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Array efficiency at Horns Rev and the effect of atmospheric stability

Array efficiency at Horns Rev and the effect of atmospheric stability. Leo E. Jensen. Horns Rev - Layout. Horns Rev – Met. masts. Horns Rev – Distance from land. Turbine 14 - Dimensions. External data - Met. masts. Mast 2: Wind speed 62 m (top) 45 m (nw/se) 30 m (nw/se) 15 m (nw/se)

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Array efficiency at Horns Rev and the effect of atmospheric stability

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  1. Array efficiency at Horns Revand the effect of atmospheric stability Leo E. Jensen

  2. Horns Rev - Layout Doc. info 271939

  3. Horns Rev – Met. masts Doc. info 271939

  4. Horns Rev – Distance from land Doc. info 271939

  5. Turbine 14 - Dimensions Doc. info 271939

  6. External data - Met. masts • Mast 2: • Wind speed • 62 m (top) • 45 m (nw/se) • 30 m (nw/se) • 15 m (nw/se) • Wind direction • 60 m • 43 m • 28 m • Temperature • 55 m (x2) • 13 m (x2) • -4 m (water) • Air Pressure • 55 m • Rain • Humidity • Mast 6&7: • Wind speed • 70 m (top) • 60 m (nw) • 50 m (nw/se) • 40 m (nw) • 30 m (nw/se) • 20 m (nw) • Wind direction • 68 m • 28 m • Temperature • 64 m • 16 m • -3 m (water) • Air pressure • 16 m • Rain Doc. info 271939

  7. Measured array efficiency Doc. info 271939

  8. Calculated array efficiency Doc. info 271939

  9. Comparison 1.043 0.999 - 1.043 0.954 - 0.999 0.954 Measurement & Calculated Efficiency Comparison Doc. info 271939

  10. Zo  0.01  0.1  0.5 ------- 0.001 Wind Shear Gradients Z [m] Doc. info 271939 V [m/s]

  11. Wind Shear as function of temperature difference Doc. info 271939

  12. Wind Shear as function of temperature difference Doc. info 271939

  13. Choice of stability classes • Tair - Twater < -0.1° : Unstable boundary layer. • -0.1° <= Tair - Twater < 1.5° : Neutral boundary layer. • 1.5° <= Tair - Twater : Stable boundary layer. Doc. info 271939

  14. Stability classes Doc. info 271939 Unstable Neutral Stable

  15. Average of all data 700 kW 425 kW Doc. info 271939 Array Efficiency 71 %

  16. Only unstable data 700 kW 450 kW Doc. info 271939 Array Efficiency 74 %

  17. Only near-neutral data 700 kW 400 kW Doc. info 271939 Array Efficiency 66 %

  18. Only stable data 625 kW 275 kW Doc. info 271939 Array Efficiency 61 %

  19. Distribution of stability classes Doc. info 271939

  20. Efficiency Losses Losses relative to all data losses All data 90.2% 9.8% 100% Unstable 91.5% 8.5% 87% Neutral 88.9% 11.1% 113% Stable 85.3% 14.7% 150% Annual mean array effeiciency Doc. info 271939

  21. Conclusions • Stability has a significant effect on array efficiency • Stability should allways be considered when calibrating models • Including stability as part of wind ressource assesment should be considered. Doc. info 271939

  22. Acknowledgements • Sten Frandsen and Rebecca Barthelmie, Risø & University of Edinburgh, for fruitfull discussions on the wake effect subject in many different R&D projects • Pierre-Elouan Réthoré, Risø/DTU for help and inspiration on sorting and graphical presentation of data • The Danish ”Public Service Obligation” (PSO) funds from Energinet.dk for supporting the installation of the wake masts and various R&D projects on this subject. Doc. info 271939

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