Preprints
https://doi.org/10.5194/wes-2021-105
https://doi.org/10.5194/wes-2021-105

  21 Oct 2021

21 Oct 2021

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

Evaluation of the global-blockage effect on power performance through simulations and measurements

Alessandro Sebastiani, Alfredo Peña, Niels Troldborg, and Alexander Meyer Forsting Alessandro Sebastiani et al.
  • DTU Wind Energy, Frederiksborgvej 399 4000, Roskilde, Denmark

Abstract. Blockage effects due to the interaction of five wind turbines in a row are investigated through both Reynolds-averaged Navier-Stokes simulations and site measurements. Since power performance tests are often carried out at sites consisting of several turbines in a row, the objective of this study is to evaluate whether the power performance of the five turbines differs from that of an isolated turbine. A number of simulations are performed, in which we vary the turbine inter-spacing (1.8, 2 and 3 rotor diameters) and the inflow angle between the incoming wind and the orthogonal line to the row (from 0° to 45°). Different values of the free-stream velocity are considered to cover a broad wind speed range of the power curve. Numerical results show consistent power deviations for all the five turbines when compared to the isolated case. The amplitude of these deviations depends on the location of the turbine within the row, the inflow angle, the inter-spacing and the power curve region of operation. We show that the power variations do not cancel out when averaging over a large inflow sector (from −45° to +45°) and find an increase in the power output of up to +1 % when compared to the isolated case. We simulate power performance ‘measurements’ with both a virtual mast and nacelle-mounted lidar and find a combination of power output increase and upstream velocity reduction, which causes an increase of +4 % of the power coefficient. We also use measurements from a real site consisting of a row of five wind turbines to validate the numerical results. From the analysis of the measurements, we also show that the power performance is impacted by the neighboring turbines. Compared to when the inflow is perpendicular to the row, the power output varies of +1.8 % and −1.8 % when the turbine is the most downwind and upwind of the line, respectively.

Alessandro Sebastiani et al.

Status: open (until 02 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wes-2021-105', Bleeg James, 24 Nov 2021 reply
  • RC2: 'Comment on wes-2021-105', Anonymous Referee #2, 24 Nov 2021 reply

Alessandro Sebastiani et al.

Alessandro Sebastiani et al.

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Short summary
The power performance of a wind turbine is often tested with the turbine standing in a row of several wind turbines, as it is assumed that the performance is not affected by the neighboring turbines. We test this assumption with both simulations and measurements, and we show that the power performance can be either enhanced or lowered by the neighboring wind turbines. Consequently, we also show how power performance testing might be biased when performed on a row of several wind turbines.