Post on 20-Jan-2016
Radar Impact AssessmentUK Offshore Wind 2003, 26-27 March 2003Dr John G Gallagher
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Contents
1 The radar impact
2 Approach
3 Computer model
4 Radar trials
5 Validation
The radar impactSection 1
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The problem• Important for Offshore and On-shore wind farms
– radar used for maritime navigation and safety
– land-based radar
– ship-based radar
– Air Traffic Control radar
• Associated electromagnetic issues
– Communications (HF, VHF to microwave)
– GPS, DGPS
– AIS
– Radar beacons (racons)
– SSR
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The radar problem
• Safety at sea and airspace safety
• Wind turbine interaction with radar affects
– Marine radar both land-based and ship-based radar
– Air Traffic Control primary radar and SSR
• by
– giving rise to false targets on radar
– obscuration of wanted targets as a result of radar shadows cast behind turbines
– corrupts information on the radar waveform
ApproachSection 2
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Need
• There is a need to understand the operational impact of siting wind turbines near radar and other electromagnetic systems
– Radar cross-section (measure of energy scattered)
– propagation of radar energy
• Who are the main stakeholders and what systems do they operate that may be affected by the wind farm
• Determine the key interaction parameters that affect the radar and other electromagnetic systems
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Approach
• DTI Renewable Energy Programme funded model
• Generate detailed electromagnetic scattering predictions of wind turbines
• In the case of radar systems configure computer model to simulate the effects of wind turbines on radar
• Carry out a trial to collect measured data of a turbines and relate it to the turbine state (pitch, yaw, RPM)
• Validate computer model using the measured data
Computer modelSection 3
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Computer model
• Modular components allow configuration for offshore and on-shore environments
– Transmission from radar
– Propagation over terrain to turbines
– Complex scattering from turbines
– Return of complex echo to radar
– Radar processing • target discrimination in range and bearing
• (MTI / Threshold Etc.)
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Radar cross-section predictions
• CAD models made from data supplied from manufacturers
• Meshed appropriately for input to RCS code
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Radar cross-section predictions• Results show RCS of complete turbine to be
generally between 10dbsm -30dBsm (10m2 - 1000m2)
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Computer model
• Display
– Takes time history data files from prediction files and displays them on the PPI display
• The computation is run on QinetiQ high performance computer facility
Radar TrialSection 4
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Radar Trials
• The QinetiQ MPR instrumentation radar measures the radar signature of a wind turbine
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Measured RCS of wind turbine
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 30
5
10
15
20
25
30
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Time (s)
RC
S (
dB
)
RCS from SWT008
Time (secs)
RCS (dBsm)
• 23 RPM
• 40° Yaw
19Doppler spectrum for three revolutions
-80
-60
-40
-20
0
20
Time (s)
Doppler(Hz
)
0 1 2 3 4 5 6 7 8
-1000
-500
0
500
1000
1500
20A radar PPI display
ValidationSection 5
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Validation• Simulation
– CAD model of turbine– Propagate electromagnetic wave– Predicted wind turbine RCS;– Radar signal process model through to PPI display
• Measurement– Gathered wind turbine truth data– Measured the RCS of a wind turbine– Collected video of a real PPI display showing a wind farm
• Compare measured data with the predicted data for validation
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RCS validation
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Display validation
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Validation
• The RCS predictions reproduce the peaks and basic
trend of the measurement data;
• The simulation agrees well with the recorded PPI
display for single turbine configurations;
• The model is shown to be between 93% and 98%
accurate for several configurations of a single
turbine.