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OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: Presented by: John Obermeier, President John Obermeier, President Otech Engineering, Inc. Otech Engineering, Inc. In collaboration with: In collaboration with: Rachael Coquilla, Ph.D. candidate Rachael Coquilla, Ph.D. candidate Dept. Mechanical & Aeronautical Engineering Dept. Mechanical & Aeronautical Engineering University of California at Davis University of California at Davis
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OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

Mar 26, 2015

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Page 1: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Considerations in Anemometer Calibration

Considerations in Anemometer Calibration

Presented by:Presented by:

John Obermeier, PresidentJohn Obermeier, PresidentOtech Engineering, Inc.Otech Engineering, Inc.

In collaboration with: In collaboration with: Rachael Coquilla, Ph.D. candidateRachael Coquilla, Ph.D. candidate

Dept. Mechanical & Aeronautical EngineeringDept. Mechanical & Aeronautical EngineeringUniversity of California at DavisUniversity of California at Davis

Page 2: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Outline

Current Standards and Test Protocols

Anemometer Calibration

Quality Control

Calibration Comparisons

Calibration Standard Considerations

Summary

Page 3: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Current Standards and Test Protocols

Current Test Standards for cup and propeller anemometers

ASTM D5096-02 ISO 17713

starting threshold

distance constant

transfer function **

off-axis response

Non-standard Protocols Measnet Otech Engineering, Inc.

…moving vehicle method…wind tunnel method

Page 4: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Anemometer Calibration

BackgroundBackground

• 30 year history30 year history

• Most widely used instrument Most widely used instrument in wind industry (over in wind industry (over 150,000+ units installed)150,000+ units installed)

• Most tested anemometer in Most tested anemometer in the worldthe world

Performance characteristics

• Rugged and survives high wind environments

• Linear range matches wind turbine energy producing speed range

• Independent of temperature

• Maintains performance for extensive periods

NRG #40 Cup AnemometerNRG #40 Cup Anemometer

Page 5: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Anemometer Calibration

Generation of an anemometer transfer function

Steady state wind speeds at set intervalsSteady state wind speeds at set intervals

Increasing and decreasing speedsIncreasing and decreasing speeds

Include specified speed rangeInclude specified speed range

Produce slope and offset from linear transfer functionProduce slope and offset from linear transfer function

Provide a measure of uncertaintyProvide a measure of uncertainty

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0 5 10 15 20 25 30

Reference Wind Speed, U (m/s)

Sp

eed

Res

idu

al, D U

(m

/s)

0

5

10

15

20

25

30

0 5 10 15 20 25 30 35 40

Anemometer Signal, f (Hz)

Ref

eren

ce W

ind

Sp

eed

, U

(m

/s)

Sample Transfer FunctionU = 0.7707 f + 0.318

R = 0.9999

Page 6: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Anemometer Calibration

22VVV tSBU Uncertainty in

Velocity Measurement

0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

4.0%

2 4 6 8 10 12 14 16 18 20 22 24 26 28

Reference Wind Speed (m/s)

Rel

ativ

e U

nce

rtai

nty

in W

ind

Sp

eed

Mea

sure

men

t OEI Wind Tunnel

OEI Vehicle Test

NIST Wind Tunnel

Page 7: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Quality Control

Recall sample transfer functionU = 0.7707 f + 0.318

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

0 10 20 30 40 50 60 70 80 90 100

time or unit count

% v

ari

ati

on

fro

m c

on

tro

lled

mea

n

UL

LL

Converted transfer functionConverted transfer functionusing using forced interceptforced intercept

U = 0.7693 U = 0.7693 ff + + 0.350.35

““slope+k” valueslope+k” value

Page 8: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Quality ControlHistogram of Slope+K Values from OEI Vehicle Tests

Dec 2002 – Jul 2005 (11,834 new NRG #40 Cup Anemometers)Standard Deviation = 0.0031 m/s per Hz

95 % of the distribution are included within ± 0.8 % of the mean

0.7500.750 0.752 0.7550.755 0.757 0.7600.760 0.762 0.7650.765 0.767 0.7700.770 0.772 0.7750.7750

200

400

600

800

1000

1200

1400

1600

1800

UL = +1%LL = -1% Mean

Nu

mb

er o

f R

ead

ing

s

Slope+K Value (m/s per Hz)

Page 9: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Calibration Comparisons

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.755 0.759 0.763 0.767 0.771 0.775

Slope (m/s per Hz)

Inte

rcep

t (m

/s)

OEI Vehicle CRES Wind Tunnel Consensus Value

Comparison of five NRG #40 anemometer calibrations (year 2002) between the OEI Vehicle and CRES Wind Tunnel test methods

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

1 2 3 4 5

Reading Number%

dif

fere

nce

fro

m0.

765

m/s

per

Hz

OEI Vehicle CRES Wind Tunnel

Correlation Coefficient, R = 0.93

Page 10: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Calibration Comparisons

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.755 0.759 0.763 0.767 0.771 0.775

Slope (m/s per Hz)

Inte

rcep

t (m

/s)

OEI Vehicle OEI Wind Tunnel Consensus Value

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

0 10 20 30 40 50 60 70 80 90 100

Reading Number%

dif

fere

nce

fro

m0.

765

m/s

per

Hz

OEI Vehicle OEI Wind Tunnel

Correlation Coefficient, R = 0.62

Comparison of 100 NRG #40 anemometer calibrations (year 2005) between the OEI Vehicle and OEI Wind Tunnel test methods

Page 11: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Calibration Standard Considerations

Must agree upon a consensus standard anemometer Must agree upon a consensus standard anemometer calibration procedure and report process (i.e. Measnet).calibration procedure and report process (i.e. Measnet).

Consensus must remain an open process.Consensus must remain an open process.

Maintain a relation to a standard instrument via round Maintain a relation to a standard instrument via round robin comparisons (i.e. RR-3 experiment).robin comparisons (i.e. RR-3 experiment).

Test ProtocolRange (m/s)

# PointsDwell Time

(sec)Hysterises

Check

Interval Duration

(sec)

ASTM D 5096-02 0 - 50% FS 10 300 - 1000 yes 30 - 100

OEI Vehicle Test 4.5 - 25 10 396 yes 18 - 98

OEI Wind Tunnel 4 - 26 12 360 yes 30

Measnet 4 - 16 13 390 yes 30

Page 12: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Calibration Standard ConsiderationsPower, Speed Frequency, and Energy Distribution for a range of wind speeds (using GE 1.5 MW wind turbine power curve)

0

20

40

60

80

100

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

Wind Speed (m/s)

No

rmal

ized

% F

S

WT Power Speed Frequency ENERGY

OEI Test Range

Measnet Test Range

Mean = 7 m/s

Page 13: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Calibration Standard Considerations

Considerations for advanced calibrations:Considerations for advanced calibrations:

Over-speedingOver-speedingDefinition: a cup anemometer’s over-estimation of Definition: a cup anemometer’s over-estimation of the mean wind due to its faster dynamic response the mean wind due to its faster dynamic response at the initial exposure to the wind than at the at the initial exposure to the wind than at the decrease of the same wind.decrease of the same wind.

Off-axisOff-axisASTM D5096-02 recommended testingASTM D5096-02 recommended testing test range test range ± 30° off-axis± 30° off-axis increments of 5° anglesincrements of 5° angles

Temperature dependenceTemperature dependence

Page 14: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Summary

To add value in the manufacture of an anemometer, it is recommended to maintain quality control by using anemometer calibration and a statistical guideline (“Slope+K”). This assures buyers that the product clearly conforms to a defined performance criteria.

When a reliable calibration transfer function is available, it is recommended that users apply the tested transfer function rather than a generic transfer function.

Uncertainty in reference wind speeds for anemometer calibration are in the range of 2%. Uncertainty claims lower than NIST using LDA technology should be questioned.

An anemometer calibration standard needs to be defined.

Page 15: OTECH ENGINEERING, Inc. 630 Peña Drive, Suite 200 Davis, CA 95616-7726 Considerations in Anemometer Calibration Presented by: John Obermeier, President.

OTECH ENGINEERING, Inc.630 Peña Drive, Suite 200Davis, CA 95616-7726

Related Measurement Standards and References

ASTM D5096-02 Standard Test Method for Determining the Performance of a Cup Anemometer and Propeller Anemometer

ASTM D4430-00e1 Standard Practice for Determining the Operational Comparability of Meteorological Measurements

ASTM D6011-96(2003) Standard Test Method for Determining the Performance of a Sonic Anemometer/Thermometer

ASTM D7145-05 Standard Guide for Measurement of Atmospheric Wind and Turbulence Profiles by Acoustic Means

ASTM D5741-96(2002)e1 Standard Practice for Characterizing Surface Wind Using a Wind Vane and Rotating Anemometer

ASTM D5527-00(2002)e1 Standard Practices for Measuring Surface Wind and Temperature by Acoustic Means

“The Maximum Type 40 Anemometer Calibration Project” Thomas J. Lockhart, CCM. Cnet, April 1998