1. Blade Reliability Case Study
Sandia Wind Turbine Blade Workshop
August 26, 2014
David Coffey

2. Overview
• Snapshot of Iberdrola Renewables
• Overview of blade failure data
• Failure modes & repair rates
• Examples of carbon spar damage
• Examples of large crack repair
• Conclusions
• Improvement Goals
Aug 26, 2014 David Coffey
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3. 3
Iberdrola Renewables - North America
Iberdrola Renewables develops, owns and operates wind plants throughout the U.S.
• 3000+ turbines
• 56 wind farms
• 18 states
• 6+ GW capacity
• 6 different OEMs
• Rotor dia. 47-102 m
O & M Engineering:
• Performance & Reliability
• Continuous Improvement
• Root cause analysis
• Reliability centered maintenance
• Failure rate projections
• Repair specifications
Aug 26, 2014 David Coffey

4. 4
Snapshot of Iberdrola Renewables Fleet
Aug 26, 2014 David Coffey

5. Blade Reliability
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“Repair required” blade
damages by year:
• 7+ years
• ~ 2600 reports
• includes end of
warranty inspections,
FM, operations etc.
Typical types of damage:
• Lightning
• Cracks
• Impact damage
• Surface/gel coat
• LE erosion

6. Blade Reliability
Aug 26, 2014 David Coffey
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Top 5 damage types:
1. Lightning
2. LE Erosion
- Light/medium/heavy
3. Cracks
4. Gel coat damage
5. “Undetermined”
includes:
• Lightning
• Ice
• Moisture
intrusion
Damages can be broken
down further by location
on blade
Top 9
represent
80%

7. Blade Reliability
Aug 26, 2014 David Coffey
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• 94% reported
damage is repairable
• Repair rates for
lightning have
improved
• Carbon spar damage
is still problematic
• Structural cracks are
less likely to be
repairable

8. Examples of carbon spar lightning damage
Repairable today Repairable tomorrow?
Aug 26, 2014 David Coffey
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9. 9
Examples of large crack repair
Aug 26, 2014 David Coffey
Upper shell
Lower shell
• Testing feasibility of large crack repairs
• Will the repairs last?
• Is it economical?

10. Blade Reliability
Conclusions:
1. Overall blade damage rates are higher than expected
2. Lightning damage, LE erosion, Gel coat damage account for 80%
of damage reported
3. 94% total repair rate for all blade damages
– 6% replacement rate drives cost of ownership
4. Ongoing cost of ownership for carbon spar blades is higher than
other blade types
– Actively seeking improved protection and repair options.
Aug 26, 2014 David Coffey
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11. Improvement Goals:
1. Blade damage
– Improved data reporting – standard method of damage categorization
– Continue to refine and improve damage reporting data base
• Clear and consistent criteria for run vs. stop decisions
• Clarify repair criteria
– Up tower repair – types and severity
– Ground repair – economic feasibility of repairs
2. Lightning protection:
– Design and test standards
• Improvements needed to IEC61400-24 lightning protection efficiency
calculations
– LPS system enhancements
3. Large crack repair
4. Carbon spar repair
Aug 26, 2014 David Coffey
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12. Thank You!
David Coffey 12