The $1.3bn project is located 90km west of the island of Sylt in water depths between 25m and 37m within the exclusive economic zone off the German North Sea coast.

Vattenfall has 51% stake in the project while the remaining 49% stake is held by German municipal utility Stadtwerke Muenchen (SWM).

About 21 of the total 72 Siemens SWT-4.0-130 turbines planned at the site have been installed. The wind farm is scheduled to be fully commissioned by early spring-time 2017.

The project is expected to generate electricity required to power 400,000 German households. It also reduces CO2emissions of 700,000t annually.

SWM offshore wind projects head Christian Moldan said: “The according-to-plan- running erection phase of our project Sandbank is a good proof point for the fact, that the offshore business makes now profitable use of the experiences already made in previous projects.

“We were able to transfer the know-how from the “sister project” DaTysk to Sandbank and thus to carry on with our successful co-operation.”

Power generated from the wind farm will be transmitted via AC power transmission link to the high-voltage direct current (HVDC) converter station SylWin alpha.