kV inner array grid cables, totalling to a length of 315km, will be laid, 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.
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 turbine with the rated power of 10MW 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 cost of the turbines.
The installation of the turbines is planned for 2022.
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 via 66kV infield cables. The electricity will be stepped up to 220kV at the platforms and transported via 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 via 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.
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 the sites one and two in April 2019. Subsea 7 was contracted for the transportation and installation of monopile foundations and cables in April 2020.
Sif Group will supply the monopile foundations, while Siemens Gamesa will provide the wind turbines. Swire Blue Ocean will install 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 will manufacture and supply the inter-array cable systems for connecting turbines with two offshore high-voltage stations.
Windcat Workboats will provide a hydrogen-powered boat for maintenance activities. Drydocks World is building the HKZ platforms Alpha and Beta.
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