Structural impact assessment of low level jets over wind turbines

2016 ◽  
Vol 8 (2) ◽  
pp. 023308 ◽  
Author(s):  
W. Gutierrez ◽  
G. Araya ◽  
P. Kiliyanpilakkil ◽  
A. Ruiz-Columbie ◽  
M. Tutkun ◽  
...  
Keyword(s):  
Impact Assessment ◽  
Wind Turbines ◽  
Low Level ◽  
Structural Impact ◽  
Low Level Jets

scholarly journals Assessment of nocturnal low-level jets during the FESSTVaL campaign 2020 for wind energy applications

2021 ◽  
Author(s):  
Eduardo Weide Luiz ◽  
Stephanie Fiedler
Keyword(s):  
Wind Power ◽  
Wind Turbines ◽  
Vertical Wind Shear ◽  
Ground Level ◽  
High Temporal Resolution ◽  
Missing Measurements ◽  
Low Level ◽  
Prevailing Wind Direction ◽  
Meteorological Observatory ◽  
Low Level Jets

<p>Due to the increasing contribution of wind power to electricity in Europe, an exact wind characterization at the height of wind turbines is important. Nocturnal Low Level Jets (NLLJ) can influence the winds at typical blade heights and therefore influence the wind power production. However, due to the often missing measurements with a sufficient precision and resolution, the occurrence frequency and spatio-temporal characteristics of NLLJs are still poorly understood. The present work characterizes the properties of NLLJs, measured with a Doppler lidar at the Lindenberg Meteorological Observatory – Richard Aßmann Observatory (Germany), during the period of June–August 2020, and evaluates the representation of NLLJs in state-of-the-science re-analysis products. The vertical profiles of 10-minute mean winds from the lidar are statistically analysed using automated detection tools. These allow to determine the frequency of occurrence, height and wind speed in the core of NLLJs as well as the vertical wind shear and momentum transport with a high temporal resolution. We intercompare NLLJ results from different previously-used identification tools to estimate the uncertainty. Our automatic detections identified NLLJs in more than about 60% of the summer nights in 2020, with NLLJ cores between 70m and 500 m above ground level and a core speed of ~3–25 m/s. The prevailing wind direction in NLLJ cores is southwest. A considerable amount of NLLJ cores occurred at heights that are in the range of modern wind turbines and rotor sizes on land, with wind speeds of ~3-12 m/s. We use the measurements of NLLJs to evaluate their representation in the ERA5 re-analysis of the European Centre for Medium-Range Weather Forecasts and plan to compare the NLLJs to regional high-resolution re-analyses developed in the research area Climate Monitoring and Diagnostics in the Hans-Ertel Centre for Weather Research.  The first comparisons suggest a frequent co-occurrence of NLLJs in the measurements and ERA5 re-analysis, but the strength and height of NLLJ cores often differ. Possible reasons are the model’s vertical resolution and the parameterization of vertical mixing in the stable boundary layer. Future work includes extending the NLLJ analysis to more lidar measurements and other regional re-analysis data.</p>

scholarly journals Sensitivity of nocturnal low-level jets to land-use parameters and meteorological quantities

2019 ◽  
Vol 16 ◽  
pp. 85-93 ◽  
Author(s):  
Astrid Ziemann ◽  
Manuela Starke ◽  
Tina Leiding
Keyword(s):  
Land Use ◽  
Wind Speed ◽  
Wind Power ◽  
Wind Turbines ◽  
Geostrophic Wind ◽  
Scale Model ◽  
Model Parameters ◽  
Height Range ◽  
Low Level ◽  
Low Level Jets

Abstract. The increasing hub height of wind turbines aims at optimizing the wind energy yield at one location and offers the possibility to provide new areas for wind power, for example forests. Inhomogeneous environmental conditions of locations for wind turbines as well as the hub heights of more than 100 m cause challenges for flow models and their potential for wind power assessment. This includes special features of the wind field like low-level jets (LLJs), frequently observed local wind maxima in the nocturnal boundary layer. To characterize the dependencies of LLJs, the micro-scale model HIRVAC2D (HIgh Resolution Vegetation Atmosphere Coupler 2D) is applied in the study. The model HIRVAC2D is capable of modelling different vegetation types by explicitly considering the highly resolved structure of varying plant parameters. Beyond that, the model enables the resolution of temporally variable atmospheric circulation patterns during day- and night-time with typical thermal stratifications. In this way, HIRVAC2D is suitable to capture the nocturnal LLJ development and its characteristics. Results of several HIRVAC2D simulations are presented in order to deduce quantitatively the sensitivity of LLJs to vegetation and model parameters as well as meteorological quantities. It is shown that the geostrophic wind speed is an important criterion for the development of LLJs within a height range between 50 and 300 m. For a geostrophic wind speed of 4 m s−1, a nocturnal LLJ occurs remarkably more frequent as for a wind speed of 10 m s−1. To interpret and evaluate this result regarding possible wind power applications, a frequency distribution of the geostrophic wind speed was calculated over 30 years exemplarily at two locations using the meso-scale model COSMO in climate mode. Additionally, the type of land use has an impact on the height and intensity of LLJs. For a grassland site, the nocturnal LLJ is noticeably more frequent in the considered height range, but with a smaller wind speed and at a lower height above ground in comparison to deciduous or coniferous forests.

Exploring the effects of low-level-jets on the energy entrainment of vertical-axis wind turbines

2021 ◽  
Vol 13 (3) ◽  
pp. 033310
Author(s):  
Diego Siguenza-Alvarado ◽  
Ali Doosttalab ◽  
Shyuan Cheng ◽  
Humberto Bocanegra Evans ◽  
Raúl Bayoán Cal ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Vertical Axis ◽  
Low Level ◽  
Vertical Axis Wind Turbines ◽  
Low Level Jets

Interaction of low-level jets with wind turbines: On the basic mechanisms for enhanced performance

2020 ◽  
Vol 12 (5) ◽  
pp. 053301 ◽  
Author(s):  
Ali Doosttalab ◽  
Diego Siguenza-Alvarado ◽  
Venkatesh Pulletikurthi ◽  
Yaqing Jin ◽  
Humberto Bocanegra Evans ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Low Level ◽  
Low Level Jets

scholarly journals A Climatology of Nocturnal Low-Level Jets at Cabauw

2009 ◽  
Vol 48 (8) ◽  
pp. 1627-1642 ◽  
Author(s):  
P. Baas ◽  
F. C. Bosveld ◽  
H. Klein Baltink ◽  
A. A. M. Holtslag
Keyword(s):  
Wind Speed ◽  
Ground Level ◽  
Geostrophic Wind ◽  
Stable Stratification ◽  
Radiative Cooling ◽  
Inertial Oscillation ◽  
Stable Boundary Layers ◽  
Above Ground Level ◽  
Low Level ◽  
Low Level Jets

Abstract A climatology of nocturnal low-level jets (LLJs) is presented for the topographically flat measurement site at Cabauw, the Netherlands. LLJ characteristics are derived from a 7-yr half-hourly database of wind speed profiles, obtained from the 200-m mast and a wind profiler. Many LLJs at Cabauw originate from an inertial oscillation, which develops after sunset in a layer decoupled from the surface by stable stratification. The data are classified to different types of stable boundary layers by using the geostrophic wind speed and the isothermal net radiative cooling as classification parameters. For each of these classes, LLJ characteristics like frequency of occurrence, height above ground level, and the turning of the wind vector across the boundary layer are determined. It is found that LLJs occur in about 20% of the nights, are typically situated at 140–260 m above ground level, and have a speed of 6–10 m s−1. Development of a substantial LLJ is most likely to occur for moderate geostrophic forcing and a high radiative cooling. A comparison with the 40-yr ECMWF Re-Analysis (ERA-40) is added to illustrate how the results can be used to evaluate the performance of atmospheric models.

Role of low-level jets and boundary-layer properties on the NBL budget technique

2005 ◽  
Vol 135 (1-4) ◽  
pp. 35-43 ◽  
Author(s):  
N. Mathieu ◽  
I.B. Strachan ◽  
M.Y. Leclerc ◽  
A. Karipot ◽  
E. Pattey
Keyword(s):  
Boundary Layer ◽  
Low Level ◽  
Low Level Jets

scholarly journals Comparing two years of Saharan dust source activation obtained by regional modeling and satellite observations

2012 ◽  
Vol 12 (10) ◽  
pp. 27667-27691
Author(s):  
I. Tegen ◽  
K. Schepanski ◽  
B. Heinold
Keyword(s):  
Regional Scale ◽  
Dust Emission ◽  
Saharan Dust ◽  
Strong Increase ◽  
Dust Source ◽  
Low Level ◽  
Mountainous Regions ◽  
Emission Fluxes ◽  
Low Level Jets ◽  
The Difference

Abstract. A regional-scale dust model is used to simulate Saharan dust emissions and atmospheric distributions in the years 2007 and 2008. The model results are compared to dust source activation events compiled from infrared dust index imagery from the geostationary Meteosat Second Generation (MSG) satellite. The observed morning maximum in dust source activation frequencies indicates that the breakdown of nocturnal low-level jets is responsible for a considerable number of dust source activation events in the Sahara. The comparison shows that the time of the day of the onset of dust emission is delayed in the model compared to the observations. Also, the simulated number of dust emission events associated with nocturnal low level jets in mountainous regions is underestimated in the model. The MSG dust index observations indicate a strong increase in dust source activation frequencies in the year 2008 compared to 2007, the difference between the two years is less pronounced in the model. The quantitative comparison of simulated dust optical thicknesses with observations at stations of the sunphotometer network AERONET shows, however, good agreement for both years, indicating that the number of observed dust activation events is only of limited use for estimating actual dust emission fluxes in the Sahara.

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