Technical Report

NREL/TP-500-46191

February 2010

Wind Turbine Generator System 

Power Performance Test Report 

for the ARE442 Wind Turbine

Jeroen van Dam and Dave Jager
National Renewable Energy Laboratory

1617 Cole Boulevard, Golden, Colorado 80401-3393

303-275-3000 • www.nrel.gov

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

Office of Energy Efficiency and Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

Contract No. DE-AC36-08-GO28308

Technical Report

NREL/TP-500-46191

February 2010

Wind Turbine Generator System 

Power Performance Test Report 

for the ARE442 Wind Turbine

Jeroen van Dam and Dave Jager

Prepared under Task No. WE102211
NOTICE

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iii

Notice

This report was prepared by the National Renewable Energy Laboratory (NREL), operated for 

the United States Department of Energy (DOE) by the Alliance for Sustainable Energy, LLC 

(Alliance), as an account of work sponsored by the United States government. The test results 

documented in this report define the characteristics of the test article as configured and under 

the conditions tested.

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INFRINGE PRIVATELY OWNED RIGHTS. 

Neither Alliance nor the U. S. Government shall be liable for special, consequential or incidental 

damages. Reference herein to any specific commercial product, process, or service by trade 

name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its 

endorsement, recommendation, or favoring by the United States government or any agency 

thereof. The views and opinions of the authors expressed herein do not necessarily state or 

reflect those of the United States government or any agency thereof or Alliance. 

NREL is a DOE Laboratory, and as an adjunct of the United States government, cannot certify 

wind turbines. The information in this report is limited to NREL’s knowledge and understanding 

as of this date. 

NREL is accredited by the American Association for Laboratory Accreditation (A2LA) and the 

results shown in this test report have been determined in accordance with the NREL’s terms of 

accreditation unless stated otherwise in the report.

This report shall not be reproduced, except in full, without the written approval of Alliance or 

successor operator of NREL.

Approval By: __________________________________________________________

Jeroen van Dam, NREL Test Engineer Date

Review By: ___________________________________________________________

Amy Bowen, NREL Test Engineer Date
iv

Contents

Contents .....................................................................................................................................iv

Table of Tables............................................................................................................................v

Table of Figures .........................................................................................................................vi

1. Background..........................................................................................................................1

2. Test Summary ......................................................................................................................1

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

4. Test Site Description...........................................................................................................6

5. Description of Test Equipment...........................................................................................8

6. Description of Test Procedure .........................................................................................10

7. Test Results .......................................................................................................................11

7.1. Tabular Results of Power Performance Test.................................................................11

7.2. Graphical Results...........................................................................................................15

8. Deviations and Exceptions ...............................................................................................22

8.1. Deviations from the Standard ........................................................................................22

8.2. Exceptions to NWTC-CT Quality Assurance System ....................................................22

Appendix A. Pictures of the Test Site .....................................................................................23

Appendix B. Equipment Calibration Sheets..........................................................................29
v

Table of Tables

Table 1. Test turbine configuration ...............................................................................................3

Table 2. Structures close to test turbine ......................................................................................7

Table 3. Criteria for test site without site calibration ....................................................................7

Table 4. Equipment used in the power performance test ............................................................8

Table 5. Uncertainty values used in the analysis.......................................................................10

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

.......................................................12

Table 7. Performance at site average density; 1.05 kg/m3 ........................................................13

Table 8. Annual energy production (AEP) at sea-level density; 1.225 kg/m3

.............................14

Table 9. Annual energy production at site average density; 1.05 kg/m3 ....................................14
vi

Table of Figures

Figure 1. Power curve summary ..................................................................................................2

Figure 2. Electrical diagram of the ARE 442 installation..............................................................4

Figure 3. ARE 442 test turbine at the NWTC...............................................................................5

Figure 4. Map of the test site .......................................................................................................6

Figure 5. Meteorological tower and instruments ..........................................................................9

Figure 6. Power curve at sea-level density; 1.225 kg/m3 ...........................................................15

Figure 7. Power curve at site average density; 1.05 kg/m3

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

Figure 8. Scatter plot of mean, standard deviation, minimum, and maximum power data. 1 Hz 

samples with 1 minute averaging. ........................................................................................17

Figure 9. Coefficient of performance at sea level density; 1.225 kg/m3 .....................................18

Figure 10. Wind turbulence intensity as a function of wind speed .............................................19

Figure 11. Wind speed and turbulence intensity as a function of wind direction........................20

Figure 12. Rotor speed as a function of wind speed (1-minute averages) and binned values ..21
1

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. In total, four turbines are 

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

performance testing is one of up to 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 a power performance test that NREL conducted on the 

ARE 442 wind turbine. For this test, the ARE 442 turbine was installed at the NWTC, close to 

Boulder, Colorado. This test was conducted in accordance with the International 

Electrotechnical Commission’s (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. However, because the ARE 442 is a small turbine as defined by IEC, NREL 

also followed Annex H that applies to small wind turbines. This test report refers to these 

procedures as the Standard.

In these summary results, wind speed is normalized to sea-level air density. Additional results 

are given in Section 7. This test was begun on December 9, 2008 and was ended on December 

28, 2008. 303.7 hours of valid data were collected during that time. The highest bin filled was 

the 18.0 m/s bin. The amount of test data is sufficient to meet the requirements of the Standard, 

Annex H.
2

Figure 1. Power curve summary

Power Performance Test Bin Wind Bin Number

ARE442 Speed Power Data Cp

(m/s) (kW) Points

Sea-Level Density Power Curve 0.51 -0.03 1,000 -9.00

1.00 -0.04 1,210 -1.61

Report Created: 31-Dec-08 1.50 -0.04 1,339 -0.53

1.99 -0.05 1,423 -0.27

Turbine Specifications: 2.50 -0.05 1,196 -0.13

2.98 -0.01 1,061 -0.02

Serial number: Y08-001C 3.49 0.08 861 0.08

Rated Power: 10000 W 4.00 0.30 713 0.19

Cut-in Wind Speed: 2.2 m/s 4.49 0.59 647 0.26

Cut-out Wind Speed: - m/s 5.00 0.91 579 0.29

Rated Wind Speed: 12 m/s 5.51 1.35 604 0.32

Rotor Diameter: 7.2 m 6.00 1.86 586 0.35

6.50 2.42 624 0.35

Control Type: Active 7.00 3.04 647 0.35

Pitch Setting: Fixed 7.49 3.70 599 0.35

8.00 4.41 535 0.35

8.49 5.19 544 0.34

Site Conditions: 9.00 6.02 478 0.33

9.50 6.81 416 0.32

Location: NWTC Boulder, CO 10.00 7.70 404 0.31

Average Air Density: 1.035 kg/m^3 10.49 8.47 384 0.29

Measurement Sectors: 214-74 °T 10.99 9.17 362 0.28

11.50 9.69 340 0.26

12.01 10.10 289 0.23

Test Statistics: 12.49 10.05 245 0.21

12.97 9.91 243 0.18

Start Date: 13.50 9.42 186 0.15

End Date: 14.00 9.00 162 0.13

Amount of Data Collected: 303.70 hours 14.48 8.58 138 0.11

Highest Bin Filled: 18.0 m/s 15.00 8.28 124 0.10

Test Completed? Yes 15.54 7.86 74 0.08

15.99 7.85 78 0.08

16.49 7.59 47 0.07

16.95 7.33 33 0.06

17.51 7.48 27 0.06

18.01 7.57 24 0.05

9-Dec-2008

28-Dec-2008

Sea-Level Air Density Normalized Power Curve ARE 442

-2

0

2

4

6

8

10

12

0 2 4 6 8 10 12 14 16 18 20

Normalized Wind Speed, m/s

Electric Power, kW

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Cp

Power

Cp
3

3. Test Turbine Configuration

Table 1. Test turbine configuration

Turbine make, model, serial number, production 

year

Abundant Renewable Energy, ARE 442, Y08-001C, 2008

Rotor diameter (m) 7.2

Hub height (m) 30.9

Tower type Free standing lattice, Valmont U4.5 x 100’

Rated electrical power (kW) 10

Rated wind speed (m/s) 12

Rotor speed range (rpm) 0-140

Fixed or variable pitch Fixed

Number of blades 3

Blade-tip pitch angle (deg) 0°, blade root flat on alternator

Blade make, type, serial number Aero Energy 089-028, 089-029, 089-030

Description of control system (device & software 

version)

Side furling with gravity return; VCL442-HV Voltage Clamp 

pulse-width modulated resistor-loading; Windy boy 

6000US

NREL measured the distance of the blade tip to the center of the rotor as 3.7 m, which would 

make the diameter 7.4 m. If the turbine has this measured rotor diameter of 7.4m instead of the 

specified diameter of 7.2m, this would reduce the peak Cp from 0.42 to 0.40.

The power transducer was connected between the NREL grid and the subpanel (Figure 2) to 

which the voltage clamp and the inverters are connected. It thus captures the combined 

consumption/production of all three components. 
4

Figure 2. Electrical diagram of the ARE 442 installation Tower base 

J-box

Uptower 

J-box

Foundation 

junction box

Met tower 

j-box

Voltage 

clamp

Resistive 

dump 

load

Resistive 

dump 

load

inverterinverter

Sub panel

Power 

measure

ment box

60A 600V 

disconne

ct

kWh 

meter

Power panel 3-3L 

120/240V

2*10AWG

L1

datashed

3*6AWG

4*14AWG

AWG 4* 3

AWG 14 * 4

LP 14106 

surge 

suppressor

) AWG 4( Ground 

Ground (6AWG)

LP 14106 

surge 

suppressor

Ground rod on the 

southeast corner

G

L1

L1L2

G

Ground rod on the north 

side of datashed

ZD16100 

surge 

suppressor

L2

2 pole 30A 

breaker

3*10AWG

3*10AWG

1*10AWG

2*14AWG

2*10AWG

1*10AWG

2*14AWG

2 pole 30A 

breaker

1 pole 15A 

breaker

2 pole 60A 

breaker 

no.27-29

Everything between 

subpanel and panel 3-3 L 

6AWG

L2

N

8AWG

8AWG

NREL 

grid

2*12AWG

2 pole 30A 

breaker

60A 600V 

disconnect

Shorting switch

SOW
5

Figure 3. ARE 442 test turbine at the NWTC
6

4. Test Site Description

The test turbine is located at site 3.3a at the NWTC located 8 miles south of Boulder, Colorado. 

The terrain primarily consists of mostly flat terrain with short vegetation. The test site has 

prevailing wind bearing 292° relative to true north. For measurements where it is important to 

accurately measure wind speed, NREL used data obtained when wind direction is between 214° 

and 74° true. In this measurement sector, the influence of terrain and obstructions on the 

anemometer is small. Figure 4 shows the turbine and meteorological tower locations. This 

figure also shows nearby obstructions and topographical features of the site. A circle indicating 

20 rotor diameters is drawn on the map. Sizes and distances of nearby obstructions are 

provided in Table 2.

Figure 4. Map of the test site

North
7

Table 2. Structures close to test turbine

Obstacle or Relative Distance Bearing Equiv. Dia. Obstructed Sector

Turbine to: Start End

(m) (deg T) (m) (deg T) (deg T)

Met A Test Turbine 18.3 290 0.8

Data Shed Test Turbine 62.8 250.6 4.3 0 0

Gaia Test Turbine 48.0 182.3 N/A 152 213

Met B Test Turbine 49.2 221.7 0.8 0 0

Mariah Test Turbine 92.0 205.6 N/A 0 0

Met C Test Turbine 93.3 211.2 0.7 0 0

Test Turbine Met Tower 18.3 110 N/A 73 147

Data Shed Met Tower 50.0 237 4.3 0 0

Gaia Met Tower 56.4 164 N/A 136 193

Met B Met Tower 45.7 200 0.8 0 0

Mariah Met Tower 92.0 194 N/A 0 0

Met C Met Tower 91.5 200 0.7 0 0

Based upon this analysis, NREL has established a measurement sector from 214° to 74°. 

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

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

site assessment. Based on the site assessment results, a site calibration is not required.

Table 3. Criteria for test site without site calibration

Description Distance Sector

(deg)

Test Site 

Condition

Pass/Fail

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

Maximum variation from best fit plane < 0.08 D <2L 360 0.02 Pass

Maximum slope of best fit plane < 5% 2-4L In 2.7% Pass

Maximum variation from best fit plane < 0.15 D 2-4L In 0.02 Pass

Steepest slope maximum < 10% 2-4L Out 3.1% Pass

Maximum slope of best fit plane < 10% 4-8L In 2.7% Pass

Maximum variation from best fit plane < 0.15 D 4-8L In 0.02 Pass

No neighboring and operating turbines <2Dn 360 0 Pass

No obstacles <2De 360 0 Pass

D = test turbine rotor diameter

L = distance between test turbine and meteorological tower

De = equivalent diameter of obstacle

In = inside preliminary measurement sector

Out = outside preliminary measurement sector

The ARE442 was connected to the electrical grid at a nominal voltage of 240 VAC at a 

frequency of 60 Hz. The grid tolerances are 5% for voltage amplitude and 1% for frequency.
8

5. Description of Test Equipment

All test equipment was calibrated; calibration sheets are included in Appendix B. Table 4 shows 

the equipment used and calibration due dates. Figure 5 shows placement of the meteorological 

instruments on the tower. The anemometer was sent out for recalibration after the test period. 

The difference between the two calibrations was within the tolerances allowed by the Standard. 

The data acquisition modules were out of calibration during the test period. They were sent out 

for post-test calibration and found to be within specification. The post-test calibration sheets are 

included in Appendix B as well.

Table 4. Equipment used in the power performance test

Instrument Make, Model Serial Number Calibration Due Date

Power transducer Secondwind Phaser 5FM-4A20 02663 28 Apr 2009

Current transducers OSI 12974 001235408

001235411

Calibrated with power 

transducer 

Primary anemometer Thies, First Class 0707886 28 Feb 2009

Reference anemometer NRG, Max 40 179500049022 In situ

Wind vane Met One, 020C with aluminum 

vane

G4706 28 Feb 2009

Pressure sensor Vaisala, PTB101B T4730007 26 Aug 2009

Temperature sensor Met One, T-200 0789020 10 Oct 2009

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

12EAE14

12A2037

12C73B4

12ECB77

31 May 2008

3 Aug 2008

9 Oct 2008
9

Figure 5. Meteorological tower and instruments

Figure 5 shows placement of the meteorological instruments on the tower. (Note that the 

Primary Anemometer is within the allowable 2.5% of hub height. To ensure that only data 

obtained during normal operation of the turbine are used in the analysis, and to ensure data are 

not corrupted, data sets are excluded from the database under the following circumstances:

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

operation,

• turbine cannot operate because of a turbine fault condition, and,

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

Two methods were used to track when any of these conditions occur during the test. With the 

first method, the logbook was checked for such events. For the second, the turbine controller 

had a status signal which was measured that indicates when the turbine is available or braked. 

A copy of the logbook is available upon request. No maintenance was performed during the test 

period.
10

6. Description of Test Procedure

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

10 kHz, which was then decimated to 1 Hz data. The averaging time was 1 minute for the mean 

values. Standard deviation, minimum, and maximum values for each averaging period were 

also collected. 

The turbine status signal for the ARE 442 was obtained by checking the release of the up-tower 

brake relay. The status signal indicated if the turbine was braked or not.

Only database A is reported since the ARE 442 does not have a cut-out wind speed.

Table 5. Uncertainty values used in the analysis

Component Uncertainty Source

Power (Inverter)

voltage transducer NA

current sensor/signal 12 W Specifications (specs)

power transducer * 0.12% Specs

data acquisition 17 W +0.08% Specs

resistor 0.01% Specs

Wind Speed

calibration 0.02 m/s Calibration sheet

operational characteristics 0.05 m/s +0.52% IEC

mounting effects 1.00% Assumption

terrain effects 2.00% IEC 

data acquisition < 0.01 m/s Assumption

Temperature

temperature sensor 0.15 °C Specs

radiation shielding 1.15 °C Assumption

mounting effects 0.11 °C IEC method

algorithm 0.00 °C Included in DAS

data acquisition 0.35 °C Specs

Air Pressure

pressure sensor 0.20 kPa Instrument specs.

mounting effects < 0.01 kPa IEC method

data acquisition 0.06 kPa Specs
11

7. Test Results

7.1.Tabular Results of Power Performance Test

Table 6 through 9 provide the power performance test results in tabular format.
12

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

Measured power curve (database A)

Reference air density: 1.225 kg/m3 Category A Category B Combined

Bin Normalized Power Cp Number of Standard Standard Standard

Wind Speed Output 1-Minute Uncertainty Uncertainty Uncertainty

(m/s) (m/s) (kW) Data Sets (kW) (kW) (kW)

0.5 0.51 -0.03 -9.00 1000 0.00 0.16 0.16

1 1.00 -0.04 -1.61 1210 0.00 0.16 0.16

1.5 1.50 -0.04 -0.53 1339 0.00 0.16 0.16

2. 1.99 -0.05 -0.27 1423 0.00 0.16 0.16

2.5 2.50 -0.05 -0.13 1196 0.00 0.16 0.16

3 2.98 -0.01 -0.02 1061 0.00 0.16 0.16

3.5 3.49 0.08 0.08 861 0.01 0.16 0.16

4 4.00 0.30 0.19 713 0.01 0.17 0.17

4.5 4.49 0.59 0.26 647 0.01 0.18 0.18

5 5.00 0.91 0.29 579 0.02 0.18 0.18

5.5 5.51 1.35 0.32 604 0.02 0.20 0.20

6 6.00 1.86 0.35 586 0.02 0.23 0.23

6.5 6.50 2.42 0.35 624 0.02 0.24 0.24

7 7.00 3.04 0.35 647 0.02 0.27 0.27

7.5 7.49 3.70 0.35 599 0.02 0.29 0.29

8 8.00 4.41 0.35 535 0.02 0.32 0.32

8.5 8.49 5.19 0.34 544 0.02 0.36 0.36

9 9.00 6.02 0.33 478 0.02 0.39 0.39

9.5 9.50 6.81 0.32 416 0.03 0.39 0.39

10 10.00 7.70 0.31 404 0.03 0.45 0.45

10.5 10.49 8.47 0.29 384 0.04 0.42 0.42

11 10.99 9.17 0.28 362 0.04 0.40 0.40

11.5 11.50 9.69 0.26 340 0.05 0.32 0.33

12 12.01 10.10 0.23 289 0.05 0.29 0.29

12.5 12.49 10.05 0.21 245 0.06 0.17 0.19

13 12.97 9.91 0.18 243 0.06 0.20 0.21

13.5 13.50 9.42 0.15 186 0.06 0.33 0.34

14 14.00 9.00 0.13 162 0.05 0.33 0.33

14.5 14.48 8.58 0.11 138 0.04 0.34 0.34

15 15.00 8.28 0.10 124 0.06 0.26 0.27

15.5 15.54 7.86 0.08 74 0.11 0.33 0.35

16 15.99 7.85 0.08 78 0.06 0.17 0.18

16.5 16.49 7.59 0.07 47 0.05 0.26 0.27

17 16.95 7.33 0.06 33 0.14 0.28 0.31

17.5 17.51 7.48 0.06 27 0.14 0.20 0.25

18 18.01 7.57 0.05 24 0.08 0.18 0.20
13

Table 7. Performance at site average density; 1.05 kg/m3

Measured power curve (database A)

Reference air density: 1.05 kg/m3 Category A Category B Combined

Bin Normalized Power Cp Number of Standard Standard Standard

Wind Speed Output 1-Minute Uncertainty Uncertainty Uncertainty

(m/s) (m/s) (kW) Data Sets (kW) (kW) (kW)

0.5 0.52 -0.03 -10.29 928 0.00 0.16 0.16

1 1.00 -0.04 -1.84 1129 0.00 0.16 0.16

1.5 1.50 -0.05 -0.63 1254 0.00 0.16 0.16

2 2.00 -0.05 -0.29 1376 0.00 0.16 0.16

2.5 2.50 -0.05 -0.16 1175 0.00 0.16 0.16

3 2.99 -0.03 -0.05 1079 0.00 0.16 0.16

3.5 3.49 0.04 0.05 862 0.00 0.16 0.16

4 3.99 0.19 0.14 714 0.01 0.17 0.17

4.5 4.50 0.46 0.24 646 0.01 0.17 0.17

5 5.00 0.73 0.27 574 0.01 0.18 0.18

5.5 5.50 1.11 0.31 549 0.02 0.19 0.19

6 6.00 1.53 0.33 585 0.02 0.21 0.21

6.5 6.50 2.04 0.35 546 0.02 0.23 0.23

7 7.00 2.59 0.35 605 0.02 0.25 0.25

7.5 7.49 3.19 0.35 618 0.02 0.27 0.27

8 7.99 3.84 0.35 550 0.02 0.30 0.30

8.5 8.50 4.51 0.34 503 0.02 0.32 0.32

9 8.98 5.25 0.34 514 0.02 0.36 0.37

9.5 9.50 6.06 0.33 459 0.02 0.39 0.39

10 10.00 6.82 0.32 398 0.03 0.39 0.39

10.5 10.51 7.67 0.31 388 0.03 0.45 0.45

11 11.00 8.41 0.30 361 0.04 0.42 0.42

11.5 11.49 9.04 0.28 344 0.04 0.39 0.39

12 12.00 9.62 0.26 327 0.05 0.36 0.37

12.5 12.50 10.02 0.24 283 0.06 0.29 0.30

13 12.98 10.06 0.22 250 0.06 0.17 0.19

13.5 13.49 10.03 0.19 243 0.06 0.17 0.19

14 13.99 9.61 0.16 186 0.06 0.32 0.33

14.5 14.50 9.16 0.14 166 0.05 0.34 0.34

15 14.99 8.83 0.12 143 0.05 0.29 0.29

15.5 15.48 8.44 0.11 126 0.05 0.33 0.33

16 15.98 8.14 0.09 89 0.07 0.28 0.29

16.5 16.52 7.80 0.08 80 0.10 0.30 0.32

17 16.98 7.77 0.07 64 0.07 0.17 0.18

17.5 17.48 7.56 0.07 43 0.05 0.24 0.24

18 17.94 7.24 0.06 27 0.20 0.33 0.39

18.5 18.48 7.60 0.06 26 0.10 0.33 0.34

19 18.98 7.53 0.05 22 0.08 0.18 0.20
14

Table 8. Annual energy production (AEP) at sea-level density; 1.225 kg/m3

Table 9. Annual energy production at site average density; 1.05 kg/m3

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 AEPextrapolated

Complete if AEP 

measured is at least 

95% of AEP 

extrapolated

m/s kWh kWh % kWh

4 7,884 1,717 22% 7,884 Complete

5 15,327 1,948 13% 15,329 Complete

6 23,516 2,144 9% 23,572 Complete

7 30,967 2,271 7% 31,330 Complete

8 36,718 2,325 6% 37,924 Complete

9 40,459 2,314 6% 43,158 Incomplete

10 42,350 2,254 5% 47,049 Incomplete

11 42,770 2,160 5% 49,696 Incomplete

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

Standard Uncertainty in AEPmeasured

AEP measured assumes zero power between highest bin and cutout

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

Reference air density: 1.050 kg/m^3

Cut-out wind speed: 25.0 m/s

Hub height 

annual average 

wind speed 

(Rayleigh)

AEP-measured AEPextrapolated

Complete if AEP 

measured is at least 

95% of AEP 

extrapolated

m/s kWh kWh % kWh

4 6,608 1,670 25% 6,608 Complete

5 13,321 1,887 14% 13,322 Complete

6 21,066 2,086 10% 21,091 Complete

7 28,513 2,230 8% 28,714 Complete

8 34,658 2,310 7% 35,419 Complete

9 39,036 2,329 6% 40,886 Complete

10 41,641 2,297 6% 45,046 Incomplete

11 42,734 2,228 5% 47,953 Incomplete

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

Standard Uncertainty in AEPmeasured

AEP measured assumes zero power between highest bin and cutout

AEP extrapolated assumes power in last bin between last bin and cutout
15

7.2. Graphical Results

Figure 6 through 9 show the results of the power performance test in graphical format. The 

12-kW ceiling of the power maxima in Figure 8 is caused by the maximum output capability 

of the inverters. Figure 10 through 12 show plots of turbulence intensity and rotor speed.

Figure 6. Power curve at sea-level density; 1.225 kg/m3

-2

0

2

4

6

8

10

12

0 2 4 6 8 10 12 14 16 18 20

Normalized Wind Speed (m/s)

Power (kW)
16

Figure 7. Power curve at site average density; 1.05 kg/m3

-2

0

2

4

6

8

10

12

0 2 4 6 8 10 12 14 16 18 20

Normalized Wind Speed (m/s)

Power (kW)
17 

Figure 8. Scatter plot of mean, standard deviation, minimum, and maximum power data. 

1 Hz samples with 1 minute averaging. 
18

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

0%

5%

10%

15%

20%

25%

30%

35%

40%

0 2 4 6 8 10 12 14 16 18 20

Wind speed (m/s)

Cp
19 

 

Figure 10. Wind turbulence intensity as a function of wind speed 
20 

Figure 11. Wind speed and turbulence intensity as a function of wind direction 
21 

Figure 12. Rotor speed as a function of wind speed (1-minute averages) and binned 

values 

Wind speed [m/s] 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0

Rotor speed [rpm] 0 0 1 5 10 17 31 48 71 81 89 97 101 105 108 111 114 117 120 123

Wind speed [m/s] 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.1

Rotor speed [rpm] 127 130 134 137 140 142 144 145 145 145 145 146 147 147 148 148 150 154 152 153
22

8. Deviations and Exceptions

8.1. Deviations from the Standard

The current transformers are not listed as compliant to IEC 60044-1, but do exceed the 

minimum accuracy required by the Standard.

8.2. Exceptions to NWTC-CT Quality Assurance System

During the test period, the data acquisition system was out of calibration. A post test calibration 

has been performed which showed that the system was within specification without adjustment. 

Thus, it can be assumed the system was within specification during the test period and no 

additional uncertainty needs to be applied.
23

Appendix A. Pictures of the Test Site
24

Figure A.1. West

Figure A.2. Southwest
25

Figure A.3. South-south-west

Figure A.4. South southeast
26

Figure A.5. East

Figure A.6. Northeast
27

Figure A.7. North northeast

Figure A.8. North
28

Figure A.9. Northwest
29

Appendix B. Equipment Calibration Sheets
30

Figure B.1. Power transducer calibration sheet
31

Figure B.2. Primary anemometer calibration sheet I
32

Figure B.3. Primary anemometer calibration sheet II
33

Figure B.4. Wind vane calibration report
34

Figure B.5. RTD-Probe calibration sheet
35

Figure B.6. Pressure transmitter calibration sheet
36

Figure B.7. NI 9217 data acquisition module calibration sheet I
37

Figure B.8. NI 9229 data acquisition module calibration sheet I
38

Figure B.9. NI 9205 data acquisition module calibration sheet I
39

Figure B.10. NI 9229 data acquisition module calibration sheet II
40

Figure B.11. NI 9217 data acquisition module calibration sheet II
41

Figure B.12. NI 9205 data acquisition module calibration sheet II
F1147-E(10/2008)

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1. REPORT DATE (DD-MM-YYYY)

February 2010

2. REPORT TYPE

Technical report

3. DATES COVERED (From - To)

4. TITLE AND SUBTITLE

Wind Turbine Generator System - Power Performance Test Report: 

ARE442 Wind Turbine

5a. CONTRACT NUMBER

DE-AC36-08-GO28308

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

J. van Dam and D. Jager

5d. PROJECT NUMBER

NREL/TP-500-46191

5e. TASK NUMBER

WE102211

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Renewable Energy Laboratory

1617 Cole Blvd.

Golden, CO 80401-3393

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NREL/TP-500-46191

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NREL

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13. SUPPLEMENTARY NOTES

14. ABSTRACT (Maximum 200 Words)

This report summarizes the results of a power performance test that NREL conducted on the ARE 442 wind turbine. 

This test was conducted in accordance with the International Electrotechnical Commission’s (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. However, because the ARE 442 is a small turbine as defined by IEC, NREL also 

followed Annex H that applies to small wind turbines. In these summary results, wind speed is normalized to sealevel air density.

15. SUBJECT TERMS

ARE442 wind turbine; power performance; small wind turbine

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