1. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 20091 47 th AIAA Aerospace Science Meeting and Exhibit Orlando, Florida, 5-8 January 2009 Anti-icing Materials International Laboratory Wind Turbine Icing and De-Icing Guy Fortin and Jean Perron Université du Québec à Chicoutimi Université du Québec à Chicoutimi

2. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 20092 Overview  INTRODUCTION  ICING EVENT FORMATION  WATER COLLECTION  ICE ACCRETION  WIND TURBINE  ICE PROTECTION SYSTEMS  CONCLUSION

3. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 20093 Introduction Atmospheric Icing Ice accretes on structure (overhead cables, pylons, satellite dishes, communication towers, airplanes, helicopters, wind turbines, offshore drilling rigs, ships, docks, bridges, roads, dams, buildings…) causing of great damages to electric lines, telecommunication networks, in the maritime, road and air transport, causing materials damages and human safety risk.

4. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 20094 Introduction Problem Description Wind turbine atmospheric icing a)Ice accumulates on the rotor blades b)Reducing aerodynamic efficiency leading to a)less power production. b)vibration c)ice shedding d)wind turbine stop e)worst case, blades collapse

5. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 20095 Icing Event Formation Atmospheric Icing Icing occurs when hot air mass meet an air mass below freezing leading to hydrometeors such as 1.Freezing drizzle 2.Freezing rain 3.Wet snow Or in presence of 1.Cloud in altitude (> 400 m) 2.Fog at ground level When temperature is below freezing

6. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 20096 Icing Event Formation Atmospheric Icing Hydrometeors are characterized by 1.Liquid Water Content which is the quantity of water contained in the air expressed as g/m³. 2.Median Volumetric Diameter of water droplet which is a representative value of the water droplet distribution expressed as µm.

7. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 20097 Icing Event Formation Atmospheric Icing How ice accrete on blade

8. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 20098 Water Collection The first parameters to evaluate ice accretion is the Impingement Mass Collection Efficiency Air Speed Impingement Surface Liquid Water Content Local Collection Efficiency Impingement Distance

9. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 20099 Water Collection Lower Limit Local Collection Efficiency Upper Limit Stagnation Point

10. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200910 Water Collection Water Droplet Trajectory Calculations 1.Droplets are spherical 2.No collision or coalescence 3.Small water droplet concentration. Drag Gravity Buoyancy Reynolds Number Inertia Parameter

11. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200911 Water Collection Local collection efficiency increases when the Median Volumetric Diameter increase

12. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200912 Water Collection Local collection efficiency decrease when the Chord increase

13. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200913 Water Collection Local collection efficiency increase when the Speed increase

14. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200914 Water Collection Local collection efficiency increases when the Angle Of Attack increase

15. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200915 Ice Accretion Thermodynamic of Ice Accretion Supercooled water droplet will freeze completely at impact to form ice on the impingement area or freeze partially to form ice on the impingement area and remaining water which runback outside of the impingement area.

16. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200916 Ice Accretion Thermodynamic of Ice Accretion Rime ice form when all water freeze at impact Rime ice is associated to colder temperature, below -10°C lower Liquid Water Content smaller Median Volumetric Diameter Iced zone is small and close to the leading edge and quite closely takes the original contour

17. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200917 Ice Accretion Thermodynamic of Ice Accretion Glaze ice form when a fraction of the water freeze at impact Glaze ice is associated to warmer temperature, above -10°C high Liquid Water Content greater Median Volumetric Diameter Iced zone is large and tend to deform the aerodynamic profile due to horns formation

18. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200918 Ice Accretion Thermodynamic of Ice Accretion The capacity of ambient environment to absorb the latent heat of solidification while determine if rime or glaze ice is formed

19. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200919 Ice Accretion Thermodynamic of Ice Accretion Surface Temperature and Freezing Fraction If the resulting surface temperature is above freezing, only a fraction of the impinging water is solidified at impact. The freezing fraction is calculated assuming a surface temperature equal to freezing.

20. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200920 Ice Accretion Thermodynamic of Ice Accretion Ice Mass Ice Thickness

21. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200921 Ice Accretion Thermodynamic of Ice Accretion Ice Shapes predict with CIRALIMA 2D

22. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200922 Wind turbine icing simulated in icing wind tunnel at AMIL LWC = 0.24 g/m³ Temperature = -5.7°C Air speed = 4.2 m/s Wind Turbine Speed = 16 RPM Wind Turbine Diameter = 80 m Time = 4.5 hours Ice Accretion Wind Turbine

23. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200923 Ice Accretion Wind Turbine Aerodynamic Degradation Lift decreased from the hub to the tip. Drag increased from the hub to the tip and was more affected than lift. Ice impact on drag and lift was more significant after 20 m.

24. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200924 Ice Protection System Type used with wind turbine Electro-thermalHot airflow MicrowavesIcephobic coating Method Anti-icing: no ice is allowed to form Deicing: allow small ice thickness to form before the deicing sequence is activated

25. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200925 Ice Protection System Advice Protect the collected area, about 14% of the chord with AOA of 6º Maintain blade temperature below 50ºC to reduce the blade delamination risks Do not protect the first third part of the blade Split blade into individual areas and controlled individually in power to reduce energy consumption

26. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200926 Ice Protection System Advice 3.5 more power to de/anti-ice the leading edge at the tip compared to the hub 1.5 more power to de/anti-ice the lower surface then the upper surface

27. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200927 Ice Protection System Anti-icing Maintain the surface blade temperature above freezing With thermal system about 10 W/in² at the tip Electro-thermal, hot airflow or microwaves About 5 times more energy is needed in evaporative mode

28. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200928 Ice Protection System Deicing Less expensive than anti-icing and minimizes runback water and refreezing water on unheated areas The allowed accreted ice is not sufficient to lead to significant aerodynamic penalties or to become a hazard With mechanical system about 2 W/in²/ice millimetre Ice thickness is not uniform Ice detector for each blade area

29. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200929 Conclusions Icing is a problem in cold climate for wind turbine due to freezing rain and drizzle, freezing fog at ground level or icing clouds when installed in altitude or frost when installed near water bodies. Ice accretion lead to aerodynamic penalties and decrease output power. Impact of glaze, rime or frost is difficult to quantify without more experimental and numerical simulations due to lack of data and knowledge. Existing ice protection systems are not adapted to wind turbine, low energy ice protection systems should be developed.

30. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200930 Conclusions Moreover, anti-icing systems are efficient when high frequency of icing event is expected or security is the most important factor. Dei-icing is more efficient than anti-icing, but is difficult to implement and more expensive. To reduce ice protection system power consumption Optimize power in function of the wind turbine rotating speed. Protect the 2/3 extremity parts of the blade only

31. 47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 200931 Conclusions Question?