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Comparing Remote Sensing
Systems to Met Towers
What You Can Learn From Vaisala’s Recent Study
Webinar, October 22, 2015
Le...
#WindWebinar
q  This webinar will be available afterwards at
www.windpowerengineering.com & email
q  Q&A at the end of the...
#WindWebinar
Michelle Froese
Senior Editor - Moderator
Windpower Engineering
& Development
Lee Alnes
Key Account Manager
V...
Page © Vaisala | www.vaisala.com/energy
Why Remote Sensing? Higher height data
10/27/154
Page © Vaisala | www.vaisala.com/energy
Why Remote Sensing? Additional advantages
10/27/155
•  Easy to install
•  No permi...
Page © Vaisala | www.vaisala.com/energy
Applications of Higher Height Data
10/27/156
Page © Vaisala | www.vaisala.com/energy
Accuracy
10/27/157
The words accuracy and uncertainty are sometimes interchanged…
...
Page © Vaisala | www.vaisala.com/energy
Uncertainty
10/27/158
Page © Vaisala | www.vaisala.com/energy
“P values” (P90, P50, . . .)
10/27/159
§ Probability of
exceedance
§ P50 – median ...
Page © Vaisala | www.vaisala.com/energy
Correlation:
R and R2
R: correlation coefficient
R2: correlation squared,
a.k.a. c...
Page © Vaisala | www.vaisala.com/energy
Validation Studies
§ Who does them
§  Wind developers and operators
§  Remote sens...
Page © Vaisala | www.vaisala.com/energy
Ongoing Validation Studies
§ Triton® Wind Profiler has been independently evaluate...
Page © Vaisala | www.vaisala.com/energy
Our Main Question
§ How does Triton uncertainty
compare to a met tower
system, in ...
Page © Vaisala | www.vaisala.com/energy
Vaisala’s Unique Position
10/27/1514
MANY DEPLOYMENTS HAD
COLLOCATED TOWERS
MANY L...
Page © Vaisala | www.vaisala.com/energy
The Data Set
§  30 Triton / Tower data sets included in the study:
§  Triton data ...
Page © Vaisala | www.vaisala.com/energy
Geographic Distribution
§ Well distributed
geographically
§ Exact locations not
sh...
Page © Vaisala | www.vaisala.com/energy
Key Take-aways
§ Certainty: Triton has the same uncertainty on mean wind speed as ...
Page © Vaisala | www.vaisala.com/energy
But what is the “Truth”?
10/27/1518
“TRUE” WIND SPEED
?
TOWER UNCERTAINTY SOURCES:...
Page © Vaisala | www.vaisala.com/energy
Conclusion: Wind speed
“When the mean wind speed differences at all 100 qualifying...
Page © Vaisala | www.vaisala.com/energy
Data Recovery
“All Tritons (both original units and those with the upgraded speake...
Page © Vaisala | www.vaisala.com/energy
Reducing Shear Extrapolation
Uncertainty
When mean winds directly measured by Trit...
Page © Vaisala | www.vaisala.com/energy
Summary: Main Points
§ Remote sensing is in widespread use and
will continue to gr...
#WindWebinar
Michelle Froese
Senior Editor - Moderator
Windpower Engineering
& Development
@Windpower_Eng
Lee Alnes
Key Ac...
#WindWebinar
Thank You
q  This webinar will be available at
www.windpowerengineering.com & email
q  Tweet with hashtag #Wi...
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Comparing Remote Sensing Systems to Met Towers

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Have you adopted remote sensing systems in your wind measurement program, or are you considering adopting them?

Watch the webinar: http://www.windpowerengineering.com/construction/towers-construction/upcoming-live-webinar-comparing-remote-sensing-systems-to-met-towers/

Published in: Engineering
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Comparing Remote Sensing Systems to Met Towers

  1. 1. Comparing Remote Sensing Systems to Met Towers What You Can Learn From Vaisala’s Recent Study Webinar, October 22, 2015 Lee Alnes Dr. Mark Stoelinga
  2. 2. #WindWebinar q  This webinar will be available afterwards at www.windpowerengineering.com & email q  Q&A at the end of the presentation q  Hashtag for this webinar: #WindWebinar Before We Start
  3. 3. #WindWebinar Michelle Froese Senior Editor - Moderator Windpower Engineering & Development Lee Alnes Key Account Manager Vaisala Dr. Mark Stoelinga Senior Scientist Vaisala Comparing Remote Sensing Systems to Met Towers Meet the Speakers…
  4. 4. Page © Vaisala | www.vaisala.com/energy Why Remote Sensing? Higher height data 10/27/154
  5. 5. Page © Vaisala | www.vaisala.com/energy Why Remote Sensing? Additional advantages 10/27/155 •  Easy to install •  No permitting delays •  Easy to move, relocate, and service
  6. 6. Page © Vaisala | www.vaisala.com/energy Applications of Higher Height Data 10/27/156
  7. 7. Page © Vaisala | www.vaisala.com/energy Accuracy 10/27/157 The words accuracy and uncertainty are sometimes interchanged… Accuracy of measurement [means] ‘the closeness of the agreement between the result of a measurement and a true value of the measurand’… Accuracy is a qualitative concept.’ It can be high or low for example but strictly it should not be used quantitatively. In practice, though, it is often used quantitatively…this unofficial definition breaks down because it inherently assumes that a true value can be defined, known and realized perfectly. … Uncertainty of measurement acknowledges that no measurements can be perfect and is defined as a '… parameter, associated with the result of a measurement, that characterizes the dispersion of values that could reasonably be attributed to the measurand.’ National Physical Laboratory (UK): http://www.npl.co.uk/reference/faqs/is-there-a-difference-between-'accuracy'-and-'uncertainty'-%28faq-length%29
  8. 8. Page © Vaisala | www.vaisala.com/energy Uncertainty 10/27/158
  9. 9. Page © Vaisala | www.vaisala.com/energy “P values” (P90, P50, . . .) 10/27/159 § Probability of exceedance § P50 – median value § P90 – 90% chance of achieving at least this value P99 P90 P75 P50
  10. 10. Page © Vaisala | www.vaisala.com/energy Correlation: R and R2 R: correlation coefficient R2: correlation squared, a.k.a. coefficient of determination. It represents the fraction of variance in the y-variable “explained” by the linear fit to the x-variable. 10/27/1510 Remotesensorwindspeed(m-1s) Tower wind speed (m-1s)
  11. 11. Page © Vaisala | www.vaisala.com/energy Validation Studies § Who does them §  Wind developers and operators §  Remote sensing manufacturer §  Research organizations § What they measure §  Wind speed, direction, etc. à comparisons §  Data recovery, up-time, power consumption, … § Not to be confused with calibration 10/27/1511
  12. 12. Page © Vaisala | www.vaisala.com/energy Ongoing Validation Studies § Triton® Wind Profiler has been independently evaluated and verified for accuracy by: § Studies in progress – 2015 10/27/1512 China Hydroelectric Corporation
  13. 13. Page © Vaisala | www.vaisala.com/energy Our Main Question § How does Triton uncertainty compare to a met tower system, in actual commercial use? 10/27/1513
  14. 14. Page © Vaisala | www.vaisala.com/energy Vaisala’s Unique Position 10/27/1514 MANY DEPLOYMENTS HAD COLLOCATED TOWERS MANY LEADING CUSTOMERS VOLUNTEERED DATA FOR A GLOBAL STUDY IN-HOUSE WIND RESOURCE ASSESSMENT EXPERTISE 2500+ TRITON LOCATIONS IN 30+ COUNTRIES
  15. 15. Page © Vaisala | www.vaisala.com/energy The Data Set §  30 Triton / Tower data sets included in the study: §  Triton data came from 24 different units manufactured between 2008 and 2014 §  A total of 100 correlation pairs (heights) were used –  Shortest tower measurement height was 34m –  Tallest tower measurement height was 120m –  Average tower to Triton distance was 134m –  Most Triton / tower elevation differences were less than 2m, and all were within 6m §  18 of the data sets used Tritons with the original speaker array §  12 of the data sets used Tritons with an improved speaker array that was released in 2013 §  All Tritons were deployed as they were shipped from the factory with no special modifications or equipment 10/27/1515
  16. 16. Page © Vaisala | www.vaisala.com/energy Geographic Distribution § Well distributed geographically § Exact locations not shown to preserve customer confidentiality 10/27/1516
  17. 17. Page © Vaisala | www.vaisala.com/energy Key Take-aways § Certainty: Triton has the same uncertainty on mean wind speed as a well designed met tower—about 1% RMSE. §  Not just in one experiment, but over 10’s of 1000’s of data-hours §  Measuring with Triton cuts met tower shear extrapolation error in half § Repeatability: You can expect continued, repeatable performance from one Triton to another § Longevity: Study included data collected over 6 years – with no degradation due to age of unit 10/27/1517
  18. 18. Page © Vaisala | www.vaisala.com/energy But what is the “Truth”? 10/27/1518 “TRUE” WIND SPEED ? TOWER UNCERTAINTY SOURCES: CALIBRATION | TURBULENCE & OFF-HORIZONTAL FLOW | SENSOR DEGRADATION | TOWER FLOW DISTORTION | TO NAME A FEW!
  19. 19. Page © Vaisala | www.vaisala.com/energy Conclusion: Wind speed “When the mean wind speed differences at all 100 qualifying anemometer measurement heights within the 30 Triton/met tower pairs are aggregated, the average percent difference is +0.09%, and the percent root mean-square of the differences is 1.27%. This is consistent with an estimated uncertainty of the Triton of approximately 1%, if the met tower measurement uncertainty is assumed to be independent and approximately 1% as well, a reasonable assumption for a large set of met towers maintained by many different Triton users.” 10/27/1519
  20. 20. Page © Vaisala | www.vaisala.com/energy Data Recovery “All Tritons (both original units and those with the upgraded speaker array, or “TPU” units) exhibit high data recovery (>=90%) up to 80m. Data recovery for the newer TPU units is considerably improved compared to that of original units at higher heights: •  17% higher at 100 m, •  47% higher at 140 m, and •  106% higher at 180 m.” 10/27/1520
  21. 21. Page © Vaisala | www.vaisala.com/energy Reducing Shear Extrapolation Uncertainty When mean winds directly measured by Triton are compared with estimates sheared up from lower met tower heights, the Triton- measured mean wind speeds exhibit uncertainties less than half that of estimates sheared up from met towers. 10/27/1521
  22. 22. Page © Vaisala | www.vaisala.com/energy Summary: Main Points § Remote sensing is in widespread use and will continue to grow § Accuracy, uncertainty, calibration, validation, correlation are frequently misunderstood or misused § Vaisala Triton has been shown to have equivalent uncertainty to met towers – all over the world 10/27/1522
  23. 23. #WindWebinar Michelle Froese Senior Editor - Moderator Windpower Engineering & Development @Windpower_Eng Lee Alnes Key Account Manager Vaisala lee.alnes@vaisala.com Dr. Mark Stoelinga Senior Scientist Vaisala mark.stoelinga@vaisala.com Comparing Remote Sensing Systems to Met Towers Questions?
  24. 24. #WindWebinar Thank You q  This webinar will be available at www.windpowerengineering.com & email q  Tweet with hashtag #WindWebinar q  Connect with Windpower Engineering & Development q  Discuss this on EngineeringExchange.com

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