Wind Shear and Uncertainties in Power Curve Measurement and Wind Resources

Antoniou, Ioannis; Pedersen, Søren M.; Enevoldsen, P.

doi:10.1260/030952409790291208

Cited by 72 publications

(81 citation statements)

References 7 publications

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“…These results are consistent with Walter (2007) and Antoniou et al (2009) who carried out the same kind of simulations with BEM models and power law profiles. Moreover, it coincides with the measurements presented in (Albers et al, 2007), where high shears gave smaller power outputs than low shear.…”

Section: Consequences On the Power Productionsupporting

confidence: 90%

“…Indeed, as mentioned earlier, at a site with different wind conditions, such as that described in (Antoniou et al, 2009) and(VanLuvanee et al, 2009), the power curve being shifted to the right, it would result in an overestimation of the AEP. The relation between the power curves depends on the wind shear conditions.…”

Section: Direct Comparison Of the Standard And Equivalent Wind Speed mentioning

confidence: 79%

“…However it does not mean that large shear necessarily results in lower power. Antoniou et al (2009) and VanLuvanee et al (2009) showed that profiles influenced by low level jets, characterised with higher shear above hub height than below hub height, resulted in higher power than other profiles (constant or power law). …”

Section: Consequences On the Power Productionmentioning

confidence: 98%

“…This shift in the mean power curve actually shows that, for this dataset, the equivalent wind speed was on average smaller than the wind speed at hub height. Note that at another site with larger wind shear above hub height than below, such as in (Antoniou et al, 2009) and (VanLuvanee et al, 2009), the equivalent wind speed may be larger than the wind speed at hub height, so that the power curve would be shifted to the right. To test the impact of the two different power curves on the AEP calculation, the power curves shown in Figure 10.1 were used to calculate the generic AEP as defined in the IEC 61400-12-1 standard, i.e.…”

Section: Direct Comparison Of the Standard And Equivalent Wind Speed mentioning

confidence: 99%

“…The profile model used in (Sumner and Masson, 2006) would probably shows some limitations at coastal sites or in places experiencing low level jets. For example, Antoniou et al (2009) found two different power curves by considering day time and night time measurements separately, in the US Midwest, resulting in an increase in AEP of 3% during the nigh time. No shear measurements were available at the turbine site, but previous studies had shown that low level jets occurred frequently at night in that region.…”

Section: Literature Reviewmentioning

confidence: 99%

See 4 more Smart Citations

Accounting for the speed shear in wind turbine power performance measurement

Wagner¹,

Courtney²,

Gottschall³

et al. 2011

Wind Energy

147

109

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Abstract:The power curve of a wind turbine is the primary characteristic of the machine as it is the basis of the warranty for it power production. The current IEC standard for power performance measurement only requires the measurement of the wind speed at hub height and the air density to characterise the wind field in front of the turbine. However, with the growing size of the turbine rotors during the last years, the effect of the variations of the wind speed within the swept rotor area, and therefore of the power output, cannot be ignored any longer. Primary effects on the power performance are from the vertical wind shear and the turbulence intensity. The work presented in this thesis consists of the description and the investigation of a simple method to account for the wind speed shear in the power performance measurement. Ignoring this effect was shown to result in a power curve dependant on the shear condition, therefore on the season and the site. It was then proposed to use an equivalent wind speed accounting for the whole speed profile in front of the turbine. The method was first tested with aerodynamic simulations of a multi-megawatt wind turbine which demonstrated the decrease of the scatter in the power curve. A power curve defined in terms of this equivalent wind speed would be less dependant on the shear than the standard power curve. The equivalent wind speed method was then experimentally validated with lidar measurements. Two equivalent wind speed definitions were considered both resulting in the reduction of the scatter in the power curve. As a lidar wind profiler can measure the wind speed at several heights within the rotor span, the wind speed profile is described with more accuracy than with the power law model. The equivalent wind speed derived from measurements, including at least one measurement above hub height, resulted in a smaller scatter in the power curve than the equivalent wind speed derived from profiles extrapolated from measurements at hub height and below only. It is well established that the turbulence intensity also influences the power performance of a wind turbine. Two ways of accounting for the turbulence were tested with the experimental data: an adaptation of the equivalent wind speed so that it also accounts for the turbulence intensity and the combination of the equivalent wind speed accounting for the wind shear only with the turbulence normalising method for turbulence intensity suggested by Albers. The second method was found to be more suitable for normalising the power curve for the turbulence intensity. Using the equivalent wind speed accounting for the wind shear in the power performance measurement was shown to result in a more repeatable power curve than the standard power curve and hence, in a better annual energy production estimation. Furthermore, the decrease of the scatter in the power curve corresponds to a decrease of the category A uncertainty in power, resulting in a smaller uncertainty in estimated AEP.The thesis is submitted to the Danish Tec...

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Section: Consequences On the Power Productionsupporting

confidence: 90%

Section: Direct Comparison Of the Standard And Equivalent Wind Speed mentioning

confidence: 79%

Section: Consequences On the Power Productionmentioning

confidence: 98%

Section: Direct Comparison Of the Standard And Equivalent Wind Speed mentioning

confidence: 99%

Section: Literature Reviewmentioning

confidence: 99%

See 3 more Smart Citations

Accounting for the speed shear in wind turbine power performance measurement

Wagner¹,

Courtney²,

Gottschall³

et al. 2011

Wind Energy

147

109

View full text Add to dashboard Cite

show abstract

On the predominance of unstable atmospheric conditions in the marine boundary layer offshore of the U.S. northeastern coast

et al. 2016

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The marine boundary layer of the northeastern U.S. is studied with focus on wind speed, atmospheric stability, and turbulent kinetic energy (TKE), the three most relevant properties in the context of offshore wind power development. Two long‐term observational data sets are analyzed. The first one consists of multilevel meteorological variables measured up to 60 m during 2003–2011 at the offshore Cape Wind tower, located near the center of the Nantucket Sound. The second data set comes from the 2013–2014 IMPOWR campaign (Improving the Modeling and Prediction of Offshore Wind Resources), in which wind and wave data were collected with new instruments on the Cape Wind platform, in addition to meteorological data measured during 19 flight missions offshore of New York, Connecticut, Rhode Island, and Massachusetts. It is found that, in this region: (1) the offshore wind resource is remarkable, with monthly average wind speeds at 60 m exceeding 7 m s−1 all year round, highest winds in winter (10.1 m s−1) and lowest in summer (7.1 m s−1), and a distinct diurnal modulation, especially in summer; (2) the marine boundary layer is predominantly unstable (61% unstable vs. 21% neutral vs. 18% stable), meaning that mixing is strong, heat fluxes are positive, and the wind speed profile is often nonlogarithmic (~40% of the time); and (3) the shape of the wind speed profile (log versus nonlog) is an effective qualitative proxy for atmospheric stability, whereas TKE alone is not.

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Effect of winds in a mountain pass on turbine performance

2013

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Mountain passes are potentially advantageous sites for the deployment of wind turbines because of road links and electrical transmission infrastructure. However, relatively little is known about wind characteristics and turbine response in these environments. Using hub height wind data from a mountain pass in Switzerland, this paper discusses the causes of the observed pass winds and how a generic wind turbine might perform in those conditions. During 3 months of winter measurements, the winds in the pass showed signatures of forcing by regional pressure gradients rather than local cooling or heating. Turbulence intensity was often less than 10%, and the magnitude of the wind shear power law exponent was less than 0.1. To understand the impact of pass winds on a wind turbine, we simulated a Wind Partnership for Advanced Component Technologies 1.5 MW wind turbine using the Fatigue, Aerodynamics, Structures, and Turbulence (FAST) aeroelastic simulator , forced by artificial wind fields of varying turbulence intensity and shear generated by the turbulence simulator TurbSim. We used the turbine simulation data to train a regression model that is used to predict the turbine response to the pass wind time series. Results showed that depending on long-term wind characteristics, wind turbines in the pass may perform differently than predicted using a power curve derived from test measurements at another location. This method of generating site-specific energy capture predictions could be combined with long-term wind resource data and specific turbine models to better predict the energy production and turbine loads at this, or any other site. Copyright

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Wind Shear and Uncertainties in Power Curve Measurement and Wind Resources

Cited by 72 publications

References 7 publications

Accounting for the speed shear in wind turbine power performance measurement

Accounting for the speed shear in wind turbine power performance measurement

On the predominance of unstable atmospheric conditions in the marine boundary layer offshore of the U.S. northeastern coast

Effect of winds in a mountain pass on turbine performance

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