World's Largest Offshore Wind Farm: Vattenfall Hits Halfway Mark with HKZ Turbine Installation

Cadeler's installation vessel Wind Osprey, which carries the turbine blades that will be installed later. Photo: Vattenfall/Charles Walker
Cadeler's installation vessel Wind Osprey, which carries the turbine blades that will be installed later. Photo: Vattenfall/Charles Walker

Offshore wind developer Vattenfall said Thursday it had hit the halfway mark with the installation of wind turbines at the Hollandse Kust Zuid (HKZ) wind farm offshore the Netherlands.

“We're halfway towards having constructed the world’s first offshore wind farm built without subsidies, a major milestone we can all be very proud of,” says Søren Andersen, Senior WTG Installation Package Manager Hollandse Kust Zuid at Vattenfall.

The Danish offshore wind installation firm Cadeler has been installing the turbines using the Wind Osprey jack-up vessel.

The crew working on the installation vessel started in April 2022, when COVID restrictions were still in place. 

“This meant testing procedures for each crew member, onboard quarantining, and managing the logistical process within such parameters,” says Anderson. “While the strict rules and regulations were lifted for most people in the spring, the COVID protocol was maintained on the vessel until only a couple of weeks ago to prevent COVID outbreaks at sea.” 

The jack-up vessel makes round trips with four turbines per trip. Depending on the weather conditions, the trips take between five and twelve days, Vatenfall said.

The crew works 12-hour shifts while on board in a two-week on, two-week off rotation. 

Unfavorable weather conditions can cause the crew to be delayed when transferring off the vessel, delaying their return home, which, per Vattenfall, can easily take a toll on the crew's morale. 

“A lot of credit must go to the installation team for continuing to stay on course and delivering the work, despite the challenges they may face,” says Andersen. 

The wind farm sports giant Siemens Gamesa's 11 MW wind turbines, and this is the first time these turbines are being installed in a serial setup and released for commercial production. 

The new generation of Siemens Gamesa 11 MW turbines have a rotor diameter of 200 meters, and a total height of 225 meters measured from the sea level to the top of the blade. Cadeler will have erected 140 turbines at HKZ before the end of the installation operation.

The size and weight of the turbines require thorough engineering and planning to load them onto the vessel, Vattenfall says.

"Realizing such innovative and large-scale projects without subsidies is a high-level achievement in an energy industry like this,” says Andersen. 

"Also, having biodiversity integrated into the design, with the creation of nature-inclusive designs, is really amazing and strengthens the motivation to deliver the project successfully,” mentions Andersen. “Creating fossil free living within one generation means generating renewable energy, while also preserving the marine ecosystem.”

Once completed in 2023, the 1.4 GW project will be the world's largest wind farm. Hollandse Kust Zuid is the first subsidy-free wind farm area in the world, It is expected to generate enough electricity to power more than two million households.

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