Equivalent wind speed for AEP · Equivalent wind speed for AEP ... Standard power curve 2 groups of...
Transcript of Equivalent wind speed for AEP · Equivalent wind speed for AEP ... Standard power curve 2 groups of...
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Equivalent wind speed for AEPRozenn Wagner
VindKraftNet03-11-2011Risø
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Risø DTU, Danmarks Tekniske Universitet
Experimental setup & Data processing
Filters:• wind direction;• no rain;• lidar signal availability 100% atall heights;• turbine status=1.
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Risø DTU, Danmarks Tekniske Universitet
Profiles classification
( )fit
mfit hub
hub
zu z uz
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RSS>0.1
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Risø DTU, Danmarks Tekniske Universitet
Standard power curve
� 2 groups of profiles result in 2 different power curves
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Risø DTU, Danmarks Tekniske Universitet
Equivalent wind speed
A1
A2
A3
A4
A5
Concept:
One wind speed representative ofthe whole wind speed profile in frontof the wind turbine rotor in term ofpower production
U1
U2
U5
U4
U3 Ueq
1/3 1/33 3
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Definition:
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Risø DTU, Danmarks Tekniske Universitet
Power curve with equivalent wind speed
� Similar power curves are obtained for both groups of profiles
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Risø DTU, Danmarks Tekniske Universitet
Comparison of the power curves
Difference due to the sheardistribution during the powercurve measurement.
How can theequivalent wind speedpower curve be usedfor AEP estimation?
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Risø DTU, Danmarks Tekniske Universitet
Annual Energy Production
XAEP
Power curve atwind farm site
Wind speed distributionat wind farm site
=
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Risø DTU, Danmarks Tekniske Universitet
AEP estimation
XPredictedAEP
Reference power curve:measured at a reference site
=
Wind speed distributionat wind farm site
Uhub power curve Uhub distribution
Ueq power curve Ueq distribution
Uhub power curve Uhub distribution
Ueq power curve Ueq distribution
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Risø DTU, Danmarks Tekniske Universitet
Illustration of the 2 cases with Høvsøre data
DataGroup 1
Reference site
Reference power curve
DataGroup 2
Estimated site
Measured windspeed
Total power estimation
case1: with uhub
case 2: with Ueq
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Risø DTU, Danmarks Tekniske Universitet
Illustration of the 2 cases with Høvsøre data
prediction: + 1.76%
Case 1
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Risø DTU, Danmarks Tekniske Universitet
Illustration of the 2 cases with Høvsøre data
prediction: + 1.76% prediction: 0.005%
�Improved AEP estimation by using the equivalent wind speed both inthe power curve and the wind speed distribution.
Case 1 Case 2
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Risø DTU, Danmarks Tekniske Universitet
More realistic applicationPower curve and wind distribution from 2 separate sites
Høvsøre
Østerild
Risø DTU’s Test Site for Large TurbinesHøvøsre
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Risø DTU, Danmarks Tekniske Universitet
Power curve measured atHøvsøre in Feb-March2009
Wind speed distributionmeasured at Østerild May2010- May 2011
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4 possible combinations, but no turbine yet.
More realistic applicationPower curve and wind distribution from 2 separate sites
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Risø DTU, Danmarks Tekniske Universitet
Combination 1:
•Equivalent power curve
•Equivalent wind speeddistribution
� Account for the shear during the powercurve measurement; expected to be thesame power curve at any site
� Account for the shear at Østerild
Reference AEP
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Risø DTU, Danmarks Tekniske Universitet
Combination 2:
•Hub height power curve
•Hub height wind speeddistribution
-2.3%
� Underestimates the power producedbecause of the shear during the powercurve measurement.
� Slightly underestimates the energyavailable because does not account forthe shear at Østerild (assumes flat windspeed profiles)
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Risø DTU, Danmarks Tekniske Universitet
Combination 3:
•Equivalent power curve
•Hub height wind speeddistribution
-0.5%
� Account for the shear during the powercurve measurement; expected to be thesame power curve at any site
� Slightly underestimates the energyavailable because does not account forthe shear at Østerild (assumes flat windspeed profiles)
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Risø DTU, Danmarks Tekniske Universitet
Summary
U_hub power curve Ueq power curve
U_hub distribution (-2.3%) (-0.5%)
U_eq distribution (ref)
The error depends both on:• the Ueq/Uhub distribution during the power curve measurement (-1.8%)• and the Ueq/Uhub distribution at the assessed site (-0.5%)
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Risø DTU, Danmarks Tekniske Universitet
More examples
Ueq/Uhub> 1Ueq/Uhub< 1
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Risø DTU, Danmarks Tekniske Universitet
Case1: Ueq/Uhub> 1
U_hub power curve Ueq power curve
U_hub distribution (-3.8%) (-2.1%)
U_eq distribution (ref)
Profiles with larger kinetic energy than flat profiles
Part of the the error due to Ueq/Uhub distribution at the assessed site largerthan before (-2.1%);� Overall error larger than previous case.
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Risø DTU, Danmarks Tekniske Universitet
Case2: Ueq/Uhub< 1
U_hub power curve Ueq power curve
U_hub distribution (0.00%) (+1.8%)
U_eq distribution (ref)
Profiles with smaller kinetic energy than flat profiles
Specific case:The Ueq/Uhub distribution are verysimilar for both datasets.
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Risø DTU, Danmarks Tekniske Universitet
Conclusions 1
The shear influences the AEP estimation in 2 ways:
1)Error in power curve due to the shear during the power curvemeasurement2)Error in available energy at the assessed site.
�Missing uncertainty terms in the standard AEP estimation
�Equivalent wind speed results in a repeatable power curve.
�Improved AEP estimation with equivalent wind speed
�It requires to measure the wind speed profiles for site assessment
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Risø DTU, Danmarks Tekniske Universitet
Conclusions 2
What to do if the equivalent wind speed distribution at the assessed site isnot available?
� If the Ueq/Uhub distributions at the two sites are similar: use the standardAEP calculation (wind speed at hub height).
� If the Ueq/Uhub distributions are different: combine the hub height speeddistribution with the equivalent power curve.
But to know the Ueq/Uhub distribution…… you need to measure the shear!
Acknowledgement: EU SafeWind
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Risø DTU, Danmarks Tekniske Universitet
Wind lidar calibration
•Comparison to cupanemometers at 5 heights
•Horizontal wind speed,sensing height error,uncertainty, direction
•Synchronised lidar/mast data
•Accrediation for Windcubescalibration
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Risø DTU, Danmarks Tekniske Universitet
Wind lidar measurement
•Rent out a Windcube
•Set up, data transfert
•Data analysis
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Risø DTU, Danmarks Tekniske Universitet
Wind Lidar – A practical course7-10 May 2012
•Lectures about the workingprinciples and limitations of lidarsystems.
•Interpreting data
•Hands-on experience with a lidaron-site
More information and registrationhttp://www.risoe.dtu.dk/da/conferences/vea_lidar_course_2012.aspx?sc_lang=en