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The Windmills Project

The Windmills Project. Team: Irene Fiori – U. of Pisa Lara Giordano – INFN Napoli Emanuele Marchetti – U. of Firenze, dept. of earth sciences Federico Paoletti – INFN Pisa Gillian Mayer – AEI Hannover. G Mayer – ILIAS WG1 meeting – Perugia – September 19th, 2005. Motivation:

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The Windmills Project

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  1. The Windmills Project Team: Irene Fiori – U. of Pisa Lara Giordano – INFN Napoli Emanuele Marchetti – U. of Firenze, dept. of earth sciences Federico Paoletti – INFN Pisa Gillian Mayer – AEI Hannover G Mayer – ILIAS WG1 meeting – Perugia – September 19th, 2005

  2. Motivation: • Measurements of seismic effects of a wind power plant on GEO 600 • Prediction for the planned wind power plant at VIRGO • In this talk: • Determination of the characteristic frequencies • GEO microseism • Windspeed and seismic wave field analysis

  3. Specifications: • All power plants have in common: • 3 blades • canonical steel tower • concrete foundations They differ in height and diameter of the rotor:

  4. Map of the site: N GEO 600 RIF has been taken directly on the foundations of T4

  5. 1. Characteristic frequencies Timeseries at an N90: • N90 was off • clear oscillation at 1.9 Hz • another persisting frequency • at 0.29 Hz

  6. 1. Characteristic frequencies • Department of steelworks determined • shapes of structural resonances* Low High frequency *) P. Schaumann, M. Seidel: Einschwingverhalten von Windenergieanlagen – Berechnungen und Messungen, Hannover, 2000

  7. 1. Characteristic frequencies Spectra of wind power plants: • Nordex S77 running • not only resonance peaks, • but also peaks which are related • to the blade pass frequency • (period T  5 s) • Enron Wind 1.5 off • two main peaks, • corresponding to two • resonance frequencies

  8. 1. Characteristic frequencies A closer look at the spectrum shows which frequencies appear: frequency correspondence • higher harmonics seem to • be present, but are difficult to • distinguish • peak around 18 Hz is very • likely the generator

  9. 2. GEO microseism Microseism Large coherence of STS-2 at low frequencies: • signals are coherent in • frequency range of windmills • 1st structural res. peak (0.3 Hz) • produced by the windmills? • different sources like the North • Sea?

  10. 2. GEO microseism Correlograms for microseism: • TCC - TFE: + 0.7 s • signal reaches TFE first • TCC - TFN: + 0.2 s • signal reaches TFN first • TFE - TFN: - 0.5 s • signal reaches TFE first

  11. 2. GEO microseism Result: • velocity: 650 m/s • (depends on day) • angle: 43° NE Problem: • There‘s no obvious source where • these waves could come from • expected sources: North Sea/Baltic Sea, Hannover Possible explanation: The measured signal could be a superposition of several (at least two) signals of different sources

  12. Map of the site: N GEO 600

  13. 3. Field measurements Aquisition times: After the second day we left the stations outside even during nighttime. For station A02 and A03 we lack GPS timing.

  14. 3. Field measurements Windspeed analysis: • seismometer output (RIF) • scales with windspeed • allows rough correction • of data taken at different • wind conditions • medium and high • wind spectra look • the same • low wind: 0.3 Hz • peak persists

  15. 3. Field measurements Detailed view of RMS in frequency bands: • Every frequency is affected by wind except from the highest band • another hint that the peak at 18 Hz has an internal source • lowest frequency band (red) shows the effect of the adjustment • of the rotor • at least a windspeed of 1 m/s is needed to make the wind power plant run

  16. 3. Field measurements Coherence: D1 - RIF, all three components other stations, only vertical component • extremly bad coherence for all stations except from D1 (25 m from RIF) • no chance to make correlograms • possible explanation: • directly on the basement (RIF) large amplification of the signal • once the signal reached the ground heavily damped, peaks get broad, • coherence is lost. • also interference from other windmills

  17. 3. Field measurements Low frequencies High resolution view of low frequency coherence between D1 and central STS-2: A dip at 0.29 Hz can clearly be seen. The correlogram shows, that the signal first reaches the STS-2, than D1. low frequency part is microseism as discussed above

  18. 3. Field measurements Higher frequencies • new measurement because of bad • coherence: • E1 near T3, E2 200 m east of E1 • much better coherence now, even at • a distance of 200 m • some high frequency peaks survive

  19. 3. Field measurements Comparison: medium wind and no wind conditions, vertical component • night-time: low antropic noise • light green/blue: spectra at no wind, • wind power plants weren‘t running • dark green/blue: spectra with medium wind, • very likely that all wind power plants were running • no significant difference in A1 spectra (near GEO)

  20. Conclusions: • all windmills have got two structural resonances, persist also when the windmills are not running • when running, one can see the blade pass frequency, the 3rd harmonic and higher harmonics of the 3rd • low frequency noise produced by the windmills is quickly damped and dominated by the local microseism • although the last picture shows that it‘s very unlikely that higher frequencies reach GEO, this cannot yet be excluded. However, if there is an effect it is certainly small.

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