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GE has manufactured a gearbox for its workhorse 1.5 MW wind turbines. It is a compound planetary gearbox made in Erie, Pennsylvania, by GE Transportation, says Robert Gleitz, general manager of GE Energy's wind business. "To date, GE Transportation has shipped nearly 100 gearboxes to GE Energy," says Gleitz.

The gearbox is not just a case of GE in-sourcing a component already available on the market from other companies. It is markedly different from existing gearboxes, says Gleitz. GE Transportation leveraged gear technology and experience from a number of GE business units, including 40+ years of experience in mining, helical gear technology from its marine group, advances in metallurgy from GE's Aircraft Engines business, and developments in structural vibration and acoustics, says Gleitz. In addition, it took advantage of special materials from its Global Research Center.

After logging around 30,000 hours of operation on prototype units, the first commercial units were quietly delivered to GE Energy last year. "The results of GE Transportation's vast gearbox experience are increased reliability over a 20-year lifespan," says Gleitz. "It also provides improved efficiency -- one to two per cent more power output for the same power input."

Engineers worked hard in the area of quiet turbine and rotor operation. Gleitz characterizes the product of their endeavours as industry-leading in terms of low vibration and vibration induced noise. He also notes that the machine has undergone successful HALT testing (Highly Accelerated Lifetime Test).

The GE gearbox features what it calls "straddle mounting of gears to bearings." Most wind turbine gearbox designs have planet bearings internally mounted to the planet gear. With the GE design, however, the planet bearings are mounted on the shaft on either side of the planet gears. The advantage, says Gleitz, is that the bearings can be sized for maximum reliability. He declines to say who the bearing supplier is. "GE Transportation purchases bearings from a number of global sources," says Gleitz.

GE is not about to cancel existing contracts with its long term wind turbine gearbox suppliers. Despite the fast ramp up from nothing to 100 gearboxes in only a year, the company is still a long way off from being able to supply the volume of units required for its annual 1.5 MW turbine sales. The company is expecting to deliver up to nearly 5000 turbines during this year and next. "In 2006, GE Transportation will supply around ten per cent of GE Energy's gearbox requirements," says Gleitz. "Both business units are working together to increase this number."