The world’s largest offshore wind farm: The Big Project London Array

The Engineer
June 25, 2012

Providing power: electricity is taken from the turbines and transferred to the shore

Of all the components that will make up the UK’s new energy landscape in the coming decades, wind is perhaps the most contentious. Supporters and opponents are seemingly entrenched in their positions, with the intermittency of wind being the biggest stumbling block to the acceptance of wind turbines and farms.

For the supporters of wind energy, the potential of offshore wind is the trump card; stronger, more sustained in magnitude and direction, and much less intermittent than onshore wind, the wind out to sea is said to offer real possibilities for the reliable generation of renewable power.

But it’s far more difficult to build off shore than on shore, and, as yet, there are no really large offshore wind farms. The current largest is Walney Island, off the coast of Cumbria, whose 102 turbines have a combined capacity of 367.2MW and power some 320,000 homes in the north west. Even that is a newcomer to the UK’s energy mix, coming on stream less than a fortnight before The Engineer went to press.

But Walney is fairly modest in size. A far larger installation, billed by its developers as the world’s first truly industrial-scale wind farm, is currently under construction. The London Array, sited in the outer Thames Estuary between the Kent and Essex coasts, will have a generating capacity of 1,000MW, making it the first wind farm to have a capacity comparable to a land-based power station; for comparison, the Sizewell B nuclear power station has a capacity of almost 1,200MW.

The site for the London Array is between two bastions of the British seaside resort, Margate and Clacton, around seven miles off the shore and in water up to 25m deep. Covering an area of about 230km2 (90 square miles), the array will, when complete, consist of 341 separate turbines, each with a capacity of 3.6MW.

The story of the London Array began in 2001, when a survey of the estuary identified the area as being suitable for a large wind farm, having high wind speeds; a range of water depths suitable for turbine installation; nearby ports for construction, operation and maintenance; suitable ground conditions; an accessible high-voltage network connection; and, not least, a ready demand for electricity. When complete and fully online, the array will generate enough electricity for 750,000 homes, its developers claim, which is about a quarter of Greater London’s population.
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