It's not just the gearbox. You've got 40 tons of rotor blades turning and changing pitch, attached to a 70-ton nacelle which turns on top of a 250-foot-high tower to catch the wind. A mechanical challenge in any environment to be sure.
The following is from John Galambos, "Brooklyn wind turbine performance over 12 years," presented at New Zealand Wind Energy Association Conference, 31 August 2005. Remember that this single turbine near Wellington (N.Z.) is a demonstration installation, with all the money necessary thrown at it to keep it going. Since most of the financial benefits in the U.S. disappear after a few years (6 years for accelerated depreciation, 10 years for production tax credit), the more likely scenario for most facilities is abandonment, as with many of those in Altamont Pass, California, and the sad specimens at South Point, Hawaii.
TECHNICAL ISSUES DURING OPERATION
Years 1 and 2
Gearbox oil issues with build up of black gunge
Part of skylight roof section vanished during 1994 storm
- oil type changed
Slip coupling operating too frequently, required replacement
- 38.5 m/s 10-sec average
- Estimated 45m/s 3-sec gust, turbine rated for 70m/s 3-sec gust
- Anemometer cup vanished (years 5 and 11 also)
Blackening of gearbox oil
- High wind shutdown changed from 25 to 22 m/s
Years 3 and 4
Blade inspections revealed gel coat failures
Tower to foundation ring flange-to-flange bolts started failing
- Appear to relate to damage from thrown stones
Numerous minor factory technical upgrades continued
- Managed by monitoring and change out
Yaw drive issues, noisy
- Driven by Service Bulletins not issues on site
Years 5 to 9
- motors and worm drive gears replaced
Pitch accumulator leaking - replacement with production loss
Controller required Y2k modifications
Yaw drive gearboxes replaced
Ongoing issues relating to EMC
Gearbox low speed shaft stiffener fitted
- Susceptible to strong local FM radio transmission
About year 10
- Factory modification for high winds
- Internal expansion sleeve to hollow shaft
- Too late, damage done, gearbox would require replacement before long.
Gearbox high speed shaft bearing failed at 9+ years
Weather mast guy hardware failed
- Noisy gearbox operation
- Before original gearbox was replaced
Gearbox replaced at 10 years
- Repair can have safety implications
Years 11 and 12
- Refurbished unit, "as new", with warranty
- Shaft end floats outside maintenance tolerances when delivered
- Bearing replaced after 3 months
- Gearbox replaced again after 13 months
- Condition monitoring trials unsuccessful
Nose cone replaced
Tower section joining bolts corroded
- Disintegrating
Pitch linkage connections failed,
- Replaced at 11 years
Yaw ring and yaw gears failed
- Rods damaged and replaced
Other
- Long outage
- No local parts
- Numerous control card replacements/updates to Service bulletins
- Included fans to control cards, oil filtering etc
- Communications issues at times – not turbine related
- Distribution disturbances have tripped the turbine
- Some misc contactor failures, replacement repairs, consumables etc.
categories: wind power, wind energy, wind farms, wind turbines
