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

Power Performance Test Report 

for the SWIFT Wind Turbine

I. Mendoza and J. Hur

National Renewable Energy Laboratory

Technical Report

NREL/TP-5000-56499

December 2012
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

15013 Denver West Parkway

Golden, Colorado 80401

303-275-3000 • www.nrel.gov

Contract No. DE-AC36-08GO28308

Power Performance Test Report 

for the SWIFT Wind Turbine 

I. Mendoza and J. Hur

National Renewable Energy Laboratory

Prepared under Task No. WE11.0205

Technical Report

NREL/TP-5000-56499

December 2012
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Page 1 of 48

Power Performance Test Report 

for the 

SWIFT Wind Turbine

in 

Boulder, Colorado 

Conducted by 

National Wind Technology Center 

National Renewable Energy Laboratory 

15013 Denver West Parkway 

Golden, Colorado 80401 

For

Wind Energy Program 

DOE/NREL

Ismael Mendoza and Jerry Hur

7 September 2012
Page 2 of 48
Page 3 of 48

Table of Contents

TABLE OF TABLES.................................................................................................................................. 3

TABLE OF FIGURES................................................................................................................................ 4

1. BACKGROUND.................................................................................................................................. 5

2. TEST SUMMARY............................................................................................................................... 5

3. TEST TURBINE CONFIGURATION .............................................................................................. 8

4. TEST SITE DESCRIPTION .............................................................................................................. 9

5. DESCRIPTION OF TEST EQUIPMENT ...................................................................................... 11

6. DESCRIPTION OF TEST PROCEDURE...................................................................................... 13

7. TEST RESULTS................................................................................................................................ 14

7.1 Tabular Results of Power Performance Test..................................................................................... 14

7.2 Graphical Results Power Performance Test...................................................................................... 18

8. DEVIATIONS AND EXCEPTIONS ............................................................................................... 25

8.1 Deviations from the Standard....................................................................................................... 25

8.2 Exceptions to NREL Quality Assurance System ......................................................................... 25

9. REFERENCE..................................................................................................................................... 25

APPENDIX A: PHOTOGRAPHS OF THE TEST SITE FROM THE TURBINE BASE................. 26

APPENDIX B: EQUIPMENT CALIBRATION SHEETS ................................................................... 31

Table of Tables

Table 1. Test Turbine Configuration and Operational Data ......................................................................... 8

Table 2. Structures Close to Test Turbine................................................................................................... 10

Table 3. Site Assessment Results................................................................................................................ 10

Table 4. Equipment Used in the Power Performance Test ......................................................................... 11

Table 5. Uncertainty Values Used in the Analysis ..................................................................................... 14

Table 6. Performance at Sea-Level Air Density; 1.225 kg/m3

.................................................................... 15

Table 7. Performance at Site Average Density; 0.99 kg/m3

........................................................................ 16

Table 8. Annual Energy Production (AEP) at Sea-Level Density; 1.225 kg/m3 ........................................ 17

Table 9. AEP at Site Average Density; 0.99 kg/m3 .................................................................................... 17

Table 10. Binned Rotor Speed from 0.5 up to 30 m/s ................................................................................ 24
Page 4 of 48

Table of Figures

Figure 1. Power curve summary ................................................................................................................... 6

Figure 2. SWIFT test turbine at the NWTC.................................................................................................. 7

Figure 3. Map of the test site ........................................................................................................................ 9

Figure 4. Meteorological tower and instruments (not to scale) .................................................................. 12

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

............................................................................ 18

Figure 6. Power curve at site average density, 0.99 kg/m3 ......................................................................... 19

Figure 7. Scatter plot of mean and standard deviation power data as measured......................................... 20

Figure 8. Coefficient of performance at sea-level average density, 1.225 kg/m3 ....................................... 21

Figure 9. Wind speed and turbulence intensity as a function of wind direction......................................... 22

Figure 10. Wind turbulence at the test site.................................................................................................. 23

Figure 11. Rotor speed as a function of wind speed (1-minute average) and binned values...................... 24
Page 5 of 48

1. Background

This SWIFT power performance test was conducted as part of the U.S. Department of Energy’s (DOE’s) 

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

expansion by providing independent testing results for small turbines. Three turbines were tested at the 

National Renewable Energy Laboratory (NREL) National Wind Technology Center (NWTC) as a part of

round two of the Small Wind Turbine Independent Testing project. Power performance testing was one of 

up to five tests that were performed on the turbines. Other tests include duration, safety and function, 

noise, and power quality. Cascade Engineering, of Grand Rapids, Michigan, distributor of the Renewable 

Devices’ SWIFT turbine in North America, was the recipient of the DOE grant and provided the turbine 

for testing.

2. Test Summary

Figure 1 is a summary of the results of the power performance test that NREL conducted on the SWIFT

small wind turbine (shown in Figure 2). In this test, the SWIFT 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 

SWIFT 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 these summary results, power was normalized to sea-level air density. This test began on 7 April 2011

and ended on 30 June 2011. During that period, NREL collected 812 hours of valid data. The highest bin 

filled was the 24 meters per second (m/s) bin. The amount of test data is sufficient to meet the 

requirements of the Standard. 
Page 6 of 48

Figure 1. Power curve summary
Page 7 of 48

Figure 2. SWIFT test turbine at the NWTC

Source: NREL PIX 22083
Page 8 of 48

3. Test Turbine Configuration

Table 1 lists the configuration of the SWIFT turbine that was tested at the NWTC.

Table 1. Test Turbine Configuration and Operational Data

Turbine manufacturer and address

Renewable Devices Ltd.

AeroMarine House, Turnhouse Aerodrome

Turnhouse Road, Edinburgh

EH12 9DN

Scotland, UK

Turbine distributor and address

Cascade Engineering

4855 Thirty-Seven St. SE 

Grand Rapids, MI 49512

Model SWIFT

Serial number N000780-N

Rotor diameter (m) 2.1 with outer ring*

Hub height (m) 14.2*

Tower type 13.7 m (45 feet) freestanding monopole

Rated electrical power (kW) 1

Rated wind speed (m/s) 11

Rotor speed range (rpm) 0-450

Fixed or variable pitch Fixed

Number of blades 5

Blade pitch angle (deg) 6 ̊ at the tip

Blade make, type, serial number Injection molded nano-fiber 

reinforced polymer, F000648

Description of control system (device and software 

version) Kaco Blueplanet 1502x, Software V2.05

*Measurements verified the rotor diameter and hub height. 
Page 9 of 48

4. Test Site Description

The SWIFT wind turbine was located at test site 3.1 of the NWTC, approximately 8 kilometers (km)

south of Boulder, Colorado. The site consisted of mostly flat terrain with short vegetation (see Appendix 

A for photos) and had prevailing winds bearing 292 degrees relative to true north. Figure 3 shows the 

turbine and meteorological (met) tower locations. This figure also shows nearby obstructions. NREL 

limited assessments of power and energy production to data obtained when winds were within a 178° to 

311° measurement sector. In this measurement sector, the influence of terrain and obstructions on the 

anemometer was small and met the requirements in the Standard without conducting a site calibration 

test.

Figure 3. Map of the test site

Source: NREL 2011

Table 2 shows obstructions that affected the wind at the location of the SWIFT wind turbine or its met 

tower according to the Standard’s obstacles assessment criteria in Annex A. The azimuth and distance 

data were relative to the SWIFT wind turbine. Several of these obstructions do not appear on the map in 

Figure 3.
Page 10 of 48

Table 2. Structures Close to Test Turbine

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 confirms that a site calibration was not required.

Table 3. Site Assessment Results

Description Distance Sector Test Site Pass/Fail

(deg) Condition

Maximum slope of best fit plane < 3% <2L 360 1.70% Pass

Maximum variation from best fit plane < 0.04 (H + D) <2L 360 0 Pass

Maximum slope of best fit plane < 5% 2 to 4L In 1.80% Pass

Maximum variation from best fit plane < 0.08 (H + D) 2 to 4L In 0 Pass

Steepest slope maximum < 10% 2 to 4L Out 2.10% Pass

Maximum slope of best fit plane < 10% 4 to 8L In 1.70% Pass

Maximum variation from best fit plane < 0.13 (H + D) 4 to 8L In 0.1 Pass

No neighboring and operating turbines <2Dn 360 0 Pass

No obstacles <2De 360 0 Pass

In = Inside preliminary measurement sector

Out = Outside preliminary measurement sector

The SWIFT turbine was connected to the electrical grid at a nominal voltage of 240 volts alternating 

current (VAC) at a frequency of 60 hertz (Hz). The grid tolerances were 5% for voltage amplitude and 

1% for frequency.

Designation Azimuth

[deg true]

Distance 

[m]

Height 

[m]

Diam/width 

[m]

Main building 45 385 15 50

Shipping containers (x2) @ 3-1 49 46 3 15

GE/DOE 77 531 80 77

CART-3 129 365 37 43

CART-2 147 431 37 40

Siemens 153 624 80 101

IUF 330 279 15 50

Quonset hut 335 198 7 20

DTF 352 246 15 20

Data shed 360 26 3.5 7
Page 11 of 48

5. 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. Note that the primary anemometer was within the allowable 2.5% of hub 

height. The primary anemometer was sent out for recalibration after the test period. The difference 

between the pre-test and post-test calibrations was less than 0.05 m/s for the range of 6 to 12 m/s and 

within the tolerances allowed by the Standard (0.1 m/s). The post-test calibration sheets are also included 

in Appendix B.

Table 4. Equipment Used in the Power Performance Test

Instrument Make, Model Serial Number Calibration Due Date

Power transducer Secondwind Phaser 5FM-4A20 04607 21 October 2011

Primary anemometer Thies, First Class 0609006 7 April 2012

Reference anemometer Met One, 010 W2390 In situ

Wind vane Met One, 020C with aluminum vane U1478 13 October 2011

Pressure sensor Vaisala, PTB101B C1020014 10 August 2011

Temperature sensor Met One, T-200 0673553 13 October 2011

Precipitation sensor Campbell Scientific, 237 None In situ

Data acquisition system Compact DAQ w/LabView-based 

data acquisition

cDAQ-9172

NI 9229

NI 9217

NI 9205

13AB4F9

14A34EE

1494F69

1496266

22 March 2012

22 March 2012

22 March 2012
Page 12 of 48

26.7

27.5m

28m

30.8

Reference

Primary Anemometer

Reference Anemometer

Wind Vane

Pressure

Temperature

14.326 m

11.354 m

10.668 m

9.14 m

Figure 4. Meteorological tower and instruments (not to scale)

Source: NREL 2011
Page 13 of 48

To ensure that only data obtained during normal operation of the turbine were used in the analysis, and to 

ensure that data were not corrupted, NREL excluded data sets from the database under the following 

circumstances: 

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

operation

• The turbine could not operate because of a turbine fault condition

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

• Failure or maintenance of the institute’s data acquisition system.

Two methods were used to track when any of these conditions occurred during the test. In the first 

method, the logbook was checked for such events. For the second, the turbine controller provided a status 

signal that indicated when the turbine was available or braked. In the second method, the status signal was

checked in the data file during analysis. No maintenance was performed during the test period.

6. 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. 

The turbine status signal for the SWIFT was obtained by checking the release of the up-tower brake relay

by monitoring its voltage supply. The status signal indicated if the turbine was available or braked.

Only database A is reported because the SWIFT turbine does not have a cut-out wind speed. 

Table 5 gives the uncertainty sources and values used in the analysis.
Page 14 of 48

Table 5. Uncertainty Values Used in the Analysis

Component Uncertainty Source

Power (Inverter)

Power transducer 0.00231 kW IEC

Data acquisition .01803 kW +0.075% Specs

Resistor 0.006% Specs

Wind Speed

Calibration 0.0179 m/s Calibration sheet

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

Mounting effects 1% Assumptions

Terrain effects 2.00% IEC 

Data acquisition 0.002 m/s Calculations based on 

sampling frequency

Temperature

Temperature sensor 0.015 ̊C Calibration sheet

Radiation shielding 0.2 ̊C Assumptions

Mounting effects 0.069 ̊C IEC method

Data acquisition 0.2 ̊C Specs

Air Pressure

Pressure sensor 0.1 kPa Calibration sheet

Mounting effects 0.005 kPa IEC method

Data acquisition 0.032 kPa Specs

7. Test Results

7.1 Tabular Results of Power Performance Test 

Table 6 through Table 9 provide the power performance test results in tabular format. 
Page 15 of 48

Table 6. Performance at Sea-Level Air Density; 1.225 kg/m3

Measured Power Curve (Database A)

Reference air density: 1.225 kg/m3

Bin

number

Normalized

wind speed

(m/s)

Power

output 

(kW) Cp

Number of 

1-minute 

data sets

Category A

standard

uncertainty

(kW)

Category B

standard

uncertainty 

(kW)

Combined

standard

uncertainty

(kW)

1 0.54 -0.01 -21.65 1121 0.00 0.02 0.02

2 1.02 -0.01 -3.19 1923 0.00 0.02 0.02

3 1.52 -0.01 -0.96 2851 0.00 0.02 0.02

4 2.00 -0.01 -0.42 3823 0.00 0.02 0.02

5 2.50 -0.01 -0.22 3866 0.00 0.02 0.02

6 3.00 -0.01 -0.13 3807 0.00 0.02 0.02

7 3.50 -0.01 -0.08 3471 0.00 0.02 0.02

8 4.00 -0.01 -0.05 3203 0.00 0.02 0.02

9 4.49 -0.01 -0.03 2850 0.00 0.02 0.02

10 4.99 0.00 0.01 2422 0.00 0.02 0.02

11 5.50 0.02 0.07 2182 0.00 0.02 0.02

12 5.99 0.05 0.11 1950 0.00 0.02 0.02

13 6.50 0.08 0.14 1604 0.00 0.02 0.02

14 6.99 0.13 0.17 1430 0.00 0.02 0.02

15 7.50 0.18 0.20 1269 0.00 0.03 0.03

16 8.00 0.25 0.22 1146 0.00 0.03 0.03

17 8.51 0.33 0.25 1095 0.00 0.04 0.04

18 9.00 0.43 0.27 1042 0.00 0.04 0.04

19 9.50 0.53 0.28 932 0.00 0.05 0.05

20 10.00 0.65 0.30 930 0.00 0.06 0.06

21 10.49 0.77 0.31 782 0.00 0.06 0.06

22 10.99 0.90 0.31 685 0.00 0.07 0.07

23 11.50 1.02 0.31 644 0.00 0.07 0.07

24 11.99 1.14 0.30 584 0.00 0.07 0.07

25 12.50 1.25 0.29 507 0.00 0.07 0.07

26 12.99 1.33 0.28 425 0.01 0.05 0.05

27 13.49 1.39 0.26 339 0.01 0.04 0.04

28 14.00 1.43 0.24 265 0.01 0.03 0.04

29 14.50 1.41 0.21 235 0.02 0.02 0.03

30 14.98 1.34 0.18 230 0.02 0.05 0.06

31 15.50 1.21 0.15 187 0.02 0.09 0.09

32 16.00 1.09 0.12 150 0.02 0.10 0.10

33 16.48 0.97 0.10 122 0.02 0.09 0.09

34 16.99 0.76 0.07 131 0.02 0.17 0.17

35 17.49 0.65 0.06 99 0.02 0.09 0.09

36 17.97 0.54 0.04 70 0.02 0.09 0.10

37 18.48 0.47 0.03 77 0.02 0.07 0.07

38 18.97 0.40 0.03 48 0.02 0.06 0.06

39 19.49 0.40 0.02 38 0.02 0.02 0.03

40 19.99 0.35 0.02 38 0.01 0.05 0.05

41 20.50 0.37 0.02 35 0.02 0.03 0.04

42 20.95 0.32 0.02 19 0.01 0.06 0.06

43 21.44 0.37 0.02 14 0.02 0.05 0.06

44 21.99 0.36 0.02 22 0.01 0.02 0.02

45 22.48 0.38 0.02 14 0.01 0.03 0.03

46 23.02 0.37 0.01 17 0.01 0.02 0.02

47 23.51 0.40 0.01 17 0.01 0.04 0.04

48 23.99 0.40 0.01 12 0.01 0.02 0.02
Page 16 of 48

Table 7. Performance at Site Average Density; 0.99 kg/m3

Measured Power Curve (Database A)

Reference air density: 0.99 kg/m3

Bin

number

Normalized

wind speed

(m/s)

Power

output (kW) Cp

Number of 

1-minute 

data sets

Category A

standard

uncertainty

(kW)

Category B

standard

uncertainty 

(kW)

Combined

standard

uncertainty

(kW)

1 0.54 -0.01 -21.65 1121 0.00 0.02 0.02

2 1.02 -0.01 -3.19 1923 0.00 0.02 0.02

3 1.52 -0.01 -0.96 2851 0.00 0.02 0.02

4 2.00 -0.01 -0.42 3823 0.00 0.02 0.02

5 2.50 -0.01 -0.22 3866 0.00 0.02 0.02

6 3.00 -0.01 -0.13 3807 0.00 0.02 0.02

7 3.50 -0.01 -0.08 3471 0.00 0.02 0.02

8 4.00 -0.01 -0.05 3203 0.00 0.02 0.02

9 4.49 0.00 -0.03 2850 0.00 0.02 0.02

10 4.99 0.00 0.01 2422 0.00 0.02 0.02

11 5.50 0.02 0.07 2182 0.00 0.02 0.02

12 5.99 0.04 0.11 1950 0.00 0.02 0.02

13 6.50 0.07 0.14 1604 0.00 0.02 0.02

14 6.99 0.10 0.17 1430 0.00 0.02 0.02

15 7.50 0.15 0.20 1269 0.00 0.02 0.02

16 8.00 0.21 0.22 1146 0.00 0.03 0.03

17 8.51 0.27 0.25 1095 0.00 0.03 0.03

18 9.00 0.35 0.27 1042 0.00 0.04 0.04

19 9.50 0.43 0.28 932 0.00 0.04 0.04

20 10.00 0.53 0.30 930 0.00 0.05 0.05

21 10.49 0.63 0.31 782 0.00 0.05 0.05

22 10.99 0.73 0.31 685 0.00 0.06 0.06

23 11.50 0.83 0.31 644 0.00 0.05 0.05

24 11.99 0.93 0.30 584 0.00 0.06 0.06

25 12.50 1.02 0.29 507 0.00 0.06 0.06

26 12.99 1.09 0.28 425 0.01 0.04 0.05

27 13.49 1.13 0.26 339 0.01 0.03 0.04

28 14.00 1.17 0.24 265 0.01 0.03 0.03

29 14.50 1.15 0.21 235 0.01 0.02 0.03

30 14.98 1.09 0.18 230 0.01 0.04 0.05

31 15.50 0.99 0.15 187 0.01 0.07 0.07

32 16.00 0.89 0.12 150 0.02 0.08 0.08

33 16.48 0.79 0.10 122 0.02 0.08 0.08

34 16.99 0.62 0.07 131 0.01 0.14 0.14

35 17.49 0.53 0.06 99 0.02 0.07 0.08

36 17.97 0.44 0.04 70 0.02 0.08 0.08

37 18.48 0.38 0.03 77 0.01 0.06 0.06

38 18.97 0.33 0.03 48 0.01 0.05 0.05

39 19.49 0.32 0.02 38 0.01 0.02 0.02

40 19.99 0.28 0.02 38 0.01 0.04 0.04

41 20.50 0.30 0.02 35 0.02 0.03 0.03

42 20.95 0.26 0.02 19 0.01 0.05 0.05

43 21.44 0.30 0.02 14 0.02 0.05 0.05

44 21.99 0.29 0.02 22 0.01 0.02 0.02

45 22.48 0.31 0.02 14 0.01 0.03 0.03

46 23.02 0.31 0.01 17 0.01 0.02 0.02

47 23.51 0.33 0.01 17 0.01 0.03 0.03

48 23.99 0.33 0.01 12 0.01 0.02 0.02
Page 17 of 48

Table 8. Annual Energy Production (AEP) at Sea-Level Density; 1.225 kg/m3

Estimated Annual Energy Production, Database A (All Valid Data)

Reference air density: 1.225 kg/m3

Cut-out wind speed: - m/s

Hub height annual 

average wind speed 

(Rayleigh)

AEP-measured

Standard 

uncertainty in 

AEP-measured

AEP-extrapolated

Complete if AEP 

measured is at least 95% 

of AEP extrapolated

m/s kWh kWh % kWh

4 301 178 62% 301 Complete

5 900 210 24% 900 Complete

6 1,745 251 15% 1,745 Complete

7 2,665 292 11% 2,666 Complete

8 3,495 331 10% 3,496 Complete

9 4,144 362 9% 4,149 Complete

10 4,592 385 8% 4,604 Complete

11 4,857 398 8% 4,880 Complete

AEP measured assumes zero power between highest bin and cut-out.

AEP extrapolated assumes power in last bin between last bin and cut-out.

Table 9. AEP at Site Average Density; 0.99 kg/m3

Estimated Annual Energy Production, Database A (All Valid Data)

Reference air density: 0.99 kg/m3

Cut-out wind speed: - m/s

Hub height 

annual average 

wind speed 

(Rayleigh)

AEP-measured

Standard 

uncertainty in 

AEP-measured

AEP-extrapolated

Complete if AEP 

measured is at least 

95% of AEP 

extrapolated

m/s KWh kWh % KWh

4 246 173 73% 246 Complete

5 734 197 27% 734 Complete

6 1,425 228 16% 1,425 Complete

7 2,176 260 12% 2,176 Complete

8 2,853 289 10% 2,854 Complete

9 3,383 314 9% 3,387 Complete

10 3,749 331 9% 3,759 Complete

11 3,965 341 9% 3,984 Complete

AEP measured assumes zero power between highest bin and cut-out.

AEP extrapolated assumes power in last bin between last bin and cut-out.
Page 18 of 48

7.2 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 19 of 48

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, 0.99 kg/m3
Page 20 of 48

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

Figure 7. Scatter plot of mean and standard deviation power data as measured
Page 21 of 48

Figure 8 shows a plot of the binned coefficient of performance as a function of wind speed at sea-level 

normalized air density.

Figure 8. Coefficient of performance at sea-level average density, 1.225 kg/m3
Page 22 of 48

Figure 9 shows a scatter plot of wind speed and turbulence intensity as a function of wind direction. 

Figure 9. Wind speed and turbulence intensity as a function of wind direction
Page 23 of 48

Figure 10. Wind turbulence at the test site
Page 24 of 48

Figure 11 shows a scatter plot and binned values of rotor speed as a function of wind speed.

Table 10. Binned Rotor Speed from 0.5 up to 30 m/s

Wind Speed (m/s) 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5

Rotor Speed (rpm) 0 1 4 5 15 17 43 75 130 152 170 194 215 231 257

Wind Speed (m/s) 8 8.5 9 9.5 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15

Rotor Speed (rpm) 274 296 316 331 347 360 368 377 382 393 395 398 397 390 384

Wind Speed (m/s) 15.5 16 16.5 17 17.5 18 18.5 19 19.5 20 20.5 21 21.5 22 22.5

Rotor Speed (rpm) 367 350 335 316 300 285 280 268 261 261 258 257 261 263 254

Wind Speed (m/s) 23 23.5 24 24.5 25 25.5 26 26.5 27 27.5 28 28.5 29 29.5 30

Rotor Speed (rpm) 257 262 270 267 276 279 277 277 289 284 301 286 - 319 307

Figure 11. Rotor speed as a function of wind speed (1-minute average) and binned values
Page 25 of 48

8. Deviations and Exceptions 

8.1Deviations from the Standard 

The reference anemometer was mounted 2.97 m below the primary. This exceeded the Standard’s 

allowable maximum of 2.5 m below the primary 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. 

8.2Exceptions to NREL Quality Assurance System

The reference anemometer was mounted 2.97 m below the primary. This exceeded the Standard’s 

allowable maximum of 2.5 m below the primary as shown in Annex G.5. 

9. Reference

Wind Turbines, Part 12-1: Power performance measurements of electricity producing wind turbines, IEC 

61400-12-1, Edition 1, 2005-12, International Electrotechnical Commission, Geneva, Switzerland, 2005.
Page 26 of 48

Appendix A: Photographs of the Test Site from the Turbine Base

Direction pictures are facing:

A1. North

A2. Northeast

A3. East

A4. Southeast

A5. South

A6. Southwest

A7. West

A8. Northwest
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Figure A1. Facing north

Source: NREL 2011

Figure A2. Facing northeast

Source: NREL 2011
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Figure A3. Facing east

Source: NREL 2011

Figure A4. Facing southeast

Source: NREL 2011
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Figure A5. Facing south

Source: NREL 2011

Figure A6. Facing southwest

Source: NREL 2011
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Figure A7. Facing west

Source: NREL 2011

Figure A8. Facing northwest

Source: NREL 2011
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Appendix B: Equipment Calibration Sheets

Figure B1. Power transducer calibration sheet I

Figure B2. Power transducer calibration sheet II

Figure B3. Power transducer calibration sheet III

Figure B4. Primary anemometer calibration sheet I

Figure B5. Primary anemometer calibration sheet II

Figure B6. Primary anemometer post-test calibration sheet I

Figure B7. Primary anemometer post-test calibration sheet II

Figure B8. Primary anemometer pre- and post-test calibration comparison; the 

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

Figure B9. Wind vane calibration sheet

Figure B10. Pressure transducer calibration sheet

Figure B11. RTD-Probe calibration sheet

Figure B12. NI 9229 data acquisition module calibration sheet I

Figure B13. NI 9217 data acquisition module calibration sheet I

Figure B14. NI 9205 data acquisition module calibration sheet I

Figure B15. NI 9229 data acquisition module calibration sheet II

Figure B16. NI 9217 data acquisition module calibration sheet II 

Figure B17. NI 9205 data acquisition module calibration sheet II
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Power 

Figure B1. Power transducer calibration sheet I, installed 20 October 2010 to 24 October 2011
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Figure B2: Power transducer calibration sheet 2

Figure B3: Power transducer calibration sheet 3

Figure B2. Power transducer calibration sheet II installed 20 October 2010 to 24 October 2011
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Figure B3. Power transducer calibration sheet III installed 20 October 2010 to 24 October 2011
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Wind Speed 

Figure B4. Primary anemometer calibration sheet I
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Figure B5. Primary anemometer calibration sheet II
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Figure B6. Primary anemometer post-test calibration sheet I
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Figure B7. Primary anemometer post-test calibration sheet II
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Figure B8. Primary anemometer pre- and post-test calibration comparison; the 

difference is less than 0.1 m/s for the range of 6 to 12 m/s
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Wind Direction

Figure B9. Wind vane calibration sheet
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Pressure 

Figure B10. Pressure transducer calibration sheet
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Temperature 

Figure B11. RTD-Probe calibration sheet
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Data Acquisition System

Figure B12. NI 9229 data acquisition module calibration sheet I
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Figure B13. NI 9217 data acquisition module calibration sheet I
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Figure B14. NI 9205 data acquisition module calibration sheet I
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Figure B15. NI 9229 data acquisition module calibration sheet II
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Figure B16. NI 9217 data acquisition module calibration sheet II
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Figure B17. NI 9205 data acquisition module calibration sheet II