4 December 2012 – Wind installations have begun to reject gearboxes in favour of direct drive turbines. This is according to a report by GlobalData. A gearbox allows the generator’s internal shaft to spin 50–250 times for each rotation of the turbine blades, and provides advantages including low noise levels and high efficiency. However, drawbacks include a high level of maintenance and low reliability.
The global wind turbine gearbox market is dominated by Winergy and China High Speed Transmission Equipment, which combined accounted for a 52% share of global wind turbine gearbox production in 2011. The total amount of gearbox units installed in the global wind market increased from 9,075 in 2006 to 21,192 in 2011 at a compound annual growth rate (CAGR) of 19%, but an increase in average turbine size and growing prominence of direct drive systems is expected to result in a decline in turbine installations with gearboxes from present levels to 12,662 by 2020.
In contrast, direct drive technology does not use a gearbox, offering slow movement of all the parts of the wind turbine systems and therefore reduced wear and tear of the system and superior reliability. Direct drive turbines have been in the wind power market for a long time, but have gained increasing popularity in recent years due to the low reliability and high refurbishment costs of gearbox components.
Enercon GmbH of Germany and Xinjiang GoldWind Science and Technology Company Limited of China are major companies manufacturing direct drive turbines, and both are perfecting their industry offerings. Enercon’s annular multiple poles generator reduces the number of moving components used, while Xinjiang’s GoldWind uses permanent magnet direct drive technology. This increases reliability substantially, and reduces maintenance costs and time, increasing production time and therefore providing improved returns.
However, the cost of permanent magnet generators depends upon the cost of rare earth materials such as Neodymium.
The share of global wind turbine installations accounted for by direct drive turbines has grown from around 18% in 2006 to 22% in 2011, and is expected to increase to 29% by 2020, with wind turbine manufacturers such as Siemens and GE shifting from gearbox turbines to permanent magnet direct drive turbines.