After years of controversy, the US has approved its first offshore windfarm, which will be built off off Cape Cod, Massachusetts.

The $1bn, 130-turbine farm will lie in Nantucket Sound and cover 24 square miles, roughly the size of Manhattan. The tip of the highest blade of each turbine would reach 440 feet above sea level.

The windfarm will be built by Cape Wind Associates and was approved by US Interior Secretary Ken Salazar, who said: “This will be the first of many projects up and down the Atlantic coast.”

The windfarm has been the subject of controversy for years, with many environmental groups opposing it, although Greenpeace have always backed the project. Supporters say it would provide a clean, renewable source of energy that could meet up to 75% of the power needs on Cape Cod, Martha’s Vineyard and Nantucket. They also say it would provide hundreds of construction jobs, decrease the region’s reliance on fossil fuels and benefit the environment by lowering emissions of greenhouse gases.

At least half a dozen offshore windfarms have been proposed along the East Coast and the Great Lakes. Their relatively shallow waters make wind energy more feasible than off the West Coast, where the ocean floor drops off precipitously.

Cape Wind says it can generate power by 2012 and aims to eventually supply three-quarters of the power on Cape Cod, which has about 225,000 residents.