power performance test report for the northern power ......1 introduction 1.1 scope this report...

Power Performance Test Report for the Northern Power Systems NW100 100 kW Wind Turbine

in Ashmore, Illinois

CONFIDENTIAL

Northern Power Systems 29 Pitman Road Barre, VT 05641

Report No. PPTR0164-A Date: March 11, 2011

Power Performance Test Report for the Northern Power Systems NW100 100 kW Wind Turbine in Ashmore, Illinois

DNV Rpt. No.: PPTR0164 Version: A Date: March 11, 2011 i

Report Title: Power Performance Test Report for the Northern Power Systems NW100 100 kW Wind Turbine in Ashmore, Illinois For: Northern Power Systems 29 Pitman Road Barre, VT 05641 Attn:

DNV Renewables (USA) Inc. 1809 7th Avenue, Suite 900 Seattle, WA 98101 USA Tel: 1-206-387-4200 Fax: 1-206-387-4201 http://www.dnv.com/windenergy

Date of First Issue: March 11, 2011 Project No. NOR00300-1

Report No.: PPTR0164 Organization Unit: ACGUS364

Version: A

Summary:

This report presents the results of power performance testing conducted on a Northern Power Systems (NPS) Northwind 100 (NW100) 100 kW wind turbine located in Ashmore, Illinois.

Prepared by: Luke Simmons, Manager, Performance & Acoustic Testing

Signature

Verified by: Timothy J. McCoy, Senior Engineer

Signature

Approved by: John Lyons, Acting Head of Section, Technology

Signature

No distribution without permission from the Customer or responsible organizational unit (however, free distribution for internal use within DNV after 3 years)

Indexing Terms

No distribution without permission from the Customer or responsible organizational unit Key Words

Strictly confidential Service Area Cleaner Energy

Unrestricted distribution Market Segment Wind Energy

© 2011 DNV Renewables (USA) Inc. All rights reserved. This publication or parts thereof may not be reproduced or transmitted in any

form or by any means, including photocopying or recording, without the prior written consent of DNV Renewables (USA) Inc.


DNV Rpt. No.: PPTR0164 Version: A Date: March 11, 2011 ii

Table of Contents

1 INTRODUCTION..................................................................................................................1 1.1 Scope...........................................................................................................................1 1.2 Turbine Description ....................................................................................................1 1.3 Site Description...........................................................................................................2 1.4 Site Conditions............................................................................................................4 1.5 Chronology .................................................................................................................5

2 TECHNICAL APPROACH..................................................................................................6 2.1 Site Calibrations..........................................................................................................6

2.1.1 Topographic Variations.....................................................................................6 2.1.2 Other Significant Obstacles...............................................................................6 2.1.3 Cumulative Effect of All Obstacles...................................................................7

2.2 Test Instrumentation ...................................................................................................7 2.3 Data Reduction Methodology...................................................................................10 2.4 Uncertainty Analysis.................................................................................................12 2.5 Anemometer Comparison .........................................................................................15

3 RESULTS .............................................................................................................................18 3.1 Power Performance Test Results ..............................................................................18

3.1.1 Collected Data .................................................................................................18 3.1.2 Results .............................................................................................................18

4 REFERENCES.....................................................................................................................26

APPENDIX A – SITE PHOTOS

APPENDIX B – MET TOWER COMISSIONING FORM

APPENDIX C – INSTRUMENTATION CALIBRATION SHEETS


DNV Rpt. No.: PPTR0164 Version: A Date: March 11, 2011 iii

List of Figures

Figure 1-1. Test Site Location ....................................................................................................3 Figure 1-2. Map of NW100 Turbine Test Site............................................................................4 Figure 2-1. Reference Met Tower Top Instrumentation.............................................................9 Figure 2-2. Primary and Control Wind Speed Comparison Baseline Period August 8, 2009, to August 20, 2009..........................................................................................................15 Figure 2-3. Root Sum of Square Systematic and Statistical Deviations for Power Performance Test Period April 7, 2010, to April 15, 2010.......................................................16 Figure 3-1. Scatter Plot of Valid Average Power versus Wind Speed at Sea Level Air Density (1.225 kg/m3).........................................................................................................19 Figure 3-2. Scatter Plot of Minimum, Maximum, and Standard Deviation of Power versus Wind Speed at Sea Level Air Density (1.225 kg/m³) ....................................................20 Figure 3-3. Summary Plot of Binned Power versus Wind Speed at Sea Level Air Density (1.225 kg/m3).........................................................................................................22 Figure 3-4. Power Coefficient versus Wind Speed at Sea Level Air Density (1.225 kg/m3)........................................................................................................................................22 Figure 3-5. Annual Energy versus Annual Average Wind Speed at Sea Level Air Density (1.225 kg/m3).........................................................................................................23 Figure 3-6. Turbulence Intensity versus Wind Speed...............................................................25 Figure 3-7. Turbulence Intensity versus Wind Direction .........................................................25 Figure 3-8. Wind Speed versus Wind Direction.......................................................................26

List of Tables

Table 1-1. Turbine Description...................................................................................................1 Table 1-2. NW100 Test Turbine Major Components.................................................................2 Table 1-3. Met Tower and Turbine Locations (WGS84, UTM Zone 16) ..................................3 Table 1-4. Meteorological Conditions for Valid Data during the Power Performance Test Period ..................................................................................................................................5 Table 1-5. Testing Chronology Milestones (local time).............................................................5 Table 2-1. Topographic Evaluation of Test Site.........................................................................6 Table 2-2. Sectors Affected by Secondary Anemometer Waking..............................................7 Table 2-3. Valid Sectors Used in Power Performance Testing ..................................................7 Table 2-4. Reference Met Tower Instrumentation......................................................................8 Table 2-5. Data Logger Recorded Data ....................................................................................11 Table 2-6. Data Filtering...........................................................................................................12 Table 2-7. Category B Uncertainty for Power Measurements..................................................14 Table 2-8. Primary and Control Wind Speed Comparison Baseline Period August 8, 2009, to August 20, 2009..........................................................................................................16


DNV Rpt. No.: PPTR0164 Version: A Date: March 11, 2011 iv

Table 2-9. Primary and Control Wind Speed Comparison Power Performance April 7, 2010, to April 15, 2010.............................................................................................................17 Table 3-1. Collected and Removed Data ..................................................................................18 Table 3-2. Measured Power Performance Data Summary–Sea Level Air Density (1.225 kg/m3).........................................................................................................21 Table 3-3. Measured and Extrapolated Annual Energy at Sea Level Air Density (1.225 kg/m3).........................................................................................................23 Table 3-4. Turbulence Intensity versus Wind Speed ................................................................24


DNV Rpt. No.: PPTR0164 Version: A Date: March 11, 2011 1

1 INTRODUCTION

1.1 Scope This report presents the results of power performance testing conducted on a Northern Power Systems (NPS) Northwind 100 (NW100) 100 kW wind turbine located in Ashmore, Illinois. The testing period pertaining to this report began on July 24, 2009, and continued through April 23, 2010. The test equipment was installed during July 2009. The current testing was conducted to document turbine performance in accordance with the IEC Power Performance Test Standard (IEC Standard) [1] for the specific turbine configuration in use during the test period. This report meets the requirements of the IEC Standard and covers the methodology, equipment, and results of the power performance testing. This test was conducted and the report prepared by the DNV Renewables (USA) Inc. (DNV) Testing and Measurements Group (TMG), an organization that is accredited by the American Association for Laboratory Accreditation (A2LA) to perform Power Performance Testing of Wind Turbines.

1.2 Turbine Description The NW100 100 kW wind turbine is a fixed-pitch, stall-regulated, variable speed, upwind, three-bladed, active yaw turbine with a direct drive magnetic generator. Table 1-1 lists general details of the NW100 turbine as communicated by the manufacturer. Table 1-2 lists the manufacturers, models, and serial numbers of significant components.

Table 1-1. Turbine Description

Item Value IEC class IEC IIA Grid frequency 60 Hz Rated power 100 kW Rotor diameter 20.9 m Rotor speed 57 rpm Generator speed 57 rpm Power regulation Variable Speed and Stall Hub height 37 m Tower type Tubular, conical welded steel Cut-in wind speed 4 m/s Cut-out wind speed 25 m/s Generator voltage 480 VAC Converter voltage 480 VAC Distribution voltage 480 VAC



Table 1-2. NW100 Test Turbine Major Components

Component Manufacturer/Model Identification Number

Blades SHFRP/NP10 1001174 Rev A 10-08031-08033-08034

Generator ePower/1001145 Rev C 1001145-00012

Controller version Northern Power Systems/1002128 Rev A 1002128-00012

Software/Parameter version Northern Power Systems 1.5.4

Nacelle anemometer NRG Systems/4025 IceFree

Hybrid Turbine Control Anemometer

UNK

1.3 Site Description The test turbine is located at the Arends Brothers dealership west of Ashmore, Illinois. The turbine test site and reference meteorological (met) tower location were chosen by NPS in consultation with DNV. The test utilized one reference met tower, located approximately 2.5 rotor diameters (D) (52.4 m) from the test turbine. The test site location is shown in Figure 1-1. The coordinates of the test turbine and met tower are presented in Table 1-3. These coordinates were verified manually while on site using a hand-held Garmin GPSMAP 60C GPS receiver. The unit is expected to be accurate to ±5 m. All measured coordinates agreed with the coordinates provided by NPS within the accuracy of the GPS receiver. A map of the topography surrounding the test turbine, including the final valid sector, is shown in Figure 1-2. Site photos are included in Appendix A.



Figure 1-1. Test Site Location

Table 1-3. Met Tower and Turbine Locations (WGS84, UTM Zone 16)

Location Easting (m) Northing

(m) Elevation

(m)

Distance to Upwind Met

(m)

Bearing to Upwind Met (degrees w.r.t.

True North)

Test Turbine 411506 4376252 209 52.4 (2.5 D) 254

Reference Met Tower 433455 4376240 210 N/A N/A



Figure 1-2. Map of NW100 Turbine Test Site

1.4 Site Conditions

The test site was subject to a range of environmental conditions during the test period. Table 1-4 describes the range of conditions for the measured and calculated meteorological variables during the power performance test period. The minimum and maximum values are based on the 10-minute averages, except in the case of wind speeds, which are based on the 1-second samples.



Table 1-4. Meteorological Conditions for Valid Data during the Power Performance Test Period

Variable Average Minimum Maximum

Hub-height measured wind speed (m/s) 6.00 0.23 22.68

Air pressure (hPa) 984.0 962.6 1000.5

Air temperature (°C) 12.2 -4.9 31.8

Air density (kg/m3*) 1.197 1.117 1.291

Relative humidity (%) 70.1 0.5 95.0

* Calculated from temperature, pressure and humidity according to the test standard [1]

1.5 Chronology Table 1-5 presents a brief chronology of the site calibration and power performance testing activities.

Table 1-5. Testing Chronology Milestones (local time)

Event Date

Test equipment installation July 23 through July 25, 2009

Power performance test start August 5, 2009,15:20

Test database complete April 23, 2010, 16:00



2 TECHNICAL APPROACH

2.1 Site Calibrations Annex A of the IEC Standard describes the process for assessing a test site to determine the need for site calibration, and the wind directions that can be used for power performance measurements. According to the IEC Standard, the test site must be evaluated by three criteria: topographic variations, neighboring and operating wind turbines, and other significant obstacles. If the topography of the site meets the criteria given in the IEC Standard, then the wind speed at the meteorological mast is assumed to be identical to the wind speed at the wind turbine. If the topographic variations exceed the criteria, then an experimental calibration of the test site is required to determine corrections to the wind speed. Additionally, all nearby obstacles must be evaluated to determine their effect on both the met tower and the test turbine.

2.1.1 Topographic Variations DNV evaluated the terrain around the test site and compared the results to the IEC criteria for requiring a site calibration. The terrain was analyzed using a United States Elevation Data Set with 30-m resolution. The software MICRODEM was used to calculate the best-fit planes and maximum deviation from the best-fit planes using the Trend Surface function, with a first order fit. Table 2-1 lists the results of this analysis for the test turbine. The turbine passes the criteria for not requiring a site calibration.

Table 2-1. Topographic Evaluation of Test Site

Slope Terrain Variation from

Plane (m)

Distance Site Value

(m) Defined Sector IEC MaximumEst. Site Value

Site Maximum

Est. Site Value

Pass/ Fail

< 2L 0-105 m 360° < 3% 0.0 2.2 <0.3 Pass

≥ 2L and < 4L 105-210 m Measurement

sector < 5% 0.3 4.5 <1.7 Pass

≥ 2L and < 4L 105-210 m

Outside measurement

sector < 10% 0.4 NA NA Pass

≥ 4L and < 8L 210-420 m Measurement

sector < 10% 0.2 7.3 <1.8 Pass

2.1.2 Other Significant Obstacles When using a primary and control anemometer, the control anemometer is considered an obstacle to the primary anemometer and further reduces the allowed sector for analysis. The



disturbed sector used to exclude waking of the primary anemometer was calculated conservatively as 50º wide as per the method outlined in Annex A of the IEC 61400-12-1 Standard. Similarly, the sectors where the secondary anemometer was waked by the primary were excluded to allow comparisons between anemometers to be made for all valid data. The orientations of the anemometers are listed in Table 2-2 and are taken into account for the final valid sector determination.

Table 2-2. Sectors Affected by Secondary Anemometer Waking

Tower Anemometer Bearing (º

True N) From

(º True N) To

(º True N)

Reference Primary 148 123 173

Reference Secondary 328 303 353

2.1.3 Cumulative Effect of All Obstacles The valid measurement sectors were determined after considering all potential obstacles, and anemometer waking for both the test turbine tower and the upwind reference met tower. Table 2-3 lists the valid sector for the test site after considering all obstacles.

Table 2-3. Valid Sectors Used in Power Performance Testing

Turbine Valid From (º True N)

Valid To (º True N)

NW100 175 295

2.2 Test Instrumentation Consistent with the IEC Standard, wind speed and wind direction were measured using sensors mounted on a reference met tower approximately 2.5 D upwind of the wind turbine. Figure 2-1 provides a representative sketch of the instrument installation at the reference met tower. A leaf wetness (precipitation) sensor was mounted at the base of the meteorology tower, near the data acquisition system (DAS). Additional reference anemometry (i.e., shear anemometer) was also installed on the met tower. A met tower commissioning sheet showing details including the sensor orientation, installed height, and calibration date can be found in Appendix B. Table 2-4 summarizes the instrumentation for the reference met tower. The instrument calibration sheets are found in Appendix C.



Table 2-4. Reference Met Tower Instrumentation

Item Location Model

Hub-height anemometer 36.6 m Windsensor P2546A

Hub-height anemometer 36.6 m Thies First Class Advanced (unheated)

Primary wind direction sensor 32.8 m Met One 020C-1

Secondary wind direction sensor 33.2 m NRG #200P

Barometric pressure sensor 31.6 m Met One 090D

Temperature/relative humidity probe 31.8 m Met One 083-D

Shear anemometer 21.3 m Windsensor P2546A

Precipitation sensor 2.5 m Campbell Scientific 237 leaf wetness sensor

The power measurement equipment was installed in the nacelle. The equipment is positioned between the generator and the step-up transformer such that it is measuring net active electric power (i.e., reduced by ancillary power draw). Analog output signals from the turbine controller were supplied by NPS for turbine status, power, nacelle wind speed, nacelle wind direction, yaw position, and rotor speed. The wind direction, barometric pressure, and wind speed sensors were furnished with a calibrated slope and offset and verified on site. The wind direction sensor offset was calibrated to true direction in-situ. The DAS measurement modules were tested for conformance to published specification.



Figure 2-1. Reference Met Tower Top Instrumentation



2.3 Data Reduction Methodology The following section describes the general methodology used to assemble the test data for evaluation. Ten-minute statistical data were calculated from the test data. Data available in the files include the fields described in Table 2-5. Data were processed using the following steps. Power performance data were filtered according to the algorithms and limiting values shown in

1. Table 2-6.

2. The air densities for each 10-minute record were calculated from temperature, pressure, and relative humidity measurements. Wind speed data were then adjusted using the method specified in the IEC Standard, to the reference density, 1.225 kg/m3.

3. Wind speed data were binned into bin widths of 0.5 m/s. Average wind speed and power measurements were calculated for each bin and the number of data points in each bin was counted.

4. Results were summarized and power coefficients were calculated following methods specified in the IEC Standard. Net measured annual energy production (AEP) was calculated as per the methods specified in the IEC Standard.



Table 2-5. Data Logger Recorded Data

Signal Signal Name Logged Measurement Units Date and time (10-minute intervals) N/A Time at beginning of sample

period Julian day 24-

hour clock

Primary wind speed Ane_A1 Average, Min, Max, Standard Deviation m/s

Secondary wind speed Ane_B1 Average, Min, Max, Standard Deviation m/s

Shear wind speed Ane_C1 Average, Min, Max, Standard Deviation m/s

Wind direction WD_A1 Vector Average, Min, Max, Vector Standard Deviation

Degrees True North

Secondary wind direction WD_B1 Vector Average, Min, Max, Vector Standard Deviation

Degrees True North

Temperature Temp Average, Min, Max, Standard Deviation m/s

Relative humidity RH Average, Min, Max, Standard Deviation % Humidity

Barometric pressure BP_hPa Average, Min, Max, Standard Deviation hPa

Precipitation Wet Average, Minimum, Maximum mV

Turbine power (digital) kW_Mod Average, Min, Max, Standard Deviation kW

Turbine power (analog) kW_Ana Average, Min, Max, Standard Deviation kW

TCU turbine power Mod_TCU_NPS_kW Average, Min, Max, Standard Deviation kW

Nacelle wind speed NPS_Wind_Speed Average, Min, Max, Standard Deviation m/s

Yaw position NPS_Yaw_Position Average, Min, Max, Standard Deviation Degrees

Nacelle wind direction NPS_Yaw_Vane Average, Min, Max, Standard Deviation Degrees

Rotor Speed NPS_Rotor_Speed Average, Min, Max, Standard Deviation RPM

Turbine status WT_OK Max Counts Watt transducer missed comms Result_Count_DMT Max Counts TCU missed comms Result_Count_TCU Max Counts DAS battery Batt_Volt Average VDC Panel temperature PTemp_C Average Counts DAS status Counts Max Counts



Table 2-6. Data Filtering

Reason for Data Removal in Order of Application Criteria

Wind direction WD_A1_VAvg ≤ 175 deg true OR WD_A1_VAvg ≥ 295 deg true Temperature Temp_Min < -5 OR Temp_Max > 50

Icing Temp_Avg < 3°C AND

WD_A1_SD < 0.3 deg or Ane_A1_Avg/Ane_B1_Avg < 0.97 or Ane_A1_Avg/Ane_B1_Avg > 1.03 or

Ane_A1_Std < 0.1 m/s Icing 3 records before any icing event OR 3 records after any icing event Manual Flag Turbine not operating in rated wind speed range Turbine offline WTG_OK_H < 600 Fault Recovery Last WTG_OK<>600 AND Ana_kW_Min < 0 DAS or digital communication failure Counts <> 600 OR ResultCount_TCU_Max > 300 or

ResultCount_DMT_Max > 0

Signal QC Filter Minimum Maximum Standard Deviation Wind speed (m/s) Calibrated Offset 50 0 Wind direction (degrees) 0 361 ≤ 0.1 Temperature (°C) -40 50 0 Pressure (hPa) 750 1100 0 Humidity (%) 0 100 0 Power (kW) -50 200 0

2.4 Uncertainty Analysis The uncertainty was calculated as required by the IEC Standard. The uncertainty is broken into Category A and Category B. Category A includes the scatter of the power measurements in the wind speed bins, while Category B includes the uncertainty of the individual measurements. The Category B uncertainty components are detailed in Table 2-7. Results of the combined uncertainty evaluation are presented in tables and as error bars on the power curves in subsequent plots of the results. All of the individual sources of uncertainty are assumed to be uncorrelated; hence, they are summed quadratically as the square root of the sum of the squares. The equation for the total uncertainty, Ui, in the power for wind speed bin i is as follows: ∑+=

j

2Bi,jj

2Aii })uc{()u(U



where uiA is the Category A uncertainty in power for wind speed bin i, uj,i

B is the combined Category B uncertainty for measurement variable j, and cj is the sensitivity between measurement variable j and the power. The Category A uncertainty for power is calculated as follows: ii

Ai Nu σ=

where σi is the standard deviation of the power measurements in wind speed bin i and Ni is the number of measurements in the bin. The Category B uncertainty for the individual measurement variables is calculated as follows: ∑=

k

2Bi,j,k

Bi,j })v{(u

where vk,j,i

B is the uncertainty in wind speed bin i for measurement variable j from uncertainty source k. In some cases, the uncertainty source is absolute and is expressed as a fixed quantity in engineering units that does not change with the measurement or wind speed bin. In other cases, the uncertainty is expressed as a percentage of the measurement reading. The sensitivity coefficients, cj, between the measurement variables and the power are based on the partial derivatives. The sensitivity between the wind speed and the power is based on the local slope of the power curve. The approach for estimating individual components of uncertainty is primarily based on specifications for instruments. The assessment of uncertainty in the wind speed related to terrain effects, uv4i, was calculated from the site calibration database following the IEC Standard. For uncertainty components expressed as an uncertainty limit (e.g., ± U) in the instrument specifications, a rectangular distribution of errors is assumed, resulting in a division by the square root of 3 on the specified instrument accuracy to obtain the standard deviation. Actual uncertainty values are reported in the results section of this report. They are reported for the uncertainty of the individual measured power results and the AEP calculation.



Table 2-7. Category B Uncertainty for Power Measurements

Measured Parameter

Source of Uncertainty Value Comments

Current transformers 0.002/√(3)*Power Metering Class 0.2, assumed uncertainty ±0.3% for 20% load

Sensor full scale 0.003* 200/√(3) Class 0.3 transducer

Data logger 0.001*200/√(3) Logger specification: ±0.1% of full input scale

Power

Sensitivity 1.0 Unity to power measurement

Anemometer calibration 0.1 m/s Calibration

Operational characteristics 3/3.1*)*005.0/05.0( iUsm + Class (A) 1.3 according to specification

Mounting effects 0.01*wind speed

Maximum expected flow distortion due to mounting effects based on mounting

configuration, which exceeds the requirements in the standards

Terrain flow distortion effects 0.02 Estimate based on IEC Standard

Data logger 0.001*wind speed Logger specification

Wind Speed

Sensitivity δP/δV)i ≈

(Pi – Pi-1)/(Vi – Vi-1) Local slope of power curve

Sensor accuracy 0.1°C/√(3) Instrument specification: ±0.1°C

Radiation shield 1.5 °C/√(3) Typical specification for radiation shield: ±1.5 °C

Mounting effects 0.0 Mounted close to hub height

Data logger 0.05 °C/√(3) Logger specification: ±0.1% of full scale

Air Temperature

Sensitivity Vi*(δP/δV)i/(3*Tavg) Partial derivative of power w.r.t.

temperature

Sensor accuracy 1.35 hPa/√(3) Instrument specification: ±1.35 hPa

Mounting effects 0.0 Mounted close to hub height

Data logger 0.95 hPa/√(3) Logger specification: ±0.1% of full scale Air Pressure

Sensitivity Vi*(δP/δV)i/(3*Bavg) Partial derivative of power w.r.t. pressure



2.5 Anemometer Comparison As an alternative to post-test calibration of the anemometers, DNV conducted an in situ comparison as per Annex K of the IEC Standard using data from the first 11 days of data collection as the basis for the measurement period for anemometer comparison. Only wind speed bins from 6 to 10 m/s were used in this analysis due to the lack of high wind speed data. The wind direction was limited to 210° to 270° true north. For the baseline period and the final two weeks of the test, the square sum of the systematic and statistical deviation and the root-sum-square of the systematic and statistical deviation was less than 0.1. The former criterion is required by Annex K of the IEC Test Standard, the latter criterion is a more appropriate measure of sensor degradation. Figure 2-2, Figure 2-3, Table 2-8, and Table 2-9 compare the primary and control wind speeds from the beginning of power performance test period through the end of the power performance test period. These comparisons verify that the calibration of the primary anemometer was maintained between the sensor installation and the conclusion of the measurement.

y = 0.9964x - 0.0746R2 = 0.9999

5

6

6

7

7

8

8

9

9

10

10

5 6 7 8 9 10

Control Anemometer [m/s]

Prim

ary

Ane

mom

eter

[m/s

]

Figure 2-2. Primary and Control Wind Speed Comparison Baseline Period

August 8, 2009, to August 20, 2009



Table 2-8. Primary and Control Wind Speed Comparison Baseline Period August 8, 2009, to August 20, 2009

Bin Center (m/s)

Number of Data Points in Bin

Average Wind Speed – Primary (m/s)

Average Wind Speed – Control (m/s)

6 21 6.21 6.31 7 26 6.92 7.01 8 9 7.88 7.97 9 3 8.65 8.76

0.00

0.01

0.02

0.03

0.04

0.05

0.06

6 7 8 9

Wind Speed Bin [m/s]

Roo

t of S

um o

f Squ

are

Sys

tem

atic

and

Sta

tistic

alD

evia

tions

[m/s

]

Figure 2-3. Root Sum of Square Systematic and Statistical Deviations for Power Performance Test

Period April 7, 2010, to April 15, 2010



Table 2-9. Primary and Control Wind Speed Comparison Power Performance April 7, 2010, to April 15, 2010

Bin Center (m/s)

Number of Data Points

in Bin

Average Wind Speed

Primary (m/s)

Systematic Deviation

Statistical Deviation

Root-Sum-Square of the Systematic and

Statistical Deviation

6 6 6.37 -0.056 0.007 0.056

7 13 6.76 -0.055 0.006 0.056

8 15 8.01 -0.024 0.010 0.026

9 7 8.76 -0.040 0.008 0.041



3 RESULTS

3.1 Power Performance Test Results The IEC Standard allows for two different methodologies to complete the database requirements. For this test, the alternative database requirements were satisfied where AEP measured was greater than 95% of AEP extrapolated using a Rayleigh wind distribution with an average wind speed of 6 m/s.

3.1.1 Collected Data Table 3-1 details the amount of data collected and the data removed for the specified reasons.

Table 3-1. Collected and Removed Data

Item Data Count

Total Collected Data 35,483

Turbine offline 342

Wind direction outside valid sector 23,157

Temperature out of range 1,787

Icing and Icing recovery 1,316

Manually flagged 4

Signal QC filter 111

Valid Data 7,361

3.1.2 Results As described in Section 2, data were processed into a set of valid data at sea level air density, or 1.255 kg/m3. A scatter plot of the mean power output as a function of wind speed for the valid test database is provided in Figure 3-1 and maximum, minimum, and standard deviation of power output for the turbine is presented in Figure 3-2. Binned and averaged results are summarized in Table 3-2 and displayed graphically in Figure 3-3. The binned and averaged power coefficient is also plotted in Figure 3-4. The AEP calculations are presented in tabular form in Table 3-3 and graphically in Figure 3-5. For the extrapolated AEP, the power value in the last bin meeting the IEC-specified 30 minutes of data is extrapolated to the bins with higher wind speeds where less than 30 minutes of data were collected. Per the definition in the IEC Standard, the measured AEP results are labeled incomplete if they are less than 95% of the extrapolated AEP results.



Table 3-4 provides tabular values of turbulence intensity versus wind speed. Scatter plots of turbulence intensity versus direction and wind speed for valid data are found in Figure 3-6 and Figure 3-7, respectively. A scatter plot of mean wind speed versus direction for valid data is found in Figure 3-8.

-20

0

20

40

60

80

100

120

140

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

Wind Speed (m/s)

Elec

tric

Pow

er (k

W)

Figure 3-1. Scatter Plot of Valid Average Power versus Wind Speed at Sea Level Air Density

(1.225 kg/m3)



-20

0

20

40

60

80

100

120

140

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

Wind Speed (m/s)

Elec

tric

Pow

er (k

W)

Avg

MaxMin

StDev

Figure 3-2. Scatter Plot of Minimum, Maximum, and Standard Deviation of Power versus Wind

Speed at Sea Level Air Density (1.225 kg/m³)



Table 3-2. Measured Power Performance Data Summary–Sea Level Air Density (1.225 kg/m3)

Hub-Height Wind Speed

(m/s)

Power Output (kW)

Power Coefficient

No. of Data Points in Bin

Category A Uncertainty

(kW)

Category B Uncertainty

(kW)

Combined Uncertainty

(kW)

0.22 -0.4 -158.926 3 0.00 0.49 0.49 0.58 -0.5 -10.940 20 0.04 0.46 0.46 1.04 -0.5 -2.119 43 0.03 0.46 0.46 1.54 -0.5 -0.669 99 0.02 0.46 0.46 2.02 -0.5 -0.280 187 0.01 0.46 0.46 2.50 -0.3 -0.086 231 0.02 0.46 0.46 3.00 0.6 0.112 292 0.04 0.51 0.52 3.52 2.3 0.259 370 0.05 0.65 0.65 4.01 4.6 0.345 519 0.05 0.82 0.82 4.50 7.1 0.378 680 0.05 0.94 0.94 5.00 10.4 0.401 602 0.06 1.17 1.18 5.50 14.3 0.413 524 0.08 1.43 1.43 6.00 18.9 0.419 600 0.10 1.76 1.76 6.49 24.4 0.427 559 0.12 2.24 2.25 7.00 30.7 0.430 514 0.15 2.64 2.65 7.51 37.6 0.427 448 0.17 3.02 3.02 8.00 43.9 0.413 403 0.18 3.06 3.07 8.50 51.1 0.400 316 0.22 3.52 3.52 8.98 57.4 0.381 251 0.23 3.46 3.46 9.50 63.8 0.358 188 0.29 3.53 3.54

10.00 69.4 0.334 119 0.41 3.41 3.44 10.49 75.1 0.312 114 0.37 3.67 3.69 10.98 79.2 0.287 100 0.42 3.15 3.17 11.47 84.0 0.267 59 0.49 3.58 3.62 11.98 87.4 0.244 49 0.59 3.05 3.11 12.43 90.7 0.227 30 0.81 3.30 3.40 13.01 95.7 0.209 17 1.29 3.77 3.98 13.55 97.8 0.189 9 2.44 2.88 3.78 13.92 103.6 0.185 8 1.15 6.03 6.14 14.46 104.4 0.166 4 2.60 2.81 3.83 14.81 103.4 0.153 2 N/A N/A N/A 15.40 97.7 0.129 1 N/A N/A N/A

Note: Italicized values are not included in the measured AEP since these bins have fewer than three data points.



-100

102030405060708090

100110120

0 2 4 6 8 10 12 14 16 18 20

Wind Speed (m/s)

Out

put P

ower

(kW

)

Figure 3-3. Summary Plot of Binned Power versus Wind Speed at Sea Level

Air Density (1.225 kg/m3)

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0 2 4 6 8 10 12 14 16 18 20

Wind Speed (m/s)

C p

Figure 3-4. Power Coefficient versus Wind Speed at Sea Level Air Density (1.225 kg/m3)



Table 3-3. Measured and Extrapolated Annual Energy at Sea Level Air Density (1.225 kg/m3)

Hub Height Annual Wind

Speed (Rayleigh) (m/s)

AEP-Measured (measured

power curve) (MWh)

Standard Uncertainty in

AEP-Measured

MWh

Standard Uncertainty

in AEP-Measured

%

AEP Extrapolated (extrapolated power curve)

MWh Complete/ Incomplete

4 83 10.1 12.2% 83 Complete 5 152 13.7 9.0% 154 Complete 6 223 16.5 7.4% 232 Complete 7 279 18.3 6.6% 311 Incomplete 8 314 19.0 6.1% 384 Incomplete 9 329 18.9 5.8% 448 Incomplete

10 330 18.3 5.5% 501 Incomplete 11 321 17.3 5.4% 543 Incomplete

0

100

200

300

400

500

600

4 5 6 7 8 9 10 11

Annual Average Wind Speed (m/s)

MW

h/ye

ar

Sea Level Measured

Sea Level Extrap

Figure 3-5. Annual Energy versus Annual Average Wind Speed at Sea Level

Air Density (1.225 kg/m3)



Table 3-4. Turbulence Intensity versus Wind Speed

Hub-Height Wind Speed

(m/s) Turbulence

Intensity 0.5 0.595

1.0 0.387

1.5 0.284

2.0 0.232

2.5 0.198

3.0 0.176

3.5 0.160

4.0 0.147

4.5 0.135

5.0 0.134

5.5 0.133

6.0 0.140

6.5 0.143

7.0 0.143

7.5 0.142

8.0 0.148

8.5 0.144

9.0 0.148

9.5 0.150

10.0 0.143

10.5 0.142

11.0 0.146

11.5 0.144

12.0 0.147

12.5 0.140

13.0 0.138

13.5 0.134

14.0 0.132

14.5 0.109

15.0 0.156

15.5 0.142



0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

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

Primary Wind Speed (m/s)

Turb

ulen

ce In

tens

ity

10-min. Avg. TI

Binned Avg. TI

Figure 3-6. Turbulence Intensity versus Wind Speed

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

170 180 190 200 210 220 230 240 250 260 270 280 290 300

Wind Direction (deg true)

Turb

ulen

ce In

tens

ity

Figure 3-7. Turbulence Intensity versus Wind Direction



0

2

4

6

8

10

12

14

16

18

170 180 190 200 210 220 230 240 250 260 270 280 290 300

Wind Direction (deg true)

Prim

ary

Win

d Sp

eed

(m/s

)

Figure 3-8. Wind Speed versus Wind Direction

4 REFERENCES

1. Wind turbine - Part 12-1: Power performance measurements of electricity producing wind turbines, IEC 61400-12-1: 2005 (E), International Electrotechnical Commission, Geneva, Switzerland, 2005.


DNV Rpt. No.: PPTR0164 Version: A Date: March 11, 2011 A-1

Appendix A – Site Photo

Photo 1. Valid Sector Topography from the Nacelle


DNV Rpt. No.: PPTR0164 Version: A Date: March 11, 2011 B-1

Appendix B – Met Tower Commissioning Form


DNV Rpt. No.: PPTR0164 Version: A Date: March 11, 2011 C-1

Appendix C – Instrumentation Calibrations


DNV Rpt. No.: PPTR0164 Version: A Date: March 11, 2011

Final Page of Test Report for Project (09-09)

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power performance test report for the northern power ......1 introduction 1.1 scope this report...

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