The Kaskasi offshore wind project is located in the German North Sea. Image courtesy of innogy.
Construction works on the project are scheduled to start in 2021. Image courtesy of innogy.
Seaway 7 received the contract to transport and install major components of the Kaskasi offshore wind farm. Image courtesy of Seaway Offshore Cables.

The Kaskasi offshore wind farm is a 342MW wind project located in the German North Sea. The project is owned and being developed by innogy, a wholly-owned subsidiary of German energy company E.ON.

The final investment decision (FID) on the Kaskasi offshore wind farm was reached in April 2020, while the key contracts valuing more than £440m ($540m) were also awarded in the same month.

The construction works on the project are expected to be started in the third quarter of 2021 with the start of operations expected in 2022.

Upon full-fledged commissioning, the Kaskasi offshore wind farm is expected to generate sufficient electricity to power more than 400,000 average German households annually, over an estimated operational life of a minimum of 25 years.

Location and site details

The Kaskasi offshore wind farm will be developed approximately 35km  north of the island of Heligoland in the German sector of the North Sea. Heligoland is a small archipelago in the North Sea that belongs to Schleswig-Holstein, the northernmost state of Germany.

The offshore wind farm will occupy a total area of approximately 17.4km2 in water depths ranging between 18m and 25m. The average wind speed at the site is reported to be 10m/s.

Kaskasi offshore wind farm make-up

The Kaskasi offshore wind farm will comprise 38 SG 8.0-167 DD wind turbines from Siemens Gamesa Renewables Energy.

With 167m-diametre rotor, 81.5m-long fiberglass-reinforced epoxy blades and 107.5m hub height, each turbine of the wind farm will have a swept area of 21,900m2.

Incorporating Siemens Gamesa Power Boost technology, each pitch-regulated, variable speed, and direct drive turbine will have a rated capacity of up to 9MW.

The SG 8.0-167 DD turbines are designed to operate at 690V voltage and 50Hz frequency.

Turbine foundations

Each turbine of the Kaskasi offshore wind farm will be mounted on a 64m-high monopile foundation.

The monopiles will be erected using the vibro piling technology from the Dutch vibro-piling specialist CAPE Holland.

Kaskasi is set to become the world’s first wind farm to utilise vibro driving techniques for installing the monopoles.

The vibro pile driving technique will ensure the faster and quieter installation of the foundations compared to the conventional method where monopiles are hammered into the seabed.

Power transmission

The electricity produced by each turbine will be gathered and transmitted through 52km of 33kV inner array grid cables to an offshore transformer substation. The topside of the wind farm’s offshore substation will measure 40m-high and 25m-wide, and weigh 14,400t.

Electricity from the offshore substation will be transported onshore via the existing HelWin2 converter platform which is owned and operated by TenneT.

Contractors involved with the Kaskasi offshore wind project

Siemens Gamesa Renewable Energy (SGRE) received the order to supply 38 SG 8.0-167 DD wind turbines for the Kaskasi offshore wind project in April 2020.

Bladt Industries was awarded two separate contracts for the supply of monopile foundations and transition pieces for the wind turbines, as well as for the engineering, production, construction, and installation (EPCI) of the offshore transformer substation for the project in the same month.

Seaway 7, the heavy lifting business unit of Subsea 7, was contracted for the transport and installation of wind turbine generator monopile foundations, offshore substation foundation, as well as the inner array grid cables for the wind farm in April 2020.

Twentsche Kabel Fabriek (TKF) has been subcontracted by Seaway 7 for supplying 52km of 33kV aluminum core inner array cables, while CAPE Holland has been subcontracted to supply its Vibro Lifting Tool (VLT) for the installation of monopile foundations.