Democrat Joe Kennedy III won the congressional seat vacated by retiring Massachusetts Democratic Representative Barney Frank after breaking with the Kennedy tradition on offshore wind.

Kennedy, whose grandfather was former U.S. Attorney General and New York Senator Robert F. Kennedy, last month broke with his great uncle, environmental activist and attorney Robert F. Kennedy, Jr., and his great-great Uncle and longtime Democratic Massachusetts Senator Edward Kennedy, by endorsing the controversial Cape Wind offshore wind project.

The 420-megawatt Cape Wind installation, to be composed of 120 3.5-megawatt Siemens (NYSE:SI) turbines, could begin construction by 2014. It is likely to be the first large-scale U.S. offshore wind undertaking despite the fact that it has struggled against intense opposition from the monied residents of Cape Cod since it was proposed in 2001. Led by patriarch Senator Ted Kennedy, the Kennedy family joined the opposition to the Nantucket Sound installation, which will be distantly visible from the beachfront of the clan’s Hyannis Port compound.

“The Cape Wind project would double the amount of alternative energy produced in Massachusetts and create good-paying jobs,” Joe Kennedy told a newspaper in his congressional district. “Offshore wind is one of the resources Massachusetts is blessed with.” 

Cape Wind has obtained all necessary permits and holds power purchase agreements with National Grid and NSTAR that were approved, despite higher than average prices, by the Massachusetts Department of Public Utilities (MDPU). The MDPU decision was validated by the Massachusetts Supreme Court, which found offshore wind offers the state “unique benefits,” such as emissions-free peak demand electricity, that justify the higher power prices.