Conference Paper

NREL/CP-500-45632

July 2009

Small Wind Turbine Testing 

Results from the National 

Renewable Energy Lab 

A. Bowen, A. Huskey, H. Link, K. Sinclair, 

T. Forsyth, and D. Jager

National Renewable Energy Laboratory

J. van Dam and J. Smith

Windward Engineering

Presented at the American Wind Energy Association

WINDPOWER 2009 Conference and Exhibition 

Chicago, Illinois

May 4–7, 2009
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1

Small Wind Turbine Testing Results from the

National Renewable Energy Lab

Amy Bowen, Arlinda Huskey, Hal Link, Karin Sinclair, Trudy Forsyth, David Jager

National Renewable Energy Laboratory

Jeroen van Dam, Joe Smith

Windward Engineering

Abstract

In 2008, the U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) began 

testing small wind turbines (SWTs) through the independent testing project. Using competitive 

solicitation, four SWTs were selected for testing at the National Wind Technology Center (NWTC).

NREL’s NWTC is accredited by the American Association of Laboratory Accreditation (A2LA) to 

conduct power performance, power quality, noise, safety and function, and duration tests to International 

Electrotechnical Commission (IEC) standards. Results of the tests conducted on each of the SWTs will be 

publicly available and likely will be used by the Small Wind Certification Council (SWCC) to certify 

SWTs. The results also could be used by states to decide which turbines are eligible for state incentives.

Reducing barriers for SWTs to enter the market will provide consumers in a range of sectors—including 

residential, ranchers/farmers, business, and community applications (e.g., schools, tribes, municipal 

utilities, rural electric cooperatives)—the opportunity to invest in indigenous energy, and to contribute to 

the shift towards energy independence. The paper reports results of testing to date, and puts the test 

results in perspective for the average consumer. Other topics addressed include a description of DOE’s 

second solicitation for independent testing, and a discussion of the DOE’s support for developing 

additional testing centers to conduct preliminary screening of SWTs to identify those turbines that are not 

ready for the commercial market.

Introduction

The independent testing project was established at the National Renewable Energy Laboratory to help 

reduce the barriers of wind energy expansion. Among these barriers is a lack of independent testing 

results for small turbines. Independent testing results will provide turbine manufacturers with a portion of 

the requirements for turbine certification. Certified turbines will give consumers confidence in small 

turbine technology and will separate reliable turbines from those that do not perform as advertised.

The turbines selected in the first round of the independent testing project were the Mariah Power 

Windspire, the Gaia-Wind 11 kW, the Abundant Renewable Energy ARE 442, and the Entegrity EW50. 

Figure 1 shows the selected turbines installed at the NWTC. Power performance, duration, noise, and 

safety and function tests are performed on all turbines. Power quality testing is performed only on threephase turbines, as the IEC Standard 61400-21 only applies to turbines with a three-phase grid connection. 

The available preliminary results of those tests to date are presented below and are subject to change. 
2

Turbines Selected

The Mariah Power Windspire was installed on May 5, 2008. It is a 120 VAC, single-phase, gridconnected, permanent-magnet generator wind turbine rated at 1 kW. The Windspire is a vertical-axis 

Giromill turbine mounted on a monopole tower, and has a rotor height of 6.1 m and a rotor area of 1.2 m 

by 6.1 m. Testing on the Windspire was terminated on January 14, 2009 after repeated turbine problems. 

Partial power performance and safety and function test data was collected on the Windspire.

The Gaia-Wind 11 kW turbine was installed on May 13, 2008. It is a downwind, two-bladed, horizontalaxis turbine. Its three-phase 11-kW induction generator delivers 480 VAC to the grid. The Gaia-Wind 

11 kW has a 133 m2 swept area and is mounted on an 18.2-m monopole tower. At the time of this writing,

data collection for duration, safety and function, and power performance testing was complete and power 

quality and acoustic noise testing were in progress.

The Abundant Renewable Energy ARE 442 was installed on June 11, 2008. It is a horizontal-axis, threebladed turbine with a swept area of 41 m2

. It operates upwind from the prevailing wind direction and uses 

a furling mechanism for power control. The ARE 442 is mounted on a 30.5-m lattice tower. The turbine is 

a single-phase, grid-connected, permanent-magnet machine that is rated at 10 kW at 240 VAC. At the 

time of this writing, data collection for power performance testing was complete and duration, safety and 

function, and acoustic noise testing were in progress.

The Entegrity EW50 was installed on March 3, 2009. The Entegrity’s three-phase induction generator 

produces 50 kW at 480 VAC. Its rotor-swept area is 176.7 m2 and it operates downwind. It is a 

horizontal-axis machine mounted on a 30.5-m monopole tower. At the time of this writing, data collection 

had begun for power performance, acoustic noise, safety and function, and duration testing of the 

Entegrity.

 

Figure 1. From left to right: the Windspire, the Gaia-Wind 11 kW, the ARE 442, the EW50
3

Duration Testing

The duration test is conducted according to section 9.4 of the IEC Standard 61400-2: Design Requirements for Small Wind Turbines. Duration testing provides information about the turbine’s structural 

integrity, quality of environmental protection, and dynamic behavior. The test requires a minimum of 

6 months of operation, 2,500 hours of power production in winds of any velocity, 250 hours of power 

production in winds of 1.2 Vave and greater, and 25 hours of power production in wind of 1.8 Vave and 

greater. Section 6.2 of IEC Standard 61400-2 defines Vave , which depends on the small wind turbine class 

as identified by the manufacturer and based on the wind speeds in which the turbine was designed to 

operate. The turbine must not experience any major failures during the test period and must achieve an

operational time fraction of 90% or greater. The operational time fraction is defined by the following.

Where TT is the total test time, TN is the time attributed to turbine faults and manufacturer-mandated 

inspections and maintenance, TU is the time during which the turbine status is unknown due to lost data or 

data-acquisition failure and maintenance, and TE is the time that is excluded from analysis due to grid 

faults and laboratory-mandated inspections or stops. 

Part of the reliable-operation requirement for the duration test includes no significant wear, corrosion, or 

damage to turbine components. The structural integrity and material degradation are investigated through 

inspections of the turbine before, during, and after the testing period. Blades, welds, and other turbine 

components were visually inspected and photographed before the test and any apparent abnormalities 

documented. After the required test data is collected, the turbine is lowered and disassembled for 

inspection of all individual components. Routine inspections of both the ARE 442 and the Gaia-Wind 

11 kW before and during the tests have not revealed any abnormalities. Post-test inspections for the GaiaWind 11 kW or the ARE 442 have not occurred. 

Duration testing on the Windspire was terminated on October 14, 2008. The turbine had experienced 

repeated problems which resulted in a low operational time fraction. These problems included repeated 

loose nuts at the base of the turbine, a broken washer at the base of the turbine, broken welds at the top of 

the turbine, airfoil displacement in the struts, and an inverter failure. 

Table 1. Preliminary Duration Results for the Gaia-Wind 11 kW

Max Gust TI @ 15 # Data T T T U T E T N O

Month 0 m/s 9 m/s 13.5 m/s (m/s) m/s (%) Points (hours) (hours) (hours) (hours) (%)

Overall 2704.9 710.6 215.0 41.9 19.0 255 7094 172.5 152.0 624.6 90.8

Jun 2008 238.2 36.2 3.8 28.6 18.5 5 518 11.3 7.8 3.3 99.3

Jul 256.0 8.5 0.3 23.9 - 0 744 78.2 2.2 38.8 94.1

Aug 115.8 4.5 0.0 19.2 - 0 744 6.3 20.0 323.0 55.0

Sep 120.5 11.7 1.8 22.4 - 0 720 36.2 30.3 174.7 73.3

Oct 236.0 45.0 12.2 32.8 17.3 10 744 0.7 1.3 0.0 100.0

Nov 348.0 98.7 22.5 37.0 20.9 40 720 22.1 0.0 0.0 100.0

Dec 339.7 160.5 54.8 41.4 17.4 68 744 7.9 27.2 32.8 95.4

Jan 2009 385.0 155.5 56.0 38.8 19.9 76 744 4.9 32.0 36.5 94.8

Feb 333.2 107.3 36.8 41.9 20.0 23 672 3.2 27.0 0.0 100.0

Mar 332.5 82.7 26.8 36.7 18.0 33 744 1.7 4.2 15.5 97.9

Hours of Power Production Above:
4

Table 1 shows the preliminary duration results for the Gaia-Wind 11 kW. The turbine accumulated 

2,704.9 hours of total run time with an operational time fraction of 90.8%.

The low operational time fraction for August and September of 2008 was caused by the failure of two 

contactors in the controller. Investigations suggest that the 2-pin flat connectors used to wire the 

contactors were poorly connected when installed at Gaia-Wind’s electrical supplier. Additionally, the 

Gaia-Wind 11 kW turbine controller originally was designed for a 50-Hz grid, and it is possible that the

contactors that originally were installed in the controller were underrated for the 60-Hz grid at the 

NWTC. It now is standard for all contactors in the controller to be installed with tube connectors for a 

more secure connection, and all turbine controllers on a 60-Hz grid are installed with the higher-rated 

contactors. Since the replacement of the contactor and pin connectors, the turbine has run with a high 

operational time fraction.

The majority of the other time classified as TN during the test is attributed to braking-time faults, vibration 

errors, and maintenance. The braking-time faults occurred when the turbine took longer to brake than 

designed; this usually occurred during high winds. The vibration errors are expected to have occurred 

from birds nesting the nacelle. With guidance from Gaia-Wind, NREL installed a screen over the opening 

in the nacelle to prevent birds from entering. Since the installation of the screen, the turbine has run 

without vibration errors.

Table 2 shows the preliminary duration results to date for the ARE 442. The ARE 442 has accumulated

2,888.8 hours of total run time with an operational time fraction of 91.3%. 

The low operational time fraction that occurred in November 2008 was caused by failure of the turbine’s 

insulated-gate bipolar transistors (IGBTs) during a simulated grid fault for safety and function testing. 

The majority of the remaining time classified as TN during the test is attributed to the over-temperature 

and overvoltage faults that the turbine experiences in high winds. The diversion loads for the turbine were 

located inside the data shed and did not dissipate heat properly, resulting in temperature faults at high 

power production. The diversion loads were moved outside of the data shed in February 2009. Since then, 

the over-temperature faults have been eliminated, however the turbine now is experiencing overvoltage 

faults.

Table 2. Preliminary Duration Results for the ARE 442

Turbulence intensity (TI) is the ratio of the wind-speed standard deviation to the average wind speed. 

Turbulence intensity is computed for each 10-minute data set and averaged to produce the monthly values 

Max Gust TI @ 15 # Data T T T U T E T N O

Month 0 m/s 10.2 m/s 15.3 m/s (m/s) m/s (%) Points (hours) (hours) (hours) (hours) (%)

Overall 2888.8 520.7 153.0 42.9 18.9 311 6576 102.5 212.0 541.9 91.3%

Jul 2008 296.0 7.5 0.0 27.8 15.8 3 744 12.5 152.2 0.0 100.0%

Aug 286.8 9.5 0.0 26.5 16.9 1 744 30.5 4.0 0.0 100.0%

Sep 217.5 8.8 0.7 23.2 13.8 8 720 49.2 5.3 0.3 100.0%

Oct 280.5 35.7 6.7 34.0 16.9 13 744 0.8 5.0 9.1 98.8%

Nov 156.0 8.2 0.0 34.3 19.5 44 720 -0.2 0.3 279.4 61.2%

Dec 379.2 131.8 41.8 42.9 18.2 72 744 1.2 10.2 120.4 83.6%

Jan 2009 466.5 146.3 44.3 42.9 20.0 93 744 0.7 1.8 76.8 89.6%

Feb 389.3 104.5 46.3 39.5 19.7 33 672 4.0 31.7 36.7 94.2%

Mar 417.0 68.3 13.2 34.9 18.4 44 744 3.8 1.5 19.1 97.4%

Hours of Power Production Above:
5

provided in Table 1 and Table 2. The average turbulence intensity at 15 m/s for the entire test period was 

19.0% for the Gaia-Wind 11 kW and 18.9% for the ARE 442.

Another factor of reliable operation is that the turbine should experience no significant power 

degradation. Each month the average power is plotted for each wind-speed bin and analyzed for any 

obvious trends in power production. Examination of power degradation plots indicated no apparent power 

degradation for the Gaia-Wind 11 kW or the ARE 442.

The dynamic behavior of the turbine is assessed by observing the turbine in a range of operating 

conditions. The turbine is observed at wind-speed intervals from cut-in wind speed to 20 m/s for at least 

one hour in total. Tower vibrations, noise, yaw behavior, and tail movement all are documented in the 

logbook and included in the duration-test report. For the ARE 442 the following dynamic observations 

were made. During high winds, the rotor operates at yaw errors of between approximately 30 degrees and 

60 degrees and the furl movements excite the tower slightly. Overall, it appears that no excessive 

vibrations are occurring. In winds of between 8 m/s and 12 m/s the turbine tracks the wind well. For the 

Gaia-Wind 11 kW, the following dynamic behavior observations were made. The turbine tracks winds 

well in all observed wind speeds. No excessive vibration was observed. There is a slight audible 

thumping noise as blades pass behind the tower.

Power Performance Testing

Power performance testing is conducted per IEC standard 61400-12-1, Power Performance Measurements 

of Electricity Producing Wind Turbines, referencing Annex H for small wind turbines when appropriate. 

Products of the test include a measured power curve, a power coefficient (CP) curve, and an estimation of 

annual energy production (AEP). 

For small turbines, statistical data is collected in 1-minute sets and sorted into 0.5-m/s-wide wind speed 

bins. Data collection is complete when the wind speed bins between 1 m/s and 14 m/s contain 10 minutes 

of data each, and the total database consists of at least 60 relevant hours. Wind speed bins are plotted 

against the corresponding bin power to produce a power curve. Power curves are normalized to sea-level 

air density; the site-specific air density at the NWTC is relatively low, 1.0 kg/m3

. The power coefficient is 

the ratio of power generated by the turbine to the power available in the wind.

Preliminary power and CP curves for the Gaia-Wind 11 kW are displayed in Figure 2. The power curve 

for the Gaia-Wind 11 kW shows power measurements that are greater than rated power. Preliminary 

power and CP curves for the ARE 442 are displayed in Figure 3; this turbine performed as expected.

The original inverter on the Windspire was optimized for power performance and failed after several 

months of operation. After the failure, a production model inverter was installed and operated until testing 

on the Windspire was suspended. The required amount of data was not collected on either inverter due to 

failures, however the incomplete preliminary power and CP curves for both configurations are shown in 

Figure 4. 
6

Figure 2. Preliminary power and CP curves for the Gaia-Wind 11 kW

Figure 3. Preliminary power and CP curves for the ARE 442

0

0.05

0.1

0.15

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0.25

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0.35

0.4

0

2

4

6

8

10

12

0 5 10 15 20

CP

Power, kW

Normalized Wind Speed, m/s

Preliminary Sea-Level Air Density Normalized Power Curve

ARE 442

Power

Cp

0

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0.15

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-2

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CP

Normalized Power, kW

Wind Speed, m/s

Preliminary Sea-Level Air Density Normalized Power Curve

Gaia-Wind 11kW

Power

Cp
7

Figure 4. Mariah Power Windspire preliminary power and Cp curves for the power optimized inverter 

(Inverter 1) and the production inverter (Inverter 2)

Annual energy production is estimated by applying the power curve generated from power performance 

testing to a Rayleigh distribution. The AEP is given for annual average wind speeds at hub height for 

4 m/s to 11 m/s. The measurements reported below assume no energy production beyond the highest 

filled bin in the power performance test. Table 3 shows the preliminary AEP as measured based on power 

performance data for the Gaia-Wind 11 kW and ARE 442. The AEP is not reported for the Windspire 

because the required amount of data was not collected.

Table 3. Preliminary Measured AEP for the Gaia-Wind 11 kW and the ARE 442

Safety and Function Testing

Safety and function testing is conducted per IEC Standard 61400-2, section 9.6, and seeks to test the 

essential functions of the turbine system. However, NREL does not limit testing to the scope of the 

standard; other features that are not required by the standard also are inspected and tested. For each 

turbine, NREL collects data to characterize the turbine’s power control, rotor-speed control, behavior 

upon loss of load, normal start-up, normal shutdown, and emergency shutdown. Additionally, NREL 

0.00

0.05

0.10

0.15

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0.25

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0.2

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1.2

1.4

1.6

0 2 4 6 8 10 12 14 16

CP

Normalized Power, kW

Wind Speed, m/s

Preliminary Sea-Level Air Density Normalized Power Curve

Mariah Power Windspire

Inverter 1 Power

Inverter 2 Power

Inverter 1 Cp

Inverter 2 Cp

AEP-Measured AEP-Measured

kWh kWh % kWh kWh %

4 17,716 1,692 9.6% 7,884 1,717 21.8%

5 32,122 2,093 6.5% 15,327 1,948 12.7%

6 46,292 2,284 4.9% 23,516 2,144 9.1%

7 58,690 2,327 4.0% 30,967 2,271 7.3%

8 68,525 2,285 3.3% 36,718 2,325 6.3%

9 75,474 2,197 2.9% 40,459 2,314 5.7%

10 79,617 2,087 2.6% 42,350 2,254 5.3%

11 81,326 1,966 2.4% 42,770 2,160 5.1%

Hub Height Annual 

Average Wind Speed 

(Rayleigh) m/s

Gaia-Wind 11kW ARE 442

Standard Uncertainty Standard Uncertainty
8

performs turbine specific tests to verify the turbine controller’s function and predicted behavior. Although

safety and function testing examines the essential functions of the turbine, it does not certify whether a 

turbine is safe to operate. Table 4 shows the preliminary safety and function data summary for the GaiaWind 11 kW. The turbine performed as designed with one exception. When the turbine was shut down 

manually using the disconnect switch and then was restarted, an over-speed error was present on the 

controller. The error had to be reset before the turbine could be started again.

Table 4. Preliminary Safety and Function Test Summary for the Gaia-Wind 11 kW

Test Method Comment Complies 

with Design

Power control Turbine controls power output per design Yes

Rotor speed control Turbine controls rpm to 61, per design Yes

Normal start-up Turbine starts after several motor pulses in design wind speed and above, 

and below cut-out; over-speed error on start-up after manual shutdown

Partially

Normal shutdown Turbine shuts down normally in winds less than cut-in and greater than

cut-out

Yes

Emergency stop Turbine stops within 2 to 3 seconds of pressing emergency stop button Yes

Loss of grid Turbine brakes immediately and stops within 2 to 3 seconds of load loss Yes

Undervoltage / 

overvoltage

In an overvoltage simulation the turbine brakes immediately Yes

High wind speed 

shutdown

Turbine stops in winds greater than 25 m/s and waits for start-up per 

the design

Yes

Rotor overspeed Turbine brakes immediately in simulated 10% overspeed and deploys tip 

brakes at 15% simulated overspeed

Yes

Generator overcharge Turbine brakes immediately in simulated generator overcharge Yes

Excessive vibration Vibration error registers on turbine controller after activating vibration 

sensor

Yes

Cable twist Cable-twist error registers on turbine controller after lifting cable-twist arm Yes

Table 5 shows the preliminary safety and function results for the ARE 442. The turbine’s two diversion 

loads originally were installed inside of the data shed per the manufacturer’s design. They later were 

moved to an enclosure outside of the data shed, after it was determined that their placement was causing

repeated over-temperature faults. When the diversion loads were installed in the data shed, the overtemperature faults would occur in high-wind conditions as heat built up inside the data shed. 

Temperatures measured near the turbine’s sensors indicated that the turbine shut down near or below its 

set point.

Table 5. Preliminary Safety and Function Test Summary for the ARE 442

Test Method Comment Complies 

with Design

Power control Power is limited by the capacity of the inverters, these max out at 

12 kW; after that, power is diverted to the diversion loads

Yes

Rotor speed control Test pending —

Yaw control The turbine tracks the wind under all conditions; due to the furl 

mechanism, the rotor almost always has a yaw error

Yes

Normal start-up Turbine starts in any winds ranging from cut-in to 25 m/s Yes

Emergency stop Turbine stops when stop button is pushed on the voltage clamp; this 

has been tested for a wide range of wind speeds

Yes
9

Loss of grid Disconnecting the grid causes an immediate shutdown; in two events

where a grid outage occurred in high-wind conditions, the IGBT’s in the 

voltage clamp failed, although the turbine still shut down

Partially

Overvoltage fault In high winds the turbine currently experiences the overvoltage fault, 

demonstrating that this feature works

Yes

Over-temperature fault Temperatures measured near the turbines sensors indicate that the 

turbine shuts down near or below its set points

Yes

Table 6 shows the partial preliminary safety and function test summary for the Windspire. Complete

safety and function test data was not collected for the Windspire before testing was terminated due to 

turbine problems.

Table 6. Preliminary Safety and Function Test Summary for the Windspire

Test Method Comment Complies 

with Design

Power control Turbine controls power output per design Yes

Rotor speed control Turbine controls rpm per design Yes

Normal start-up The turbine starts normally; it experiences two resonance modes at 

approximately 60 rpm and 300 rpm

Yes

Normal shutdown The turbine shuts down normally as winds drop below cut-out, 

however it maintain a low rpm (3–10) when braked; the turbine was 

not designed to shut down in high winds

Yes

Emergency stop Turbine stops within 2 to 3 seconds of opening the disconnect 

switch

Yes

Loss of grid Turbine stops within 2 to 3 seconds of load loss Yes

Rotor over speed Data was not collected for this test Unknown

Overvoltage/undervoltage Data was not collected for this test Unknown

Power Quality

IEC standard 61400-21 for power quality is defined for three-phase turbines and only is required for

medium- or high-voltage systems. Power quality testing only will be performed for the Gaia-Wind 11 kW 

and the Entegrity EW50 because they both are three-phase systems. Measurements include reactive 

power, flicker, voltage fluctuations, and harmonics. At the time of this writing, there was no data 

available for either turbine.

Noise Testing

IEC standard 61400-11 does not contain information specific to small wind turbines, however, they will 

be addressed specifically in the revision. The noise test characterizes emissions from a turbine in terms of 

sound power level, one-third octave levels, and tonality. For small wind turbines the IEC standard is 

followed with some modifications. Ten-second averages are used instead of 1-minute averages to better 

characterize the more-dynamic nature of small wind turbines. Also, to determine the sound pressure levels 

at the integer wind speeds, binning data is used instead of regression analysis. At the time of this writing, 

there were no results available for noise testing.
10

Consumer Perspective

The TN value from the duration test gives the consumer an idea of how much downtime to expect from a 

turbine per year based on maintenance and faults. The operational time fraction for the Gaia-Wind 11 kW 

was 90.8% for the entire test period. Based on this number, the typical consumer could expect the turbine 

to be available to produce power 90.8% of the time. Although the actual time that the turbine is faulted 

can vary, NREL suspects that it might be less than reported here because the primary contributor to 

downtime—the failed contactors—appears to have been neutralized. 

Because the downtime for the ARE occurs mostly in high winds, the operational time fraction of a 

particular turbine depends on the wind-speed distribution. Additionally, the furl mechanism could

function differently in greater air densities, which also could affect the operational time fraction.

The average annual energy usage per household is approximately 11,000 kWh and the average energy 

usage per commercial establishment is approximately 77,000 kWh (Energy Information Administration 

2009). Figure 5 shows the average annual energy used by consumers compared with the AEP estimated at 

an average hub-height wind speed of 6 m/s for the ARE 442 and Gaia-Wind 11 kW. 

Figure 5. Average annual energy used by consumers compared with annual energy production at a 

hub-height wind speed of 6 m/s

Regional Test Centers

In the fall of 2008, the NWTC held a small wind testing workshop for perspective test sites. Based on the 

response generated at the meeting, the NWTC began developing the concept of regional test centers. 

NREL plans to conduct a competitive solicitation to select test centers that want to develop small turbine 

testing capabilities. NREL will partially fund the test centers and will provide technical support.

0

10000

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50000

60000

70000

80000

Energy (kWh)

AEP at 6 m/s Average Hub Height

Avg Commerical

Gaia-Wind 11 kW

ARE 442

Avg Residential
11

The Future of Independent Testing

At the time of this writing, proposals had been received and reviewed for the second solicitation of 

independent testing. It is expected that installation will begin on these turbines during the fall of 2009. 

Testing on the ARE 442 and the Gaia-Wind 11 kW is expected to continue through the spring of 2009 

and possibly beyond. Testing on the Entegrity EW50 is expected to continue through the spring of 2010.

References

Energy Information Administration (January 2009). “Table 5. U.S. Average Monthly Bill by Sector, 

Census Division, and State 2007.” Official energy statistics. U.S. Department of Energy, 

http://www.eia.doe.gov/cneaf/electricity/esr/table5.html. Accessed April 9, 2009. 
F1147-E(10/2008) 

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Small Wind Turbine Testing Results from the National Renewable 

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DE-AC36-08-GO28308

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A. Bowen, A. Huskey, H. Link, K. Sinclair, T. Forsyth, D. Jager, 

J. van Dam, and J. Smith

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NREL/CP-500-45632

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NREL

11. SPONSORING/MONITORING 

AGENCY REPORT NUMBER

12. DISTRIBUTION AVAILABILITY STATEMENT

National Technical Information Service

U.S. Department of Commerce

5285 Port Royal Road

Springfield, VA 22161

13. SUPPLEMENTARY NOTES

14. ABSTRACT (Maximum 200 Words)

In 2008, the U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory began testing small wind 

turbines (SWTs) through the independent testing project. Four SWTs were selected for testing at NREL’s National 

Wind Technology Center, accredited by the American Association of Laboratory Accreditation to conduct power 

performance, power quality, noise, safety and function, and duration tests to IEC standards. Results of tests 

conducted will be publicly available and likely used by the Small Wind Certification Council to certify SWTs. Results 

also could be used by states to decide which turbines are eligible for state incentives. Reducing market barriers for 

SWTs will provide a range of consumer sectors—including residential, ranchers/farmers, business, and community 

applications (e.g., schools, tribes, municipal utilities, rural electric cooperatives)—the opportunity to invest in 

indigenous energy and contribute to energy independence. The paper reports results of testing to date, and puts the 

results in perspective for the average consumer. Other topics addressed include a description of DOE’s second 

solicitation for independent testing, and a discussion of the DOE’s support for developing additional testing centers to 

conduct preliminary screening of SWTs to identify turbines not ready for the commercial market.

15. SUBJECT TERMS

Wind; small wind turbines; power performance; power quality; manufacturer; safety and function; three-phase grid 

connection; noise testing

16. SECURITY CLASSIFICATION OF: 17. LIMITATION 

OF ABSTRACT

UL

18. NUMBER 

OF PAGES

19a. NAME OF RESPONSIBLE PERSON

a. REPORT

Unclassified

b. ABSTRACT

Unclassified

c. THIS PAGE

Unclassified 19b. TELEPHONE NUMBER (Include area code)

Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18