The €2.9 billion agreement covers 300 turbines that will be supplied to UK projects between 2014-17. Dong has acquired the 154-metre rotor version of the turbine, which will feature what is currently the world's longest turbine blade.



Under the deal, Dong will pay Siemens a cancellation fee in the event the total orders do not go through.

It is the first major deal for Siemens 6MW. The only other contract is for the 30MW Block Island test project off Rhode Island.

Dong and Siemens have a long history of working together and have jointly developed the 6MW machine. In January 2011, Siemens signed a DKK 450 million (€60 million) research and development agreement with Dong for the machine.



Under the deal, Siemens supplied two of its 6MW direct-drive turbines for testing at Dong Energy’s Avedore Holme test site.



It is likely a proportion of the turbines will go to the 1GW combined Heron and Nord projects within the Hornsea Round 3 zone. Dong, acquired a 33% stake in the zones from Mainstream Renewable Energy earlier this year. Additionally, Siemens is also a stakeholder within the Smart Wind consortium that won the Hornsea tender and is set to build a factory at nearby Hull.



Dong also has a stake, alongside Centrica, in the 4.3GW Celtic Array Round 3 concession in the Irish Sea. Earlier this week, the two released plans to develop the 2.2GW Rhiannon project within the zone.



Speaking about the deal, Carsten Krogsgaard Thomsen, Acting CEO of Dong said: "The agreement will enable Dong to install a significantly larger turbine from 2014 compared to the turbines, we know today. The agreement is a key element of DONG Energy’s strategy to significantly expand offshore wind and will strengthen our position as market leader in the offshore area."

In November 2011, Siemens launched a version of its 6MW offshore turbine with a 154-metre rotor. The first 6MW direct-drive turbine was launched in June this year with a 120-metre rotor.

The turbine is to replace the company's popular 3.6MW offshore machine, dubbed the workhorse of the offshore sector.