1. RF-Emissions from Wind Energy Plants An Example Secondary and Primary Emission

2. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 2 What do you see? the sun, right the moon, well......but: you seethe sun, folded by the moon

3. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 3 What do you see? the moon, well...... but, you see the sun, folded by the moon, folded by the earth You know, what you see,... and you see what you know

4. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 4 The Microwave Case Example: Point – to – Point Microwave Link in C-Band Energy Reflected by Wind Mills

5. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 5 The undisturbed signal Microwave link in C-Band spectrum waterfall plot

6. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 6 The scene I Microwave link between Airport and remote short wave transmitter station distance: ~ 35 km

7. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 7 The scene II Transmitter antenna C-Band (~ 4 GHz) 2 m parabolic dish -3 dB beam with of transmitting antenna: 2 x 1.3° =2.6 ° that means, 50% of energy is transmitted inside this cone, but also 50 % outside.

8. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 8 The scene III yellow lines: -10 dB beam with (10 % of the transmitted energy ist distributed outside this cone) yellow circle and picture: wind energy park

9. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 9 Wind Farm Weilerswist 10 x Enercon E53/800 diameter: 53 m Hub height: 74 m min. speed: 12 rpm (36 blades per Minute) max. speed: 29 rpm (117 Blades per Minute) output voltage: 400 volts max. electrical output power: 800 kW power control: pitch supplied population by this windfarm: 7300 habitants

10. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 10 The Scene IV Distance between transmitter and wind plant: min. 7,6 km; max. 8,7 km Distance between wind park and receiving antenna: min. 3,3 km; max. 4,2 km angle between main lobe and wind park: ~ 30 degrees

11. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 11 The scene V Wind mills seen from my house closer view

12. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 12 C-Band-Receiver Standard Gain Horn w Waveguide (BP-Filter) Preamplifier (Gain ~25dB, NF < 3 dB) Spectrum Analyzer Aaronia HF-60105 (with Software)

13. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 13 Detection of reflected energy from a single wind turbine spectrum analyzer de facto in time domain mode 2,93 s per sweep at virtually zero span 1,2 s beween 2 blades, 3,6 s per turn 17 turns per minute rotational speed is variable, following wind speed

14. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 14 Example @ virtually no wind wind calm ( @ 10.01.2010 22:45 hour) sweep time: 23 s/Trace wind speed at the last 24 hours (recorded ~ 2 km away from the wind park)

15. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 15 1st Example @ heavy wind 16.01.2010 10:19-11:19 hour received RF power varies @ about 10 dB total RF power plot during the last 24 hr

16. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 16 2nd example @ heavy wind short time fluctuations of RF- Power long time fluctuations of RF- Power (last 24 hours) Wind speed, measured by an anemometer approx. 2 km away from wind farm (last 24 hours)

17. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 17 mutual coupling Echos from the wind mills with high dynamic and sometimes very distinct time behaviour mutual coupling between some of the 30 blades and radar crossing section: 5000 square meters (EADS) 35 dBm^2 (Eurocontrol)

18. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 18 Transmitter is switched off this frequency is clean since the end of January 2010 24 hour plot

19. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 19 Trends I Past&Present Past: Dense Microwave Link Infrastructure Present: Decline of earthbound communication grids in L-, C- and X-Band

20. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 20 Trends II Present&Future Feeders in the K- and Q-Band mobile com antennas (pico- and femtocells) handsets (UHF, L-, S-, C-Band) with frequency agility MIMO structures WLAN @ 2,695 and 5,7 GHz HAPS (high altitude power stations) Satellite radio stations LEO´s (low orbiting satellites), partly with beam steering

21. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 21 Trends III (LEO´s, MEO´s and) geostationary satellites sometimes beacons in the X- and K-Band Downstreams in the L-,C-, X-, K- and Ka-Band seen from pole position by courtesy of Fraunhofer FHR, Wachtberg

22. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 22 Optical and RF Picture

23. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 23 Search for primary emission @ Distance ~ 200 m Frequency range 1,25-1,40 GHz Out of band rejection @ GSM bands: > 100 dB NF 4,1 dB On-Source / Off-Source- Measurement (Antenna AZM= 90° turned) Reduction of raw-Data with Program Audacity works as digital oscilloscope, FFT-Analyzer or autocorrelation spectrometer, with high dynamic range

24. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 24 L-Band Receiver Helical Antenna LHC n=20 BP Filter 1,25-1,4 GHz Amplifier G ~30 dB BP-Filter 1,25-1,4 GHz Amplifier G ~20 dB Back-Diode Detector Video-Amp. G ~30 dB MP3-Player as 16 bit D/A-Converter, fSample = 33,2 kHz, Program Audacity

25. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 25 First results Wind Turbine (on and off source) Electric fence and RADAR Noise from the city Motorcycle

26. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 26 Conclusion: Remarkable Secondary Emissions Pulsar–like scattering Less Primary Emissions detected Further investigations at different types of wind generators are needed Emissions critical for radio astronomy

27. Göteborg, April, 27, 2010 Secondary RF Emissions from Wind Energy Plants Karl Grypstra, MPIfR 27 Thanks for your attention