Characterising wind fluctuations at the Horns Rev offshore wind farm. Claire Vincent and Gregor Giebel (Risø-DTU) Pierre Pinson (DTU-IMM). Introduction. Episodes of severe wind variability are observed at Horns Rev.
Characterising wind fluctuations at the Horns Rev offshore wind farm
Claire Vincent and Gregor Giebel (Risø-DTU)
Pierre Pinson (DTU-IMM)
Examples from 2000 and 2001
The Hilbert-Huang Transform
1. Decompose the data, so that each component is a mono-component signal.
2. Use the Hilbert transform to calculate the instantaneous frequencies and their amplitudes at each time.
Empirical Model Decomposition
Fastest oscillations in the time series
Quick response to non-stationarities in the data
Original time series
Period: 2.4 hours
1/2.4 = 0.4 cycles per hour
Episode of enhanced variability
Results: Seasonality of wind fluctuations
More intense fluctuations in winter and autumn
Results: The effect of wind direction
What does the wind ‘see’ from different directions?
Results: Variability and Pressure Tendency
Results: Variability and Precipitation
Rmax at time t is the maximum observed 10 minute rain amount within the interval [t – 90mins, t + 90 mins]
Rain is observed in discrete 0.25 mm quantiles.
Contours show probability density function of variability for each Rmax value.
Results: Variability and Stability
10 minute cup anemometer data: 4 year time series
12 Hz sonic anemometer data: 10 month time series
Summary of Results
A ‘classic’ event