April 29, 2010 could be the date looked upon years from now as a turning point in U.S. renewable energy policy and production.

Nearly a decade after the 2001 proposal, a slew of court victories and state approvals, and a largely favorable environmental impact analysis report by the federal government, the Cape Wind was yesterday approved for construction yesterday by U.S. Interior Secretary Ken Salazar. The 130-turbine wind farm — to be sited at Horseshoe Shoal in Nantucket Sound off the shore of Cape cod, Massachusetts – will be developed by Energy Management Inc. At peak generation, the entire project is expected to generate 468 megawatts (mW) of electricity, enough energy to meet 75 percent of energy needs in Cape Cod.

As detailed in the Cape Wind plan, 440-foot-tall wind turbines will float five miles off the southern coast of Cape Cod, Massachusetts.

Proponents of the Cape Wind project, such as Massachusetts Governor Deval Patrick and Communications Director for Cape Wind Mark Rodgers, say that the wind farm will boost the Massachusetts economy and give the state a reliable, in-state source of electricity. It will also improve the air quality of Cape Cod, which the American Lung Association says has the worst quality of air in Massachusetts.

Critics argue that the project is too costly, with construction cost estimates ranging from $ 1 billion to as high as $2.6 billion. Other arguments focus on the project’s potential aesthetic and environmental impacts. According to to the Cape Cod Times, lawsuits aimed at blocking construction are almost an inevitability.

The road thus far, to federal approval, has been a long one. Seventeen different federal and state agencies were required to sign off on the proposal under the National Environmental Policy Act and the Massachusetts Environmental Policy Act. The first signs of approval came in 2004 when all agencies returned with positive draft environmental impact statements.

Wednesday’s momentous decision came two months after Secretary Salazar announced that he was considering a decision on the Cape Wind project.

Offshore wind farms are roughly twice as expensive as land wind farms, but have significant advantages. The most energy-consuming communities are mostly located along the coasts. Offshore wind farms can provide those communities with wind power without having to build extensive, over-land transmission lines. Ocean breezes are also stronger than inland winds, and if built far enough off the coast, the turbines will not shield the view from locations in Cape Cod that have become tourist destinations based on the scenic views they provide.

The Cape Wind project is not only a major milestone for the country, but also for Massachusetts, which has enacted a number of pro-solar policies, including provisions for solar energy rebates, favorable net-metering standards and solar access laws.