Wind Turbine Generator System Pika T701 Acoustic Test Report

Transcription

1 Wind Turbine Generator System Pika T701 Acoustic Test Report Conducted by High Plains Small Wind Test Center Colby, KS November 10, 2015 Approval By: Ruth Douglas Miller, Lead Engineer, Date Review By: Arlinda Huskey, NWTC, Date

2 Table of Contents 1 Background Test Summary Test Turbine Configuration Test Site Description Test Equipment Equipment Descriptions Instrument Locations Results Test Conditions Standardized Wind Speed Calculation Apparent Sound Power Level One-Third Octave Analysis Tonality Uncertainty Exceptions Exceptions to the Standard Exceptions to the Quality Assurance System References Appendix A. Calibration Sheets Appendix B. American Wind Energy Association Standard Acoustic Analysis Appendix C Uncertainty Assumptions Appendix D. Pictures List of Figures Figure 1. Pika T701 wind turbine at High Plains Test Center... 6 Figure 2. Wiring diagram of turbine and inverter installation. 6 Figure 3. High Plains SWTC wind rose for May 2014-May Figure 4. Aerial view of the Pika T701 turbine and met tower at the HP test site... 8 Figure 5. Measured and binned sound pressure levels as a function of the standardized wind speed 11 Figure 6. Hub-height sound power levels as a function of the standardized wind speed Figure 7. One-third octave levels (db) vs frequency Figure 8. Classification of spectral lines for tone Figure 9. Classification of spectral lines for tone Figure A1. Calibration sheet for the primary anemometer, p 1 of Figure A2. Calibration sheet for the primary anemometer, p 2 of Figure A3. Calibration sheet for the secondary anemometer, p 1 of Figure A4. Manufacturer specification sheet for the wind vane, p 1 of Figure A5. Manufacturer specification sheet for the wind vane, p 2 of 2 21 Figure A6. Manufacturer specification sheet for the temperature probe, p 1 of Figure A7. Manufacturer specification sheet for the temperature probe, p 2 of Figure A8. Calibration sheet for the pressure transducer Figure A9. Calibration sheet for the power transducer, p 1 of Figure A10. Calibration sheet for the power transducer, p 2 of Figure A11. Calibration sheet for the power transducer, p 3 of Figure A12. Voltage module (temperature & pressure), mfger calibration certificate pg 1 of Figure A13. Current module (for power transducer) mfger calibration certificate pg 1 of

3 Figure A14. NI 9421 digital input module (for both anemometers) mfger data sheet pg 1 of Figure A15. Calibration sheet for the NoiseLab Sound Measuring System, p 1 of Figure A16. Calibration sheet for the NoiseLab Sound Measuring System, p 1 of Figure A17. Calibration sheet for the NoiseLab Microphone Unit, p 1 of Figure A18. Calibration sheet for the NoiseLab Microphone Unit, p 2 of Figure A19. Calibration sheet for the NoiseLab Acoustical Calibrator p 1 of Figure A20. Calibration sheet for the NoiseLab Acoustical Calibrator p 2 of 2 36 Figure D1. Picture of the sound board during the test, 12 March, Figure D2. The test turbine viewed from the reference microphone position, 12 March Figure D3. Test turbine viewed from the met mast, 12 March, Figure D4. Picture of the sound board during the test, 30 March, Figure D5. The test turbine viewed from the reference microphone position, 30 March Figure D6. Test turbine viewed from the met mast, 30 March, List of Tables Table 1. Test Results Summary... 4 Table 2. Pika T701 Wind Turbine General Data... 5 Table 3. System wiring summary 7 Table 4. Sources of Noise Near the Turbine on 12 March, Table 5. Sources of Noise Near the Turbine on 30 March, Table 6. Equipment Used for Acoustic Test... 9 Table 7. Reference Microphone Positions for Turbine and Background Measurements Table 8. Test Parameters Used in Wind Speed Calculations Table 9. Sound Pressure and Power Levels for Standardized Integer Wind Speeds (6 m/s through 11 m/s) Table 10. One-Third Octave Analysis for Wind Speed Bins 6 Through 8 m/s Table 11. One-Third Octave Analysis for Wind Speed Bins 9 Through 11 m/s Table 12. Tonality Results (In dba) Table 13. Type B Uncertainty Components for Sound Power Levels and Tonality Table B1. AWEA Rated Sound Level

4 1 Background The Pika Wind T701 1-kW small wind turbine was tested in accordance with AWEA (American Wind Energy Association) Small Wind Turbine Performance and Safety Standard (AWEA Standard ) and IEC (International Electrotechnical Commission) Standard Wind Turbine Generator Systems - Part 11: Acoustic Noise Measurement Techniques, IEC , Edition 2.1, This test report refers to these procedures collectively as the Standard. Testing of the Pika T701 was conducted under contract as part of NREL s Regional Test Center (RTC) program. 2 Test Summary The Pika T701 is a three bladed, Horizontal Axis Wind Turbine. It has a 3.0-meter rotor diameter resulting in a rotor swept area of 7.1 m2. The data presented in this report was collected during acoustic tests conducted at High Plains Small Wind Test Center in Colby, KS. Testing was conducted on 12 March 2015 and 30 March This test was conducted in accordance with the International Electrotechnical Commission s (IEC) standard, Wind Turbine Generator Systems - Part 11: Acoustic Noise Measurement Techniques, IEC , Edition 2.1, The additional requirements of AWEA (American Wind Energy Association) Small Wind Turbine Performance and Safety Standard (AWEA Standard ) were also considered. Table 1. Test Results Summary Standardized wind speed at 10 m height, Vs [m/s] Power output calculated from power curve {W] Measured pitch angle [ ] Estimated rotor speed [rpm: 42.5 x wind speed] N/A N/A N/A N/A N/A N/A Apparent sound power level [dba] Combined uncertainty in sound power level, UC [dba] Frequency band of most prevalent tone [Hertz (Hz)] Tonality, ΔLk [dba] Tonal audibility, ΔLa,k [dba] NR The difference between total and background noise was less than 3 db. According to Section 8.2 of the Standard, the wind turbine noise was less than the background noise. 3 Test Turbine Configuration The data presented in this report was collected during acoustic tests conducted from 12 March 2015 and 30 March 2015 at the High Plains Regional Test Center (HPRTC) in Colby, Kansas. The Pika Energy T701 model specifications are summarized in Table 2. This turbine will be referred to as the Pika T701 for the rest of this report. A photo of the T701 turbine and met tower is included as Figure 1. 4

5 Table 2. Summary of T701 published specifications. *: rotor diameter was verified manually by measuring the radius of the rotor when it was on the ground. Parameter Value Units Manufacturer and address Pika Energy Inc 35 Bradley Dr Stop 1 Westbrook, ME Turbine Serial Number T Inverter Serial Number X Production Date 2014 Tower Type Tilting Monopole Tower Height 16.8 m Hub Height m Blade make, type, serial number Pika Energy, glass-filled polypropylene, no serial number Turbine Control System Pika Energy proprietary Turbine Interface Pika Energy Review (via inverter) Turbine Type Horizontal axis propeller Number of Blades 3 Rotor Diameter 3.0* m Rotor Swept Area 7.1 m 2 Blade Pitching Fixed, 0.8 at 75% of blade length 11m/s Reference Power (REbus DC) 1.6 kw 11m/s Reference Power (AC after 1.45 kw inverter) Cut-in Wind Speed 3.3 m/s Rated Wind Speed 11 m/s Rated Rotor Speed 420 RPM Speed Regulation Type Stall regulation w/ redundant mechanical brake Yaw Control Passive, upwind with tail IEC Turbine Design Class II Turbine DC Output Voltage (nominal) 380 V Turbine Max Output Current 7 A Inverter Output Voltage 220/240 VAC Inverter Output Current Max 13 A Inverter Output Frequency 60 Hz 5

6 Figure 1. T701 Turbine installed at High Plains Regional Test Center; view west from data shed, met tower behind turbine. A one line diagram of the installation wiring for the turbine is shown in Figure 2. The Pika T701 was connected to the Pika X3001 grid-tie inverter via Pika s REbus DC Microgrid technology (internal to the inverter in Figure 2) operating at approximately 380VDC, in accordance with the Pika T701 installation manual. The Pika X3001 was connected to the electric utility at a nominal voltage of 240VAC and frequency of 60Hz. The inverter electrical connection to the grid was done in accordance with the Pika X3001 Installation manual. Wiring between the tower top and the inverter were provided by Pika Energy and installed as part of the turbine system. Specifications for the installed wires from the tower base control panel to the grid point of common connection (PCC) are listed in Table 3. The total length of the wire run was approximately 65 meters. Figure 2. Wiring diagram of turbine and inverter installation 6

7 Table 3. System wiring summary Segment Type Approx. length Turbine to tower base junction box AWG-12 Type UF, 2 conductor + ground 16.9m Tower base junction box to inverter AWG-12 Type THHN, 2 conductor + 48m, compliant with AWEA ground minimum 8 rotor diameters Inverter to subpanel AWG-12 Type NM-B 2m 4 Test Site Description The test site is located about 1 mile south and two miles west of the town of Colby, KS. It is essentially flat with no obstructions: no site calibration is needed as per Annexes A and B of the Standard. Prevailing winds measured at the test site are from the north in winter, south in summer (see wind rose in Fig. 3); the average wind speed at 30m is over 7 m/s. Figure 4 shows an aerial view of the site, perimeter outlined in red. Figure 7 shows a plot of the turbines, obstacles and data shed positions to scale. The turbine is located 122.3m east and 30m north of the SW corner of the site. Other obstacles on the property include two 3-m tall power poles at (-21.4, 0) and (-13.4, 0), a 3-m tall data shed at (153, 30), the turbine s own met tower (110, 30) and a second wind turbine 30m tall, D=12.75m with its associated met tower, (64, 30) and (32, 30) respectively (measurements in meters east and north of the SW corner.) A dirt road forms the property s southern border; the other borders are farm implement tracks. Exclusion sectors for the Pika T701 are 60 to 120 degrees East of true North: exclusion for the wake of the turbine on its own met tower; and 238 to 301 degrees East of true North: exclusion for neighboring turbine and associated met, and two power poles on-site. The data shed does not impose exclusion sectors. A summary of the test site conditions is listed in Table 6. Note the turbine-to-met-tower distance is 0.3m greater than the 2-4D standard requirement; see Fig. 12, p. 16, and Deviations and Exceptions, p. 30. Figure 3. High Plains SWTC wind rose for May 2014-May

8 Figure 4. Aerial view of the Pika T701 and its met tower at the test site. Red circle: Pika met. Green circle: Pika tower. Blue boxes: data shed and transformer pad. Green arrow from turbine to data shed: 30.5m. From met to turbine: 12.3m center-to-center. Table 4. Sources of Noise Near the Turbine: Data collected 12 March 2015 Designation Bearing from Sound Distance from Height Width Meas. Board Sound Meas. Board [ True] [m] [m] [m] Prevailing Wind Direction 210 NA NA NA Met Tower Data Shed Neighboring Turbine Neighboring Met Tower (guyed tower) Table 5. Sources of Noise Near the Turbine: Data collected 30 March 2015 Designation Bearing from Sound Distance from Height Width Meas. Board Sound Meas. Board [ True] [m] [m] [m] Prevailing Wind Direction 322 NA NA NA Met Tower Data Shed Neighboring Turbine Neighboring Met Tower (guyed tower)

9 5 Test Equipment 5.1 Equipment Descriptions All test equipment is listed in Table 6 and was calibrated except the temperature sensor (see Exceptions); calibration sheets are included in Appendix A. Table 4 shows the equipment used and calibration due dates. Figure 8 shows placement of the meteorological instruments on the met mast (note that the pressure transducer is located near the base of the met mast). The temperature probe on the met mast employs a radiation shield. Acoustic data was collected and partly analyzed using NoiseLAB with a patch upgrade to Further analysis was conducted using NoiseLAB Batch Processor The microphone system was calibrated prior and subsequent to each data collection session using a calibrator that conforms to IEC Class I. The meteorological Data Acquisition System is comprised of National Instruments modules and LabVIEW programming. The National Instruments cards and chassis were located in the site s data shed, as was the computer running LabVIEW. End to end checks were conducted on all non acoustic data channels and results are reported in the turbine commissioning report. The acoustic data collection system was calibrated at the start of each measurement period. All measurement periods were an average of approximately 25 minutes with either the turbine operating or not operating (for background noise measurements). The longest measurement period was approximately 85 minutes with all turbines on the site parked for collection of background data. Table 6. Equipment Used for Acoustic Test Channel Instrument Make & Model Mfger Accuracy Calibration Dates Primary wind NRG 1 st Class +/-0.06 Anemometer speed Ser # m/s 3 Dec, 2013 Turbine power Ohio Semitronics PC5-059EY25 +/-0.5% of full AC Watt transducer output Ser # scale 23 Oct, 2013 Wind direction Wind Vane NRG #200P 1% N/A Turbine Status Internal to Pika Inverter Download from Pika web server Reference wind speed Anemometer NRG #40H: Ser. # % 3 Dec, 2013 Air Pressure Pressure sensor NRG BP20: Ser. # / kpa 15 Nov, 2010 Air Temperature Temperature sensor NRG #110S: Ser. #3365 +/- 1.1 C max Rain Wetness sensor Novalynx Rotor speed Not available Not available N/A Microphone BSWA Tech Model MPA 211: # Jan, 2014 Microphone Unit Bruel & Kjaer Type 4189 A Jan, 2014 Acoustic Calibrator BSAW CA111: # Jan, 2014 DAS NI 9205 (voltage: WS channel) 3,230 μv 28 Oct.,

10 DAS NI /-0.18% slope +/-0.06% offset 28 Oct., 2013 DAS NI 9421 digital negligible 5.2 Instrument Locations The primary anemometer on the meteorological tower was used to derive the standardized wind speed. This tower was located 12.3 m from the test turbine, at a bearing of 270 E of true north, with the anemometer at a height of 16.9 m. The wind vane was mounted at a height of m on the meteorological tower. The turbine tower center was 4.1 rotor diameters from the meteorological tower center, 0.3m greater than the 2-4D standard requirement; see Deviations and Exceptions. Table 7 provides the location of the microphone for the measurement sessions. Table 7. Reference Microphone Positions for Turbine and Background Measurements on 12 March, 2015 and 30 March, 2015 Reference Location (H+D/2) Minimum distance Maximum distance Actual Microphone Location Allowable Measurement Tolerance [m] [m] [m] [m] [m] ± Results 6.1 Test Conditions The analysis was done using the measured wind speed and 10-second averages of the data. The range of standardized wind speeds and wind directions used for the analysis were 4.5 to 12.5 m/s and 195 to 337 east of true north, respectively. The range of temperature and pressure were 16.5 C to 27.3 C and 91.1 kpa to 94.5 kpa, respectively. 6.2 Standardized Wind Speed Calculation Standardized wind speed, Vs, was calculated using Equation 1 below (eq. 7 in the Standard) and the values in Table 8, where Vz is the measured wind speed. 10

11 Table 8. Test Parameters Used in Wind Speed Calculations Parameter Symbol Value Hub height (m) H 16.9 Roughness length (m) z Anemometer height (m) z 16.9 Reference roughness length (m) z 0ref 0.05 Reference height (m) z ref Apparent Sound Power Level Sound pressure levels were binned by wind speed. Integer wind speeds values were calculated using interpolation between bins and extrapolation at the ends. The sound pressure levels were then background-corrected according to the Standard. Figure 3 shows the scatter plot of the sound pressure levels of the validated total (operating plus background) and background noise, along with the binned sound pressure levels. The measured and background corrected apparent sound pressure level at standardized wind speeds of 6 through 11 m/s are shown in Table 9, along with the calculated sound power levels. Figure 4 shows the sound power levels graphed against the standardized wind speed. 60 Measured Sound Pressure Level vs. Wind Speed 55 Sound Pressure Level dba Turbine Data Background Data Binned BG corrected Total Binned Total Binned Background Standardized Wind Speed m/s Figure 5. Measured and binned sound pressure levels as a function of the standardized wind speed 11

12 Table 9. Sound Pressure and Power Levels for Standardized Integer Wind Speeds (6-11 m/s) Wind Speed Bin [m/s] Total Sound Pressure Level [dba)] Background Sound Pressure Level [dba] Background Corrected Sound Pressure Level [dba] Sound Power Level [dba] Type A Uncert. [dba] Type B Uncert. [dba] Combined Uncert. [dba] sound power level dba Sound Power Level standardized wind speed m/s Figure 6. Hub-height sound power levels as a function of the standardized wind speed, with uncertainty. 6.4 One-Third Octave Analysis One-third octave levels were analyzed at standardized wind speeds of 6, 7, 8, 9, 10, and 11 m/s. The results are provided in Tables 10 and 11, and Figure 5. Table 10. One-Third Octave Analysis for Wind Speed Bins 6 Through 8 m/s Center Frequency 6 m/s One-Third Octave Levels 7 m/s One-Third Octave Levels [Hz] [dba] [dba] [dba] 20 NR NR NR 25 NR NR NR 31.5 NR NR NR 12 8 m/s One-Third Octave Levels

13 40 NR NR NR 50 NR NR NR 63 NR 27.4±2.6* NR ±2.4* NR NR ± ±2.1* 29.1±2.0* ± * 33.3± ±2.8 NR 30.1±2.1* ± * 37.2± ±2.3 NR 37.4± ± ±2.1* 35.3±2.0* ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±2.0* 33.4± ±2.1* 28.9±2.0* 30.6±2.1* ±2.0* NR 28.4±2.0* 8000 NR NR NR NR NR NR * The difference between total and background noise was less than 6 db but greater than 3 db. A standard background correction of 1.3 db was applied according to Section 8.2 of the Standard. NR The difference between total and background noise was less than 3 db. According to Section 8.2 of the Standard, the wind turbine noise was less than the background noise. Table 11. One-Third Octave Analysis for Wind Speed Bins 9 Through 11 m/s Center Frequency 9 m/s One-Third Octave Levels 10 m/s One-Third Octave Levels [Hz] [dba] [dba] [dba] 20 NA 16.5±2.1* 20.1±2.3* 25 NA 20.0±2.2* 24.0± NA 22.3±2.1* 25.9±2.3* 40 NA NA 27.9±2.3* 50 NA NA 29.1±2.3* 63 NA NA NA 80 NA NA NA 100 NA NA NA 125 NA NA NA 160 NA NA NA 11 m/s One-Third Octave Levels 13

14 200 NA NA NA 250 NA NA NA 315 NA NA NA ±3.2 NA 42.2±2.3* ±2.2 NA 41.8±2.1* ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±2.0* 35.1±2.0* 36.3±2.0* 5000 NA NA NA 6300 NA NA NA 8000 NA NA NA NA NA NA * The difference between total and background noise was less than 6 db but greater than 3 db. A standard background correction of 1.3 db was applied according to Section 8.2 of the Standard. NR The difference between total and background noise was less than 3 db. According to Section 8.2 of the Standard, the wind turbine noise was less than the background noise. 60 Sound Pressure Level (dba) Hz 25 Hz 31.5 Hz 40 Hz 50 Hz 63 Hz 80 Hz 100 Hz 125 Hz 160 Hz 200 Hz 250 Hz 315 Hz 400 Hz 500 Hz 630 Hz 800 Hz 1000 Hz 1250 Hz 1600 Hz 2000 Hz 2500 Hz 3150 Hz 4000 Hz 5000 Hz 6300 Hz 8000 Hz Hz frequency (Hz) 5 m/s 6 m/s 7 m/s 8 m/s 9 m/s 10 m/s 11 m/s Figure 7. Bar graph: 1/3-octave levels (db) vs frequency 14

15 6.5 Tonality During observation of the turbine in all wind speeds, no prominent tones or changes in sound were noticed. The turbine does not furl or adjust blade pitch, so no physical changes at higher wind speed would cause a change in associated noise. While it whirrs more loudly at high wind speed, the turbine does not make sounds markedly different at any particular wind speed or range of wind speeds. The tonality analysis resulted in reportable tones for xx m/s, as shown in Table 12. Figure 6. Classification of spectral lines for the 3,849 Hz tone (typical in the 10 m/s bin) Figure 7. Classification of spectral lines for the 3,921 Hz tone (typical in the 11 m/s bin) 6.6 Uncertainty The type A uncertainties for sound power levels, one-third octave levels, and tonality were calculated using the methods prescribed in the Standard. The type B uncertainty components are shown in Table 13. Var Table 13. Type B Uncertainty Components for Sound Power Levels and Tonality Description Type B Uncertainty for Sound Power Level (SPL) dba Type B Uncertainty for 1/3 Octave Levels (TOB) dba Type B Uncertainty for Tonality dba Comment UB1 Calibration Assumption; some instruments out of cal so used high value UB2 Instrument Assumption, used typical value UB3 Board The board was placed well and used the typical value UB4 Distance Assumption, used typical value UB5 Impedance Assumption, used typical value UB6 Turbulence Assumption, used typical value Calculated per IEC Ed. UB7 Wind speed, Varies with Varies with wind Varies with 1.0, , and converted to dba measured wind speed speed wind speed for SPL and TOB. Typical value for tonality UB8 Direction Assumption, used typical value UB9 Background Varies with wind speed Varies with wind speed and onethird octave center frequency bin Varies by tone Difference between measured bin center SPL and backgroundcorrected bin center SPL 15

16 7 Exceptions 7.1 Exceptions to the Standard The analysis prescribed in the standard was altered for the small wind turbine by using 10-second averages instead of 1-minute averages to better characterize the dynamic nature of this turbine. In addition, binning by wind speed was used instead of regression analysis, and the integer values were calculated by interpolating between bins and extrapolating at the ends. 7.2 Exceptions to the Quality Assurance System The primary anemometer and data acquisition modules were used past the calibration due dates. The instruments and modules were post-test calibrated. The anemometer and modules were found to be within tolerances. References International Electrotechnical Commission (IEC). (2006). Wind Turbine Generator Systems Part 11 Acoustic Noise Measurement Techniques, IEC , Ed 2.1, , Geneva, Switzerland. 16

17 Appendix A - Calibration Data Sheets for Pika T701 Test Instruments Primary Anemometer Pre-Test Calibration Figure A1. Primary anemometer manufacturer calibration sheet pg 1 of 2. 17

18 Figure A2. Primary anemometer manufacturer calibration sheet pg 2 of 2. 18

19 Secondary Anemometer Figure A3. Secondary anemometer 3 rd -party calibration sheet pg 1 of 1. 19

20 Wind Direction Vane Figure A4. Wind direction vane manufacturer specification sheet pg 1 of 2. 20

21 Figure A5. Wind direction vane manufacturer specification sheet pg 2 of 2. 21

22 Temperature Probe Figure A6. Temperature probe manufacturer specification sheet pg 1 of 2. 22

23 Figure A7. Temperature probe manufacturer specification sheet pg 2 of 2. 23

24 Pressure Transducer Figure A8. Pressure transducer manufacturer calibration sheet pg 1 of 1. 24

25 Power Transducer Figure A9. Power transducer manufacturer calibration sheet pg 1 of 3. 25

26 Figure A10. Power transducer manufacturer calibration sheet pg 2 of 3. 26

27 Figure A11. Power transducer manufacturer calibration sheet pg 3 of 3. 27

28 DAS Boards Figure A12. Voltage module (for temperature & pressure), manufacturer calibration certificate pg 1 of 1. 28

29 Figure A13. Current module (for power transducer) manufacturer calibration certificate pg 1 of 1. 29

30 Figure A14. NI 9421 digital input module (for both anemometers) manufacturer data sheet pg 1 of 9. Remaining pages available on request. 30

31 Figure A15. Calibration certificate for NoiseLab Sound Measuring System p 1 of 2. 31

32 Figure A16. Calibration certificate for NoiseLab Sound Measuring System p 2 of 2. 32

33 Figure A17. Calibration certificate for NoiseLab Microphone Unit p 1 of 2. 33

34 Figure A18. Calibration certificate for NoiseLab Microphone Unit p 2 of 2. 34

35 Figure A19. Calibration certificate for NoiseLab Acoustical Calibrator p 1 of 2. 35

36 Figure A20. Calibration certificate for NoiseLab Acoustical Calibrator p 2 of 2. 36

37 Appendix B. American Wind Energy Association Standard Acoustic Analysis The American Wind Energy Association (AWEA) standard requires that the wind turbine sound levels be measured and reported in accordance with the IEC standard, and includes the following modifications: Using a 10-second averaging period Using the measured wind speed Using the method of bins Covering a wide wind speed range as possible Describing any obvious changes in sound at high wind speeds Reporting the AWEA Rated Sound Level. The data were collected at one-second intervals and averaged by the data acquisition systems (NoiseLab for acoustic measurements and the Labview VI for all other measurements) to 10-second intervals. To ensure that the acoustic data were collected downwind from the turbine, the wind direction was filtered to assure that the measurement board was within 15 degrees of the downwind position. The data were also filtered by the provided status to determine the total (operating plus background), background, and interrupted/excluded data. The data were binned by the standardized wind speed into 1m/s wind speed bins centered on the integer wind speed. The bin centers were calculated by interpolation (and extrapolation at the ends). The AWEA Rated Sound Level is defined as: the sound level that will not be exceeded 95% of the time (assuming an average wind speed of 5 m/s); a Rayleigh wind speed distribution; 100% availability; and an observer location that is 60 m from the rotor center. This requirement defines the AWEA wind speed to be 9.8 m/s at hub height. The total and background noise for 9.8 m/s were obtained by interpolation between the 9 and 10 m/s binned values. The two values are used to obtain the background corrected sound pressure level. Next, the sound power level is calculated at the hub by adding a correction for hub height. The AWEA Rated Sound Level is then calculated by subtracting the 60-m distance correction: L AWEA = L 9.8m + 10 log (4 π ) 10 log (4 π 60 2 ) where L 9.8m is the background-corrected sound pressure level at the microphone at 9.8 m/s hub-height wind speed, 22.59m is the slant distance in meters from the hub to the ground, and the reference crosssectional area of the sound pressure is 1m 2. Hub height being 16.94m and microphone distance 14.94m, the slant distance 22.59m = ( ). Table B1. AWEA Rated Sound Level AWEA Rated Sound Level dba Combined Uncertainty dba

38 Appendix C. Uncertainty Calculations Type B uncertainty values are described in Section 6; UB7a, the wind speed uncertainty, is further described below. Type A uncertainty was calculated thus: the deviation of sound pressure level of each measurement point from the average sound pressure level within its 1-m/s wind speed bin was squared, and these numbers were summed within each wind speed bin. The square root of the sum divided by the number of data points less two is equal to the type A error: UA = ( (SPLavg SPLmeas) 2 /(N 2). The same formula was used for 1/3-octave uncertainty. The wind speed uncertainty was calculated using the same formula used for this uncertainty in the power performance report. The values below are: n= wind speed bin; U = operational characteristic error. Calibration and mounting effects are each 0.01; terrain effect is 0.02, and error from the digital data acquisition system is assumed negligible. All these errors are squared and summed; the square root of the result is multiplied by the sensitivity factor which is the difference in sound pressure levels between adjacent wind speed bins divided by the difference in wind speeds. UB7a = U(n) + ( ) U(n) 2 SPL(n) SPL(n 1) U(n) U(n 1) 38

39 Appendix D. Pictures Figure D1. Picture of the sound board during the test 12 March,

40 Figure D2. The test turbine as viewed from the reference microphone position 12 March

41 Figure D3. The test turbine as viewed from the meteorological mast 12 March

42 Figure D4. Picture of the sound board during the test 30 March,

43 Figure D5. The test turbine as viewed from the reference microphone position 30 March 2015; met mast to left. 43

44 Figure D6. The test turbine as viewed from the meteorological mast 30 March