1. Wind turbines and LOFAR
Hans van der Marel
ASTRON
Wind Turbine meeting, Chalmers
ASTRON is part of the Netherlands Organisation for Scientific Research (NWO)

2. LOFAR Low Frequency Array 10 - 90 MHz (LBA) 110 - 250 MHz (HBA)
Arranged in stations
Station connected with fibres
Station correlation
Central correlator (Groningen)

3. LOFAR locations
Core
Remote stations
International stations

4. LOFAR core and environment
Large receiving surface
Short baselines
Susceptible to interference
Radio quiet zone coordination zone of ~ 6 km
Wind turbines!

5. Wind turbines in Drenthe
Up to 200 MW in 2020
At least 3 MW per wind turbine
Clusters of at least 5 wind turbines
No wind turbines in LOFAR zone 1 (radio quiet zone)
Only wind turbines in LOFAR zone 2 (coordination zone) if they do not impede the LOFAR project

6. Windfarm ‘Hondtocht’ LOFAR monitoring survey in October 2006
Local authority: Dronten (Flevoland)
Wind turbine: Vestas - V66 - 1,75 MW
Number of wind turbines: 8
Installed capacity: 14,75 MW
Rotor axis height: 67 metres
Rotor diameter: 66 metres
Measurements by: Mark Bentum and Harm-Jan Stiepel
Processing by: Rob Millenaar and Albert-Jan Boonstra

7. Measurement set-up R&S ESMB monitoring receiver (9 kHz - 3 GHz)
R&S HE010 active antenna (9 kHz - 80 MHz)
VULP 9118G passive antenna ( MHz)
Miteq MHz amplifier (18 dB)
Rotors for azimuth and polarisation
(R&S FSP spectrum analyzer (9 kHz - 3 GHz))

8. Measurements Scatter measurements of FM transmitters
Spectrum measurements wind turbine ON / OFF
MHz
MHz
‘Standard’ LOFAR monitoring measurements
Spectrum analyzer measurements
Amplitude
Emission

9. Spectrum Measurements (1)

10. Spectrum measurements (2)

11. Amplitude measurements on FM transmitter frequency

12. Emission measurements (inside wind turbine near electronics cabinet)

13. Emission measurements (2)

14. Emission measurements (3)

15. Conclusions Electronics is potential source of emission
Partly shielded by wind turbine structure
Might be different for other wind turbines
Amplitude modulation due to variable reflections
For LOFAR frequencies AM on already distorted channels due to dispersion
More investigations needed:
Emission and reflections of bigger wind turbines and other types
Dispersion and reflections at higher frequencies