Synergistic Effects of Turbine Wakes and Atmospheric Stability on Power Production at an Onshore Wind Farm

Wharton, Sonia; Lundquist, Julie K.; Marjanovic, Nikola

doi:10.2172/1035607

Cited by 5 publications

(8 citation statements)

References 25 publications

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“…Specifically, stable or unstable stratification affects the level of turbulence in the atmosphere that consequently affects the wake recovery. The relation between atmospheric stratification and wind‐farm efficiency has been analysed in several works like those by Hansen et al, 22 Wharton et al, 23 Vanderwende and Lundquist 24 and Ghaisas et al 7 Generally, it is stated that stable conditions dampen turbulence and consequently slow down the wake recovery, resulting in stronger wake losses. On the contrary, unstable conditions enhance the mixing in the atmosphere, increasing turbulence and therefore the wake recovery, resulting in lower wake losses.…”

Section: Discussionmentioning

confidence: 99%

Data analysis and simulation of the Lillgrund wind farm

et al. 2020

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The power production of the Lillgrund wind farm has been investigated by means of SCADA data covering almost 10 years of operation, wake models and numerical simulation tools, such as WindSim, OpenFOAM and ORFEUS. The analysis of the SCADA data provided the quantification of wake losses and of blockage effects, results that enable a benchmark to assess the uncertainty of other numerical methods of industrial use. The results have been analysed in terms of global array efficiency for different wind directions, wind velocity and stratification conditions. A comparison of the present results with the Jensen and Ainsle models indicated that the two used wake models are affected by an error of about 8–10% in the estimation of the array efficiency, while the error does not vary significantly when using numerical tools such as ORFEUS, WindSim and OpenFOAM. By comparing wind statistics available before the park construction, an assessment of the blockage of the Lillgrund farm was performed with contrasting results from the other numerical tools, highlighting how challenging is to assess farm blockage with current industrial settings.

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Section: Discussionmentioning

confidence: 99%

Data analysis and simulation of the Lillgrund wind farm

et al. 2020

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“…The effect of atmospheric stability on wake evolution, turbine loads and power production has become an emerging research topic. A number of studies have documented the influence of the atmospheric stability on turbine loads and power both experimentally (Barthelmie et al ., Wharton et al ., Schepers et al ., and Hansen et al Churchfield et al ., Lee et al ., and Lavely et al …”

Section: Introductionmentioning

confidence: 99%

On atmospheric stability in the dynamic wake meandering model

et al. 2013

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The present study investigates a new approach for capturing the effects of atmospheric stability on wind turbine wake evolution and wake meandering by using the dynamic wake meandering model. The most notable impact of atmospheric stability on the wind is the changes in length and velocity scales of the atmospheric turbulence. The length and velocity scales in the turbulence are largely responsible for the way in which wind turbine wakes meander as they convect downstream. The hypothesis of the present work is that appropriate turbulence scales can be extracted from the oncoming atmospheric turbulence spectra and applied to the dynamic wake meandering model to capture the correct wake meandering behaviour. The ambient turbulence in all stability classes is generated using the Mann turbulence model, where the effects of non-neutral atmospheric stability are approximated by the selection of input parameters.In order to isolate the effect of atmospheric stability, simulations of neutral and unstable atmospheric boundary layers using large-eddy simulation are performed at the same streamwise turbulence intensity level. The turbulence intensity is kept constant by calibrating the surface roughness in the computational domain. The changes in the turbulent length scales due to the various atmospheric stability states impact the wake meandering characteristics and thus the power generation by the individual turbines.The proposed method is compared with results from both large-eddy simulation coupled with an actuator line model and field measurements, where generally good agreement is found with respect to the velocity, turbulence intensity and power predictions.

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“…Past field campaigns reflect these complexities and point to conflicting trends in the impact of atmospheric stability on power production. Wharton and Lundquist observed increased power for stable over neutral and unstable conditions, while Vanderwende and Lundquist and Wharton et al . observed increased power for unstable over neutral and stable conditions in actual wind farms.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of layout and atmospheric stability effects in wind farms using large‐eddy simulation

et al. 2017

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Large‐eddy simulation (LES) has been used previously to study the effect of either configuration or atmospheric stability on the power generated by large wind farms. This is the first study to consider both stability and wind farm configuration simultaneously and methodically with LES. Two prevailing wind directions, two layouts (turbines aligned versus staggered with respect to the wind) and three stabilities (neutral and moderately unstable and stable) were evaluated. Compared with neutral conditions, unstable conditions led to reduced wake losses in one configuration, to enhanced wake losses in two and to unchanged wake losses in one configuration. Conversely, stable conditions led to increased wake losses in one, decreased wake losses in two and unchanged wake losses in one configuration. Three competing effects, namely, rates of wake recovery due to vertical mixing, horizontal spread of wakes and localized regions of acceleration caused by multiple upstream wakes, were identified as being responsible for the observed trends in wake losses. The detailed flow features responsible for these non‐linear interactions could only be resolved by the LES. Existing analytical models ignore stability and non‐linear configuration effects, which therefore need to be incorporated. Copyright © 2017 John Wiley & Sons, Ltd.

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Synergistic Effects of Turbine Wakes and Atmospheric Stability on Power Production at an Onshore Wind Farm

Cited by 5 publications

References 25 publications

Data analysis and simulation of the Lillgrund wind farm

Data analysis and simulation of the Lillgrund wind farm

On atmospheric stability in the dynamic wake meandering model

Evaluation of layout and atmospheric stability effects in wind farms using large‐eddy simulation

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