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Wind Farm Noise Impact Assessment WIND SHEAR

Wind Farm Noise Impact Assessment WIND SHEAR. Wind shear ……. what is wind shear ? how does wind shear affect wind farm noise ? how should wind shear be dealt with ?. V u. V L. What is wind shear ?. What causes wind shear ?. ground roughness. V U. log(H U /z 0 ). x. V U. =. V L.

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Wind Farm Noise Impact Assessment WIND SHEAR

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  1. Wind Farm Noise Impact Assessment WIND SHEAR

  2. Wind shear ……. • what is wind shear ? • how does wind shear affect wind farm noise ? • how should wind shear be dealt with ?

  3. Vu VL What is wind shear ?

  4. What causes wind shear ? ground roughness

  5. VU log(HU/z0) x VU = VL log(HL/z0) HU VL HL Modelling wind shear due to ground roughness z0 = ground roughness length ground roughness

  6. What causes wind shear ? atmospheric effects

  7. What causes wind shear ? atmospheric effects

  8. What causes wind shear ? atmospheric effects

  9. What causes wind shear ? atmospheric effects

  10. m HU VU x VU = VL HL HU VL HL Modelling wind shear due to atmospheric effects m= shear exponent atmospheric effects

  11. 8 80 6 40 80 Hourly averaged wind speed, m/s 20 4 10 2 00:00 06:00 12:00 18:00 24:00 Time of day, hh:mm Diurnal variations in wind speeds Height above ground, m After G.P van den Berg, WTG Noise 2005, Berlin

  12. Diurnal variations in wind shear Wind shear is generally highest in evening/night which are measured under ETSU-R-97

  13. Wind shear as a function of wind speed

  14. Diurnal and seasonal variations in wind shear all wind speeds

  15. Diurnal and seasonal variations in wind shear 3 m/s to 5 m/s wind speeds only

  16. Diurnal and seasonal variations in wind shear 6 m/s to 8 m/s wind speeds only

  17. VH V10 Why is wind shear important for wind farm noise ?

  18. Wind shear – effect on turbine sound power

  19. ETSU-R-97 Wind Farm Noise – setting acceptable limits ETSU-R-97 sets noise limits as a function of 10m height wind speed

  20. Source Sound Power Level ETSU-R-97 Noise Limit Wind Farm Noise Immission Level Calculating wind farm noise at receptors Wind turbine noise emissions are also specified as a function of 10m height wind speed Noise Propagation Calculation Algorithm Standardisedfrom hub height

  21. VH V10 Using a hub height mast only + background noise and turbine SWL’s both related to the same ‘real’ wind speed + requires no assumptions about site specific shear profile - typically requires >50m high mast

  22. VH V2 V1 V10 Using measurements at two heights + Similar to first method + Lesser measurement height: use shorter mast and shear measured between two heights to extrapolate up to hub height - typically requires up to 50m high mast

  23. VH Wind speed at 10m height (m/s) V10 Using a 10m mast only + cheapest and easiest option - Need to have data or make assumptions on shear profile on the site + IOA GPG provides simplified corrections for use

  24. Wind shear is important for wind farm noise … and best practice guidance is contained in the IoA GPG

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