Preprints
https://doi.org/10.5194/wes-2021-36
https://doi.org/10.5194/wes-2021-36

  10 May 2021

10 May 2021

Review status: this preprint is currently under review for the journal WES.

Meso- to micro-scale modeling of atmospheric stability effects on wind turbine wake behavior in complex terrain

Adam S. Wise1, James M. T. Neher1, Robert S. Arthur2, Jeffrey D. Mirocha2, Julie K. Lundquist3,4, and Fotini K. Chow1 Adam S. Wise et al.
  • 1Department of Civil and Environmental Engineering, University of California, Berkeley, Berkeley, California, USA
  • 2Lawrence Livermore National Laboratory
  • 3Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado, USA
  • 4National Renewable Energy Laboratory, Golden, Colorado, USA

Abstract. Most detailed modeling and simulation studies of wind turbine wakes have considered flat terrain scenarios. Wind turbines, however, are commonly sited in mountainous or hilly terrain to take advantage of accelerating flow over ridgelines. In addition to topographic acceleration, other turbulent flow phenomena commonly occur in complex terrain, and often depend upon the thermal stratification of the atmospheric boundary layer. Enhanced understanding of wind turbine wake interaction with these terrain-induced flow phenomena can significantly improve wind farm siting, optimization, and control. In this study, we simulate conditions observed during the Perdigão field campaign in 2017, consisting of flow over two parallel ridges with a wind turbine located on top of one of the ridges. We use the Weather Research and Forecasting model (WRF) nested down to micro-scale large-eddy simulation (LES) at 10 m resolution, with a generalized actuator disk (GAD) wind turbine parameterization to simulate turbine wakes. Two case studies are selected, a stable case where a mountain wave occurs and a convective case where a recirculation zone forms in the lee of the ridge with the turbine. The WRF-LES-GAD model is validated against data from meteorological towers, soundings, and a tethered lifting system, showing good agreement for both cases. Comparisons with scanning Doppler lidar data for the stable case show that the overall characteristics of the mountain wave are well-captured, although the wind speed is underestimated. For the convective case, the size of the recirculation zone within the valley shows good agreement. The wind turbine wake behavior shows dependence on atmospheric stability, with different amounts of vertical deflection from the terrain and persistence downstream for the stable and convective conditions. For the stable case, the wake follows the terrain along with the mountain wave and deflects downwards by nearly 100 m below hub-height at four rotor diameters downstream. For the convective case, the wake deflects above the recirculation zone over 50 m above hub-height at the same downstream distance. This study demonstrates the ability of the WRF-LES-GAD model to capture the expected behavior of wind turbine wakes in regions of complex terrain, and thereby to potentially improve wind turbine siting and operation in hilly landscapes.

Adam S. Wise et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on wes-2021-36', Alfredo Peña, 12 May 2021
    • AC1: 'Reply on CC1', Adam Wise, 02 Jun 2021
  • RC1: 'Comment on wes-2021-36', Dries Allaerts, 08 Jun 2021
    • AC2: 'Reply on RC1', Adam Wise, 28 Jul 2021
  • RC2: 'Comment on wes-2021-36', Anonymous Referee #2, 25 Jun 2021
    • AC3: 'Reply on RC2', Adam Wise, 28 Jul 2021

Adam S. Wise et al.

Adam S. Wise et al.

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Short summary
Wind turbine wake behavior in hilly terrain depends on various atmospheric conditions. We modeled a wind turbine located on top of a ridge in Portugal during typical nighttime and daytime atmospheric conditions and validated these model results with observational data. During nighttime conditions, the wake deflected downwards following the terrain. During daytime conditions, the wake deflected upwards. These results can provide insight into wind turbine siting and operation in hilly regions.