the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Brief communication: How does complex terrain change the power curve of a wind turbine?
- DTU Wind Energy, Frederiksborgvej 399 4000, Roskilde, Denmark
- DTU Wind Energy, Frederiksborgvej 399 4000, Roskilde, Denmark
Abstract. The power performance of a wind turbine in complex terrain is studied by means of Large Eddy Simulations (LES). The simulations show that the turbine performance is significantly different compared to what should be expected from the available wind. The reason for this deviation is that the undisturbed flow field behind the turbine is non-homogeneous and therefore results in a very different wake development and induction than seen for a turbine in flat homogeneous terrain.
Niels Troldborg et al.
Status: open (until 07 Jun 2022)
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RC1: 'Great simulations to understand the interplay between power curve response and complex terrain and roughness characteristics', Javier Sanz Rodrigo, 13 May 2022
reply
Interesting case study discussing the differences between power curves in flat vs complex terrain supporting the need for site-specific calibration. The numerical approach and results are well described and solid. The only limitation I see is on the statistical significance of the assessment, with only 6 10-min samples per case to compute ensemble averages. Also, the generalization of the simulation results to real world campaigns needs to be discussed a bit more. In particular, the limited representativeness of the simulations when we compare with the statistis of a site calibration campaign that averages a much wider range of flow cases. Nevertheless, I would agree with the general conclusion of the study, that power curves are site specific, with good examples provided in this study. I believe this is a well-established conclusion in the wind industry. Please elaborate more on the statistical aspects to enrich the discussion of the case study.
Comments:
P2.35: Please specify the hub-height and rotor diameter of the reference turbine
P2.42: "the grid cells has dimensions" > the grid cells have dimensions
P3.58: In addition to the roughness length and friction velocity it would be useful to present the hub-height wind speed, turbulence intensity, inflow angle and rotor-based wind shear (power-law exponent) and wind veer. These are more useful to understand the range of conditions in terms of siting parameters. Can you provide a table with this info?
P3.72: With only 6x10-min samples, have you reached converged statistics to make an unbiassed assessment of the differences between flat and complex terrain? Please justify if 1.5 hr simulation time is long enough.
P4.Fig2: The velocities are scaled with the free-stream velocity at the position of the wind turbine > at hub-height right? I would add a third row with the difference between the two contour plots, without and with turbine, to highlight and quantify differences more clearly.
P4.82: "and, as shown in Fig. 2f), this causes" (add commas)
P4.92: For completeness, can you add the formula for induced velocity that you use to plot Fig.3b?
P5.111: "… a site calibration cannot stand alone when verifying the power performance of turbines in complex terrain". I wouldn't reach this conclusion without a more complete assessment that would replicate the statistics that you gather in a IEC 61400-12 site calibration campaign. This study shows that the differences can be large in a few 10 min samples but these differences may average out when you use a large number of samples over a period that captures a representative range of stability, wind speed and direction changes.
P6.114: including in wind farms > I would rather say "including in waked conditions"
Niels Troldborg et al.
Niels Troldborg et al.
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