BUILDING IN RHODE Island isn’t easy. Hurricanes and tropical storms barrel through its quaint coastline towns, interrupting perfect summer weekends. Freezing winters bring blizzards that can shut down the entire state. And every season features corrosive salty winds, biting at the coast as if sent by a Britain still seething at the first American colony to declare independence.But one company sees the state’s incessant wind as a utility. Deepwater Wind has partnered with General Electric Renewable Energy to build the first offshore wind farm in the United States, off the coast of Block Island. Hooked up to the grid by the end of 2016, the system could supply 90 percent of the tourist destination’s power within the next few years. But it hasn’t been easy. Designing and building spinning fans hundreds of feet tall that stay sutured to the ocean floor in the face of currents and wicked winds has taken almost three years of work.