On the Offshore Advection of Boundary-Layer Structures and the Influence on Offshore Wind Conditions

Dörenkämper, Martin; Optis, Mike; Monahan, Adam H.; Steinfeld, Gerald

doi:10.1007/s10546-015-0008-x

Cited by 60 publications

(64 citation statements)

References 25 publications

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“…Accordingly, the turbines near this corner of the wind farm are the ones closest to the shore. Since the wind speed tends to increase with increasing distance from the coast [10,11], the increase in the wind speed from the northwest corner moving east along the northern face of Rødsand II is consistent with what one would expect from the shape of the coastline and the layout of the wind farm. In contrast, the northernmost row of Nysted is almost parallel with the coastline, and there is little variation in the inflow wind speeds from the north.…”

Section: Coastal Effectssupporting

confidence: 78%

Wake effects between two neighbouring wind farms

Nygaard

Hansen

2016

J. Phys.: Conf. Ser.

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Wake effect on a uniform flow behind wind-turbine model V L Okulov, I V Naumov, R F Mikkelsen et al.Simulation of wake effects between two wind farms K S Hansen, P-E Réthoré, J Palma et al. Abstract. We address the issue of wake effects between two neighbouring offshore wind farms by analysing simultaneous production data from Rødsand II and Nysted. The upstream wind farm is found to not just perturb the flow in its wake, but also to cause speed-ups at the positions of some downstream turbines. We use the data to perform a validation of a simple wake model for flow cases corresponding to wind directions of maximum internal and external wake effects.

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Section: Coastal Effectssupporting

confidence: 78%

Wake effects between two neighbouring wind farms

Nygaard

Hansen

2016

J. Phys.: Conf. Ser.

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“…the horizontal wind speed gradient due to a varying distance to shore (fetch), and wind farm wakes from other wind farms both influence the wind resource. Dörenkämper et al (2015) found that large "horizontal streaks of reduced wind speeds that under stable stratification are advected several tens of kilometres over the sea" can severely affect offshore wind farms. Correct prediction of the wind resource influenced by either land or adjacent wind farms, or a combination of the two, is a challenging problem.…”

Section: Introductionmentioning

confidence: 99%

Applications of satellite winds for the offshore wind farm site Anholt

et al. 2018

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Abstract. Rapid growth in the offshore wind energy sector means more offshore wind farms are placed closer to each other and in the lee of large land masses. Synthetic aperture radar (SAR) offers maps of the wind speed offshore with high resolution over large areas. These can be used to detect horizontal wind speed gradients close to shore and wind farm wake effects. SAR observations have become much more available with the free and open-access data from European satellite missions through Copernicus. Examples of applications and tools for using large archives of SAR wind maps to aid offshore site assessment are few. The Anholt wind farm operated by the utility company Ørsted is located in coastal waters and experiences strong spatial variations in the mean wind speed. Wind speeds derived from the Supervisory Control And Data Acquisition (SCADA) system are available at the turbine locations for comparison with winds retrieved from SAR. The correlation is good, both for free-stream and waked conditions. Spatial wind speed variations along the rows of wind turbines derived from SAR wind maps prior to the wind farm construction agree well with information gathered by the SCADA system and a numerical weather prediction model. Wind farm wakes are detected by comparisons between images before and after the wind farm construction. SAR wind maps clearly show wakes for long and constant fetches but the wake effect is less pronounced for short and varying fetches. Our results suggest that SAR wind maps can support offshore wind energy site assessment by introducing observations in the early phases of wind farm projects.

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“…In this study we will investigate possible creation mechanisms of boundary layer rolls that exist in the coastal zone. Other types of streaky structures elongated in the along-wind direction have also been observed and can be formed by lee effects from terrain [1] or from orography inhomogeneities [2]. In these types of features, however, each streak is created from a certain source, behaving like a wake.…”

Section: Introductionmentioning

confidence: 99%

A Case Study of Offshore Advection of Boundary Layer Rolls over a Stably Stratified Sea Surface

Svensson

Bergström

Nilsson

et al. 2017

Advances in Meteorology

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Streaky structures of narrow (8-9 km) high wind belts have been observed from SAR images above the Baltic Sea during stably stratified conditions with offshore winds from the southern parts of Sweden. Case studies using the WRF model and in situ aircraft observations indicate that the streaks originate from boundary layer rolls generated over the convective air above Swedish mainland, also supported by visual satellite images showing the typical signature cloud streets. The simulations indicate that the rolls are advected and maintained at least 30-80 km off the coast, in agreement with the streaks observed by the SAR images. During evening when the convective conditions over land diminish, the streaky structures over the sea are still seen in the horizontal wind field; however, the vertical component is close to zero. Thus advected feature from a land surface can affect the wind field considerably for long times and over large areas in coastal regions. Although boundary layer rolls are a well-studied feature, no previous study has presented results concerning their persistence during situations with advection to a strongly stratified boundary layer. Such conditions are commonly encountered during spring in coastal regions at high latitudes.

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On the Offshore Advection of Boundary-Layer Structures and the Influence on Offshore Wind Conditions

Cited by 60 publications

References 25 publications

Wake effects between two neighbouring wind farms

Wake effects between two neighbouring wind farms

Applications of satellite winds for the offshore wind farm site Anholt

A Case Study of Offshore Advection of Boundary Layer Rolls over a Stably Stratified Sea Surface

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