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

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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The Microwave Case

Example:

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

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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The undisturbed signal

Microwave linkin C-Band

• spectrum

• waterfall plot

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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The scene I

Microwave link

between Airport and remote short wave transmitter station

distance: ~ 35 km

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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.

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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The scene V

• Wind mills seen from my house

• closer view

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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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Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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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Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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)

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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)

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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)

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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Transmitter is switched off

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

24 hour plot

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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Trends I Past&Present

• Past: Dense Microwave Link Infrastructure

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

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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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Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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Optical and RF „Picture“

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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“

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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First results

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

Noise from the city Motorcycle

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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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

Göteborg, April, 27, 2010

Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR

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Thanks for your attention