Alstom installed the 6MW prototype at the Belwin 2 wind farm in October last year making it the first of the model to be put in place offshore. But it had to wait ten months for a grid connection.
The Haliade 150-6MW is installed at the Belwind facility off the coast of Belgium.
It is currently being tested to ensure it optimised for use in the sea and to see how it reacts in an offshore environment. Tests are expected to last three weeks.
The Haliade is being manufactured at Alstom's new Saint Nazaire facility. Five of the turbines will be used at the 30MW Block Island demonstration offshore project in the US.