47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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.

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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.

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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

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

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

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

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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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.

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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.

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

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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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.

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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.

47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 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

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