Articles

Temporal Wake Modelling – Validation with iSpin Measurement (Presentation)

Wind Europe Offshore Conference 2019, Copenhagen

Author: H.S. Pedersen, W. Langreder, H. Hohlen

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Key words: wake, losses, time domain

 

Production data coupled with measured velocity deficits allowed us to get an unusual insight into wakes and have been the ideal test bench to test wake models. While 10-minute averaging is not suitable for temporal modelling of wakes, an improved wake modelling capability in absolute numbers can be shown when coupling the wake decay constant to turbulence intensity.

Spectral correction to recover full 10min variability from hourly mesoscale data (Presentation)

Wind Europe Offshore Conference 2019, Copenhagen

Author: L. Svenningsen, B.H. Jacobsen, M.L. Thøgersen

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Key words: mesoscale, ERA5, spectrum

 

We show a cost-effective solution to correct the spectrum of mesoscale data from our EMD-WRF-Europe+ data set to match the spectrum of 10-minute time series. Specifically in offshore context, this correction opens up the door to use mesoscale data as “if it was a real mast”.

Losses and Uncertainties – What’s new (Presentation)

Wind Energy Denmark 2019, Herning

Author: W. Langreder, M.L. Thøgersen

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Key words: losses, uncertainty, calibration, lidar, wakes, blockage

 

Some thoughts about losses and uncertainties are set in perspective to the latest benchmark initiative WP3 from NREL, US. Specifically, anemometer classification, Lidar uncertainty, impact of quality of topographic maps, wake modelling and blockage are touched upon.

The Importance of Adding the Temporal Component to Wake Losses a Verification Study (Presentation)

AWEA Wind Resource & Project Conference 2019, Renton

Author: W. Langreder, H.S. Pedersen, A.N. Kishore

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Key words: wake, losses, time domain

 

Can we model the diurnals of wake losses? Operational data from three wind farms is used to show improvements when using a time-varying wake decay constant, which is coupled to turbulence.

Vertical extrapolation – Uncertainty in Complex Terrain? (Presentation)

Vindkraftnet Meeting Aalborg, 13.5.2019
Author: W. Langreder, M. Jogararu, T.G. Sørensen

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Key words: complex terrain, vertical extrapolation, WAsP, uncertainty, IEC -15

When is a terrain complex? Is it really only the steepness? Some examples of complexity in a different sense are shown. We show that a one-size-fits-all approach is not suitable as the uncertainty of vertical extrapolation using WAsP depends on the terrain typ.

Reference Wind Data – Challenges When Doing Short Measurement Campaigns in Complex Terrain? (Presentation)

Vindkraftnet Meeting Aalborg, 13.5.2019
Author: M.L. Thøgersen, L. Svenningsen, T.G. Sørensen

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Key words: ERA5, seasonality, windscanner, recast, NEWA

One of the challenges as part of the recast project (http://www.recastproject.dk/), where EMD is project partner, is developing a method to mitigate temporal uncertainty which are connected to short-term measurements. As part of that we evaluate different long-term data sources, next to others also time-series from NEWA.

Hack the Error Codes from Wind Turbines (Poster)

WindEurope Bilbao, 2-4.4.2019
Author: H.S. Pedersen, W. Langreder

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Key words: post-construction, SCADA, losses

Our poster summarises the losses from analysing nearly 700 years of production data. The benefits of post-construction analysis are explained.

Consistent Direct-Drive Version of the NREL 5MW Turbine (Paper)

WindEurope Global Wind Summit Hamburg, 25-28.9.2018
Author: R.M.M. Slot, L. Svenningsen, M.L. Thøgersen, J.D. Sørensen (Department of Civil Engineering, Aalborg University)

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Key words: loads, direct-drive, load response, fatigue, aeroelastic models

To provide windPRO users with the option of doing load-response evaluations of wind turbines in both a geared and a direct-drive configuration, we have developed a consistent direct-drive version of the NREL 5MW reference turbine for the use with the FAST aeroelastic model.

Towards Revenue Assessment (Presentation)

Wind Europe Tech Workshop Operating Wind Farms, Vilnius 15-16.5.2018
Author: H.S. Pedersen, W. Langreder

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Key words: availability, losses, revenue, spot market

Follow us when we combine availability with spot market prices. Availability comes in different forms, and we show what the impact is in situations where the electricity is sold on the spot market.

Site-Assessment and Icing Impact Using ERA5 Assimilation Data (Presentation)

WinterWind, 5-7.2.2018
Author: M.L. Thøgersen, L. Svenningsen, T.G. Sørensen, D. Lindholm

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Key words: ERA5, ice, cold climate

A Sensitivity study shows the impact of boundary data, model resolution and microphysics on icing. We show the superiority of ERA5, however at the same time the cloud microphysics scheme seems more important that the choice of reanalysis data.

From Icing to Production Loss (Presentation)

WinterWind, 5-7.2.2018
Author: D. Lindholm, M.L. Thøgersen, H.S. Pedersen, W. Langreder

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Key words: icing, cold climate, losses

Today’s models are described and compared with each other. When comparing with instrumental icing we demonstrate the importance of correcting for the inter-annual variability of icing. We introduce an icing index when comparing tools to get from icing to production loss.

Optimising Lidar Campaigns – What to Keep in Mind Using a Roaming Lidar (Stand Presentation)

WindEurope Global Wind Summit Amsterdam 28-30.11.2017
Author: W. Langreder

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Key words: lidar, measurement, seasonality, uncertainty

Do roaming LIDARs increase precision? We discuss two scenarios and show cases where a roaming LIDAR does not improve the quality of the results. We also show how to identify critical sites where roaming instrumentation might decrease the accuracy.

Vertical Extrapolation Uncertainty (Poster)

WindEurope Global Wind Summit Amsterdam 28-30.11.2017
Author: W. Langreder, M. Jogararu

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Key words: complex terrain, vertical extrapolation, WAsP, uncertainty, IEC -15

In preparation of the upcoming IEC61400-15 we compare two different practices with empirical results. Clearly, the definition of vertical extrapolation uncertainty needs to be distinguished depending on the terrain type and roughness.

Vertical Extrapolation Uncertainty (Presentation)

Brazil Windpower, 29-31.8.2017
Author: W. Langreder, M. Jogararu, S.A. Costa (EMD Brasil)

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Key words: complex terrain, vertical extrapolation, WAsP, uncertainty, IEC -15

In preparation of the upcoming IEC61400-15 we compare two different practices with empirical results. Clearly, the definition of vertical extrapolation uncertainty needs to be distinguished depending on the terrain type and roughness.

Long-term Correction: Facts and Fiction (Presentation)

India IWTMA, 25-27.4.2017
Author: T. Sørensen, W. Langreder

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Key words: MCP, long-term correction

Despite long-term data having increased in quality, long-term correction is far from being an easy task. We show you possible pitfalls and discuss how to avoid them.

Impact of Various National Codes on Wind Farm Design (Presentation)

Wind Europe Tech Workshop Wind Turbine Sound, Gdansk 17-18.11.2016
Author: T. Sørensen

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Key words: noise, national codes, impact

Follow us when comparing the impact of various national codes on wind farm design.

Uncertainty in Wind Climate Parameters and Their Influence on Wind Turbine Fatigue Loads (Paper)

Renewable Energy, Volume 90, May 2016, Pages 352-361
Author: H.S. Toft, L. Svenningsen, M.L. Thøgersen, J.D. Sørensen (Department of Civil Engineering, Aalborg University), W. Moser (Nordex GmbH)

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Keywords: Loads, Uncertainty modelling, Site assessment, Fatigue loads, Reliability analysis

This paper presents a probabilistic framework for assessment of the structural reliability level of wind turbines in fatigue loading. Uncertainty of the site-specific wind climate parameters at each turbine position is estimated based on the local wind measurements, speed-up factors and the distance between the wind turbine and the measuring position. The framework is demonstrated for a wind turbine project in flat terrain.

Wind Climate Parameters for Wind Turbine Fatigue Load Assessment (Paper)

Sol. Energy Eng 138(3), 031010 (Apr 05, 2016) (8 pages)
Author: H.S. Toft, L. Svenningsen, M.L. Thøgersen, J.D. Sørensen (Department of Civil Engineering, Aalborg University), W. Moser (Nordex GmbH)

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Key words: Loads, Density, Fatigue, Turbulence, Wind shear, Wind velocity, Stress, Climate, Wind, Wind turbines

This paper investigates the accuracy of fatigue loads estimated using this equivalent wind climate required by the current design standard by comparing damage equivalent fatigue loads estimated based on wind climate parameters for each 10 min time-series with fatigue loads estimated based on the equivalent wind climate parameters.

Assessment of Wind Turbine Structural Integrity Using Response Surface Methodology

Author: H.S. Toft, L. Svenningsen, M.L. Thøgersen, J.D. Sørensen (Department of Civil Engineering, Aalborg University), W. Moser (Nordex GmbH)

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Key words: Loads, Response surface methodology, Fatigue loads, Extreme loads

A new approach to assessment of site-specific wind turbine loads is proposed. The approach can be applied in both fatigue and ultimate limit state. Two different response surface methodologies have been investigated. The model uncertainty introduced by the response surfaces is determined to be small. The statistical uncertainty introduced by a limited number of seeds is determined.

Støjkatalog over Ældre Vindmøller i Danmark (Report)

Grontmij, June 2014

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Key words: noise, 1/1 octave

As a consequence of the changes of requirement for calculation of noise due to wind turbines from 2011 in Denmark, the 1/1 or 1/3 octave data has to be used, also for older WTG types. This catalogue bundles available documentation in a concise format.