A German company called RePower Systems is in the process of installing the world's largest wind turbines offshore in the Scottish North Sea. The turbines are rated at 5MW, and have a rotor blade diameter of 126 metres (413 feet) – the size of two soccer fields when spread out. They've been operating as a prototype at the onshore location of Brunsbüttel with an availability of over 95% since 2004.
RePower says the wind turbines (each weighing 900 metric tonnes in total) will be transported 25 kilometres on the open sea at the beginning of August, to be mounted on special jacket structures anchored underwater at a depth of 44 metres with the help of a floating crane. A premiere not just for REpower, but also for offshore wind energy in general: never before have turbines been assembled in such deep water.
REpower is participating in the "Beatrice Demonstrator Project" to test the performance of the 5 megawatt turbine on the open sea and to take a step closer to achieving its goal of making wind energy competitive. Two 5Ms are to be installed near the Beatrice oil field in Moray Firth, 25 kilometres off the Scottish East coast and at a water depth of over 40 metres. The demonstrator project is part of the EU-supported "DOWNVinD" project, Europe's largest research and development programme in the field of renewable energies with a total volume of EUR 30 million. Talisman Energy (UK) and Scottish & Southern Energy (SSE) are the coordinators of the project, in which a large number of research and development organisations are participating from all over Europe. REpower is the exclusive turbine supplier.
Website: RePower 5M
See also this older article from RenewableEnergyAccess about the 5M turbines.