fortis wind turbine acoustic noise report

3933 US Route 11 Cortland, NY 13045 Telephone: (607) 753-6711 Facsimile: (607) 753-1045 www.intertek.com

of 35 This report is for the exclusive use of Intertek’s Client and is provided pursuant to the agreement between Intertek and its Client. Intertek’s responsibility and liability are limited to the terms and conditions of the agreement. Intertek assumes no liability to any party, other than to the Client in accordance with the agreement, for any loss, expense or damage occasioned by the use of this report. Only the Client is authorized to permit copying or distribution of this report and then only in its entirety. Any use of the Intertek name or one of its marks for the sale or advertisement of the tested material, product or service must first be approved in writing by Intertek. The observations and test results in this report are relevant only the sample tested. This report by itself does not imply that the material, product or service is or has ever been under an Intertek certification program.

Intertek Testing Services NA, Inc. SD 12.1.2 (11/11/10) Informative

April 23, 2012 Intertek Test Report No. 100146060CRT-002 Project No. G100146060 Johan Kuikman Phone: 310505515666 Fortis Wind Energy BV Aduarderdiepsterweg 9b email: [email protected] 9475-EL-HOOGKERK Netherlands Subject: Acoustic noise emission test report for the Fortis Wind Energy Montana 5 kW grid-tied horizontal axis

wind turbine tested at the Intertek Small Wind Turbine Regional Test Center (RTC). Dear Ms. Huskey, T This Test Report represents the results of the evaluation and tests of the above referenced equipment under Intertek Project No. G100146060, as part of the US Department of Energy and National Renewable Energy Laboratory (DOE/NREL) Subcontract Agreement No. AEE 0-40878-02, to the requirements contained in the following standard:

IEC 61400-11 Wind Turbine Generator Systems – Part 11: Acoustic Noise Measurement Techniques Edition 2.1, November 2006.

This investigation was authorized by signed proposal number Q500233379, May 25, 2010. A production sample was installed at the Intertek RTC on January 14th, 2011. Acoustic noise measurements were taken on four separate days in April and May of 2011. This Test Report completes the acoustic testing phase of the Fortis Montana under Intertek Project No. G10014606. If there are any questions regarding the results contained in this report, or any of the other services offered by Intertek, please do not hesitate to contact the signatories on this report. Please note, this Test Report on its own does not represent authorization for the use of any Intertek certification marks.

Completed by: Joseph Spossey Reviewed by: Tom Buchal Title: Project Engineer Title: Senior Staff Engineer

Signature:

Signature

Fortis Wind Energy BV Test Report No. 100146060CRT-002 April 23, 2012

of 35 Intertek Testing Services NA, Inc. SD 12.1.2 (11/11/10) Informative

Wind Turbine Generator System Acoustic Noise Emissions Test Report

for the

Fortis Wind Energy Montana at

Intertek Small Wind Regional Test Center



1.0 Background This test is conducted as part of the DOE/NREL Subcontract Agreement No. AEE-0-40878-02 for the testing of small wind turbines at regional test centers. The Fortis Wind Energy, B.V., Montana Wind Energy System was accepted into this program by Intertek and DOE/NREL. The full scope of type testing provided by Intertek for the Fortis Montana horizontal-axis wind turbine is covered by this agreement. This Test Report is a summary of the results of acoustic noise emission testing, and is one of four tests to be performed on the Fortis Montana turbine; the other three being duration, safety and function, and power performance. Results for these other tests are summarized in their respective Test Reports. The Fortis Montana turbine is installed at Test Station #2 at the Intertek RTC in Otisco, NY. The Fortis Montana is designed for grid-connected power delivery, with a maximum power output of 5 kW. It is classified as a Class II upwind direct drive turbine with speed and power control through horizontal furling and electric dampening. The Fortis Montana has a three-phase brushless variable speed generator with permanent magnet excitation that is rated for operation at 220V. The turbine system has multiple output configurations; for testing at the Intertek RTC, the output and grid interconnect is provided by a WB5000-US “WindyBoy” inverter at 240V single phase. The tower and foundation were designed and approved by Nello Corporation. The designs were based off of the Subsurface Investigation and Geotechnical Evaluation detailed in Atlantic Testing Laboratories report number CD3119E-01-05-10. The electrical network at the testing location is single/split phase 120/240 VAC at 60 Hz. Refer to the wiring diagrams in Appendix B for additional detail. A summary of the test turbine configuration and manufacturer’s declared ratings can be found in Table 1 below.

2.0 Test Objective The purpose of the acoustic test is to characterize the noise emissions of the Fortis Wind Energy Montana. This involves using measurement methods appropriate to the noise emission assessment at locations close to the turbine, in order to avoid errors due to sound propagation, but far enough away to allow for the finite source size. The evaluation herein characterizes the wind turbine noise with respect to a range of wind speeds and directions. Characterizations of the turbine’s apparent sound power level, 1/3 octave bands, and tonality are made.

3.0 Test Summary Testing and analysis of the Fortis Wind Energy Montana was performed in accordance with the edition 2.1 of IEC 61400-11. Method 2 for the direct measurement of wind speed was employed versus determination of wind speed from the measured power curve. This method was chosen due to the ability to accurately measure wind speed at hub height because of the meteorological tower installed per IEC 61400-12-1 Power Performance Measurements of Electricity Producing Wind Turbines. Figure 1 below is the summary of results from the acoustic noise test conducted on the Fortis Montana turbine. In Figure 1, wind speed is standardized to reference conditions at 10 m above ground level and a roughness length of 0.05 m. The amount of test data analyzed to produce Figure 1 is sufficient to meet the database requirements of the Standards.



Figure 1 – Acoustic noise test results summary



Turbine manufacturer Fortis Wind Energy B.V. Model Montana Rated Electrical Power (kW) 5.0 kW Rotor Diameter (m) 5.0 m (16.4 ft.) Verified by Intertek as 5.0419 m (16 ft 6.5 in)

Hub Height (m) 36.8 m (120 ft 9 in)

Swept Area (m 2) 19.63 m2 (211.3 ft2) Distance from rotor centre to tower axis 0.43 m (1 ft 5 in) Tower Type(s) Lattice IEC 61400-2 SWT Class (I, II, III, or IV) II Cut-in Wind Speed 2.5 m/s (5.6 mph) Rated Wind Speed 12 m/s (26.8 mph) Survival Wind Speed 60 m/s (134 mph)

Generator identification Fortis / Inensus 5 kW Serial # 100709

Generator specifications 5 kW, 220 VAC, 50 Hz 3-phase, 350 RPM

Inverter identification SMA, Windy Boy WB5000US Serial #: 2001308424

Inverter specifications 5000 W, 240VAC Single phase, 60 Hz UL 1741 Listed

Rectifier/Controller identification Windy Boy, WBP-Box 500 Serial #: 1290001136

Rectifier/Controller specifications Inputmax – 3 phase 440 VAC, 11.5 A

Outputmax – 500 VDC, 30 A IP54 Outdoor (mounted indoors)

Diversion load identification Heine Resistors, RFB 6-7 Serial #: 024261020003c

Diversion load specifications 6kW, 42 Ω ± 10%, IP 23 (mounted outdoors)

Active brake switch identification Inensus Serial #: 0191002003

Active brake switch specifications 400 V, 15 A IP40 (mounted indoors)

Blade identification Fortis Serial #s: 3311, 3312, 3313

Blade specification Fiberglass epoxy, NACA 4415 airfoils Rotor speed range (rpm) 20 – 450 Fixed or variable pitch Fixed Number of Blades 3 Blade Tip Pitch Angle (deg) 10°

Table 1 – Test turbine configuration and manufacturer’s declared specifications

4.0 Engineering Judgments or Deviations A linear regression was used for the determination of the background sound pressure levels, as opposed to the 4th order regression mentioned in the Standard. No added uncertainty is necessary to be added resulting from this deviation, as the linear regression showed a higher correlation to the measured data pairs of background noise data.



5.0 Test Site Description The RTC has class IV winds, and can accommodate turbines that produce 120V or 240V, 60 Hz power. It is on a hilltop, with previous agricultural land use, near the township of Otisco, NY. It was surveyed, analyzed and developed to be a test site for Intertek’s customers. The Fortis Montana is installed and tested at RTC test station #2, which has no prominent obstructions to the east, south, or west as determined by obstacle assessment in accordance with the first edition of IEC 61400-12-1 Wind Turbines – Part 12-1: Power performance measurements of electricity producing wind turbines, dated December 2005. The roughness length of the test location is estimated at 0.05 meters for farmland with some vegetation. This value is given in Table 1 of IEC 61400-11. The meteorological equipment tower is located due south of the turbine, 41 ft from the turbine, exactly 2.5 times the diameter of the rotor. Figure 2 below shows the layout of the RTC and identifies the test location in the red box. The elevation data points are plotted in 10 meter intervals. Figure 3 below shows a zoomed view of the turbine and meteorological tower locations. The Fortis Montana was the only turbine installed at the RTC over the duration of this test; therefore no turbines were in operation during the measurement program.

Figure 2 - Intertek RTC topographical survey



Figure 3 below shows the location of the Fortis Montana and its measurement tower (“Met2”).

Figure 3 - Fortis Montana and meteorological tower (Met2) locations

The Fortis Montana turbine was the only turbine installed at the RTC during the measurement period; therefore no turbines were in operation during the measurement program. The only noise source identified during the measurement period was the interstate that runs north-south in the valley 2.5 miles to the east of the test site. The background noise generated is consistent in all recordings and has no effect on turbine noise data as it is removed in background correction in accordance with the Standard.



6.0 Test Equipment The test equipment utilized during the acoustic noise measurement program can be found in the Appendix. The meteorological equipment utilized during this test program is in compliance with the IEC 61400-12-1. Figure 4 below identifies meteorological equipment locations on the meteorological mast. Calibration certifications of all equipment used during testing are kept on file in the Intertek project file.

Figure 4 – Instrument locations on the meteorological mast



7.0 Test Procedure 7.1 General The general method applied during this test program directly follows the method described in IEC 61400-11:2006. The main purpose is to provide apparent A-weighted sound power levels and spectra at integer wind speeds from 6 to 10 m/s. As mentioned in Section 3.0 above, the only deviation from the standard is that Method 2, which is also described in the standard, was followed. Method 2 allows for direct measurement of wind speed by an anemometer, versus the determination of wind speed from the measured power curve. This is Intertek’s preferred method, considering all meteorological measurements are being taken by the met tower per the power performance test requirements. Correction to reference conditions was carried out per the standard. Acoustic noise data was gathered on four separate days during the months of April and May in 2011. On all four days, winds were primarily out of the South, ranging from 156° to 232° with respect to true North. Me teorological and wind turbine data has been gathered continuously since commissioning of the Montana on February 4th, 2011. The anemometer for wind speed measurement was located at 36.043 m (118 ft 3 in) above ground level. Table 2 below shows the date, time, microphone location, and allowable wind sector for each day acoustic measurements were taken.

Date Start Time

End Time

Microphone Location Horizontal Distance Allowable

Sector 22-Apr-11 12:29:00 16:34:00 334° 39 m (128 feet) 13 9° to 169° 27-Apr-11 14:20:00 15:55:00 358° 39 m (128 feet) 16 3° to 193° 13-May-11 12:20:00 17:00:00 346° 39 m (128 feet) 15 1° to 181° 26-May-11 12:15:00 13:42:00 46° 39 m (128 feet) 211 ° to 241°

Table 2 – Acoustic measurement information 7.2 Measurements and procedures 7.2.1 Measurement positions In order to fully characterize the noise emissions of the Fortis Montana, the following measurement positions are required. 7.2.1.1 Acoustic measurement position Only the required reference microphone location, as defined in Figure 5 below, is used for the acoustic measurement location. The direction of the position is accurate within ±15° relative to the wind direction at the time of measurement. The horizontal distance from the wind turbine tower vertical centreline to the reference microphone position, R0, was determined using Equation 1 below. In Equation 1, D is the diameter of the turbine and H is the hub height of the turbine. Using the specified tolerance of 20%, this requires the reference microphone location to be within the range of 32.5 m to 48.7 m (106.5 ft to 159.8 ft).

Equation 1 Calculating R0 according to Equation 1 results in a length of 40.6 m (133.17 ft). At 40.6 m the inclination angle φ was greater than 40°, and thus outside of the requi red range of 25° to 40°. In order to obtain an inc lination angle of 39° a reference microphone distance of 146 feet was needed. This value is within the allowable range mentioned above.



To minimize influence due to the edges of the reflecting board on the measurement results, the board was positioned flat on the ground. The edges and gaps under the board were levelled out by means of sand.

Figure 5 – Standard pattern for microphone measurement positions (plan view)

Source: IEC 61400-11: Edition 2.1, November 2006 7.2.1.2 Wind speed and direction measurement positi on The test anemometer and wind direction transducer are the same instruments mounted on the permanent meteorological mast for power performance testing according to the first edition of IEC 61400-12-1 Wind turbines – Part 12-1: Power performance measurements of electricity producing wind turbines, dated December 2005. The location of the instrumentation on the permanent meteorological tower is shown in Section 6 above. The sensors are installed at locations that are compliant with the requirements of the Standards. Method 2 of IEC 61400-11 is used for the direct measurement of wind speed by the anemometer on the permanent meteorological tower. Figure 6 below was used to determine the acceptability of the permanent meteorological tower location. Given that the anemometer is mounted at the same hub height as the turbine, the angle β as defined in Figure 6 is 90°.



During the measurement periods identified in Table 2, the anemometer was not in the wake of any portion of any other wind turbine or structure.

Figure 6 – Allowable region for meteorological mast position as a function of β (plan view)

Source: IEC 61400-11: Edition 2.1, November 2006 7.2.2 Acoustic measurement procedures Acoustic measurements at wind speeds up to 15 m/s at hub height were made for the purpose of determining apparent sound power levels, one-third octave band levels, and the presence of any tonal characteristics. For all acoustic measurements taken during the periods indicated in Table 2 above, the following considerations apply:

The complete measurement chain was calibrated at least at one frequency before and after the measurements, or if the microphone was disconnected during repositioning

All acoustical signals were recorded and stored for later analysis Periods with intruding intermittent background noise (as from an aircraft) were omitted from the database With the wind turbine stopped, and using the same measurement setup, the background noise was

measured immediately before or after each measurement series of wind turbine noise and during similar wind conditions

The equivalent continuous A-weighted sound pressure level and one-third octave band spectrum were measured at the microphone locations described in Table 2 above. Each measurement for A-weighted sound pressure level and one-third octave band spectrum was integrated over a period of 1 minute for both turbine and background



noise, as this is the required averaging interval of the Standard. One-third octave bands with centre frequencies ranging from 20 Hz to 16 kHz were recorded, but values centred on 50 Hz to 10 kHz are reported per the requirements of the standard. A minimum of 3 measurements within ±0.5 m/s at each integer wind speed were required for both sound pressure and one-third octave analysis. 7.2.3 Non-acoustic measurements Wind speed was determined according to Method 2 of the IEC 61400-11 standard, for the determination of wind speed with an anemometer. This is the preferred method for analysis in compliance with the Standards. The wind speed measurement results were adjusted to a height of 10 m and the reference roughness length of 0.05 m as described in section 7.3 below. Direct measurement of wind speed by an anemometer was used for both turbine plus background noise and background noise measurements. Wind speed data was averaged over a 1 minute period to align with the averaging of acoustic measurements. Wind direction was measured by a wind direction vane to ensure that measurement locations are kept within 15° of nacelle azimuth positions with respect to upwind, and to measure the position of the anemometer. Wind direction was also averaged over a 1 minute period. Air temperature and pressure were measured and recorded according to the requirements of IEC 61400-12-1. For purposes of development of this Test Report, temperature and pressure was also averaged over a 1 minute period. 7.3 Data reduction procedures 7.3.1 Wind speed The wind speeds measured at the anemometer on the meteorological mast were corrected to wind speeds at reference conditions, Vs, using Equation 2 below:

Equation 2 Where: z0ref is the reference roughness length of 0.05 m; z0 is the roughness length; H is the rotor centre height; zref is the reference height, 10 m; z is the anemometer height. Equation 3 uses the following principles:

The correction for the measured height to the rotor centre height uses a logarithmic wind profile with the site roughness length z0 to account for the actual site conditions.

The correction from rotor centre height to reference conditions uses a logarithmic wind profile with a reference roughness length z0ref. This describes the noise characteristic independent of the terrain.

The roughness length z0 was estimated according to Table 1 of the IEC 61400-11 standard. A roughness length 0.05 m was used for the Intertek RTC.



7.3.2 Correction for background noise All measured sound pressure levels were corrected for the influence of background noise. For average background sound pressure levels that are 6 dB or more below the combined level of wind turbine and background noise, the corrected value was obtained using Equation 3 below:

Equation 3 Where: Ls is the equivalent continuous sound pressure level, in dB, of the wind turbine operating alone; Ls+n is the equivalent continuous sound pressure level, in dB, of the wind turbine plus background noise; Ln is the background equivalent continuous sound pressure level, in dB. Where the equivalent continuous sound pressure level of the wind turbine plus background noise was less than 6 dB but more than 3 dB higher than the background level, the correction is by subtraction of 1.3 dB and marked with an asterisk, “ * “. These data points are not used for the determination of apparent sound power level. If the difference is less than 3 dB, no data points are reported, but it will be reported that the wind turbine noise level was less than the background noise level. 7.3.3 Apparent sound power level and one-third octa ve band Apparent sound power level is determined by 4th order regression, as required by the Standard, and is based upon the noise emissions from the wind turbine at the integer wind speeds 6, 7, 8, 9 and 10 m/s. A 4th order regression is used when the correlation coefficient is 0.8 or greater. Turbine noise emissions were measured at the reference position by a series of at least 30 measurements concurrent with measurements of the wind speed. Background noise emissions were measured immediately before or after turbine noise in similar environmental conditions, and also for a period of at least 30 minutes. Data was integrated over a period of1 minute. At least three measurements of both turbine noise and background noise were required to be within ±0.5 m/s of each integer wind speed. The regression is performed on both turbine noise and background noise separately. Once equivalent continuous sound pressure levels of turbine noise and background noise are determined at the integer wind speeds, they are corrected as described in Section 7.3.2 above. The apparent sound power level, LWA,k, at the integer wind speeds is calculated using Equation 4 below and from the background corrected sound pressure level, LAeq,c,k, as defined as Ls in Equation 3 above:

Equation 4 Where: LAeq,c,k is the background corrected A-weighted sound pressure level at the integer wind speeds and

under reference conditions; R1 is the slant distance in meters from the rotor centre to the microphone; S0 is a reference area, S0 = 1 m2. The 6 dB constant in Equation 4 accounts for the approximate pressure doubling that occurs for the sound level measurements on a ground board. One-third octave band levels of the wind turbine noise are also corrected for the corresponding one-third octave band levels of background noise according to the procedure detailed above.



7.3.4 Tonality 7.3.4.1 General methodology Narrowband analysis is used to determine the presence of tones in the noise at the same wind speeds as the sound power level measurement. For each wind speed bin, the two one-minute periods closest to the integer wind speed value are analyzed for the presence of tones. The two one-minute measurements are divided into 12 ten-second periods, from which 12 energy averaged narrowband spectra using the Hanning window are obtained. For each of the 12 ten-second periods in each of the integer wind speeds;

The sound pressure level Lpt,j,k of any tones present are determined. The sound pressure level of masking noise Lpn,j,k in a critical band around the tone are determined. The tonality ∆Ltn,j,k, the difference between the sound pressure level of the tone and the masking noise

level, is determined. Overall tonality, ∆Lk, is determined as the energy average of the 12 individual ∆Ltn,j,k. Refer to Equation 5 below to calculate the bandwidth of a critical band around a tone. In Equation 5, fc is the centre frequency in Hz.

Equation 5 7.3.4.2 Identifying possible tones The following procedure is used to identify possible tones:

1. Find local maxima in the spectrum. 2. Calculate the average energy in the critical band centered on each local maximum, not including the line

of the local maximum and the two adjacent lines. 3. If the local maximum is more than 6 dB above the average masking noise level, then it is a possible tone.

7.3.4.3 Classification of spectral lines within the critical band The critical band is positioned with centre frequency coincident with the possible tone frequency. Within each critical band, every spectral line is classified as tone, masking, or neither, using the following procedure.

1. Calculate the L70% sound pressure level, where L70% is the energy average of the 70% of spectral lines in the critical band with the lowest levels.

2. Define a criterion level equal to the L70% level plus 6 dB; a. A spectral line is classified as “masking” if its level is less than the criterion level. Lpn,avg is the

energy average of all spectral lines classified as masking. b. A spectral line is classified as “tone” if its level exceeds Lpn,avg plus 6 dB. c. Where several adjacent lines are classified as “tone”, the line having the greatest level is

identified. Adjacent lines are only classified as a “tone” if their levels are within 10 dB of the highest level.

d. A spectral line is classified as “neither” if it cannot be classified as either “tone” or “masking” as described above. Spectral lines identified as “neither” are ignored in further analysis.

Figures 8 through 11 in IEC 61400-11 are illustrations of the items defined in this section.



7.3.4.4 Determination of the tone level and correct ion for background noise The sound pressure level of the tone, Lpt,j,k is determined by energy summing all spectral lines identified as tones within the critical band as defined in 7.3.4.3 of this Test Report. For comparison with the corresponding analysis of the wind turbine noise, it must be ensured that any identified tones do not originate from the background noise. In order to determine this, a 2-minute narrowband spectrum of the background noise is determined using the two 1-minute measurements closest to the integer wind speed. The background corrected energy average of the spectral lines identified as “masking” within the critical band, Lpn,avg,j,k, is determined following the same procedure identified within Section 7.3.2 of this Test Report. Background levels in the same critical band and integer wind speed as used during tonal analysis are used for comparison. The background noise level is calculated from the energy sum of all lines in the critical band. The background noise level must be at least 6 dB lower than the wind turbine noise in the relevant critical bands. 7.3.4.5 Determination of the masking noise level The masking noise level, Lpn,j,k, is defined in Equation 5 below. In Equation 5, the effective noise bandwidth is 1.5 times the frequency resolution, which includes a correction for the use of the Hanning window.

Equation 5 7.3.4.6 Determination of tonality and audibility The difference between the tone level, Lpt,j,k and the level of the masking noise in the corresponding critical band is given in Equation 6 below:

Equation 6 If no tone was identified according to 7.3.4.3 for some of the 12 ten-second spectra so that ∆Ltn,j,k is undefined, it is be replaced by the value defined in Equation 7 below:

Equation 7

The 12 ∆Ltn,j,k are energy averaged to one ∆Lk, k = 6, 7, 8, 9, 10 for each wind speed bin. Tones in different spectra with frequencies within 10% of the critical bandwidth are understood to be the same tone. If this occurs, the average frequency is used to determine the tonal audibility. For each value of ∆Lk, a frequency dependent correction is applied to compensate for the response of the human ear to tones of different frequency. The tonal audibility, ∆La,k, is given in Equation 8 below:

Equation 8 In Equation 8, La is the frequency dependent audibility criterion, which is defined in Equation 9. In Equation 9, f is the frequency of the tone, in Hz.



Equation 9

A corresponding value of ∆La,k is calculated for each value of ∆Lk. Where tonal audibility is greater than or equal to -3.0 dB, the values of ∆La,k are reported. If the tonal audibility is less than -3.0 dB the tones are not reported.

8.0 Test Results

8.1 Database A total of 91 one-minute data points were included in the database; 52 of which were turbine noise data points. Table 3 below shows the total number of measurements at each integer wind speed that were included in the database.

Turbine + Background Background Only Vs Data points Vs Data points 5 5 5 5 6 16 6 14 7 6 7 5 8 9 8 4 9 6 9 4 10 8 10 9

Table 3 – Measurement database Plots of wind speed, wind direction, temperature, and pressure during the measurement periods are shown in Figures 7, 8, 9, and 10 below.



Figure 7 – Standardized wind speed during the measurement periods

Figure 8 – Wind direction during the measurement periods



Figure 9 – Air temperature during the measurement periods

Figure 10 – Air pressure during the measurement periods



8.2 Apparent sound power level 8.2.1 Uncertainty Type A and Type B uncertainties are expressed in the form of standard deviations and are combined by the method of combination of variances to form the combined standard uncertainty. The combined standard uncertainty is found as the root sum of the squared components: UA, UB1, UB2, UB3, UB4, UB5, UB6, UB7, UB8, and UB9. Type B, UB, uncertainty is determined by using the typical values provided in Table D.1 in IEC 61400-11, Annex D. The standard typical values were used for UB2 through UB9. The value for UB1 was derived from the calibration data sheet uncertainties. Table 4 below shows the Type B uncertainties used in the determination of results within this Test Report.

Item Description Type B Value Type Source

UB1 Calibration 0.54 Actual Calibration UB2 Measurement Chain 0.20 Typical IEC 61400-11 UB3 Board 0.30 Typical IEC 61400-11 UB4 Distance 0.10 Typical IEC 61400-11 UB5 Impedance 0.10 Typical IEC 61400-11 UB6 Turbulence 0.40 Typical IEC 61400-11 UB7 Wind Speed Measured 0.90 Typical IEC 61400-11 UB8 Direction 0.30 Typical IEC 61400-11 UB9 Background 0.10 Typical IEC 61400-11

Table 4 – Type B Uncertainties Type A uncertainty, UA is evaluated by using statistical methods to a series of repeated determinations. UA, the parameter describing the type A uncertainty is the standard error of the estimated LAeq,c,k at each integer wind speed. LAeq,c,k is the equivalent continuous A-weighted sound pressure level corrected for background noise at each integer wind speed and corrected to reference conditions, where k = 6, 7, 8, 9, and 10. Table 5 below shows the continuous A-weighted sound pressure levels and the type A uncertainties at integer wind speeds.

Wind Speed LAeq,c,k Type A Uncertainty

m/s dB(A) dB(A) 5 45.74 2.00 6 48.64 2.07 7 50.84 1.24 8 52.97 2.05 9 55.34 2.25 10 56.62 1.60

Table 5 – Continuous A-weighted sound pressure levels and type A uncertainty at integer wind speeds



Table 6 below shows the apparent sound power levels and combined uncertainty, Uc, at integer wind speeds.

Wind Speed LWA,k Combined Uncertainty

m/s dB(A) dB(A) 5 85.74 2.29 6 88.33 2.36 7 90.88 1.67 8 93.21 2.34 9 95.18 2.51 10 96.70 1.96

Table 6 – Apparent sound power levels and combined uncertainty at integer wind speeds 8.2.2 Apparent sound power level results The apparent sound power level (LWA,k) at integer wind speeds was derived following the procedure outlined in section 7.3.3 of this report, with the deviation mentioned in section 4.0 of this report. Using the 4th order regression for turbine noise, and the linear regression for background noise, the apparent sound power level was determined. Figure 11 below shows the measured data pairs of sound pressure levels recorded at various standardized wind speeds and the fitted regressions.

Figure 11 – 60 second averaged A-weighted sound pressure levels as a function of standardized wind speed



A linear regression was used for background noise due to the higher correlation coefficient of the linear regression versus a 4th order regression. The poor correlation for the 4th order regression is likely due to the two background noise data points that appear to be outliers in Figure 11 above. After further investigating these data points there was no intruding intermittent noise or other reason to support their exclusion from the database; therefore, they remain in the database and the linear regression was chosen. Figure 12 below shows the combined uncertainty at apparent sound power levels at integer wind speeds. The uncertainty is shown using error bars in the y-direction.

Figure 12 – Combined uncertainty at apparent sound power levels at integer wind speeds



8.3 One-third octave band spectra 8.3.1 Uncertainty For the one-third octave band spectra a similar approach as described in section 8.2.1 above is followed, but with the modifications as described in IEC 61400-11, Annex D. For category A uncertainty the UA for each band is the standard error on the averaged band level, computed as the standard deviation divided by , where N is the number of measured spectra. For category B uncertainty the UB3 value is considered to be much larger than for apparent sound power levels, and is estimated in IEC 61400-11, Annex D as a typical value of 1.7 dB. The other category B values remain the same, as described in Table 7 in section 8.2.1 of this Test Report. The combined uncertainty, Uc, is again the root sum square of the category A and category B values. 8.3.2 One-third octave results The A-weighted third octave spectra at integer wind speeds were derived following the procedure outlined in Section 7.3.3 of this Test Report. Figures 13 and 14 below show the background corrected third octave spectra over the range of 6 to 10 m/s. For areas in Figures 13 and 14 where no data is shown, this represents turbine continuous sound pressure levels that were less than the background continuous sound pressure levels.

Figure 13 – Third octave spectra at the 6 m/s, 7 m/s, and 8 m/s integer wind speeds



Figure 14 – Third octave spectra at the 9 m/s and 10 m/s integer wind speeds



Table 7 below represents the correction to all measured sound pressure levels for the influence of background noise on the turbine. The data marked with an asterisk, “ * “, indicates corrected data when the continuous sound pressure level of the wind turbine plus the background noise is less than 6 dB but more than 3 dB higher than the background level. Where data is missing, the turbine continuous sound pressure levels were less than the background continuous sound pressure levels.

6 m/s 7 m/s 8 m/s 9 m/s 10 m/s Frequency

Ls Uc Ls Uc Ls Uc Ls Uc Ls Uc Hz dB(A) dB(A) dB(A) dB(A) dB(A) dB(A) dB(A) dB(A) dB(A) dB(A)

50 *30.5 3.3 34.2 2.6 36.6 2.5 63 *31.5 3.3 35.5 2.6 37.5 2.5 80 *31.6 3.4 35.5 2.7 37.4 2.6 100 *32.9 3.3 36.6 2.6 38.5 2.5 125 *34.6 3.0 37.4 2.6 39.3 2.5 160 31.0 3.5 *34.5 3.1 37.5 2.6 39.4 2.5 200 37.0 2.9 37.7 2.5 37.5 2.7 38.5 2.5 40.0 2.4 250 *33.0 3.2 37.1 2.8 39.9 2.4 41.5 2.4 315 *34.2 3.1 38.2 2.7 41.0 2.4 42.7 2.3 400 *35.7 2.8 38.9 2.5 41.1 2.3 42.9 2.3 500 *32.9 3.9 *36.6 2.8 40.1 2.5 42.6 2.3 44.3 2.2 630 36.9 3.0 39.4 2.5 42.8 2.3 45.3 2.2 46.8 2.2 800 38.7 2.7 41.0 2.3 44.6 2.2 47.0 2.1 48.3 2.1 1000 40.3 2.5 42.9 2.3 46.1 2.2 48.4 2.1 49.5 2.1 1250 40.5 2.5 43.3 2.2 45.3 2.2 47.0 2.1 48.3 2.1 1600 37.6 2.7 42.1 2.3 44.3 2.2 46.3 2.1 47.6 2.1 2000 *32.3 3.2 37.6 2.4 42.5 2.2 46.1 2.1 47.5 2.1

2500 *28.9 3.6 32.8 2.6 37.7 2.3 42.5 2.1 44.6 2.1

3150 *26.1 4.0 *30.2 2.8 33.5 2.5 37.4 2.2 39.8 2.2

4000 *26.0 3.3 *28.9 3.0 32.1 2.5 34.1 2.4

5000 *30.5 3.6 *28.1 2.9 30.0 2.7

6300 *25.6 3.3

8000

10000 Table 7 –Background corrected one-third octave spectra and combined uncertainty at integer wind speeds



8.4 Tonality 8.4.1 Uncertainty For tonality a similar approach, as described in section 8.2.1 and 8.3.1 above, is followed. The modifications as described in IEC 61400-11, Annex D are followed. For category A uncertainty, UA for each tone is the standard error on the averaged tone level. For category B uncertainty, UB3 can be estimated to be 1.7 dB. As the reported value ∆Ltn is a difference, and as the wind speed is expected to be of secondary importance, the values of UB1, UB4, and UB6 can be estimated to be smaller than for LWA, see Table D.1 in the IEC 61400-11 standard. For the results determined in this test report, the values of UB1, UB4, and UB6 are identical to those shown in Table 6 within this report. 8.4.2 Tonality results The presence of tones at integer wind speeds were derived following the procedure outlined in Section 7.3.4 of this Test Report. The analysis only yielded one reportable tone at the 7 m/s integer wind speed. The results are shown in Table 8 below. The parameter K below represents the integer wind speed. ∆Lk represents the difference between the tone level and the level of the masking noise in the critical band around the tone at the integer wind speeds. ∆Ltnj,k represents the tonality of the ‘jth’ spectra at ‘kth’ wind speed. ∆La,k represents the difference between the tonality and the audibility criterion at integer wind speeds. UA represents the category A uncertainty, UB represents the category B uncertainty, and UC represents the combined uncertainty.

k [m/s] 7 Freq [Hz] 216

∆Ltn1,k 0.82

∆Ltn2,k 3.67

∆Ltn3,k 2.22

∆Ltn4,k 0.58

∆Ltn5,k 0.85

∆Ltn6,k 0.25

∆Ltn7,k 1.12

∆Ltn8,k 0.04

∆Ltn9,k 0.04

∆Ltn10,k 1.57

∆Ltn11,k 0.04

∆Ltn12,k 0.04

∆Lk dB(A) -0.28

∆La,k dB(A) 1.77

UA dB(A) 1.76

UB dB(A) 2.03

UC dB(A) 2.69 Table 8 – Tonality results at the 7 m/s integer wind speed



Figure 15 below graphically shows the reportable tone at the 7 m/s integer wind speed with classification of spectral lines (masking, neither, or tone).

Figure 15 – Ten second spectrum showing the reportable tone at the 7 m/s integer wind speed



Appendix The following sections can be found within this Appendix:

A Test Equipment B Wiring Diagrams C Photographs D Calibration Certificates for Acoustical Equipment



A Test Equipment A.1 Calibrated equipment

Measurement Manufacturer Model Serial Cal Date Cal Due

Power Transducer * Ohio Semitronics DMT-

1040EY40 10051959 4/19/2011 4/19/2012

Current Transformer* Ohio Semitronics 12975 (200:5A) 002277039 4/19/2011 4/19/2012 Wind Speed 1** Adolf Thies GmbH 4.3351.00.141 04100019 5/3/2010 5/3/2011 Wind Speed 2 Adolf Thies GmbH 4.3519.00.141 04100712 5/3/2010 5/3/2011 Wind Direction Adolf Thies GmbH 4.3150.00.141 04100018 5/4/2010 5/4/2011

Temperature / Humidity Adolf Thies GmbH 1.1005.54.241 85764 4/15/2010 4/15/2011 Barometric Pressure Vaisala PTB330 F1420001 4/8/2010 4/8/2011

Microphone*** BSWA Technology MP201 461272 9/9/2010 9/9/2011 Preamplifier BSWA Technology MA211 470789 9/9/2010 9/9/2011

DAQ Module National

Instruments USB-9233 151A3AF 9/9/2010 9/9/2011

Acoustical Calibrator BSWA Technology CA111 470103 8/24/2010 8/24/2011 *PT/CT calibrated as a system **All sensors on the meteorological tower were sent out near their calibration due dates and replaced with newly calibrated instruments. Records of the new instruments, and verification of the original instruments maintaining calibration throughout the test period, are maintained within the Intertek project file. ***BSWA equipment, NI module, and acoustic laptop calibrated both as a system and individually. Note: All instruments were replaced with newly calibrated instruments post their calibration due dates.

A.2 Non-calibrated equipment

Description Manufacturer Model Comments Windscreen Scantek Inc. WS1-80T

Data Acquisition Backplane

National Instruments

9178 Compact DAQ

Digital I/O signal verified with LabVIEW

Data Acquisition Module National

Instruments NI 9203 Digital I/O signal verified with LabVIEW

A.3 Software

Description Manufacturer Model Comments Acoustic Data Recording And Analysis Software

Delta NoiseLab Pro Verified software

Excel Analysis Microsoft 2003 Verified software



B Wiring Diagrams B.1 Typical wiring diagram for the Fortis Montana



B.2 Location of Intertek power measurement



C Photographs C.1 April 2011 - Microphone and sound board



C.2 February 2012 - Met tower, field board, and turbine tower looking t oward point of acoustic measurement



D Calibration Certificates for Acoustical Equipment D.1 Microphone and preamplifier



D.2 Sound level meter



D.3 Acoustical calibrator

fortis wind turbine acoustic noise report

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