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

RF-Emissions from Wind Energy Plants

An Example

Secondary and Primary Emission

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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What do you see?

• the sun, right

• the moon, well......but: you see the sun, folded by the moon



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What do you see?

the moon, well...... but, you see the sun, folded by the moon, folded by the

earthYou know, what you see, ... and you see what you know



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The Microwave Case

Example:

Point – to – Point Microwave Linkin C-BandEnergy Reflected by Wind Mills



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The undisturbed signal

Microwave linkin C-Band

• spectrum

• waterfall plot



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The scene I

Microwave link

between Airport and remote short wave transmitter station

distance: ~ 35 km



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The scene II

Transmitter antennaC-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, butalso 50 % outside.



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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



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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



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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



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The scene V

• Wind mills seen from my house

• closer view



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C-Band-Receiver

• Standard Gain Hornw Waveguide (BP-Filter)

• Preamplifier (Gain

~25dB, NF < 3 dB) • Spectrum Analyzer

Aaronia HF-60105(with Software)



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Detection of reflected energyfrom a single wind turbine

spectrum analyzer de facto in time domain mode2,93 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



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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 thewind park)



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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



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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)



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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)



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Transmitter is switched off

• this frequency is „clean“ since the end of January 2010

24 hour plot



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Trends I Past&Present

• Past: Dense Microwave Link Infrastructure

• Present:Decline of earthboundcommunication grids in L-, C- and X-Band



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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 agilityMIMO 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



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Trends III

• (LEO´s, MEO´s and) geostationary satellites

• sometimes beacons in the X- and K-BandDownstreams in the L-,C-, X-, K-and Ka-Band

• seen from „pole position“

by courtesy of Fraunhofer FHR, Wachtberg



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Optical and RF „Picture“



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Search for primary emission@ Distance ~ 200 m

• Frequency range 1,25-1,40 GHzOut of band rejection @ GSMbands: > 100 dBNF 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 autocorrelationspectrometer, with high dynamic range



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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“



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First results

Wind Turbine (on and off source) Electric fence and RADAR

Noise from the city Motorcycle



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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



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Thanks for your attention

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

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