Charnock’s Roughness Length Model and Non-dimensional Wind Profiles Over the Sea

Peña, Alfredo; Gryning, Sven‐Erik

doi:10.1007/s10546-008-9285-y

Cited by 59 publications

(37 citation statements)

References 25 publications

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“…In order to minimize flow blockage effects, the computational domain is set to a height L z = 1045.9 m in all the simulations. A constant streamwise pressure gradient is used to drive the flow within the boundary layer, which has a height of δ = 500 m. This value is consistent with the boundary-layer depth observed by Peña and Gryning [23] at…”

Section: Case Descriptionsupporting

confidence: 72%

A Numerical Study of the Effects of Wind Direction on Turbine Wakes and Power Losses in a Large Wind Farm

2013

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In this study, large-eddy simulations (LESs) were performed to investigate the effects of changing wind direction on the turbine wakes and associated power losses in the Horns Rev offshore wind farm. In the LES framework, the turbulent subgrid-scale stresses are parameterized using a tuning-free Lagrangian scale-dependent dynamic model, and the turbine-induced forces are computed using a dynamic actuator-disk model with rotation (ADM-R). This dynamic ADM-R couples blade-element theory with a turbine-specific relation between the blade angular velocity and the shaft torque to compute simultaneously turbine angular velocity and power output. A total of 67 simulations were performed for a wide range of wind direction angles. Results from the simulations show a strong impact of wind direction on the spatial distribution of turbine-wake characteristics, such as velocity deficit and turbulence intensity. This can be explained by the fact that changing the wind angle can be viewed as changing the wind farm layout relative to the incoming wind, while keeping the same wind turbine density. Of particular importance is the effect of wind direction on the distance available for the wakes to recover and expand before encountering other downwind turbines (in full-wake or partial-wake interactions), which affects the power losses from those turbines. As a result, even small changes in wind direction angle can have strong impacts on the total wind farm power output. For example, a change in wind direction of just 10• from the worst-case full-wake condition is found to increase the total power output by as much as 43%. This has important implications for the design of wind farms and the management of the temporal variability of their power output.Energies 2013, 6 5298

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Section: Case Descriptionsupporting

confidence: 72%

A Numerical Study of the Effects of Wind Direction on Turbine Wakes and Power Losses in a Large Wind Farm

2013

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“…In the EU-Norsewind project the vertical extrapolation is being investigated using data from an array of wind profiling lidars observing at 70 to 200 m above sea level installed in the Northern European Seas. Lidar-based results show that the wind profile deviates from the surface-layer wind profile high in the boundary layer [38][39][40][41]. Mesoscale modeling of the offshore wind resource is on-going and comparison of results is in progress, yet beyond the scope of the present paper.…”

Section: Examination Of Wind Resource Statisticsmentioning

confidence: 91%

SAR-Based Wind Resource Statistics in the Baltic Sea

Hasager¹,

Badger²,

Peña³

et al. 2011

Remote Sensing

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104

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Ocean winds in the Baltic Sea are expected to power many wind farms in the coming years. This study examines satellite Synthetic Aperture Radar (SAR) images from Envisat ASAR for mapping wind resources with high spatial resolution. Around 900 collocated pairs of wind speed from SAR wind maps and from 10 meteorological masts, established specifically for wind energy in the study area, are compared. The statistical results comparing in situ wind speed and SAR-based wind speed show a root mean square error of 1.17 m s for the 14 existing and 42 planned wind farms.

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“…Wind profiles onshore have been extensively discussed in number of the atmospheric studies so far. In addition, wind profiles offshore have been also analyzed with measurements take from offshore meteorological masts [2][3][4][5][6] , as offshore wind power generation has been increasing in northern European countries. By analyzing the measurements taken from a met mast, Lange et al (2004) [2] showed that the offshore wind profiles not only have smaller vertical wind shears than those onshore, which is attributable to the small aerodynamic roughness over the sea, but also are strongly dependent on atmospheric stability, which is determined by the temperature gradient between the air and seawater, and the surface wind speed.…”

Section: Introductionmentioning

confidence: 99%

“…However, since the log profile model, which assumes a neutral stability condition, does not take into account the stability effects, it cannot be used for offshore wind profile estimations. Thus, new wind profile models based on Monin-Obkhov similarity (MOS) theory, which adds a correction term for the stability effects to the log profile model, have been developed [4][5][6] . These previous studies have focused mainly on the winds from the open ocean, which are not significantly influenced by land.…”

Section: Introductionmentioning

confidence: 99%

Offshore wind profile measurements using a Doppler LIDAR at the Hazaki Oceanographical Research Station

et al. 2014

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Vertical wind speed profiles near the coast were observed using a Doppler Light Detection and Ranging (LIDAR) system at the Hazaki Oceanographical Research Station (HORS) from September 17 to 26, 2013. The accuracies of the theoretical wind profile models of the log profile model and the Monin-Obukov similarity (MOS) theory were examined by comparing them to those of the observed wind profiles. As a result, MOS, which takes into account the stability effects during wind profile calculations, successfully estimated the wind profile more accurately than the log profile model when the wind was from a sea sector (from sea to land). Conversely, both models did not estimate the profile adequately when the wind was from a land sector (from land to sea). Moreover, the wind profile for the land sector was found to include an obvious diurnal cycle, which is relevant to the stability change over land. Consequently, it is found that the atmospheric stability plays an important roll to determine the offshore wind speed profiles near the coast for not only the sea sector but also the land sector.

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Charnock’s Roughness Length Model and Non-dimensional Wind Profiles Over the Sea

Cited by 59 publications

References 25 publications

A Numerical Study of the Effects of Wind Direction on Turbine Wakes and Power Losses in a Large Wind Farm

A Numerical Study of the Effects of Wind Direction on Turbine Wakes and Power Losses in a Large Wind Farm

SAR-Based Wind Resource Statistics in the Baltic Sea

Offshore wind profile measurements using a Doppler LIDAR at the Hazaki Oceanographical Research Station

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