February 14, 08
275' Tall Sway Turbine to Float 20 Miles off Shore

Sway Turbine is developing an arresting-looking turbine that will float 20 miles or more out in the frigid waters of the North Sea, where stiff, constant breezes could someday power vast fields of windmills.

Environmentalists have mixed emotions about wind power. It's clean, it's renewable, but people don't want to look at those towers. Also, it's getting hard to find spots for turbine farms in densely populated areas. The 80-turbine Horns Reef wind farm 10 miles off the coast of Denmark enjoys 20-knot winds and produces 160 megawatts at peak power (maybe 65 megawatts on average). But shallow-water projects ruin sea vistas, which is why the 130-turbine Cape Wind project planned for a location 5 miles out from Hyannis, Mass. has not been built.

Borgen's solution: put the windmills farther out, where no one but the whales can see them. "Two thousand windmills would power all of Norway's houses," says Borgen. Such a park would cover 400 square miles, a speck in the vast northern sea. The catch is that the water is hundreds of feet deep, so no ordinary concrete platform will do. Borrowing technology from the offshore drilling industry, Borgen has designed a floating, strawlike mast on which to mount his turbines. These masts will be tethered to the ocean floor by a 3-foot-wide steel pipe called a tension leg. Sway has landed a $30 million investment from Norway's oil-and-gas giant StatoilHydro.

Borgen's mast extends 275 feet above the water and 300 feet below, weighted at the bottom with 2,400 tons of gravel as ballast. Borgen strengthened his narrow structure by adding a brace-and-wire support on the windward side, similar to the wires that stabilize the mast of a yacht. The 180-foot blades go on the leeward side of the mast. To keep the turbine blades facing the wind, Borgen designed a joint at the bottom of the mast that will rotate based on a computer reading of wind direction. Read