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| Titel |
Spectral analysis of wind velocity and output power from a wind farm. |
| VerfasserIn |
Rudy Calif, François G. Schmitt |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053674
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| Zusammenfassung |
| Wind energy production is very sensitive to atmospheric turbulent wind. Thus, the
high variability of the wind wind velocity can lead to electrical power variations of
the order of the nominal power output. Consequently, for the forecasting of wind
power for the next minutes or next days, for the modeling of the dynamics and for
the optimisation of design and material of wind turbines, a precise understanding
of small and large scales turbulent wind field is very important. The wind in the
atmospheric boundary layer has a Reynolds Number (ratio of inertial to viscous
force) Re -ă 106 characterizing a huge intermittency of the wind velocity at all
temporal or spatial scales. These scales range from large scale variations (years)
to very short variations (few minutes down to seconds). In this study, we present
a spectral analysis of the wind velocity and wind power data. Spectral analysis
allows to detect the scaling behavior. For a scaling process, the following power
law is obtained over a range of frequency f, E(f) ~ f-β, with β the slope of the
power spectrum. The power spectra are determined for wind velocity and wind
power data from the wind energy production site of Petit-Canal in Guadeloupe
(French West Indies). The wind velocity was measured with an ultrasonic anemometer
during July 2005 sampled at 20Hz, and a cup anemometer during the year 2006
sampled to 1Hz. These measurements are obtained at 38m (125ft) above the ground,
from the cliff edge. The wind power delivered by a wind farm was recorded with a
sampling rate fs = 1Hz, during three years (January 2006 to January 2009). It was
found that the wind velocity and wind power spectra could be broken into high and
low- frequency regimes according to the parameters given by this analysis. Firstly,
the turbulent velocity, for low frequencies 10-7Hz < f < 0.5Hz corresponding
to time scales 2s < t < 107s, the spectrum possesses a spectral slope parameter
β = 1.29 and for the high-frequencies 0.5Hz < f < 10Hz, corresponding to time
scales 0.1s < t < 2s possesses a spectral slope slightly greater than 5-3, β = 1.67.
Concerning the output power of the wind farm, for low frequencies f < 2.10-4Hz
corresponding to time scales t > 5000s, the power spectra shows a power-law with
β = 1.22 and for the high frequencies 2.10-4Hz < f < 0.5Hz corresponding to time
scales 2s < t < 5000s, the power spectra displays a power-law near the exact
value 5/3, β = 1.65. Finally, to highlight temporal correlation between velocity and
power data, the cross-correlation is given for times scales corresponding to low-
frequencies. |
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