NorthWind 100: New Turbine Powers Up
By Seth Kantner
The spring storms off the sea ice spun Kotzebue Electric Association’s new NorthWind 100 wind turbine into action last month, producing the machine’s first kilowatt of commercial power in the world. The NorthWind 100, a nearly quarter-million dollar next-generation prototype built by Northern Power Systems came online in Kotzebue in mid-May.
The wind turbine system recently installed in Kotzebue won R&D Magazine’s “R&D 100 Editors’ Award” in 2000. Only two other similar turbines exist – the first with the manufacturer in Vermont, and a second in Colorado at the National Renewable Energy Lab.
“It’s nice to demonstrate other equipment that can work in rural Alaska,” says KEA General Manager Brad Reeve.
The electric cooperative was assisted financially by the manufacturer, the U.S. Department of Energy and by NASA, says Matt Bergan, engineer in charge of KEA’s award-winning wind program. “(NASA is) monitoring recorded data through a dedicated computer at the site.”
NASA is interested in wind turbines for possible use on Mars, although the 45,000-pound turbine and tower still remain prohibitively heavy.
The machine was shipped to Kotzebue last summer not by space shuttle, but by old-fashioned, ocean-going barge. The pilings, which add a further ten thousand pounds, were drilled into the permafrost in April. The next prototype of the turbine, according to Bergan, is bound for Antarctica. “It (Kotzebue) is not as extreme,” says Bergan, referring to cold weather testing, “but it’s getting there.”
“We’ve maxed it out at 120 kw,” he says. “It shut itself down.” Bergan goes on to explain that at sea level air is denser — as is the colder air in Kotzebue — than the air at the test site in Colorado. This caused the turbine to exceed its 100kw recommendation at a mere 36mph.
The machine is tuned to the location, which in this case means a stronger field current to make the turbine harder to turn and to effectively slow it down. Internally, the NorthWind 100 is braked by increasing electrical resistance, and is also assisted by a disc brake as large as a washtub. One selling point of the new machine is that the tower is tubular and the turbine is enclosed in a steel box. Unlike KEA’s other ten wind generators — the 66kw Atlantic Orient Company turbines — all maintenance on the Polar 100 can be done out of the elements. “It’s still cold in there,” says Bergan. “There’s no insulation, but you are out of the wind, rain, snow.”
Bergan explains that KEA does most of the required annual maintenance on their wind turbines in the summer. “If there is a problem, I think it (the NorthWind 100) will be harder to fix, more expensive to fix.”
“It’s a much more complicated wind turbine,” Bergan says, comparing the Northern Power Systems machine to the $75,000 AOC’s. “There’s lots more wiring. Lots more controls.” For example, the generator does not have a tail fin to point it into the wind as smaller traditional upwind generators do, nor does it simply track like the three-blade downwind models. It instead relies on sensors that monitor wind direction and transmit this information to a motor that rotates the entire encapsulated turbine to face the blades into the wind.
Bergan shrugs when asked about long-term reliability, and admits it’s an unknown. Design life, he says, is rated at 20-30 years. This is tied to how many million-revolutions the bearings can turn, and on the length of the loan. “It’s interesting how finance and engineering co-mingle.”
Other than an initial oil leak in the rotation device, he says the NorthWind 100 is working well and produces not only more power than the AOC’s, but begins spinning at a lower wind velocity.
NASA’s interest in wind systems is for possible future use on Mars where Martian global dust storms can darken the red planet for a month at a time. Although at the present cost of roughly $10,000 per pound to place a payload in low-earth orbit, the 45,000 pound generator and tubular tower still remain far too heavy to ship to Mars. “There’s a lot of emphasis right now to develop lower cost heavy-mass launch vehicles,” says NASA scientist David Bubenheim.
On Earth, wind speed of about 10 meters (33 feet) per second is needed to make electricity while on Mars about 30 meters (98 feet) is needed because of the extremely thin air, says Bubenheim. The key issue at the South Pole, Mars and Alaska is maintainability in extreme environments, he says. Wind machines must be able to operate in conditions of low temperature, frost and the presence of abrasive materials such as sand.