Richard J.A.M. Stevens

Professor at the University of Twente

Wind energy · Turbulence · Environmental flows

Publication 125 · Atmospheric turbulence

Low-frequency wind speed variations and their impact on wind farm performance

Y. Liu, A. Stieren, R.J.A.M. Stevens, J. Renewable Sustainable Energy 18, 043304 (2026).

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Main finding

During prescribed low-frequency wind-speed changes, downstream turbine power depends on earlier inflow as well as current speed because wakes take time to advect and adjust. This wake-history asymmetry is demonstrated numerically, not established as a field-validated mesoscale response law.

Imposed wind speed over eighteen hours with the resulting wind farm power beneath
How to read the figure. A prescribed hub-height wind speed varying over eighteen hours (a), with the acceleration and deceleration events marked, and the resulting farm power at two thrust settings (b, c). The same wind speed gives different power depending on whether the farm is speeding up or slowing down: the farm carries the memory of its own wake history. This is conditional numerical evidence under prescribed forcing, not a field-validated mesoscale response law. Open the full-resolution figure. Figure 4. Y. Liu et al. (2026). No separate licence is stated here; consult the original publication and credited source before reuse.

Why this matters

Low-frequency inflow acceleration changes wake age, making downstream power depend on prior as well as current wind conditions.

Research context

The study draws on concurrent-precursor and wind-farm LES methods and on earlier dynamic-flow and spectral-coherence work. A related later paper, Modeling Multiscale Atmospheric Interactions in Wind-Farm Power Spectra (read the finding), uses the same imposed signal and numerical strategy to build a multiscale spectral-coherence model.

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