1.
Method for Estimating Wind Turbine
Production Losses Due to Icing
Winterwind 2012 – International Wind Energy
Conference
Ville Turkia, Saara Huttunen, Tomas Wallenius,
VTT Technical Research Centre of Finland

2.
03/02/2012 2
Production loss estimation
Overview of the process
Numerical weather
Cylinder icing model prediction (NWP) model Energy production
with icing model with losses due to icing
acc. ISO12494 standard
Ice accretion on Power curves for
operating wind turbine blade iced up wind turbine
using TURBICE using FAST
Start of icing
Iced airfoil aerodynamics
using FLUENT(CFD)
Light icing
Moderate icing

3.
03/02/2012 3
Production loss estimation
Ice model &
relation between cylinder and blade
Ice accretion in NWP
 Numerical weather prediction with icing modelling
 Icing modelling according to ISO 12494 – Atmospheric icing of
structures
 Ice accretion on stationary cylinder (Ø 0,03m)
Accurate ice modelling on cylinder and wind turbine
blade
 TURBICE ice accretion calculations for
 ISO 12494 cylinder
 Wind turbine blade
 Using representative weather conditions /k
 Windspeed = 7 m/s
 Corresponding rotational speed
 Temperature = -7 C *k
 LWC = 0,2 g/m3
 Droplet size = 25 microns
 Rime ice (glaze ice cases included in the future)

4.
03/02/2012 4
Production loss estimation
Iced wind turbine rotor blades
Ice accretion on blade using TURBICE
0.1
 Outer 3rd part of the blade is considered iced
 Different icing times – Different ice mass/shape
0.08
 No ice
 Start of icing–roughness
 Light icing (some hours of icing) –roughness and larger 0.06
mass of accreted ice
 Moderate icing (long lasted icing) – roughness and horn 0.04
type ice shape
0.02
Wind tunnel verifications and field observations
 Ice accretion experiments in VTT icing wind tunnel
0
 Observations from Olos wind farm, Finland -0.1 -0.05 0 0.05 0.1
-0.02
-0.04
-0.06
Start of icing Light icing Moderate icing No ice

5.
03/02/2012 5
Production loss estimation
Iced airfoil aerodynamics
CFD simulation and force coefficients
 ANSYS FLUENT 1.6
 Spalart-Allmaras turbulence model
 Lift coefficient from CFD analysis 1.4
 Drag coefficient affected by large and small scale surface
roughness 1.2
 Large scale surface roughness – CFD analysis
 Small scale surface roughness – theoretical modification 1
0.8
0.06 CL
0.05 0.6
0.04
CD 0.4
0.03
0.02 0.2
0.01
0
0 -6 -4 -2 0 2 4 6 8 10
-6 -4 -2 0 2 4 6 8 10
-0.2
Angle of Attack ( ) Angle of Attack ( )
Start of icing Light icing Moderate icing No ice Start of icing Light icing Moderate icing No ice

6.
03/02/2012 6

7.
03/02/2012 7
Production loss estimation
Annual energy production
Power curves 3500.00
 FAST simulations to generate power curves
 Multi-MW turbines 3000.00
 CL and CD from aerodynamics analysis (CFD + theoretics)
2500.00
 Already initial icing (roughness at the leading edge) affects the
power curve 2000.00
P (kW)
1500.00
Energy production losses 1000.00
 Can be calculated using weather time series and the
corresponding power curve for each icing condition 500.00
 Energy production without icing – Energy production with icing = 0.00
Lost energy due to icing 0.00 5.00 10.00 15.00 20.00
WS (m/s)
Start of icing Light icing Moderate icing No ice

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03/02/2012 8
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9.
03/02/2012 9
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