Richard J.A.M. Stevens

Professor at the University of Twente

Wind energy · Turbulence · Environmental flows

Publication 100 · Wind-farm flow

A wind-farm wake changes more than the next farm's first row

A. Stieren and R.J.A.M. Stevens, Flow 2, E21 (2022).

Read the article Open-access version

The article and figure are open access under CC BY 4.0.

Main finding

An upstream wind-farm wake changed power and turbulent transport throughout the downstream farm, not only at its first row. Increasing the gap from 5 to 15 km raised the downstream first-row power from 67% to 87% of the upstream first-row value in the tested staggered cases.

Normalized power by turbine row for upstream and downstream wind farms with different layouts and inter-farm gaps
How to read the figure. Panels (a) and (c) normalize every row by the first row of the upstream farm, making the incoming wake penalty directly visible. Open symbols with dashed lines denote the upstream farm; filled symbols denote the downstream farm. Panel (a) compares staggered farms separated by 5, 10, and 15 km, while panel (c) compares the complete staggered, aligned, and staggered-to-aligned layouts at 10 km. Panels (b) and (d) instead normalize each farm by its own first row, so they show internal row-to-row development rather than the absolute farm-to-farm penalty. Open the full-resolution figure. Figure 17, cropped. A. Stieren and R.J.A.M. Stevens (2022), CC BY 4.0.

Why this matters

The upstream wake is not merely an entrance correction. In the staggered cases, its power penalty extends through multiple rows: the downstream and upstream curves become similar by approximately row 3 for the 15 km gap, but only near the final row for the 5 km gap. The tested distances therefore demonstrate persistent farm-to-farm interaction, not a universal safe-separation rule.

Research context

The study uses neutral, barotropic, North-Sea-like large-eddy simulations of two directly aligned farms, each with 72 actuator-disk turbines. The farms are separated by 5, 10, or 15 km and use one turbine size, thrust coefficient, wind direction, and atmospheric state. The five-hour statistics have no error bands, and layout comparisons also change farm width. Figures 12–13 show that downward kinetic-energy transport above the downstream farm increases with the incoming wake, but flux, turbulence, shear, internal-boundary-layer development, and power change together; the simulations therefore support, but do not uniquely isolate, the proposed transport mechanism. The reported power is model-derived, with no field validation, operational losses, or annual-energy calculation.

View in the complete publication list Related wind-farm LES research