1a-03 he dww2010 p1 v1
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Dutch Wind Workshops, October 2010
Atmospheric stability and wind profilesat two wind farm sites in the North Sea
Ameya Sathe, TU Delft
Sven-Erik Gryning, Risø DTU
Alfredo Peña, Risø DTU
Acknowledgements:
1.OWEZ data - WE@Sea program, Noordzeewind,
Senter Novem2.Horns Rev data – Tall Wind project, Vattenfall A/s,
DONG Energy A/S, NORSEWinD project
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Objective
Atmospheric stability and wind profileanalysis in marine conditions (only longmarine fetch is considered)
• Using existing theoretical models• Comparing with measurements
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Basic theory
Monin-Obukhov similarity theory (MOST)
Standard surface layer wind profilea = 12, p = -1/3, b = 5
Non-dimensional wind profile
For details
Theory ResultsMeasurements Conclusions
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Extended wind profile
For details
Theory ResultsMeasurements Conclusions
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Some important basic considerations
Theory ResultsMeasurements Conclusions
c = 0.15
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Site 1
Theory ResultsMeasurements Conclusions
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Site 2
Theory ResultsMeasurements Conclusions
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Measurement Details
OWEZ
Horns Rev
Measurement heights = 21, 70, 116 mSea surface temperature (SST) = -3.8 m,
corrected by -0.82 ⁰C
Period of analysis = July 2005 –
December 2008
Measurement heights = 15, 30, 45 m
Sea surface temperature (SST) = - 4 m
Period of analysis = April 1999 –
December 2006
Theory ResultsMeasurements Conclusions
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Statistics of atmospheric stability
Theory ResultsMeasurements Conclusions
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Statistics of atmospheric stability
Theory ResultsMeasurements Conclusions
N Di i l i d fil St d d f l
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Non-Dimensional wind profiles – Standard surface layertheory
Theory ResultsMeasurements Conclusions
N di i l i d fil E t d d i d
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Non-dimensional wind profiles – Extended windprofile model
Theory ResultsMeasurements Conclusions
OWEZ
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Conclusions
• Using MOST, 10-min measurements can be used to derivestatistics of atmospheric stability reasonably well
• Over a long marine fetch, the conditions in the North Sea aremainly unstable and neutral
• Standard surface-layer theory of wind profile works in theunstable and neutral conditions for the entire boundary layer
• Under stable conditions, the extended wind profile model ispreferable, or any model that scales the wind profile by atleast z
i , since its effect is clearly visible.
• The quality of temperature measurements is of utmostimportance
Theory ResultsMeasurements Conclusions
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Questions for the audience
Some examples of wind profile models are:
– Logarithmic wind profile
– Exponential wind profile – Standard surface layer diabatic wind profile
– Extended wind profile model
– Many more (not listed here because they are not studied)
• Do we need to use such sophisticated w ind profilemodels for w ind energy?
• Is atmospheric stability analysis important for w ind
energy?• Does the audience have questions on my analysis?
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Correction of SST at OWEZ
Theory ResultsMeasurements Conclusions
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