Effects of turbine spacing on the power output of extended wind-farms

TL;DR

This study uses large eddy simulations to analyze how turbine spacing and arrangement affect wind-farm power output, wake recovery, and energy transfer, revealing different behaviors for aligned and staggered configurations.

Contribution

It provides new insights into the influence of turbine layout on power production and wake dynamics using detailed LES simulations.

Findings

Power output depends on geometric mean of spacings in staggered layouts.

Aligned layouts show strong dependence on streamwise spacing for power output.

Vertical kinetic energy flux correlates with wake recovery and differs between configurations.

Abstract

We present results from large eddy simulations (LES) of extended wind-farms for several turbine configurations with a range of different spanwise and streamwise spacing combinations. The results show that for wind-farms arranged in a staggered configuration with spanwise spacings in the range $\approx[3.5,8]$D, where $D$ is the turbine diameter, the power output in the fully developed regime depends primarily on the geometric mean of the spanwise and streamwise turbine spacings. In contrast, for the aligned configuration the power output in the fully developed regime strongly depends on the streamwise turbine spacing and shows weak dependence on the spanwise spacing. Of interest to the rate of wake recovery, we find that the power output is well correlated with the vertical kinetic energy flux, which is a measure of how much kinetic energy is transferred into the wind-turbine region by the mean flow. A comparison between the aligned and staggered configurations reveals that the vertical kinetic energy flux is more localized along turbine rows for aligned wind-farms than for staggered ones. This additional mixing leads to a relatively fast wake recovery for aligned wind-farms.