An Analytical Model for the Effect of Vertical Wind Veer on Wind Turbine Wakes

Abkar, Mahdi; Sørensen, Jens Nørkær; Porté‐Agel, Fernando

doi:10.3390/en11071838

Cited by 65 publications

(53 citation statements)

References 46 publications

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“…Note that assuming an elliptical shape for the wake allows the model to take into account the effect of turbine aspect ratio. As previously shown [22,31,[34][35][36][37][38][39][40], σ z and σ y are varying quasi-linearly with downwind distance in turbulent inflow as…”

Section: Gaussian Wake Modelsupporting

confidence: 54%

Theoretical Modeling of Vertical-Axis Wind Turbine Wakes

Abkar

2018

Energies

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In this work, two different theoretical models for predicting the wind velocity downwind of an H-rotor vertical-axis wind turbine are presented. The first model uses mass conservation together with the momentum theory and assumes a top-hat distribution for the wind velocity deficit. The second model considers a two-dimensional Gaussian shape for the velocity defect and satisfies mass continuity and the momentum balance. Both approaches are consistent with the existing and widely-used theoretical wake models for horizontal-axis wind turbines and, thus, can be implemented in the current numerical codes utilized for optimization and real-time applications. To assess and compare the two proposed models, we use large eddy simulation as well as field measurement data of vertical-axis wind turbine wakes. The results show that, although both models are generally capable of predicting the velocity defect, the prediction from the Gaussian-based wake model is more accurate compared to the top-hat counterpart. This is mainly related to the consistency of the assumptions used in the Gaussian-based wake model with the physics of the turbulent wake development downwind of the turbine.

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Section: Gaussian Wake Modelsupporting

confidence: 54%

Theoretical Modeling of Vertical-Axis Wind Turbine Wakes

Abkar

2018

Energies

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“…The annual cycle of turbulence dissipation rate offshore is more influenced by the wind-land interaction rather than the seasonal cycle itself. An annual cycle also emerges in wind veer, another important atmospheric variable which affects the structure of wind turbine wakes (Bodini et al, 2017;Abkar et al, 2018;Churchfield & Sirnivas, 2018). We calculate wind veer as the difference in 2-minute average wind direction, retrieved from the lidar, between 40 m and 200 m ASL, which represent typical vertical limits for the rotor of modern offshore wind turbine models.…”

Section: Resultsmentioning

confidence: 99%

Offshore Wind Turbines Will Encounter Very Low Atmospheric Turbulence

Bodini¹,

Lundquist²,

Kirincich³

2020

J. Phys.: Conf. Ser.

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Key Points:• strength and persistence of wind plant wakes depends on turbulence dissipation rate • turbulence dissipation rate offshore is small with a weak diurnal cycle • dissipation rate is larger when flow is from the land, which tends to be in wintertime at this site AbstractThe rapid growth of offshore wind energy requires accurate modeling of the wind resource, which can be depleted by wind farm wakes. Turbulence dissipation rate ( ) governs the accuracy of model predictions of hub-height wind speed and the development and erosion of wakes. Here we assess the variability of turbulence kinetic energy and using 13 months of observations from a profiling lidar deployed on a platform off the Massachusetts coast. Offshore, is 2 orders of magnitude smaller than onshore, with a subtle diurnal cycle. Wind direction largely influences the annual cycle of turbulence, with larger values in winter when the wind flows from the land, and smaller values in summer, when the wind is mainly from open ocean. Because of the weak turbulence, wind plant wakes will be stronger and persist farther downwind in summer.

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“…An annual cycle also emerges in wind veer, another important atmospheric variable that affects the structure of wind turbine wakes (Abkar et al, 2018;Bodini et al, 2017;Churchfield & Sirnivas, 2018). We calculate wind veer as the difference in 2-min average wind direction, calculated from the lidar, between 40 and 200 m ASL, typical vertical limits for the rotor of offshore wind turbines.…”

Section: Resultsmentioning

confidence: 99%

U.S. East Coast Lidar Measurements Show Offshore Wind Turbines Will Encounter Very Low Atmospheric Turbulence

Bodini

Lundquist

Kirincich

2019

Geophysical Research Letters

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The rapid growth of offshore wind energy requires accurate modeling of the wind resource, which can be depleted by wind farm wakes. Turbulence dissipation rate (ϵ) governs the accuracy of model predictions of hub‐height wind speed and the development and erosion of wakes. Here we assess the variability of turbulence kinetic energy and ϵ using 13 months of observations from a profiling lidar deployed on a platform off the Massachusetts coast. Offshore, ϵ is 2 orders of magnitude smaller than onshore, with a subtle diurnal cycle. Wind direction influences the annual cycle of turbulence, with larger values in winter when the wind flows from the land, and smaller values in summer, when the wind flows from open ocean. Because of the weak turbulence, wind plant wakes will be stronger and persist farther downwind in summer.

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An Analytical Model for the Effect of Vertical Wind Veer on Wind Turbine Wakes

Cited by 65 publications

References 46 publications

Theoretical Modeling of Vertical-Axis Wind Turbine Wakes

Theoretical Modeling of Vertical-Axis Wind Turbine Wakes

Offshore Wind Turbines Will Encounter Very Low Atmospheric Turbulence

U.S. East Coast Lidar Measurements Show Offshore Wind Turbines Will Encounter Very Low Atmospheric Turbulence

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