Field Results of New Sodar
Transducer Horn
DEWEK 2015 Proceedings
Andrew Hastings-Black
Introduction
 Many thanks to DEWEK for accepting this presentation.
 Education
 B.A., Physics, Tufts University
 M.Sc. Candidate, Applied Physics, Columbia University
 Industry
 Second Wind, Inc., Triton R&D, 2008 – 2014
 Vaisala Oyj, Triton R&D, 2014 – present day
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Triton Sonic Wind Profiler
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Triton Sonic Wind Profiler
 Commercialized in 2008
 Monostatic, phased array sodar, 7W power consumption
 500+ systems delivered, 6 continents
 13 million operational hours with 98.5% uptime
 Heated mirror option and supplementary fuel cell option
 Used both in WRA and wind farm operations
 Excellent reliability and performance, widely adopted by
largest developers
 Bankable data – accepted by key financiers and
independent engineers
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Triton Sonic Wind Profiler
Triton cross-section
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Speaker array
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Individual speaker
Triton Sonic Wind Profiler
 Wide deployment in diverse conditions shows weaknesses
 Atmospheric absorption of sound, geographical+seasonal
 𝐶𝑇2 stability variations, diurnal
 Speaker efficiency temperature-dependence, seasonal
 Turbine hub heights increasing
 Data recovery financing requirements ~90%
 Clear need for higher data recovery at higher heights
 Redesign speaker horn
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Wave front path
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New Horn Design Key Characteristics
 Horn length creates 4.5 kHz resonant peak
 Increases speaker efficiency in SoDAR bandwidth
 Increases signal strength and microphone sensitivity
 Improves SNR
 Central waveguide
 Increases speaker Directivity Index
 Reduces phased array sidelobe intensity
 Reduces fixed echoes
 Enables operation at multiple wavelengths
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Frequency Response
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Polar Response
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Directivity Index
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Hardware and Operating Strategy
 KSN 1005A Speakers
 𝜆 = 76 𝑚𝑚
 𝑓𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑡 ∝ 𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒
 42 Vpp
 70 ms pulse width
 G2 Speakers
 𝜆 ∈ 70, 72, 74, 76 , 78, 80 mm
 𝑓𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑡 ∝ 𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒, 𝜆
 42 Vpp
 70 ms pulse width
 NB: Only changes to Triton configuration are (1) speaker
horn, and (2) operating strategy to stay near resonant peak
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Comparison with Legacy Triton
 G2 Speaker  Triton Performance Upgrade (“TPU”)
 160 TPUs deployed world wide
 23 TPU-Legacy pairs within 50 km and in similar terrain
 Total dataset length: 20 years
 Average measurement campaign: 10 months
 Data filtered using standard Triton filtering guidelines
 QF > 90%
 |VWS| < 1.5 m/s
 Data recovery =
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𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒𝑠 𝑎𝑓𝑡𝑒𝑟 𝑓𝑖𝑙𝑡𝑒𝑟𝑖𝑛𝑔
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑜𝑡𝑒𝑛𝑡𝑖𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒𝑠 𝑖𝑛 𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑚𝑒𝑛𝑡 𝑝𝑒𝑟𝑖𝑜𝑑
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Seasonal Distribution of Data
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Data Recovery Plots
92%
80 m
TPU
Legacy
Uptime
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Data Recovery Improvement
 Improvement at nearly all sites:
 +3% @ 80m, +7% @ 100m, +10% @120m
 Normalizing for uptime:
 20/23 TPU sensors get 90% data recovery at 80m
 23/23 TPU sensors get 85%
 14/23 Legacy sensors get 90% data recovery at 80m
 20/23 Legacy sensors get 85%
 Biggest improvement in winter months
 +7% @ 80m, +11% @ 100m, +16% @120m
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Data Accuracy
 Resonant design difficult to manufacture.
 Very important that speakers be “well-matched”
 Poor matching causes errors in wind speed measurement
𝜎𝑠𝑝𝑒𝑎𝑘𝑒𝑟 → 𝜎𝑏𝑒𝑎𝑚 𝑎𝑛𝑔𝑙𝑒 → 𝜎𝑤𝑖𝑛𝑑 𝑠𝑝𝑒𝑒𝑑
 If we quantify 𝜎𝑤𝑖𝑛𝑑 𝑠𝑝𝑒𝑒𝑑 as a function of 𝜎𝑠𝑝𝑒𝑎𝑘𝑒𝑟 we can
control speaker matching to ensure that every array has
consistent beam pattern
 Simulate phased array, compare with field data
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Monte Carlo Simulation Detail
 R (v. 2.14)
 RStudio (v. 0.97)
 Linux Fedora release 14 (Laughlin)
 ‘seque’ package by J.D. Long
 Calls virtual clusters using Amazon EC2 instances
 𝑚𝑎𝑡𝑐ℎ𝑖𝑛𝑔 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 = 𝑟 = 𝑀𝑜𝑑(𝐴𝑛𝑜𝑟𝑚 𝑒 𝑖𝜃𝑛𝑜𝑟𝑚 − 𝑒 𝑖∗0 )
 6 wavelengths (70 mm – 80 mm)
 100 random permutations, per-grouping, per-wavelength
 50850 data points per simulation
 36 speakers per array  7.7 billion calculations
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Data Accuracy
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Simulation
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Simulation
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Simulation
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Data Accuracy
Grouping 1
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Data Accuracy
Grouping 2
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Data Accuracy
Grouping 3
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Data Accuracy
Grouping 4
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Data Accuracy
Grouping 5
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Data Accuracy
Triton Matching
Passband
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Data Accuracy
 No significant difference in uncertainty between wavelengths
 Final passband between Grouping 1 and Grouping 2
 3 standard deviations ~ 1.25% total wind speed error
 How does the model agree with field data?
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Data Accuracy
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Further Research
 Upcoming accuracy evaluation from 3Tier using tower
datasets from resource assessment campaigns
 ~1% sensor uncertainty for Legacy and TPU Tritons
 Monte Carlo Simulation of enclosure effects
 Include inhomogeneous atmosphere
 TPU development partners:
Thanks for listening!
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