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Impact of Negative Geostrophic Wind Shear on Wind Farm Performance
PRX Energy 1, 023007 – Published 23 September, 2022
DOI: https://doi.org/10.1103/PRXEnergy.1.023007
Abstract
Baroclinicity, which leads to height-dependent driving pressure gradients, occurs in various situations such as the flow transition between land and sea, and sloping terrain. It has been shown that baroclinicity modifies the structure of the atmospheric boundary layer. For example, negative shear baroclinicity creates additional turbulence at higher elevations, which might influence the energy entrainment into large wind farms. Here, we use large-eddy simulations to study the effect of baroclinicity-induced negative shear on the wind farm power production and energy entrainment into a large wind farm. In agreement with the literature, our simulations show that negative geostrophic wind shear significantly modifies the mean wind velocity in the atmospheric boundary layer. Specifically, for the cases considered in the study, the negative geostrophic shear causes a change in the mean velocity up to 2.3 m/s at hub height, which greatly alters the wind farm power production. Additionally, we demonstrate with an energy budget analysis that a wind farm does not necessarily benefit from the additional turbulence created by the negative geostrophic wind shear. The reason for this is that the baroclinicity-induced negative shear alters the height and strength of the low-level jet and creates an upward flux above the jet, limiting the energy entrainment into the wind farm. Our results show that wind resources are altered in the boundary layer due to negative geostrophic wind shear and should be considered in wind farm modeling and power forecasts.
Physics Subject Headings (PhySH)
synopsis
Wind Farms Perform Under Pressure
Simulations show that negative wind shear can reduce the power output of wind farms.
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Popular Summary
Using state-of-the-art simulations, the authors explore the effect of baroclinicity on wind farm performance. Such baroclinicity leads to height-dependent pressure gradients in the atmosphere. Typical wind farm models neglect baroclinic effects even though baroclinicity strongly influences atmospheric dynamics, for example, at flow transitions between land and sea. Consequently, baroclinicity influences the available wind resources and the performance of wind farms. In this study the authors focus on negative shear baroclinicity. They reveal that this type of baroclinicity can give rise to an upward turbulent flux above the wind farm, which reduces the overall energy entrainment into the farm. This contradicts the generally accepted view that atmospheric turbulence aids the energy entrainment into wind farms. Therefore, the authors argue that it is essential to account for atmospheric baroclinicity and incorporate its effects in wind farm design tools.
Article Text
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