The world’s two most powerful wind turbines, with blades up to 500ft in diameter, are to be built on the Northumberland coast in clear view of northeast England’s most renowned shorelines.

One will tower over Blyth, a rundown former shipbuilding centre whose construction yards are being used to assemble the giant machines.

The other will stand in shallow waters just off the town where it will be used as a prototype for the hundreds of machines planned for wind farms in the North Sea.

The two machines are planned to be up to 650ft high, including their blades. At that height they would be more than 200ft taller than the current tallest turbines in Britain. They would also dwarf Nelson’s column, which is about 170ft high, and outstrip the Gherkin office tower in the City at 591ft. Each could generate up to 7.5 mega-watts of power, enough for 4,000-5,000 homes.

Such projects alarm environmentalists who warn that the thousands of giant turbines planned by the government will destroy Britain’s last unspoilt landscapes.

Others disagree. Charles Rose, director of Hainsford Energy, which was last week granted planning permission for the giant onshore turbine, plus six smaller ones, said he believed such machines could enhance the landscape. “These turbines will become icons for the whole wind energy industry,” said Rose. “What’s more, they will be largely built in this country.”

The second giant machine, to be built offshore, has been commissioned by the Crown Estate. Rob Hastings, director of marine estates at the estate, said the aim was to boost the development of tall wind turbines. “This is a great opportunity to help establish a new industrial base to advance the UK’s leadership in renewable energy.”

All the machines are to be built by Clipper Windpower Marine, a California company that runs wind farms in America.

It has taken over part of the former dockyards at Blyth next to the government-sponsored New and Renewable Energy Centre, one of the few sites in the world capable of testing the blades for such big machines.

David Still, the managing director of Clipper, said: “There are great economies of scale in building large turbines. We may eventually go even bigger.”

The sheer scale of such projects shows the opportunities and risks involved with converting Britain to wind power.

The government has said it wants to generate 15% of Britain’s energy from renewable sources by 2020. Since there are no easy substitutes for transport fuels or gas, most of this will have to come from green electricity.

Some hope the project will make the recession-hit northeast the hub of Britain’s burgeoning renewable energy industry.

Blyth is ideally placed. Its deep harbour and shipyards have placed it at the heart of the wind power industry. In 1993 Britain’s first wind farm was built around its harbour.

The nine turbines had a maximum capacity of just 300kW and stood just 140ft high.

Rose plans to replace these with the six new 2.5MW machines, each standing 340ft high, including blades, and generating eight times as much power. The larger “landmark” machine will be sited on a near-by wharf.

For now, the world’s most powerful wind turbines are in Germany where two Enercon E-126 machines were recently installed in Emden. They are about the same height as those planned for Blyth but slightly less powerful at 7MW.

However, some environmental groups warn that the rush for renewable energy could destroy landscapes.

Neil Sinden, policy director of the Campaign to Protect Rural England, said: “Climate change is the overwhelming threat to the environment but it would be madness to desecrate the countryside, one of the nation’s most valued environmental assets, in tackling it.”

Additional reporting: Georgia Warren

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