Siemens and Van Oord have installed 75 of the 150 4MW turbines at the 600MW Gemini wind farm in the Dutch North Sea.
The units are being transported from Esbjerg in Denmark to the project about 85km off Groningen.
The project, which is expected to be completed in 2017, delivered first power in February.
Gemini is being developed by four partners: Canadian independent renewable energy company Northland Power (60%); Siemens (20%); Van Oord (10%); and Dutch utility HVC (10%).
Image: turbines being installed at Gemini (Van Oord)
