Measuring the impact of atmospheric conditions and array depth on wake losses
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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.

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Measuring the impact of atmospheric conditions and array depth on wake losses

Measuring the Impact of Atmospheric Conditions and Array Depth on Wake Losses

Anna Marsh – DNV KEMA

04 – 07 Feb 2013, Vienna Austria


Contents
Contents Depth on Wake Losses

Introduction to the test site

Measurements

Comparison to models

Conclusions


Introduction to the site
Introduction to the Site Depth on Wake Losses


Turbine row grouping 225 245 direction sector
Turbine Row Grouping – 225º Depth on Wake Losses- 245º Direction Sector

2 km Grid Lines (about 25 D)

Lidar


Measured shear profiles by ti
Measured Shear Profiles by TI Depth on Wake Losses

Rotor


Measured wake by row ti
Measured Wake by Row - TI Depth on Wake Losses

Relative Power = % Power Difference Relative to Front Row

TI Range


Measured shear profiles by shear difference across rotor
Measured Shear Profiles by Depth on Wake LossesShear Difference Across Rotor

Shear Difference Across Rotor =

Top Shear (80m/120m Alpha)

Minus

Bottom Shear (40m/80m Alpha)

Top Shear

Rotor

Shear Difference

Bottom Shear


Measured wake by row shear difference across rotor
Measured Wake by Row – Shear Difference Across Rotor Depth on Wake Losses

Shear Difference


Wake models
Wake Models Depth on Wake Losses

Single 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

9


Measured vs modelled wakes rows 1 15
Measured vs. Modelled Wakes Rows 1-15 Depth on Wake Losses

-Measured Wakes



Measured vs fuga model stable and unstable conditions
Measured vs. Depth on Wake LossesFuga Model – Stable and Unstable Conditions



Conclusions
Conclusions Depth on Wake Losses

  • 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

Special thanks to project participants who shared data for this study.


Dnv kema energy sustainability
DNV KEMA Energy & Sustainability Depth on Wake Losses

  • 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

  • Risk, performance, and quality management

  • Research & innovation

  • Offices in over 30 countries


Anna Marsh Depth on Wake Losses

Senior Engineer

DNV KEMA Energy & Sustainability

Palace House

3 Cathedral Street

London SE1 9DE

Tel: +44 20 7716 6591

Mobile: +44 79 6972 9915

[email protected]

www.dnvkema.com

www.dnv.com/windenergy

www.dnvkema.com


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