NREL is a national laboratory of the U.S. Department of Energy, Office of Energy 

Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Contract No. DE-AC36-08GO28308

Wind Turbine Generator System 

Power Performance Test Report

for the Entegrity EW50 Wind 

Turbine

J. Smith, A. Huskey, D. Jager, and J. Hur

Technical Report

NREL/TP-5000-51392

May 2011
NREL is a national laboratory of the U.S. Department of Energy, Office of Energy 

Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

National Renewable Energy Laboratory

1617 Cole Boulevard

Golden, Colorado 80401

303-275-3000 • www.nrel.gov

Contract No. DE-AC36-08GO28308

Wind Turbine Generator 

System Power Performance 

Test Report for the Entegrity 

EW50 Wind Turbine

J. Smith, A. Huskey, D. Jager, J. Hur

Prepared under Task No. WE10.2211

Technical Report

NREL/TP-5000-51392

May 2011
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Page 1 of 50

Wind Turbine Generator System

Power Performance Test Report

for the

Entegrity EW50 Wind Turbine

Conducted for

National Renewable Energy Laboratory

1617 Cole Blvd.

Golden, CO 80401

Conducted by

National Wind Technology Center

National Renewable Energy Laboratory

1617 Cole Blvd.

Golden, CO 80401

Joe Smith, Arlinda Huskey, Dave Jager, Jerry Hur

22 March 2011
Page 2 of 50
Page 3 of 50

Contents

List of Tables...............................................................................................................................4

List of Figures .............................................................................................................................5

1. Background..........................................................................................................................6

2. Test Summary ......................................................................................................................6

3. Test Turbine Configuration.................................................................................................9

Test Site Description ................................................................................................................10

4. Description of Test Equipment.........................................................................................12

5. Description of Test Procedure .........................................................................................15

Test Results...............................................................................................................................16

5.1. Tabular Results of Power Performance Test................................................................16

5.2. Graphical Results Power Performance Test ................................................................20

6. Exceptions..........................................................................................................................27

6.1. Exceptions to the Standard ..........................................................................................27

6.2. Exceptions to NWTC Quality Assurance System .........................................................27

A. Appendix - Photographs of the Test Site from the Turbine Base .................................28

B. Appendix - Equipment Calibration Sheets ......................................................................35
Page 4 of 50

List of Tables

Table 1. Test turbine configuration ...............................................................................................9

Table 2. Structures close to test turbine .....................................................................................11

Table 3. Criteria for test site without site calibration ...................................................................11

Table 4. Equipment used in the power performance test ...........................................................12

Table 5. Uncertainty values used in the analysis........................................................................15

Table 6. Performance at sea-level air density, 1.225 kg/m3

........................................................17

Table 7. Performance at site average density, 1.050 kg/m3 .......................................................18

Table 8. Annual energy production at sea-level air density, 1.225 kg/m3 ..................................19

Table 9. Annual energy production at site average density, 1.050 kg/m3 ...................................19
Page 5 of 50

List of Figures 

Figure 1. Power curve summary ...................................................................................................7

Figure 2. Entegrity EW50 test turbine at the NWTC. PIX # 16390. ..............................................8

Figure 3. Map of area surrounding Entegrity’s EW50 at NWTC’s 1E1test site...........................10

Figure 4. Meteorological tower and instruments .........................................................................13

Figure 5. Power curve at sea-level density, 1.225 kg/m3 ............................................................20

Figure 6. Power curve at site average density, 1.050 kg/m3

.......................................................21

Figure 7. Scatter plot of mean, standard deviation, minimum, and maximum power data .........22

Figure 8. Scatter plot of mean power data, zoomed to show secondary power curve ...............23

Figure 9. Coefficient of performance at sea-level density, 1.225 kg/m3

......................................24

Figure 10. Wind turbulence intensity as a function of wind speed ..............................................25

Figure 11. Wind speed and turbulence intensity as a function of wind direction.........................26
Page 6 of 50

1. Background

This test is being conducted as part of the U.S. Department of Energy’s (DOE) Independent 

Testing project. This project was established to help reduce the barriers of wind energy 

expansion by providing independent testing results for small turbines. Five turbines are being 

tested at the National Wind Technology Center (NWTC) as a part of round 1 of this project. 

Power performance testing is one of up to five (5) tests that may be performed on the turbines, 

including duration, safety and function, noise, and power quality tests. 

2. Test Summary

Figure 1 is a summary of the results of the power performance test that the National Renewable 

Energy Laboratory (NREL) conducted on Entegrity Wind System Inc.’s EW50 small wind turbine 

(shown in Figure 2). In this test, the EW50 turbine was installed at the NWTC near Boulder, 

Colorado. This test was conducted in accordance with the International Electrotechnical 

Commission (IEC) standard, Wind Turbine Generator Systems Part 12: Power Performance 

Measurements of Electricity Producing Wind Turbines, IEC 61400-12-1 Ed.1.0, 2005-12. 

Because the Entegrity EW50 is a small turbine according to the IEC definition, NREL also 

followed Annex H, which applies to small wind turbines. This test report refers to these 

procedures as the “Standard.”

In the summary results shown in Figure 1, power is normalized to sea-level air density, as 

required by the Standard. However this method of density correction gives unrealistically high 

power output for sea-level. During installation the blades on the EW50 were pitched to 

accommodate the average density at the NWTC, in order to achieve the designed peak output 

of 65kW.

This test began on 1 November 2009 and ended on 31 December 2009. During that period 533

hours of valid data were collected. The highest bin filled was the 20.5 m/s bin. The amount of 

test data is sufficient to meet the requirements of the Standard. 
Page 7 of 50

Figure 1. Power curve summary
Page 8 of 50

Figure 2. Entegrity EW50 test turbine at the NWTC. PIX # 16390.
Page 9 of 50

3. Test Turbine Configuration

Table 1 lists the configuration of the Entegrity EW50 that was tested at the NWTC.

Table 1. Test turbine configuration

Turbine make & model Entegrity EW50

Gearbox serial number 543132-007

Generator serial number C0812180024

Rotor diameter (m) 14.9

Hub height (m) 31.1

Tower type 30.5m (100ft) freestanding monopole

Rated electrical power (kW) 50

Rated wind speed (m/s) 11.3

Rotor speed range (rpm) 65

Fixed or variable pitch Fixed

Number of blades 3

Blade pitch angle (deg) 5.14 ̊ to 5.17 ̊ at 75% span

Blade make, type, serial number Entegrity, epoxy/glass fiber, 7.2m, 150kg, 

s/n: 284, 285, 283 with tip brakes

Control system (device and software version) TMC microprocessor by Orbital A/S in 

Entegrity enclosure version: “EW15 2.031”

Measurements verified the rotor diameter and hub height. The blades were pitched at the most 

aggressive pitch setting. Rated power and rated wind speed are as published by Entegrity, and 

provided to NREL as required by the Independent Testing project. 
Page 10 of 50

Test Site Description

The EW50 turbine is located at site 1E1 at the NWTC, which is approximately 8 km south of 

Boulder, Colorado. The terrain consists of mostly flat terrain with short vegetation (see Appendix 

A for photos of the test site). The site has prevailing winds bearing approximately 290 degrees 

relative to true north. It is important to accurately measure wind speed; NREL uses data 

obtained when the wind direction is between 272 and 350 degrees true. In this measurement 

sector, the influence of terrain and obstructions on the anemometer is small. Figure 3 shows 

the turbine and meteorological tower locations as well as nearby obstructions and topographical 

features of the site.

Figure 3. Map of area surrounding Entegrity’s EW50 at NWTC’s 1E1test site

Table 2 shows obstructions which affect the wind at the location of the EW50 or its met tower 

according to the Standard’s obstacles assessment criteria in Annex A. The azimuth and 
Page 11 of 50

distance data are relative to the EW50. Several of these obstructions do not appear on the map 

in Figure 3.

Table 2. Structures close to test turbine

Description azimuth

[deg true]

distance

[m]

height

[m]

diam / width

[m]

Blade Test Facility 36 137 8 20

NW100-a 251 170 25 19

Industrial Users Facility 56 231 15 50

Dynamometer Test Facility 66 322 15 20

Concrete factory 250 676 30 40

CART-3 119 705 37 43

CART-2 130 740 37 40

GE/DOE 90 851 80 77

Siemens 138 908 80 101

NREL completed a site assessment to determine if the site fails the requirements of Annex A

and B of the Standard and would therefore require a site calibration. Table 3 shows the results 

from the site assessment, which confirm that a site calibration was not required.

Table 3. Criteria for test site without site calibration

D = test turbine rotor diameter 

L = distance between test turbine and meteorological tower 

De = equivalent diameter of obstacle 

EW50 Site: 1e1

Preliminary Measurement Sector: 272 to 350 deg True

Criteria for Test Site without Site Calibration Testing

Criterion Description Distance Sector allowable Test Site Pass/Fail

(deg) Condition

1 Maximum slope of best fit plane < 3% <2L 360 3% 2.3% Pass

2 Maximum variation from best fit plane < 0.04 (H + D) <2L 360 +/-1.8m 0.3 Pass

3 Maximum slope of best fit plane < 5% 2-4L In 5% 2.2% Pass

4 Maximum variation from best fit plane < 0.08 (H + D) 2-4L In +/-3.6m 0.1 Pass

5 Steepest slope maximum < 10% 2-4L Out 10% 2.6% Pass

6 Maximum slope of best fit plane < 10% 4-8L In 10% 2.2% Pass

7 Maximum variation from best fit plane < 0.13 (H + D) 4-8L In +/-5.9m 1.9 Pass

8 No neighboring and operating turbines <2Dn 360 0 0 Pass

9 No obstacles <2De 360 0 0 Pass

Site Calibration Required? no

absolute value used for site condition

In = Inside Preliminary Measurement Sector

Out = Outside Preliminary Measurement Sector
Page 12 of 50

The EW50 was connected to the electrical grid at a nominal voltage of 480 VAC at a frequency 

of 60 Hz. The grid tolerances are 5% for voltage amplitude and 1% for frequency.

4. Description of Test Equipment

All test equipment was calibrated; Appendix B contains the calibration sheets. Table 4 shows 

the equipment used and calibration due dates. Figure 4 depicts the placement of the 

meteorological instruments on the tower. The primary anemometer was sent out for 

recalibration after the test period. The difference between the pre-test and post-test calibrations 

is less than 0.04m/s for the range of 6 to 12m/s, and this is within the tolerances allowed by the 

Standard (0.1m/s).

Table 4. Equipment used in the power performance test

Instrument Make and Model Serial Number Calibration Due Date

Power transducer Ohio Semitronics, DMT 1040E 07070473 12 Feb 10

Current transformers Ohio Semitronics, 12974

001293045

001235428

001293049

Calibrated with power 

transducer

Primary anemometer Thies, First Class 0707884 25 Feb 10

Reference anemometer NRG, Max 40 179500049025 25 Feb 10

Wind vane Met One, 020C with Aluminum Vane U1477 25 Feb 10

Pressure sensor Vaisala, PTB101B C1020015 3 Sept 10

Temperature sensor Met One, T200 0549828 10 Oct 09

Precipitation sensor Campbell Scientific, 237 None In situ

Data acquisition 

system

Compact DAQ w/LabView 

cDAQ backplane (9172)

NI 9229

NI 9217

NI 9205

12E4CEB

13DEC38

13FAE1C

13E3D05

n/a

10 Nov 09

16 Dec 09

12 Nov 09
Page 13 of 50

Figure 4. Meteorological tower and instruments

To ensure that only data obtained during normal operation of the turbine are used in the 

analysis, and to ensure that data are not corrupted, NREL excluded data sets from the database 

under the following circumstances:

• External conditions other than wind speed are out of the normal range for turbine 

operation

• The turbine cannot operate because of a turbine fault condition
Page 14 of 50

• The turbine is manually shut down or in a test or maintenance operating mode.

The primary method for checking such events will be reviewing the logbook. The second 

method is to validate the data file before analysis1

 

1 Prior to installation it was mutually agreed by Entegrity and NREL that the EW50 controller’s log would 

be used as an additional means to validate data from the database (e.g. logging grid disturbances); the 

EW50 controller’s log was sent to a server via cell phone reception, and then emailed daily to Entegrity 

and NREL staff. However this service was terminated by Entegrity and emails ceased after 11 July 09.

. 
Page 15 of 50

5. Description of Test Procedure

NREL conducted the test according to the procedures in the Standard. The sampling rate was 

10 kHz, decimated to 40 Hz. The averaging time was 1 minute for the mean values. NREL also 

collected standard deviation, minimum, and maximum values for each averaging period. 

Only database A is reported because the turbine did not reach cut-out wind speeds during the 

test period. 

Table 5 gives the uncertainty sources and values used in the analysis. 

Table 5. Uncertainty values used in the analysis

Component Uncertainty Source

Power

power transducer w/ transformers 0.087% calibration sheet

Data Acquisition System 0.45kW +0.075% NI9229 specs

Resistor 0.006% Specs

Wind Speed

Calibration 0.006 m/s calibration sheet

operational characteristics 0.052m/s +0.52% IEC eq. (I.2)

mounting effects 1% documented assumptions

terrain effects 2% IEC 

Data Acquisition System 0.001 m/s calculations based on sampling frequency

Temperature

temperature sensor 0.058  ̊C calibration

radiation shielding 0.2  ̊C calculations and assumptions

mounting effects 0.07  ̊C calculations based on IEC assumptions

Data Acquisition System 0.2  ̊C NI9217 specs

Air Pressure

pressure sensor 0.1 kPa calibration

mounting effects 0.004 kPa IEC method

Data Acquisition System 0.034 kPa NI 9205 specs
Page 16 of 50

Test Results

5.1.Tabular Results of Power Performance Test 

Table 6 through Table 9 list the power performance test results. Table 6 shows the binned 

power performance results at sea-level normalized air density. Table 7 shows the binned power 

performance results normalized to the site average air density for the NWTC.

Reporting power normalized to sea-level air density is required by the Standard. However the 

prescribed method of density correction gives unrealistically high power output for sea-level. 

For each EW50 installation, the blades should be pitched to accommodate the site’s air density, 

such that the peak output is 65kW.
Page 17 of 50

Table 6. Performance at sea-level air density, 1.225 kg/m3

Measured power curve, database A (All valid data)

Reference air density: 1.225 kg/m3

Bin

Number

Hub height

wind

speed

m/s

Power

output

(kW)

CP

Number 

of Data 

Sets

Category A

Standard

Uncertainty

(kW)

Category B

Standard

Uncertainty

(kW)

Combined

Standard

Uncertainty

(kW)

1 0.54 -0.46 -27.61 636 0.00 0.45 0.45

2 1.02 -0.50 -4.28 1485 0.01 0.45 0.45

3 1.51 -0.63 -1.68 2203 0.02 0.45 0.45

4 2.00 -0.69 -0.80 2562 0.03 0.45 0.45

5 2.50 -0.80 -0.47 2435 0.04 0.45 0.45

6 3.00 -1.03 -0.35 2506 0.04 0.45 0.45

7 3.50 -1.30 -0.28 2535 0.05 0.45 0.46

8 3.99 -1.76 -0.26 2233 0.05 0.46 0.46

9 4.49 -2.06 -0.21 1872 0.05 0.46 0.46

10 5.00 -1.80 -0.13 1718 0.05 0.45 0.46

11 5.50 -0.18 -0.01 1610 0.05 0.63 0.63

12 5.99 2.05 0.09 1429 0.07 0.80 0.81

13 6.49 5.22 0.18 1248 0.09 1.09 1.09

14 7.00 8.33 0.22 1124 0.12 1.14 1.15

15 7.49 12.15 0.27 982 0.15 1.46 1.47

16 7.99 15.86 0.29 861 0.19 1.47 1.49

17 8.50 20.36 0.31 726 0.21 1.85 1.86

18 9.00 23.97 0.30 590 0.30 1.60 1.63

19 9.50 28.34 0.31 477 0.40 2.02 2.06

20 9.99 32.08 0.30 427 0.46 1.84 1.90

21 10.50 37.62 0.30 368 0.38 2.74 2.76

22 11.00 40.41 0.28 298 0.55 1.52 1.62

23 11.50 43.73 0.27 255 0.73 1.84 1.98

24 11.98 48.39 0.26 232 0.60 2.72 2.78

25 12.48 51.89 0.25 190 0.56 2.12 2.19

26 12.99 55.27 0.23 171 0.66 2.04 2.14

27 13.51 58.09 0.22 136 0.80 1.76 1.94

28 14.00 61.20 0.21 114 0.64 2.12 2.21

29 14.47 64.90 0.20 86 0.30 2.72 2.74

30 15.00 66.69 0.18 74 0.40 1.26 1.32

31 15.49 69.33 0.17 56 0.40 1.99 2.03

32 16.02 70.65 0.16 58 0.41 1.04 1.12

33 16.48 70.37 0.15 43 0.58 0.53 0.78

34 17.02 72.63 0.14 43 0.66 1.74 1.86

35 17.48 73.34 0.13 34 0.43 0.78 0.89

36 18.01 73.33 0.12 36 0.55 0.47 0.73

37 18.51 74.81 0.11 33 0.42 1.35 1.42

38 19.05 73.39 0.10 19 0.73 1.26 1.46

39 19.53 73.10 0.09 20 0.57 0.55 0.79

40 20.00 71.78 0.08 18 0.65 1.36 1.51

41 20.49 72.11 0.08 11 0.73 0.57 0.93
Page 18 of 50

Table 7. Performance at site average density, 1.050 kg/m3

Measured power curve, database A (All valid data)

Reference air density: 1.050 kg/m3

Bin

Number

Hub height

wind

speed

m/s

Power

output

(kW)

CP

Number 

of Data 

Sets

Category A

Standard

Uncertainty

(kW)

Category B

Standard

Uncertainty

(kW)

Combined

Standard

Uncertainty

(kW)

1 0.54 -0.40 -27.61 636 0.00 0.45 0.45

2 1.02 -0.43 -4.28 1485 0.01 0.45 0.45

3 1.51 -0.54 -1.68 2203 0.02 0.45 0.45

4 2.00 -0.59 -0.80 2562 0.02 0.45 0.45

5 2.50 -0.69 -0.47 2435 0.03 0.45 0.45

6 3.00 -0.89 -0.35 2506 0.04 0.45 0.45

7 3.50 -1.11 -0.28 2535 0.04 0.45 0.45

8 3.99 -1.51 -0.26 2233 0.05 0.46 0.46

9 4.49 -1.77 -0.21 1872 0.04 0.45 0.46

10 5.00 -1.54 -0.13 1718 0.04 0.45 0.46

11 5.50 -0.16 -0.01 1610 0.04 0.59 0.59

12 5.99 1.76 0.09 1429 0.06 0.73 0.73

13 6.49 4.47 0.18 1248 0.08 0.96 0.97

14 7.00 7.14 0.22 1124 0.10 1.00 1.01

15 7.49 10.41 0.27 982 0.13 1.27 1.28

16 7.99 13.59 0.29 861 0.16 1.28 1.29

17 8.50 17.45 0.31 726 0.18 1.60 1.61

18 9.00 20.55 0.30 590 0.25 1.39 1.41

19 9.50 24.29 0.31 477 0.34 1.75 1.78

20 9.99 27.50 0.30 427 0.39 1.60 1.65

21 10.50 32.25 0.30 368 0.32 2.36 2.38

22 11.00 34.64 0.28 298 0.47 1.32 1.40

23 11.50 37.49 0.27 255 0.62 1.59 1.71

24 11.98 41.48 0.26 232 0.51 2.34 2.40

25 12.48 44.47 0.25 190 0.48 1.83 1.89

26 12.99 47.37 0.23 171 0.57 1.76 1.85

27 13.51 49.79 0.22 136 0.69 1.53 1.68

28 14.00 52.46 0.21 114 0.55 1.83 1.91

29 14.47 55.63 0.20 86 0.26 2.35 2.36

30 15.00 57.17 0.18 74 0.34 1.11 1.16

31 15.49 59.43 0.17 56 0.34 1.73 1.76

32 16.02 60.56 0.16 58 0.35 0.92 0.99

33 16.48 60.32 0.15 43 0.49 0.51 0.71

34 17.02 62.26 0.14 43 0.57 1.51 1.61

35 17.48 62.86 0.13 34 0.37 0.71 0.80

36 18.01 62.85 0.12 36 0.47 0.47 0.67

37 18.51 64.13 0.11 33 0.36 1.18 1.24

38 19.05 62.90 0.10 19 0.62 1.11 1.27

39 19.53 62.65 0.09 20 0.49 0.52 0.72

40 20.00 61.52 0.08 18 0.56 1.19 1.31

41 20.49 61.81 0.08 11 0.63 0.54 0.83
Page 19 of 50

Table 8 shows the annual energy production at sea-level normalized air density. Table 9 shows 

the annual energy production (AEP) at the site average air density at the NWTC.

Table 8. Annual energy production at sea-level air density, 1.225 kg/m3

Estimated annual energy production, database A (all valid data)

Reference air density: 1.225 kg/m^3

Cut-out wind speed: 25.00 m/s

Hub height 

annual average 

wind speed 

(Rayleigh)

AEP-measured

Standard 

Uncertainty in 

AEP-measured

AEPextrapolated

Complete if AEP 

measured is at 

least 95% of AEP 

extrapolated

m/s kWh kWh % kWh

4 10,848 3,136 10% 10,848 Complete

5 42,283 5,243 7% 42,284 Complete

6 84,579 7,228 5% 84,645 Complete

7 131,784 8,799 4% 132,513 Complete

8 177,850 9,864 3% 181,216 Complete

9 217,719 10,454 3% 227,036 Complete

10 248,443 10,656 3% 267,162 Incomplete

11 269,306 10,570 2% 299,808 Incomplete

AEP measured assumes zero power between highest bin and cutout

AEP extrapolated assumes power in last bin between last bin and cutout

Table 9. Annual energy production at site average density, 1.050 kg/m3 

Estimated annual energy production, database A (all valid data)

Reference air density: 1.050 kg/m^3

Cut-out wind speed: 25.00 m/s

Hub height 

annual average 

wind speed 

(Rayleigh)

AEP-measured

Standard 

Uncertainty in 

AEP-measured

AEPextrapolated

Complete if AEP 

measured is at 

least 95% of AEP 

extrapolated

m/s kWh kWh % kWh

4 9,298 2,745 10% 9,298 Complete

5 36,242 4,539 7% 36,243 Complete

6 72,497 6,231 5% 72,553 Complete

7 112,958 7,571 4% 113,582 Complete

8 152,443 8,479 3% 155,328 Complete

9 186,616 8,981 3% 194,602 Complete

10 212,951 9,152 3% 228,996 Incomplete

11 230,834 9,076 2% 256,978 Incomplete

AEP measured assumes zero power between highest bin and cutout

AEP extrapolated assumes power in last bin between last bin and cutout
Page 20 of 50

5.2.Graphical Results Power Performance Test 

Figure 5 through Figure 11 show the results of the power performance test.

Figure 5 shows a plot of the binned power curve normalized to sea-level air density. 

Figure 5. Power curve at sea-level density, 1.225 kg/m3
Page 21 of 50

Figure 6 shows a plot of the binned power curve at the site average air density during the test 

period.

Figure 6. Power curve at site average density, 1.050 kg/m3
Page 22 of 50

Figure 7 shows a scatter plot of statistics for power for the turbine.

Figure 7. Scatter plot of mean, standard deviation, minimum, and maximum power data

There are several minimums around 5m/s, with power values between -60 and -140kW. These 

events are due to the EW50 motor starting, which is part of the normal & automatic operation.

There is also a second power curve, which is negative and most distinctive between 7 and 

12m/s. Figure 8 shows the average power in this region. This power curve is due to the EW50 

operating in the upwind position.
Page 23 of 50

Figure 8. Scatter plot of mean power data, zoomed to show upwind power curve
Page 24 of 50

Figure 9 shows a plot of the binned coefficient of performance as a function of wind speed at 

sea-level normalized air density. 

Figure 9. Coefficient of performance at sea-level density, 1.225 kg/m3
Page 25 of 50

Figure 10 shows a scatter plot and binned turbulence intensity as a function of wind speed. 

Figure 10. Wind turbulence intensity as a function of wind speed
Page 26 of 50

Figure 11 shows a scatter plot of wind speed and turbulence intensity as a function of wind 

direction. 

Figure 11. Wind speed and turbulence intensity as a function of wind direction
Page 27 of 50

6. Exceptions

6.1.Exceptions to the Standard

The power transducers are not compliant with IEC 60688, but they do exceed the minimum 

accuracy required by the Standard. This should have no effect on results or uncertainty.

The current transformers are not compliant with IEC 60044-1, but they do exceed the minimum 

accuracy required by the Standard. This should have no effect on results or uncertainty.

The reference anemometer is mounted 2.8m below the primary. This exceeds the Standard’s 

allowable 2.5m as shown in Annex G.5. This should have no effect on results or uncertainty, 

because the primary anemometer was post-test calibrated and the reference anemometer was 

not used for an in situ calibration.

The connection to the grid is approximately 100m from the turbine base. This exceeds the 

maximum of three times the tower height, as required by Annex H.e. This may slightly lower the 

power curve. The power cables were sized for this distance; 1/0 copper for 100m. The 

additional 7m of 1/0 copper cable to reach the grid, which are in excess of the distance allowed 

by the Standard, results in a power loss of 54Watts when the turbine is operating at 65kW or

0.08%. 

The temperature sensor is 3.6m below hub height. This is not 1.5 rotor diameters below hub 

height as required by Annex H.j. The cross-sectional area of the sensor is small in comparison 

to the diameter, therefore inflow blockage is minimal. Measuring the temperature close to hub 

height will result in less uncertainty.

The air pressure sensor is 4.4m below hub height. This is not 1.5 rotor diameters below hub 

height as required by Annex H.j. The cross-sectional area of the sensor is small in comparison 

to the diameter, therefore inflow blockage is minimal. Measuring the pressure close to hub 

height will result in less uncertainty.

6.2.Exceptions to NWTC Quality Assurance System

The data acquisition modules were used beyond the calibration due date. The modules were 

post-test calibrated and found to be in compliance within the specifications. Appendix B includes 

the post-test calibration sheets.

The temperature sensor was used beyond its calibration due date. It was post-test calibrated 

and the calibration coefficients were found to match the initial calibration coefficients within the

margin of uncertainty. Appendix B includes the post-test calibration sheet for the temperature 

senor.
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A. Appendix - Photographs of the Test Site from the Turbine Base

Direction pictures are facing:

A.1. North

A.2. Northeast

A.3. East-northeast

A.4. East

A.5. Southeast

A.6. South

A.7. South-southwest

A.8. Southwest

A.9. West

A.10. Northwest

A.11. North-northwest
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Figure A.1. Facing North. PIX #18724.

Figure A.2. Facing Northeast. PIX #18725.
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Figure A.3. Facing East-northeast. PIX #18726.

Figure A.4. Facing East. PIX #18727.
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Figure A.5. Facing Southeast. PIX #18728.

Figure Facing A.6. South. PIX #18729.
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Figure A.7. Facing South-southwest. PIX #

Figure A.8. Facing Southwest. PIX #18731.
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Figure A.9. Facing West. PIX #18732.

Figure A.10. Facing Northwest. PIX #18733.
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Figure A.11. Facing North-northwest. PIX #18734.
Page 35 of 50

B. Appendix - Equipment Calibration Sheets

B.1. Primary anemometer calibration sheet; installed 25Feb09, removed 24Feb10

B.2. Primary anemometer post-test calibration sheet

B.3. Primary anemometer pre- & post-test calibration comparison; the difference is 

less than 0.1m/s for the range of 6 to 12m/s

B.4. Power transducer calibration sheet; installed 25Feb09, removed 8Feb10

B.5. Wind vane calibration sheet; installed 25Feb09, removed 24Feb10

B.6. RTD probe calibration sheet; installed 25Feb09, removed 8Feb10

B.7. RTD probe post-test calibration sheet

B.8. RTD calibration comparison

B.9. Pressure transducer calibration sheet; installed 10Sep09, removed 17Aug10

B.10. NI 9229 data acquisition module calibration; installed 25Feb09, removed 3Feb10

B.11. NI 9217 data acquisition module calibration; installed 25Feb09, removed 3Feb10

B.12. NI 9205 data acquisition module calibration ; installed 25Feb09, removed 3Feb10

B.13. NI 9229 data acquisition module post-test calibration

B.14. NI 9217 data acquisition module post-test calibration 

B.15. NI 9205 data acquisition module post-test calibration
Page 36 of 50

Figure B.1. Primary anemometer calibration sheet; installed 25Feb09, removed 24Feb10
Page 37 of 50

Figure B.2. Primary anemometer post-test calibration sheet
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Figure B.3. Primary anemometer pre- and post-test calibration comparison; the 

difference is less than 0.1m/s for the range of 6 to 12m/s
Page 39 of 50

Figure B.4. Power transducer calibration sheet; installed 25Feb09, removed 8Feb10
Page 40 of 50

Figure B.5. Wind vane calibration sheet; installed 25Feb09, removed 24Feb10
Page 41 of 50

Figure B.6. RTD probe calibration sheet; installed 25Feb09, removed 8Feb10
Page 42 of 50

Figure B.7. RTD probe post-test calibration sheet
Page 43 of 50

Figure B.8. RTD calibration comparison

Temp Resistance Temp Resistance

0 99.95 -10.16 96.027

25 109.69 -0.13 99.948

50 119.35 9.88 103.855

19.88 107.745

29.87 111.618

39.87 115.49

m b m b

2.577305 -257.636 2.570556 -257.046

Origonal Calibration Post-test Cal.

y = 2.5773x - 257.64

R2 = 1

y = 2.5706x - 257.05

R2 = 1

-20

-10

0

10

20

30

40

50

60

90 95 100 105 110 115 120

Temperature [C]

Resistance [Ohms]

Temperature Calibration Curve

Origonal Calibration

Post-test Cal.

Linear (Origonal Calibration)

Linear (Post-test Cal.)
Page 44 of 50

Figure B.9. Pressure transducer calibration sheet; installed 10Sep09, removed 17Aug10
Page 45 of 50

Figure B.10. NI 9229 data acquisition module calibration; installed 25Feb09, removed 

3Feb10
Page 46 of 50

Figure B.11. NI 9217 data acquisition module calibration; installed 25Feb09, removed 

3Feb10
Page 47 of 50

Figure B.12. NI 9205 data acquisition module calibration; installed 25Feb09, removed 

3Feb10
Page 48 of 50

Figure B.13. NI 9229 data acquisition module post-test calibration
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Figure B.14. NI 9217 data acquisition module post-test calibration
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Figure B.15. NI 9205 data acquisition module post-test calibration