National Geographic: Even with the Obama administration’s approval of the nation’s first offshore wind energy project–the long-disputed Cape Wind farm in Massachusetts’ Nantucket Sound–experts still see one major barrier to harnessing coastal renewable power in the United States. This time, it’s not Ted Kennedy. It’s the cost. Primarily because of the need for more robust turbine parts to withstand tough weather conditions and salty water, offshore wind energy costs about twice per kilowatt-hour …