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Measuring the Impact of Atmospheric Conditions and Array Depth on Wake Losses. Anna Marsh – DNV KEMA. 04 – 07 Feb 2013, Vienna Austria. Contents. Introduction to the test site Measurements Comparison to models Conclusions. Introduction to the Site. - PowerPoint PPT Presentation
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Measuring the Impact of Atmospheric Conditions and Array Depth on Wake LossesAnna Marsh – DNV KEMA04 – 07 Feb 2013, Vienna Austria
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
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Contents
Introduction to the test site
Measurements
Comparison to models
Conclusions
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
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Introduction to the Site
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
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Turbine Row Grouping – 225º - 245º Direction Sector2 km Grid Lines (about 25 D)
Lidar
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
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60% 80% 100% 120% 140%Relative Wind Speed
40
50
60
70
80
90
100
110
120
130
140
150
160
Height
TI Range< 4%4% to 8%> 8%
Measured Shear Profiles by TI
Rotor
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
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Measured Wake by Row - TIRelative Power = % Power Difference Relative to Front Row
TI Range
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
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60% 80% 100% 120%Relative Wind Speed
40
50
60
70
80
90
100
110
120
130
140
150
160
Height
Measured Shear Profiles by Shear Difference Across RotorShear Difference Across Rotor =Top Shear (80m/120m Alpha)
Minus
Bottom Shear (40m/80m Alpha)
Change in Shear< -0.4-0.4 to -0.2-0.2 to 0.0> 0.0
Rotor
Top Shear
Bottom Shear
Shear Difference
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
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Measured Wake by Row – Shear Difference Across Rotor
Shear Difference
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
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Wake ModelsSingle turbine wake models
Park Eddy Viscosity
Combination methods Square root of sum of squares (SS) Energy balance (EB)
Accounting for atmospheric conditions Time Series Park and Eddy Viscosity Model
Fuga
Data used in Measured and Modelled Results August through December data Filtered for 6m/s to 12m/s
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MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
Measured vs. Modelled Wakes Rows 1-15
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- Measured Wakes
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
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Measured vs. Eddy Viscosity Model - TI
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
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Measured vs. Fuga Model – Stable and Unstable Conditions
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
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Measured vs. Time Series Average of Models - TI
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
Conclusions Wake losses are significantly influenced by TI and shear across the rotor.
Models underestimate wakes in some conditions and over predict wakes in other conditions. For some projects, the errors will cancel out.
Results are consistent with other DNV KEMA studies and observations.
Recommendations- Measure parameters that impact wakes, such as shear across and above the rotor- Modify wake models to account for conditions that can be measured- More wake model validation studies comparing atmospheric conditions and wakes
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Special thanks to project participants who shared data for this study.
MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
DNV KEMA Energy & Sustainability Part of DNV Group—an independent
foundation with HQ in Norway founded in 1864—with 11,000 employees globally
200+ wind energy experts
30 GW+ energy assessments globally
Testing, inspections, certification, consulting
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MEASURING THE IMPACT OF ATMOSPHERIC CONDITIONS AND ARRAY DEPTH ON WAKE LOSSES
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www.dnvkema.com
Anna MarshSenior EngineerDNV KEMA Energy & Sustainability
Palace House3 Cathedral StreetLondon SE1 9DETel: +44 20 7716 6591Mobile: +44 79 6972 [email protected]/windenergy
