Saturday, November 05, 2005

Wind turbines require high maintenance

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 moeny 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
  • oil type changed
Part of skylight roof section vanished during 1994 storm
  • 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)
Slip coupling operating too frequently, required replacement
  • High wind shutdown changed from 25 to 22 m/s
Blackening of gearbox oil

Years 3 and 4

Blade inspections revealed gel coat failures
  • Appear to relate to damage from thrown stones
Tower to foundation ring flange-to-flange bolts started failing
  • Managed by monitoring and change out
Numerous minor factory technical upgrades continued
  • Driven by Service Bulletins not issues on site
Yaw drive issues, noisy
  • motors and worm drive gears replaced
Years 5 to 9

Pitch accumulator leaking - replacement with production loss

Controller required Y2k modifications

Yaw drive gearboxes replaced

Ongoing issues relating to EMC
  • Susceptible to strong local FM radio transmission
Gearbox low speed shaft stiffener fitted
  • Factory modification for high winds
  • Internal expansion sleeve to hollow shaft
  • Too late, damage done, gearbox would require replacement before long.
About year 10

Gearbox high speed shaft bearing failed at 9+ years
  • Noisy gearbox operation
  • Before original gearbox was replaced
Weather mast guy hardware failed
  • Repair can have safety implications
Gearbox replaced at 10 years
  • 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
Years 11 and 12

Nose cone replaced
  • Disintegrating
Tower section joining bolts corroded
  • Replaced at 11 years
Pitch linkage connections failed,
  • Rods damaged and replaced
Yaw ring and yaw gears failed
  • Long outage
  • No local parts
Other
  • 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.

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