It is an upgrade of the company's existing 6.2MW offshore machine but will be fitted with a 152-metre rotor. The previous model had a 126-metre rotor.
The greater blade length means an increase in the swept area of about 50% and, the company claims, a 20% increase in yield at wind speeds of 9.5m/s.
The prototype has already been sold to German developer EWE, which also operates a 5MW Senvion prototype nearby.
Senvion was sold in January by its parent company Suzlon to US-based private equity group Centrebridge Partners for €1 billion.