Wind Turbines have steadily grown in size to the point where the largest models have blades of more than 100 meters in diameter. The Gearbox (which connects the rotor shaft to the generator) continues to be the component whose failure results in the most significant cost and downtime. Therefore, the reliability of the gearbox is one of the biggest concerns in the wind industry. At present, wind turbines are generally designed for a 20-year design life; however today’s gearboxes generally have an operational life of 7-11 years, per Sandy Butterfield, former NREL Chief Wind Turbine Engineer.
Some estimate that the current risk of failure of the gearboxes may have an economic impact as high as $300 Million USD. Gearbox failures are so expensive because of the high cost of repairing or replacing the gearbox, and due to the resulting downtime associated with the replacement. The gearbox itself typically represents about 10% of the total cost of the wind turbine system. With downtime, transportation of the gearbox, and labor, typical gearbox replacement costs range from $300K-$775K USD.
With these very high costs, improved reliability of the gearbox can truly have a huge economic payoff. It comes down to the need for accurately predicting the aerodynamic and inertial loads transferred from the huge composite blades over a wide range of operating systems. In many cases flexibility of components such as shafts, bearings, gears, etc. can become very important.
For further background, see the article:
“Wind Turbine Gearbox Reliability” at:
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