47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009 1
4747thth AIAA Aerospace Science Meeting AIAA Aerospace Science Meeting and Exhibitand Exhibit
Orlando, Florida, 5-8 January 2009Orlando, Florida, 5-8 January 2009
Anti-icing Materials International LaboratoryAnti-icing Materials International Laboratory
Wind Turbine Icing and De-Icing
Guy Fortin and Jean PerronGuy Fortin and Jean Perron Université du Québec à ChicoutimiUniversité du Québec à Chicoutimi
47th Aerospace Science Meeting and Exhibit, Orlando, Florida, 2009 2
OverviewOverview
INTRODUCTION ICING EVENT FORMATION WATER COLLECTION ICE ACCRETION WIND TURBINE ICE PROTECTION SYSTEMS CONCLUSION
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IntroductionIntroduction
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.
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IntroductionIntroduction
Problem Description
• Wind turbine atmospheric icing a) Ice accumulates on the rotor bladesb) Reducing aerodynamic efficiency leading to
a) less power production.b) vibration c) ice sheddingd) wind turbine stope) worst case, blades collapse
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Icing Event FormationIcing Event Formation
Atmospheric Icing
Icing occurs when hot air mass meet an air mass below freezing leading to hydrometeors such as
1. Freezing drizzle2. Freezing rain3. Wet snow
Or in presence of1. Cloud in altitude (> 400 m)2. Fog at ground level
When temperature is below freezing
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0
10
20
30
40
50
60
70
80
90
100
110
0 10 20 30 40 50 60 70 80 90 100
Diameter (µm)
Fre
qu
en
cy (
%)
Diameter Volume
MVD = 20.8 µm
Icing Event FormationIcing Event Formation
Atmospheric Icing
Hydrometeors are characterized by1. 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.
0
2
4
6
8
10
12
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 97 101
105
109
113
117
121
125
129
133
137
141
145
149
Diameter (µm)
Dro
plet
Fre
quen
cy (
%)
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Icing Event FormationIcing Event Formation
Atmospheric Icing
How ice accrete on blade
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Water CollectionWater Collection
Water Collection
The first parameters to evaluate ice accretion is the Impingement Mass
Collection EfficiencyAir Speed
Impingement Surface
Liquid Water Content
impaimp AULWCE m
sup
inf
1 s
sds
HE
Local Collection Efficiency
Impingement Distance
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Water CollectionWater Collection
Water Collection
Lower LimitLocal Collection Efficiency
Upper Limit
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
-0.16 -0.14 -0.12 -0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06
Curvilinear Abscissa
Lo
cal C
olle
ctio
n E
ffic
ien
cy
Stagnation Point
dy
ds
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Water CollectionWater Collection
Water Collection
Water Droplet Trajectory Calculations1. Droplets are spherical2. No collision or coalescence3. Small water droplet concentration.
gvvK
C
dt
vd
w
ada
d
dDd
11
24
Re
Drag Gravity Buoyancy
Reynolds Number Inertia Parameter
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Water CollectionWater Collection
Water Collection
Local collection efficiency increases when the Median Volumetric Diameter increase
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
-0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1
Curvilinear Abscissa
Lo
cal C
olle
ctio
n E
ffic
ien
cy
MVD = 10 µm MVD = 20 µm MVD = 50 µm
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Water CollectionWater Collection
Water Collection
Local collection efficiency decrease when the Chord increase
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1
Curvilinear Abscissa
Lo
cal C
olle
ctio
n E
ffic
ien
cy
Chord = 0.5 m Chord = 1.0 m Chord = 3.0 m
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Water CollectionWater Collection
Water Collection
Local collection efficiency increase when the Speed increase
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
-0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1
Curvilinear Abscissa
Lo
cal C
olle
ctio
n E
ffic
ien
cy
U = 15 m/s U = 30 m/s U = 67 m/s
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Water CollectionWater Collection
Water Collection
Local collection efficiency increases when the Angle Of Attack increase
0
0.1
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0.5
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0.7
0.8
-0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1
Curvilinear Abscissa
Lo
cal C
olle
ctio
n E
ffic
ien
cy
AOA = 0º AOA = 4º AOA = 8º
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Ice AccretionIce 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.
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Ice AccretionIce Accretion
Thermodynamic of Ice Accretion
Rime ice form when all water freeze at impactRime 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
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Ice AccretionIce Accretion
Thermodynamic of Ice Accretion
Glaze ice form when a fraction of the water freeze at impactGlaze 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
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Ice AccretionIce 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
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Ice AccretionIce 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.
0/ radcdssevapsubcvkinadhf QQQQQQQQ
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Ice AccretionIce Accretion
Thermodynamic of Ice Accretion
Ice Mass
subevapimpice mfmmm
Ice Thickness
ice
iceice
me
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Ice AccretionIce Accretion
Thermodynamic of Ice Accretion
Ice Shapes predict with CIRALIMA 2D
-0.100
-0.075
-0.050
-0.025
0.000
0.025
0.050
0.075
0.100
-0.075 -0.050 -0.025 0.000 0.025 0.050 0.075 0.100 0.125 0.150 0.175
-28.3ºC -13.3ºC -7.8ºC -4.4ºC
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Wind turbine icing simulated in icing wind tunnel at AMIL
LWC = 0.24 g/m³Temperature = -5.7°CAir speed = 4.2 m/sWind Turbine Speed = 16 RPMWind Turbine Diameter = 80 mTime = 4.5 hours
Ice AccretionIce Accretion
Wind Turbine
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Ice AccretionIce Accretion
Wind Turbine
Aerodynamic Degradation
s
s
solds
news
T
TfTf
TT
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.
0
0.1
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0.3
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0.5
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0.7
0.8
0 5 10 15 20 25 30 35 40 45
r(m)
Lift
Co
eff
icie
nt
0
0.05
0.1
0.15
0.2
0.25
0.3
Dra
g C
oe
ffic
ien
t
Lift Coefficient Clean Airfoil Lift Coefficient Iced AirfoilDrag Coefficient Clean Airfoil Drag Coefficient Iced Airfoil
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Ice Protection SystemIce Protection System
Type used with wind turbineElectro-thermal Hot airflowMicrowaves Icephobic coating
MethodAnti-icing: no ice is allowed to form Deicing: allow small ice thickness to form
before the deicing sequence is activated
s
s
solds
news
T
TfTf
TT
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Ice Protection SystemIce 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
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Ice Protection SystemIce 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
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Ice Protection SystemIce 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
-0.04
-0.02
0
0.02
0.04
-0.02 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 0.22
(m)
(m)
without heatingwith heating
About 5 times more energy is needed in evaporative mode
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Ice Protection SystemIce 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
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ConclusionsConclusions
• 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.
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ConclusionsConclusions
• 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
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ConclusionsConclusions
Question?