The age of offshore wind power is about to begin in the United States, as investor Deepwater Wind starts to install turbines for the Block Island Wind Farm near Providence, Rhode Island. The Providence Journal has a report (see: "Block Island Wind Farm: Historic project enters final stage," by Alex Kuffner).
"The final round of work involves three main ships: the Brave Tern, a 433-foot-long Norwegian vessel that specializes in putting up offshore wind turbines; and two 137-foot-long support ships, the Caitlyn and the Paul, both owned by Louisiana-based Montco Offshore," the Journal reported. "All three are jack-up vessels that can extend telescopic legs down to the ocean floor and raise their hulls above the water for stability unmatched by regular floating ships." Brave Tern is the workhorse, the paper reported—able to precisely position an 800-ton load more than 300 feet above the waves. Below, the Brave Tern arrives in Rhode Island waters.
The scale of the giant turbines is a challenge for operations, not just construction, notes Wired (see: "The U.S. is finally getting its first offshore wind farm," by Brendan Cole). "The blades on Deepwater Wind’s turbines, which have been arriving at Block Island over the last month, will be almost 250 feet long," Wired points out. "That means the top and the bottom of the rotors will be separated by 500 feet or more. Anything covering that much area will have to deal with widely variable wind conditions, says Cristina Archer, a professor at the University of Delaware who studies offshore wind farms. Sometimes the wind will be the same speed across the whole turbine, but that speed will change dramatically over the course of the day. Other times, the winds can be steadily 10 miles per hour faster at the top than at the bottom." If turbulence becomes too great, the big rotor can be locked down. But the wind pressures on the structure will still be severe—requiring a heavy-duty anchorage to the sea floor.
After the Block Island facility is done, reported Wired, the developers hope to make another wind farm farther off shore—and 30 times as powerful.