Excerpts from: Performance, Duration and Acoustic test reports for the Skystream 3.7 wind generator

Excerpts from: Performance, Duration and Acoustic test reports for the Skystream 3.7 wind generator Report One: Power performance measurement on the Skystream 3.7 according to IEC 61400-12-1 and BWEA Report Two: Duration Test on the Skystream 3.7 wind turbine Report Three: Acoustic noise measurements on the Skystream 3.7 according to BWEA-SWT Southwest Windpower, Inc. 1801 W. Route 66 Flagstaff, Arizona 86001 Phone: 928-779-9463 Fax: 928-779-1485 Mobil: 928-380-3527 Web: www.skystreamenergy.com

WINDTEST Kaiser-Wilhelm-Koog GmbH Report WT 7650/09 -replaces WT7361/09- Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm-Koog, Germany according to IEC 61400-12-1 and BWEA Kaiser-Wilhelm-Koog, 2009-11-02 Seite 1 von 55

Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm-Koog, Germany according to IEC 61400-12-1 and BWEA Report no.: Kind of report: Site or location: Client: WT 7650/09 -replaces WT7361/09- Site Calibration Report TASWT, Kaiser Wilhelm-Koog, Germany Southwest Windpower Mrs. Ketter F. Ulrich 1801 W Route 66 Flagstaff, AZ 86001 USA Contractor: WINDTEST Kaiser-Wilhelm-Koog GmbH Sommerdeich 14 b 25709 Kaiser-Wilhelm-Koog Germany Order no.: 4270 08 04397 252 Order date: 2008-07-17 Report author: Dipl.-Ing. Axel Sachse test engineer Department Loads and Performance Report verifier: Dipl.-Ing. Martin Arndt Deputy Head of Department Loads and Performance Kaiser-Wilhelm-Koog 2009-11-02 Dipl.-Ing. Axel Sachse Dipl.-Ing. Martin Arndt This report in excerpts may only be copied with written consent of WINDTEST Kaiser-Wilhelm-Koog GmbH. It totally consists of 55 pages incl. all annexes.

Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm- Koog, Germany according to IEC 61400-12-1 and BWEA report WT 7650/09 2009-11-02 Table of Contents 1 Introduction...3 2 Results...4 3 Wind turbine...5 4 Measurement...6 4.1 Logbook of the measurement...6 4.2 Site...6 4.3 Measuring program...7 5 Measuring equipment...9 5.1 Data acquisition...9 5.2 Wind speed...9 5.3 Wind direction...10 5.4 Electric power...10 5.5 Temperature and atmospheric pressure...10 6 Data evaluation...10 7 Measurement results...11 7.1 Power curve...11 7.2 Uncertainty analysis...12 7.3 Power coefficient c p...14 7.4 Annual energy production (AEP)...15 8 Deviations...15 9 References...15 10 Enclosures...16 WINDTEST Kaiser-Wilhelm-Koog GmbH Page 2 of 55

Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm- Koog, Germany according to IEC 61400-12-1 and BWEA report WT 7650/09 2009-11-02 1 Introduction The scope of this report is the measurement of the power performance of the Skystream 3.7 wind turbine, which was carried out by WINDTEST Kaiser-Wilhelm-Koog GmbH (WINDTEST) at the Test Area for Small Wind Turbines (TSWT) at Kaiser-Wilhelm-Koog. The measurement which is documented in this report covers the period from 2008-11-14 to 2009-03-22. The measurement was performed and evaluated in accordance with the IEC 61400-12-1 Ed.1: Wind turbines Part 12-1: Power performance measurements of electricity producing wind turbines [1], IEC 61400-12 Wind turbine generator systems, part 12: wind turbine power performance testing, 1998 [2] and with BWEA Small Wind Turbine Performance and Safety Standard [3]. The results given in this report relate only to the wind turbine mentioned in this report and cannot be transferred to other sites. This report was drawn up impartially in accordance with state-of-the-art technology and with best knowledge and conscience. WINDTEST Kaiser-Wilhelm-Koog GmbH Page 3 of 55

Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm- Koog, Germany according to IEC 61400-12-1 and BWEA report WT 7650/09 2009-11-02 2 Results The valid datasets are normalised to sea level air density, referring to ISO standard atmosphere (1.225 kg/m 3 ). The average of the measured air density (during periods of valid data collection) is 1.262 kg/m 3, which is within the range of 1.225 ± 0.05 kg/m 3. Thus - according to [1] - an additional normalisation to this air density (rounded to the nearest 0.05 kg/m 3 ) is not required. A differentiation regarding database A / B is not applicable, as cut-out behaviour has not been reached during measurement period according to the measured status signals. power output [kw] 3,00 0,60 2,80 2,60 0,50 2,40 2,20 0,40 2,00 1,80 1,60 0,30 1,40 1,20 0,20 1,00 0,80 0,10 0,60 0,40 0,20 0,00 0,00-0,20-0,10 0 2 4 6 8 10 12 14 16 18 20 wind speed [m/s] Figure 1: Result according to [1] cp WS_corr [m/s] P [kw] cp [] 0,56-0,018-1,04-0,018-1,52-0,018-2,02-0,017-2,51-0,012-3,00 0,003 0,017 3,51 0,034 0,119 4,03 0,084 0,195 4,46 0,132 0,226 5,00 0,203 0,247 5,49 0,285 0,261 6,00 0,391 0,275 6,50 0,510 0,282 6,99 0,643 0,285 7,49 0,799 0,288 7,99 0,968 0,288 8,50 1,146 0,284 8,99 1,333 0,279 9,48 1,531 0,273 9,98 1,745 0,267 10,47 1,938 0,256 10,97 2,101 0,242 11,47 2,242 0,226 11,93 2,301 0,206 12,45 2,363 0,186 12,97 2,403 0,167 13,50 2,403 0,148 13,99 2,425 0,135 14,52 2,388 0,118 15,02 2,412 0,108 15,45 2,403 0,099 15,99 2,393 0,089 16,50 2,321 0,078 17,00 2,299 0,071 17,41 2,274 0,065 17,95 2,246 0,059 - - - 18,99 2,203 0,049 WINDTEST Kaiser-Wilhelm-Koog GmbH Page 4 of 55

Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm- Koog, Germany according to IEC 61400-12-1 and BWEA report WT 7650/09 2009-11-02 Enclosure 3 Technical data of the wind turbine (manufacturer s certificate) WINDTEST Kaiser-Wilhelm-Koog GmbH Page 22 of 55

Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm- Koog, Germany according to IEC 61400-12-1 and BWEA report WT 7650/09 2009-11-02 WINDTEST Kaiser-Wilhelm-Koog GmbH Page 23 of 55

Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm- Koog, Germany according to IEC 61400-12-1 and BWEA report WT 7650/09 2009-11-02 Enclosure 11 Power curve (table and plot) WINDTEST Kaiser-Wilhelm-Koog GmbH Page 48 of 55

Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm- Koog, Germany according to IEC 61400-12-1 and BWEA report WT 7650/09 2009-11-02 WINDTEST Kaiser-Wilhelm-Koog GmbH Page 49 of 55

Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm- Koog, Germany according to IEC 61400-12-1 and BWEA report WT 7650/09 2009-11-02 Enclosure 12 Plot of wind speed vs. wind direction WINDTEST Kaiser-Wilhelm-Koog GmbH Page 50 of 55

Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm- Koog, Germany according to IEC 61400-12-1 and BWEA report WT 7650/09 2009-11-02 Enclosure 13 Plot of turbulence intensity vs. wind speed WINDTEST Kaiser-Wilhelm-Koog GmbH Page 51 of 55

Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm- Koog, Germany according to IEC 61400-12-1 and BWEA report WT 7650/09 2009-11-02 Enclosure 14 Uncertainty calculation MEASURED POWER CURVE: IEC Test (database A) coverage factor (assuming normal distributions): k=1 reference air density: 1,225 kg/m³ category A category B cut-out windspeed: m/s combined bin hub height power cp no. of standard standard (expanded) no. wind output values data sets uncertainty uncertainty uncertainty speed [m/s] [kw] (1 min. avg.) [kw] [kw] [kw] 1 0,56-0,018-15,405 468 0,000 0,011 0,011 2 1,04-0,018-2,391 1204 0,000 0,010 0,010 3 1,52-0,018-0,773 2082 0,000 0,010 0,010 4 2,02-0,017-0,311 3471 0,000 0,010 0,010 5 2,51-0,012-0,118 5236 0,000 0,010 0,010 6 3,00 0,003 0,017 6353 0,000 0,011 0,011 7 3,51 0,034 0,119 6465 0,000 0,013 0,013 8 4,03 0,084 0,195 9502 0,000 0,017 0,017 9 4,46 0,132 0,226 9778 0,000 0,020 0,020 10 5,00 0,203 0,247 6018 0,001 0,023 0,023 11 5,49 0,285 0,261 5407 0,001 0,030 0,030 12 6,00 0,391 0,275 4924 0,001 0,039 0,039 13 6,50 0,510 0,282 4619 0,002 0,046 0,046 14 6,99 0,643 0,285 4570 0,002 0,054 0,054 15 7,49 0,799 0,288 4194 0,003 0,066 0,066 16 7,99 0,968 0,288 3534 0,003 0,075 0,075 17 8,50 1,146 0,284 3093 0,003 0,082 0,082 18 8,99 1,333 0,279 2543 0,003 0,093 0,093 19 9,48 1,531 0,273 1688 0,004 0,102 0,102 20 9,98 1,745 0,267 959 0,006 0,113 0,114 21 10,47 1,938 0,256 553 0,007 0,110 0,110 22 10,97 2,101 0,242 335 0,008 0,096 0,096 23 11,47 2,242 0,226 182 0,009 0,088 0,089 24 11,93 2,301 0,206 105 0,010 0,051 0,052 25 12,45 2,363 0,186 47 0,021 0,050 0,054 26 12,97 2,403 0,167 27 0,021 0,043 0,048 27 13,50 2,403 0,148 25 0,015 0,035 0,038 28 13,99 2,425 0,135 33 0,014 0,039 0,041 29 14,52 2,388 0,118 37 0,017 0,043 0,046 30 15,02 2,412 0,108 38 0,013 0,039 0,042 31 15,45 2,403 0,099 32 0,011 0,036 0,038 32 15,99 2,393 0,089 14 0,017 0,036 0,039 33 16,50 2,321 0,078 12 0,019 0,066 0,069 34 17,00 2,299 0,071 8 0,008 0,038 0,039 35 17,41 2,274 0,065 3 0,039 0,042 0,058 36 17,95 2,246 0,059 2 0,070 0,040 0,080 #NV #NV #NV #NV #NV #NV #NV 37 18,99 2,203 0,049 2 0,066 0,062 0,091 #NV #NV #NV #NV #NV #NV #NV WINDTEST Kaiser-Wilhelm-Koog GmbH Page 52 of 55

Power performance measurement of the Skystream 3.7 at Kaiser-Wilhelm- Koog, Germany according to IEC 61400-12-1 and BWEA report WT 7650/09 2009-11-02 Enclosure 15 Annual energy production (AEP) ESTIMATED ANNUAL ENERGY PRODUCTION (AEP) (database A) extrapolation of the power curve between the highest WT: IEC Test measured wind speed and the cut-out wind speed cut-out wind speed: m/s with the average power at highest measured wind speed reference air density: 1,225 kg/m³ coverage factor k: 1 hub height AEP-measured Expanded uncertainty of AEPmeasured AEP-extrapolated annual average (measured (extrapolated wind speed power curve) power curve) (Rayleigh) [m/s] [MWh] [MWh] [%] 4,0 1,736 0,208 11,980 5,0 3,416 0,295 8,626 6,0 5,349 0,368 6,883 7,0 7,207 0,418 5,798 8,0 8,737 0,447 5,116 9,0 9,814 0,462 4,709 10,0 10,439 0,469 4,497 11,0 10,683 0,473 4,427 values marked with *: power curve incomplete acc. to IEC criteria for database [MWh] 1,736 3,416 5,349 7,207 8,737 9,814 10,439 10,683 WINDTEST Kaiser-Wilhelm-Koog GmbH Page 53 of 55

WINDTEST Kaiser-Wilhelm-Koog GmbH Duration Test on a Southwest Windpower Skystream 3.7 wind turbine, Bushland, Texas, USA Report WT 6534/08 May 2008

WINDTEST Kaiser-Wilhelm-Koog GmbH Duration Test on a Southwest Windpower Skystream 3.7 wind turbine, Bushland, Texas, USA Report-No.: WT 6534/08 Site or measuring place: Customer: Supplier: Bushland, Texas, United States of America Southwest Windpower Flagstaff, Arizona, USA WINDTEST Kaiser-Wilhelm-Koog GmbH Sommerdeich 14b 25709 Kaiser-Wilhelm-Koog Contract date of issue 2008-05-19 Order No.: 4270 08 04298 252 prepared: checked: Dipl.-Ing. A. Sachse (Test engineer) Kaiser-Wilhelm-Koog, 22 th May 2008 Dipl.-Ing. O. Bruhn (Head of Loads Group) This report may only be copied in excerpts with written consent of WINDTEST Kaiser-Wilhelm-Koog GmbH. It comprises of a total of 39 pages, including the enclosures.

Page 2/39 Table of Contents 1 Introduction... 3 2 History of the turbine... 3 3 Test site... 4 4 Measurements... 4 4.1 Measurement system...4 4.2 Data Results from measurements...5 4.2.1 Power production...6 4.2.2 Reliable operation...7 4.2.3 Power production degradation...7 5 Dynamic behaviour... 10 6 Condition of the turbine after the test... 11 6.1 Type plates...11 6.2 Blades...11 6.3 Generator...12 6.4 Nacelle with inverter and controller unit...13 6.5 Tower and foundation...13 7 Conclusion...13 8 Deviations... 13 9 Literature... 13 10 Enclosures...14 WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH

Page 3/39 1 Introduction A Skystream 3.7 wind turbine with a rated power of 1.8 kw and a rotor diameter of 3.7 m was erected at the Conservation and Production Research Laboratory (USDA-ARS) west of Bushland, Texas, United States of America in order to perform a duration test. A detailed description of the turbine and its components is given in enclosure A. USDA-ARS has installed the necessary measurement equipment and conducted the duration test. The manufacturer of the turbine, Southwest Windpower (SWWP), got in touch with Germanischer Lloyd Industrial Services USA (GLIS USA) to check the database derived from the duration test and inspect the turbine after completion of the test. This service was provided in close cooperation with Windtest Kaiser-Wilhelm-Koog GmbH (WTK) as an accredited institute for tests and measurements on small wind turbines, amongst others. The scope of this report are the results of the duration test according to the IEC 61400-2 standard [1]. 2 History of the turbine The turbine was erected at the USDA-ARS site in August of 2006. Different turbine components like rotor and inverter unit have been changed until the final setup for the test was completely installed in November of 2006. USDA-ARS has maintained a log book that includes information about all test related activities performed at the turbine or at the measurement system. Table 1 gives an overview about significant turbine and test related activities. Date Comment 2006-08-28 First run of a former version of the turbine 2006-11-17 new nacelle, tower flange bolts and isolators have been installed, original rotor remained in use 2007-29-01 Inverter software update, Start of duration test 2007-04-19 RV-board of the turbine replaced 2007-12-07 Turbine was manually shut down due to approaching ice storm 2007-12-10 Turbine was powered back on, but was still in brake mode 2008-01-10 USDA-ARS had to disassemble the nacelle to reengage the turbine 2008-03-31 End of duration test 2008-04-03 Site visit and inspection by GLIS USA Table 1, turbine history (source: USDA-ARS logbook) WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH

Page 4/39 3 Test site The test site is located west of the city of Bushland near Amarillo, Texas, USA. The coordinates of the turbine are: 35 11 09.4 N and 102 04 57.1 W The elevation of the site is 1,160 m. The annual average wind speed at the site is 6 m/s at 10 m height and the prevailing wind direction is 215 magnetic. A photo series of the test site is given in enclosure B. 4 Measurements 4.1 Measurement system The test setup consists of the turbine under test on a 10 m monopole tower and a 10 m tilt up met tower that is located 9.1 m (2.5 times rotor diameter) from the turbine at 230 magnetic. Following quantities have been measured during the test: Signal name Input Sampling rate Storage WS (hub height wind speed) WD (hub height wind direction) Power (active turbine power) Table 2, Signal list Frequency 1 Hz 1 min average Analogue 1 Hz 1 min average Analogue 1 Hz 1 min average Used measurement sensors and data logger are given in Table 3. Type Manufacturer Model Serial number Anemometer Met One 010C F2273 Wind vane Met One 024A D4614 Multifunction electric meter Simpson GIMA 1002194 Current transformer Simpson 37029 None Data logger Campbell CR23X 7016 Table 3, Sensor list WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH

Page 5/39 Calibration certificates could only partially be provided by USDA-ARS. Most of the documents are outdated or do not fulfil the quality standards of WTK. A post calibration has been performed for the anemometer, the data logger as well as for the watt transducer and the current transformers (as a set). See enclosures C, D and E. The accuracies of the devices were within the tolerances specified by the manufacturer. The measurement range of active turbine power is only accurate for the turbine in power producing mode as negative power values (consumption of the turbine and the measurement system) can only be displayed as positive values. This effect results in an approximate 30 Watt offset in power measurements when the turbine is not producing. The accuracy of the watt transducer is 0.6% according to the specification sheet of the device. The accuracy of the three phase current transformer is 1% according to the spec sheet of the manufacturer of the device. The signal quality of the wind speed measurement has been checked by using a handheld oscilloscope. The wind direction sensor has been installed at a different met tower in a distance of approximately 100 m at 50 magnetic. The wind direction calibration has been verified by in situ. A deviation of only 3 has been noticed. A correction of the results was not necessary. It was not possible to gather the maximum instantaneous wind speed during the measurement period nor any turbulence intensities as only 1 minute averages of the wind speed were available. Maximum, minimum or standard deviation of one minute time series could not be provided. The highest measured 1 min wind speed average was 23.2 m/s. The highest 1 Hz wind speed sample at 10 m height from a nearby weather station located at the USDA test site was 24.5 m/s (2008-02-03). 4.2 Data Results from measurements The derived database from the duration test has been checked on the criteria mentioned in the IEC standard [1]. It was necessary to average the 1 min data sets in order to get 10 minute mean values as required by the IEC standard [1]. Therefore only consecutive 1 minute datasets have been used. Incomplete series have been discarded. For each 10 consecutive 1 min sets their mean, max, min and standard variation values have been calculated for further evaluations. Following picture gives an overview about the calculated 10 min data sets: WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH

Page 6/39 Figure 1, 10 minute data sets, unfiltered 4.2.1 Power production The duration test is considered as complete as the following criteria of the IEC standard [1] have been met: Criteria Required Achieved Duration of the test 6 month 14 month Power production at any wind 2,500 hours 3,350 hours Power production at 1.2 * V ave (1.2 * 8.5 m/s = 10.2 m/s) 250 hours 473 hours Power production at 1.8 * V ave (1.8 * 8.5 m/s = 15.3 m/s) Table 4, Duration test criteria 25 hours 26.5 hours As the power measurement was not very accurate in the lower power range a rather conservative filter criterion was chosen to find power production data sets. Power production was defined as: Power_min (10 min) > 200 Watt WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH

Page 7/39 The measurement sector has been chosen as 0 360 magnetic to provide a sufficient data base. It is assumed that the actual wind speed is even higher than the measured wind speed outside the measurement sector (when the anemometer is in the wake of neighbouring turbines or other obstacles). 4.2.2 Reliable operation The turbine showed mostly a normal behaviour during the period of the test. The operational time fraction during the test has been determined according to Equation 1. TT TN TU T O = T T T T Equation 1, operational time fraction U E E With: T T : T N : T U : T E : total time period turbine known to be non-operational turbine status is unknown time excluded from analysis TT is considered as the time between start and stop of the duration test (427.4 days) TN is considered as the time when the turbine is stopped for any reason other than included in TU or TE (38.7 days) TU is considered as the time when no data were recorded or the measurements were not reliable (4.7 days) TE is considered as the time between 2007-12-07 16:20 and 2007-12-10 12:00 when the turbine was shut down due to a approaching ice storm (2.8 days) 427.4 38.7 4.7 2.8 O = = 90,8% 427.4 4.7 2.8 An operational time fraction of 90% is required by the IEC standard [1]. 4.2.3 Power production degradation A degradation of the power performance of the turbine could not be observed. To check a degradation of power performance of the turbine the procedure described in the IEC [1] has been used: The power level of the turbine has been binned by wind speed for each month of the duration test (first month February 2007, 14 th month March 2008). The binned power levels have been plotted as a function of time, to find possible trends. No results can be provided for June and July of 2007 as the wind speed measurement was not reliable during this time. This procedure is only useful for a wind speed range from approximately cut in wind speed to rated wind speed. The deviation of the power values above rated wind speed is significant; a correlation can not be identified. WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH

Page 10/39 The following picture represents the 10 minute mean power values as a function of 10 minute mean wind speed values for the first 30 days of the test as well as the last 30 days of the test. A significant degradation of power is not apparent. W 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 period1: min10_power_mean period2: min10_power_mean 0 0 5 10 15 20 25 m/s Figure 5, power vs. wind speed, period 1 first 30 days, period 2 last 30 days of the test period 5 Dynamic behaviour The turbine has been observed during the site visit at wind speeds between approximately 5 and 12 m/s for approximately 1.5 hours. No abnormal behaviour could be noticed. The USDA- ARS personnel have also reported that no noticeable oscillations had occurred during the test period. An appropriate test device for monitoring the dynamic behaviour during the test was not implemented in the measurement system. WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH

Page 11/39 6 Condition of the turbine after the test The turbine was inspected on 2008-04-03 at the test site. 6.1 Type plates A picture of the turbine s type plate is given in enclosure F. Type plates of blades, generator or other components could not be found. A manufacturer s certificate provided by SWWP can be found as enclosure A. 6.2 Blades The blades have been visually inspected while mounted on the turbine. The blades have been numbered for better separation. Cracks have been found at the surface of each blade near the trailing and leading edges at the suction side of the blade as well as at the blade root. Cracks are approximately 0.1 to 0.5 mm wide and run along the bonding edges of the two blade shells. Pictures of the cracks are attached in enclosure F. Figure 6, Blade 1, suction side, location of cracks WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH

Page 12/39 Figure 7, Blade 2, suction side, location of cracks Figure 8, Blade 3, suction side, location of cracks The bolts that are connecting the blades to the hub are partially rusted. Picture attached in enclosure F. 6.3 Generator No anomaly has been observed. WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH

Page 13/39 6.4 Nacelle with inverter and controller unit Marks of condensed water have been found inside the nacelle (enclosure F). Most of the screws that are securing the inverter unit are corroded (enclosure F). Grease is leaking from the yaw bearing (enclosure F). 6.5 Tower and foundation No anomalies have been observed on the tower. 7 Conclusion The turbine under test has been tested for fourteen month. During that time the turbine was reliable running and producing power so that the duration test can be considered as completed. An inspection of the turbine after the test showed some minor corrosion problems. Minor problems can easily be resolved during scheduled maintenance. The problems found at the blades may, extrapolated to the lifetime of the turbine, lead to an unreliable operation of the turbine. It is recommended to further investigate the reason and severity of the cracks. 8 Deviations The duration test has been performed with the following deviations to the IEC 61400 2: Average turbulence intensity at 15 m/s and highest instantaneous measured wind speed could not be determined. Dynamic behaviour of the turbine hasn t been observed for wind speeds higher than 12 m/s. Measurement sector has been chosen as 0-360 magnetic, no additional wind direction filtering has been done. 9 Literature [1] IEC 61400-2 Ed.2: WIND TURBINES - Part 2: Design requirements for small wind turbines WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH

Page 14/39 10 Enclosures Enclosure A: Manufacturer s certificate... 15 Enclosure B: Photo series of the test site... 17 Enclosure C: Calibration certificate of the anemometer... 19 Enclosure D: Calibration certificate of the watt transducer and current transformer... 25 Enclosure E: Calibration certificate of the data logger... 28 Enclosure F: Photos of turbine inspection... 30 WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH

Page 15/39 Enclosure A: Manufacturer s certificate WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH

Page 16/39 WT 6534/08: Duration Test on a Southwest Windpower Skystream 3.7Bushland, Texas, USA WINDTEST Kaiser-Wilhelm-Koog GmbH