RWE Innogy will hold a 60 per cent stake in this joint venture, with Stadtwerke München holding 30 per cent and Siemens the remaining 10 per cent.
The total investment, which will be divided between the partners, amounts to more than €2bn (£1.7bn), including the grid connection to the coast.
Gwynt y Môr is to be built with an installed capacity of 576MW in Liverpool Bay off the North Wales coast. Work will start towards the end of 2011 to erect the first foundations for a total of 160 wind turbines.
All permits for the wind farm, covering an area of 79km2, have already been obtained.
In its first phase of expansion, the wind farm is planned to generate electricity as early as 2013. The project is expected to be completed in 2014. From then onwards it is forecast to generate around 1,950 gigawatt hours of electricity annually, which is claimed to be enough to supply 400,000 households.
For this project, Siemens Energy will receive the contract for the supply, erection and maintenance of the wind turbines, plus electrical connection to the mainland. The value of the contract for Siemens is around €1.2bn.
Using high-voltage sea cables, power will be transmitted to the Welsh town of St. Asaph and then distributed by inland distribution. Siemens will also be responsible for maintenance of the wind farm for five years, with the option of an extension for a further seven years.
To build Gwynt y Môr, RWE Innogy has arranged for another offshore construction ship to be built by the Korean shipyard Daewoo.
The first of these offshore construction ships, the largest in the world, was ordered by the company at the end of last year for the erection of the German offshore wind farm Nordsee Ost (North Sea East). The order value for each ship is around €100m.