1. Mapping of icing in Sweden!
On the influence from icing on wind
energy production !
Øyvind Byrkjedal
!
Kjeller Vindteknikk
oyvind.byrkjedal@vindteknikk.no
Wintewind 2012, Skellefteå 07.02.2012

2. Outline!
Ÿ The meso-scale model WRF!
Ÿ Calculations of icing!
Ÿ Icing map!
Ÿ Production loss due to icing!
Ÿ Future development!
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3. Icing!
Ÿ ISO standard – atmospheric icing on structures!
• ice loads are important in the design of masts,
powerlines, other structures in cold climate!
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4. Icing conditions!
Ÿ Temperatures below freezing!
in-cloud
Ÿ cloud or fog containing small water droplets!
icing
Ÿ Something to freeze to!
Ÿ Lifting of airmasses !
condensation
height
wind
west east 4

5. Mesoscale model!
Ÿ The meso-scale refers to the time and spatial scale of the features
resolved by the model. The model resolves low-pressure systems and
fronts.
Ÿ WRF – Weather Research and Forecasting
Ÿ The model describes the atmosphere dynamics (wind, temperature
and humidity), and includes physical description of radiation, cloud
formation, precipitation, snow, surface processes, etc.
Ÿ The model performes calculations in the time domain, no steady-
state model
Ÿ Typical model resolution down to 1km x 1km
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6. 16.08.2011 6

8. dM/dt > 10g/hr! dM/dt > 50g/hr!

9. Model verification!
Ÿ A project funded by Energimyndigheten:
!
Ÿ ice measurements at 8 sites!
Ÿ production data from 3 wind farms!
Ÿ This has lead to a large improvement in
our knowledge about icing and its effect
on wind power production!
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10. Modeling of ice load!
Ice load:
model (blue)
observed (red)
Ice load:
model (blue)
observed (red)
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11. Sublimation!
SUBLIMATION MELTING

12. Modeling of ice load!
Ÿ The model describes:!
• timing of ice accumulation!
• timing of sublimation and melting!
Ÿ The model underestimates large ice
loads!
Ÿ Some icing events found in the model
but not from observations.!
Ÿ Uncertainty also for the observations.!
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13. Power production!
Ÿ Icing will change the
aerodynamic properties of
the WT blade. !
Ÿ Result in reduced power
output.!
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14. Power production!
Ÿ Power curve May 2010!
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15. Power production!
Ÿ Power curve November 2009!
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16. Estimating production loss!
Power [% of rated]
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17. Estimating production loss!
Ice load:
model (blue)
observed (red)
100%
Production loss: 50%
model (blue)
observed (red)
0%
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18. Power production index!
Power index [%]
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19. Future development!
Ÿ Meso-scale model:!
Ÿ Further development of the meso-scale model and optimize
the use of the model for icing calculations!
Ÿ Forecasting of icing!
Ÿ Production loss calculations!
Ÿ Calculation of ice loads directly on the blade!
Ÿ Calculations of the aerodynamic change of the WT blade
and its effect on power yield!
Ÿ More data needed!!
Ÿ Data on droplet sizes and distributions!
Ÿ The production loss model is tuned to the available data at a
limited number of sites. This is a limitation, how well will
other sites be represented?!
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20. Thank you!
!
Wind and icing map are now available for Sweden:
www.vindteknikk.no !
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