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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
2
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
3
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
4
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
5
The undisturbed signal
Microwave linkin C-Band
• spectrum
• waterfall plot
Göteborg, April, 27, 2010
Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR
6
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
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
Göteborg, April, 27, 2010
Secondary RF Emissions from Wind Energy PlantsKarl 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
Göteborg, April, 27, 2010
Secondary RF Emissions from Wind Energy PlantsKarl 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
Göteborg, April, 27, 2010
Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR
11
The scene V
• Wind mills seen from my house
• closer view
Göteborg, April, 27, 2010
Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR
12
C-Band-Receiver
• Standard Gain Hornw Waveguide (BP-Filter)
• Preamplifier (Gain
~25dB, NF < 3 dB) • Spectrum Analyzer
Aaronia HF-60105(with Software)
Göteborg, April, 27, 2010
Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR
13
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
Göteborg, April, 27, 2010
Secondary RF Emissions from Wind Energy PlantsKarl 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 thewind park)
Göteborg, April, 27, 2010
Secondary RF Emissions from Wind Energy PlantsKarl 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
Göteborg, April, 27, 2010
Secondary RF Emissions from Wind Energy PlantsKarl 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)
Göteborg, April, 27, 2010
Secondary RF Emissions from Wind Energy PlantsKarl 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)
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
19
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
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 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
21
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
Göteborg, April, 27, 2010
Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR
22
Optical and RF „Picture“
Göteborg, April, 27, 2010
Secondary RF Emissions from Wind Energy PlantsKarl Grypstra, MPIfR
23
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
25
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
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