The bank is investing £241m to jointly purchase, alongside Japan’s Marubeni Corporation, a 50% stake in the Westermost Rough offshore wind farm, from DONG Energy. The deal is estimated to be around £500m.

Once operational, Westermost Rough will generate more than 800GWh of net renewable electricity, equivalent to the electricity consumption of around 200,000 homes, a city the size of York.

In addition, GIB has also agreed to acquire a 10% stake in the Gwynt y Môr offshore wind farm, from RWE Innogy for £220m. The project, off the coast of north Wales, is in the late stages of construction.

The largest offshore wind farm under construction in Europe, Gwynt y Môr will generate more than 1,700 GWh of net renewable electricity each year once operational. This is equivalent to the electricity consumption of around 400,000 households or meeting the electricity requirements of a city the size of Bristol.

The GIB says the proceeds of both sales are expected to be reinvested back into renewable energy projects in the UK.

GIB chief executive, Shaun Kingsbury, said: “The UK has ambitious plans to build on its position as a world leader in offshore wind. We have two roles to play in supporting those plans. Firstly, to directly invest to help developers recycle their capital into the next wave of new renewable energy projects. Secondly, to invest on fully commercial terms to create a demonstration effect which others will follow.”

The Westermost Rough project will use Siemens’ next generation 6 MW direct drive turbines, which are almost twice the size of the majority of wind turbines operating in UK waters.

According to the GIB, this is the first time these new turbines will be commercially deployed in the UK and the project is the first time that the bank has taken construction risk in an investment.

Kingsbury said: “DONG Energy’s Westermost Rough wind farm is a critical project in the development of the UK’s offshore wind sector. For the first time we will see the commercial deployment of a 6 MW wind turbine, almost double the size of the typical existing turbines. This is an important step in reducing the costs of offshore wind construction and power generation.”

The investment follows manufacturing giant Siemens and its partner Associated British Ports (ABP) announcement last week that the two groups are investing a total of €371m (£311m) in new offshore wind production facilities in Britain.

Commenting on the GIB’s announcement, WWF-UK head of climate and energy policy Nick Molho, said: “The Green Investment Bank’s decision to invest in two offshore wind projects and support the use of the latest turbine technology in one of them provides a much needed boost to the sector.

“Coupled with a decision by Siemens last week to develop an offshore wind factory in the UK, this is helping to create the conditions needed to cut the cost of offshore wind in the years to come and provide important benefits for our economy,” added Molho.

Leigh Stringer

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