Global Blockage Effects in Wind Farms

Abstract

An experimental and numerical study of wind-farm blockage has been performed to quantify the velocity reduction that the first row of a wind farm experiences due to other turbines downstream. In the present study, an attempt is made to demonstrate the existence of a two-way coupling between individual turbines and wind farm. Several staggered layouts were tested in the wind-tunnel experiments by changing the spacing between rows, spacing between the turbines in the same row and the amount of wind turbines involved. Three turbines located in the first row were monitored to assess their sensitivity to the turbines downstream. One of the experiments was replicated by means of numerical simulations performed in ORFEUS, a linearised code developed at KTH, in order to complement the experimental results. Simulations were performed at the same thrust coefficient and with a more distant ceiling to assess the eventual interference of the ceiling on the experimental results. Additionally, simulations performed at different thrust coefficients were done to assess its effect on the blockage phenomenon.