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The generics of wind turbine nacelle anemometry

The generics of wind turbine nacelle anemometry. Assessment of productive capacity. Nacelle anemometry serves multiple purposes and it is frequently used for verifying productive capacity of wind projects. Thus, erection of expensive met masts is saved

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The generics of wind turbine nacelle anemometry

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  1. The generics ofwind turbine nacelle anemometry

  2. Assessment of productive capacity • Nacelle anemometry serves multiple purposes and it is frequently used for verifying productive capacity of wind projects. Thus, erection of expensive met masts is saved • Question: is it meaningful to use the nacelle anemometer?

  3. The nacelle anemometer is meant to measure the free wind… but the flow around the nacelle is complicated – exposed to numerous sources of disturbances

  4. Major influence parameters

  5. Specific problem • When we are doing performance verification, what are we actually looking for? Answer: a possible change in power relative to a warranted power curve • Generics: while the reading of the nacelle anemometer is disturbed by a number of effects, some disturbances are related to the wind turbine rotor’s action on the flow • “Calibration” components of the nacelle anemometer:

  6. Betz 1D rotor model

  7. Calibration of nacelle anemometer

  8. Nacelle anemometry: what is the generic problem? Measuring the reference PC, and calibrating the nacelle anemometer: Measuring the PC in the field, but the real PC is:

  9. For the 1-D rotor – relation between dp and dv For the Betz rotor, we have: Assume a change in power relative to warranted power, at free wind speed u: Measured nacelle wind speed v1: However, presumed free wind speed:

  10. The ”1-D” generic error of nacelle anemometry Resulting change and error in power at wind speed u: The error relative to the actual change in power:

  11. Approx. state of art: CP,max~0.5 The relative generic error for 1-D rotor

  12. Illustration of generic error

  13. Siemens, CFD 3-D RANS rotor flow

  14. DTU: CFD 3-D RANS rotor flow

  15. 3-D induction

  16. Computed and measured performance characteristics

  17. Comparison of Cp and CT with 1-D ideal Betz distrib.

  18. Comparison of Cp and CT with 1-D ideal Betz distrib.

  19. Conclusions • For 1D Betz rotor: Nacelle anemometry introduces an error which is of the order 75%. The error is one-sided and may in principle be corrected for • For 3D rotor: the induction close to the rotor center and the nacelle is typically small and the error is in general terms less. However, the gradients is the induction factor are here large, which makes the uncertainty of the error large • These wind speed gradients close to the nacelle make it an attraktive option to measure the flow speed, say, 10-20m in front of the spinner

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