Preprints
https://doi.org/10.5194/wes-2021-7
https://doi.org/10.5194/wes-2021-7

  23 Feb 2021

23 Feb 2021

Review status: a revised version of this preprint was accepted for the journal WES.

Recovery Processes in a Large Offshore Wind Farm

Tanvi Gupta and Somnath Baidya Roy Tanvi Gupta and Somnath Baidya Roy
  • Centre for Atmospheric Sciences, Indian Institute of Technology Delhi, New Delhi, 110016, India

Abstract. Wind turbines in a wind farm extract energy from the atmospheric flow and convert it into electricity, resulting in a localized momentum deficit in the wake that reduces energy availability for downwind turbines. Atmospheric momentum convergence from above, below and sides into the wakes replenish the lost momentum, at least partially, so that turbines deep inside a wind farm can continue to function. In this study, we explore recovery processes in a hypothetical offshore wind farm with particular emphasis on comparing the spatial patterns and magnitudes of horizontal and vertical recovery processes and understanding the role of mesoscale processes in momentum recovery in wind farms. For this purpose, we use the Weather Research and Forecasting (WRF) model, a state-of-the-art mesoscale model equipped with a wind turbine parameterization, to simulate a hypothetical large offshore wind farm with different wind turbine spacings under realistic initial and boundary conditions. Results show that vertical turbulent transport of momentum from aloft is the main contributor to recovery in wind farms except in cases with strong background winds and high inter-turbine spacing where horizontal advective momentum transport can also contribute equally. Vertical recovery shows a systematic dependence on wind speed and wind farm density that can be quantified using low-order empirical equations. Wind farms significantly alter the mesoscale flow patterns, especially for densely packed wind farms under high wind speed conditions. In these cases, the mesoscale circulations created by the wind farms can transport high momentum air from aloft into the atmospheric boundary layer (ABL) and thus aid in recovery in wind farms. This is a novel study that is one of the first to look at wind farm replenishment processes under realistic meteorological conditions including the role of mesoscale processes. Overall, this study significantly advances our understanding of recovery processes in wind farms and wind farm-ABL interactions.

Tanvi Gupta and Somnath Baidya Roy

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-2021-7', Enrico Antonini, 02 Mar 2021
    • AC1: 'Reply on CC1', Tanvi Gupta, 06 Mar 2021
  • RC1: 'Comment on wes-2021-7', Anonymous Referee #1, 12 Mar 2021
    • AC2: 'Reply on RC1', Tanvi Gupta, 15 Apr 2021
  • RC2: 'Comment on wes-2021-7', Anonymous Referee #2, 29 Mar 2021
    • AC3: 'Reply on RC2', Tanvi Gupta, 15 Apr 2021

Tanvi Gupta and Somnath Baidya Roy

Model code and software

Files for calculating recovery processes using WRF Vr 4.2.1 Gupta, Tanvi and Baidya Roy, Somnath https://doi.org/10.5281/zenodo.4552414

Tanvi Gupta and Somnath Baidya Roy

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Short summary
Wind turbines extract momentum from atmospheric flow and convert that to electricity. This study explores recovery processes in wind farms that replenish the momentum so that wind farms can continue to function. Experiments with a numerical model show that momentum transport by turbulent eddies from above the wind turbines is the major contributor to recovery except for strong wind conditions and high wind turbine density where horizontal advection can also play a major role.