On the Influence of Low-Level Jets on Energy Production and Loading of Wind Turbines

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

10.5194/ems2021-166 ◽

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 &#8211; Richard A&#223;mann Observatory (Germany), during the period of June&#8211;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&#8211;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. &#160;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&#8217;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>

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

Advances in Science and Research ◽

10.5194/asr-16-85-2019 ◽

2019 ◽

Vol 16 ◽

pp. 85-93 ◽

Cited By ~ 1

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.

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Structural impact assessment of low level jets over wind turbines

Journal of Renewable and Sustainable Energy ◽

10.1063/1.4945359 ◽

2016 ◽

Vol 8 (2) ◽

pp. 023308 ◽

Cited By ~ 12

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

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

Journal of Renewable and Sustainable Energy ◽

10.1063/5.0047194 ◽

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

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

Journal of Renewable and Sustainable Energy ◽

10.1063/5.0017230 ◽

2020 ◽

Vol 12 (5) ◽

pp. 053301 ◽

Cited By ~ 1

Author(s):

Ali Doosttalab ◽

Diego Siguenza-Alvarado ◽

Venkatesh Pulletikurthi ◽

Yaqing Jin ◽

Humberto Bocanegra Evans ◽

...

Keyword(s):

Wind Turbines ◽

Low Level ◽

Low Level Jets

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Effect of Wind Turbine Classes on the Electricity Production of Wind Farms in Cyprus Island

Conference Papers in Energy ◽

10.1155/2013/750958 ◽

2013 ◽

Vol 2013 ◽

pp. 1-6 ◽

Cited By ~ 2

Author(s):

Yiannis A. Katsigiannis ◽

George S. Stavrakakis ◽

Christodoulos Pharconides

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Energy Production ◽

Wind Farms ◽

Electricity Production ◽

Wind Speeds ◽

Wind Potential

This paper examines the effect of different wind turbine classes on the electricity production of wind farms in two areas of Cyprus Island, which present low and medium wind potentials: Xylofagou and Limassol. Wind turbine classes determine the suitability of installing a wind turbine in a particulate site. Wind turbine data from five different manufacturers have been used. For each manufacturer, two wind turbines with identical rated power (in the range of 1.5 MW–3 MW) and different wind turbine classes (IEC II and IEC III) are compared. The results show the superiority of wind turbines that are designed for lower wind speeds (IEC III class) in both locations, in terms of energy production. This improvement is higher for the location with the lower wind potential and starts from 7%, while it can reach more than 50%.

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A Climatology of Nocturnal Low-Level Jets at Cabauw

Journal of Applied Meteorology and Climatology ◽

10.1175/2009jamc1965.1 ◽

2009 ◽

Vol 48 (8) ◽

pp. 1627-1642 ◽

Cited By ~ 101

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.

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Development and Field Testing of an Inclined Flanged Compact Diffuser for a Micro Wind Turbine

Volume 6B: Energy ◽

10.1115/imece2014-37883 ◽

2014 ◽

Cited By ~ 2

Author(s):

Sandip Kale ◽

S. N. Sapali

Keyword(s):

Wind Turbine ◽

Wind Velocity ◽

Wind Turbines ◽

Energy Production ◽

Cost Effective ◽

Field Testing ◽

International Electrotechnical Commission ◽

Average Wind Speed ◽

Average Wind ◽

Power Curves

Micro wind turbines installed in various applications, experience average wind speed for most of the time during operations. Power produced by the wind turbine is proportional to the cubic power of the wind velocity and a small increase in wind velocity results increases power output significantly. The approach wind velocity can be increased by covering traditional wind turbine with a diffuser. Researchers are continuously working to develop a compact, lightweight, cost effective and feasible diffuser for wind turbines. The present work carried out to develop a diffuser with these stated objectives. A compact, lightweight inclined flanged diffuser developed for a micro wind turbine. Bare micro wind turbine and wind turbine covered with developed efficient inclined flanged diffuser tested in the field as per International Electrotechnical Commission (IEC) standards and results presented in the form of power curves. The prediction of annual energy production for both wind turbines determined as per IEC standards.

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