This document discusses leading edge erosion on wind turbine blades and a new protective coating called ProBlade. It summarizes that: 1) Leading edge erosion increases operation and maintenance costs and decreases annual energy production for wind turbines. 2) Testing shows ProBlade provides over 5 times better erosion resistance compared to polyurethane tape and over 50 times better than gel coat alone, with less aerodynamic impact. 3) ProBlade offers a significant improvement in leading edge protection that can help secure annual energy production as tip speeds and rainfall in turbine locations increase globally.

1. By
SECURE ANNUAL ENERGY PRODUCTION BY A LEAP IN LEADING EDGE PROTECTION OF WIND TURBINE BLADES
SANDIA BLADE WORKSHOP 2014 Albuquerque, NM
Michael Drachmann Haag
All rights reserved, February 2013

2. SECURE ANNUAL ENERGY PRODUCTION BY A LEAP IN LEADING EDGE PROTECTION OF WIND TURBINE BLADES
1.Introducing LM Wind Power
2.Leading Edge Erosion is Affecting the Cost of Energy
3.Aerodynamic Testing and Results
4.Understanding Water Droplet Erosion (WDE)
5.Rain Erosion Testing and Results
6.The Journey towards Excellence
7.Conclusions and Outlook

3. 2013
... the longest track record of supply and innovation in the industry…
From technology pioneering to global industrial excellence
1st generation Lightning- Protection; Vortex generators
VARTM vacuum infusion technology
Pre-bending
The world’s longest rotor blade introduced; LM Blade Monitoring
FutureBlade technology (carbon/glass hybrid
LM the world’s largest manufacturer of rotor blades
Rotor blade production starts in Denmark
Wind tunnel inaugurated
Tailor-made aerodynamics with LM profiles
Establishing a leading position through technology excellence and industrialization
1989
1996
1999
2002
2003
2004
2005
2006
2010
LM Drain-Receptor; LM Diverter-Strips; Multi-Receptor lightning protection; LM SuperRoot
1978
2008
GloBlade Introduction
2011
Newer longest blade record (LM 73.5)
2012
Launch of GloBlade 3
2013
Manufacturing 2.0
New Offshore blades for China (73+, 66)
>160,000 blades delivered ~23% of global installed base
1978
ProBlade Collision Barrier for improved leading edge protection

4. Introducing ProBladeTM Collision Barrier
ProBladeTM Collision Barrier is a new leading edge protective material system with outstanding erosion properties. Highly flexible 2-component solvent-free UV-resistant polyurethane based paint system. Proprietary application procedure developed and solely owned by LM Wind Power. It is applied where it is needed – directly at the leading edge. ……taking advantage of our reliable and cost efficient polyester gel coat surface on the rest of the blade surface. Offering minimum aerodynamic influence and less noise generation than tape.

5. …..leading edge erosion is affecting the Cost of Energy…..
Resulting in increased O&M cost and signifcant loss in AEP

6. Airline layout: Top view: 37 m x 14 m LM Wind Power LSWT wind tunnel tests: Objective: Minimize aerodynamic impact of the leading edge protection system Test: LM airfoil (24% relative thickness) with: Clean LE ProBlade PPT Zigzag tape (5%c suction and 10%c pressure side)
Aerodynamic Testing at LM Wind Power
•Max wind speed: 105 m/s
•Reynolds number: up to 6 million
•Turbulence intensity: 0.1%

7. Aerodynamic Results
•Adding leading edge protection has an impact on aerodynamic performance compared to a clean airfoil.
•PPT may result in drag increase up to 100% (loses in AEP of around 1.5% compared to the clean blade).
•ProBlade application has been optimized to minimize any aerodynamic effects, resulting in loses in AEP of less than 0.7%.
•Aerodynamic impact of leading edge protection systems will in general be much lower than an eroded LE (worse than zigzag tape).
Maximum lift decreases
Drag increases

8. WDE affecting parameters Blade Tip Speed Material Properties Turbine location (on/off-shore) Droplet size distribution at site Annual rainfall Capacity factor of turbine Configuration and build-up of base material
What is affecting Water Droplet Erosion (WDE)?
Droplet properties
Diameter: d
Density: ρL
Angle of attack: θ
Speed of impact: v
θ
Material properties
Density: ρS
Strain at Failure
Toughness
Tear strength
Modulus of Elasticity: ES

9. Increasing Tip Speeds….
Alstom Haliade 150-6MW
XEMC Darwind XD115-4.5 MW

10. New markets are evolving….
Figure shows the mean annual rainfall (mm) all over the world
Source: Defence Standard 00-35 Part 4 Section 6 p. 190
NASA, “Precipitation, Fog And Icing”

11. Data driven learning experience…..
Site
Kirkby Moor, UK
Region
Europe
Location
On-shore
Blade Length [m]
17
Tip Speed [m/s]
62
Rainfall [mm/year]
See graph
Average wind speed [m/s]
6,75
Mean Daily Sun Irradiation [J/m2]
65
Annual Average Temperature [°C]
9,83
Leading Edge Material
Polyester Gel Coat
Operating Time [Years]
18
Average Tip Categorization at site
3,14

12. Initial turbine design – 1980-1990’s
Current turbine design – 2000’s
New turbine design – 2010’s
Current RET Testing
Instantenous impact force is increasing

13. Principle: Whirling Arm Duration: Variable Vroot: 123 m/s Vcenter: 140 m/s Vtip: 157 m/s Rain: 30-35 mm/h Droplet size: 1-2 mm Temperature: 20-25°C ASTM G73 ISO (under development)
Rain Erosion Testing at LM Wind Power

14. ProBlade® performance
Gel-coat vs. PPT vs. ProBlade®
ProBlade 5,4x vs PPT
54x vs Gel Coat
Gel-coat 1x
PPT 10x vs Gel Coat
LM developed application method shows a 5,4 times increase in performance compared to PPT in accelerated rain erosion testing

15. Polyurethane Protective Tape
- Failure Mechanism
Mass removal
Film Rupture
Droplet Impact

16. The journey towards excellence….
Building the
Foundation
Using field data and analyzing extreme sites and operating conditions
Fully correlated and validated leading edge erosion reliability models

17. Securing AEP is becoming harder with increasing tip speeds and markets evolving in harsher climates. Selecting the right leading edge protection is now more essential than ever before. Through field studies and theoretical understanding we now know what happens when water droplets collide with our blades. A new approach to experimental validation has assisted us in defining the correct Critical-to-Quality parameters for developing a reliable leading edge protection system. ProBlade offers a significant improvement in leading edge protection over known products when applied with LM’s proprietary application procedure. Furthermore, ProBlade has a clear aerodynamic advantage over PPT. ProBlade is running on selected prototype turbines to enable understanding of its life-time expectancy.
Conclusions

18. 3D scanning is employed to get an exact replicate of the surface after leading edge erosion. This methodology is an enabling technology for improved understanding of the failure mechanisms behind water droplet erosion. Drone inspections are beginning to offer easier access to high quality field inspection of blades at lower cost. This technology is a key enabler in establishing prevententive maintenance schemes . LM Wind Power have already encountered this technology and received impressive data.
Outlook

19. Erosion System
Impact Energy
Droplet size, Impact velocity, Impact angle
Damping Behaviour
Water film, Surface characteristics, Elasticity of base materiale
Erosion Resistance of Material Hardness, Elasticity, Fatigue resistance, Ductility
Secure Annual Energy Production by a leap in leading edge protection of wind turbine blades, by controlling and understanding the complete erosion system

20. Thank you for your time
Contact details:
Head quarters:
Michael Drachmann Haag
LM Wind Power Group
Lead Engineer
Jupitervej 6
Materials & Processes
6000 Kolding
Denmark
Tel
+45 7984 0384
Tel
+ 45 79 84 00 00
Mob
+45 51388384
Fax
+45 79 80 00 01
E
mdh@windpower.com
E
info@lmwindpower.com
W
lmwindpower.com
Note:
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