Image credit Lloyd Alter
It was hard to find anyone to speak to at Greenbuild about the odd looking Honeywell Windtronics turbine; it was a busy booth. But I got to see it again at the Cottage Life Show in Toronto and it is actually very interesting; instead of the usual design where the blades turn a shaft which is connected to a generator, here the whole thing is a generator, with magnets at the tips of the blade whizzing past stator coils in the ring on the perimeter.
Windtronics claims that building the turbine this way drastically reduces mechanical resistance, and gives greater energy production at low wind speeds, as shown on the graph above. The designer, Imad Mahawili, told Popular Mechanics last year:
"It takes 7 to 8 mph to overcome the resistance of gears," Mahawili says, "and the loss from gears on average at any speed costs about 20 to 25 percent in aerodynamic efficiency." So Mahawili removed the gear system, replacing it with a simple hub and bearings. Then, "We looked at the wheel system, near the hub," Mahawili says, and found that "for 1 rpm [revolution per minute], the velocity at the rim of the wheel is nine times faster." In response, he placed the magnets that he uses to create electricity (in place of a gearbox) near the rim.
Tyler Hamilton of Clean Break writes that it is example of green tech growing in the rust belt:
WindTronics made the decision in summer 2009 to manufacture the machines in Windsor, Ontario, which had been pummelled by the auto crisis and recession and suffered from huge unemployment. In that context it was a good-news story because the Michigan-based parent company, EarthTronics, said the facility it was taking over was a former Magna International autoparts plant where 200 new jobs would be created.
I should note that Paul Gipe of Wind-Works, who has taken me to task for being overly enthusiastic before, is unconvinced by the whole thing, suggesting that operating at a greater range of wind speeds in not necessarily a huge advantage:
In my books I emphasize that this is usually a tip off to watch for. There's very little energy in the wind at low speeds. So if a wind turbine claims to capture wind energy at very low wind speeds, the response should be "so what. There's not enough energy there to make a difference."
Where Rotor meets Stator