This document summarizes a presentation on blade reliability from a wind turbine operator. It discusses the operator's fleet of over 3000 turbines across the US, and provides data on reported blade damage over 7 years. The top damage types - lightning, leading edge erosion, cracks and gel coat damage - account for 80% of issues. While 94% of reported damages can be repaired, damage to carbon spars and large structural cracks are less likely to be repairable. The presentation concludes that overall damage rates are higher than expected and repairing carbon blades drives up the cost of ownership. It identifies goals around improving damage reporting, lightning protection, and expanding repair options for large cracks and carbon spars.

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
Aug 26, 2014 David Coffey
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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