A national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

National Renewable Energy Laboratory 

Innovation for Our Energy Future 

Testing Small Wind Turbines at 

the National Renewable Energy 

Laboratory 

Preprint 

K. Sinclair and A. Bowen 

To be presented at WindPower 2008 

Houston, Texas 

June 1–4, 2008 

Conference Paper 

NREL/CP-500-43452 

June 2008 

NREL is operated by Midwest Research Institute ● Battelle Contract No. DE-AC36-99-GO10337 
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Testing Small Wind Turbines at the 

National Renewable Energy Laboratory 

Karin Sinclair and Amy Bowen 

National Renewable Energy Laboratory 

National Wind Technology Center 

1617 Cole Blvd, Golden, CO 80401 

Karin_sinclair@nrel.gov; 303 384-6946 

Amy_Bowen@nrel.gov; 303 384-6931 

Introduction 

Reducing barriers to wind energy expansion, stabilizing the market, and expanding the 

number of small wind turbine (SWT) systems installed in the United States are important 

goals for the Department of Energy’s (DOE) Wind and Hydropower Technologies 

Program. One of the barriers for the distributed wind market is the lack of SWT systems 

that are independently tested and certified. 

The National Renewable Energy Laboratory (NREL) has testing capabilities that are 

accredited by the American Association of Laboratory Accreditation (A2LA). Currently, 

NREL is one of only two facilities in the United States that are A2LA accredited. To 

help industry provide consumers with more certified SWT systems, DOE/NREL 

launched a project in 2007 called Independent Testing. Through a competitive 

solicitation, NREL selected four commercially available SWT systems to test in 

2008/2009. The turbines will be tested to standards adopted by the International 

Electrotechnical Commission (IEC) and in compliance with the draft American Wind 

Energy Association (AWEA) standards for small wind turbine systems. 

The resultant test data may be used by the Small Wind Certification Council (SWCC), a 

nonprofit organization formed with support from DOE, AWEA, state energy offices, and 

turbine manufacturers to certify SWT systems. Certification by the SWCC is expected to 

commence in 2009. Test data could also be submitted to a certifying body as partial 

input for international certification. 

SWTs that are tested and certified will give consumers greater confidence that the 

systems they install will perform within specified wind regimes as advertised by the 

manufacturer. 

Turbines Selected

Of the four turbines selected from NREL’s competitive solicitation, subcontracts have 

been executed with three of the turbine manufacturers (Mariah Power, Abundant 

Renewable Energy, and Gaia Wind). The fourth subcontract (Entegrity Wind Systems) is 

awaiting subcontracting approval, which is anticipated to be completed in the summer of 

2008. Each of the turbines in the current test cycle is described in the following section. 

1 
Mariah Power

Mariah Power’s Windspire is a 1.2-kW vertical-axis Giromill wind turbine. The turbine’s 

tower is 9.1-meters tall and its rotor area is 1.2 x 6.1 meters. The turbine has a 

permanent-magnet generator that has a single-phase output at 120 volts AC. 

Mariah Power’s Windspire Giromill wind turbine (NREL PIX 15704). 

2 
Abundant Renewable Energy

The Abundant Renewable Energy ARE 442 is a 10-kW 3-bladed horizontal-axis upwind 

turbine. It has a hub height of 30.9 meters and a rotor diameter of 7.2 meters. The turbine 

has a three-phase permanent-magnet generator that operates at variable voltages up to 

410 volts AC. 

Abundant Renewable Energy ARE 442 (NREL PIX 15734). 

3 
Gaia-Wind 

The Gaia-Wind 11-kW turbine is a three-phase induction generator that operates at 480 

volts. The turbine’s downwind rotor has a 13 meter diameter and its tower is 18 meters 

tall. The two-bladed, oversized rotor is designed for low to moderate wind speeds. 

Gaia-Wind 11-kW turbine (NREL PIX 15705). 

4 
Entegrity Wind Systems

The Entegrity Wind Systems EW50 is a 50-kW 3-bladed horizontal-axis downwind 

turbine. The turbine’s rotor diameter is 15 meters and its hub height is 30.5 meters. It has 

a three-phase induction generator that operates at 480 volts AC. 

Entegrity Wind Systems EW50 (NREL PIX 15568). 

Tests and Testing Approach 

The suite of tests that will be conducted on each of the SWTs will include duration, 

power performance, acoustic noise emissions, safety and function, and power quality. 

Each is briefly described below. Tests are performed to IEC standards and in compliance 

with NREL’s A2LA accredited Quality Assurance (QA) system. Duration, power 

performance, and safety and function test data will be collected using a National 

Instruments-based data acquisition system and compiled through custom LabVIEW 

software. 

Duration testing is performed to summarize the turbine’s performance over long periods 

of time. Test data will be sorted monthly into time classes specified by the standard and 

submitted to the client in an informal report. Duration testing will be performed 

according to IEC Standard 61400-2. 

Power performance testing produces a power vs. wind speed graph to summarize the 

turbine’s power generation performance at different wind speeds. This test will be 

performed according to IEC Standard 61400-12-1, referencing Appendix H for small 

5 
turbines. Data are analyzed for rejections based on wind direction, turbine status, and 

instrument readings, and then compiled through an Excel-based program to produce a 

power curve. 

Acoustic Noise Emissions testing summarizes typical noise levels emitted from the 

turbine at different wind speeds. Sound data are recorded (one tower height plus half a 

rotor diameter down wind from the tower base) and processed using Noiselab software. 

Noise testing will be performed according to IEC Standard 61400-11. 

Safety and Function testing is performed to verify the turbine displays the behavior it is 

designed to have as represented by the manufacturer. Features to be tested will be drawn 

from the wind turbine documentation and may possibly include additional NREL 

specified features. The testing will be conducted in accordance with IEC Standard 

61400-2. 

Power Quality testing will be performed on the Gaia-Wind 11-kW and Entegrity EW50 

turbines according to IEC Standard 61400-21. This testing includes assessment of power, 

flicker, and harmonics levels for compliance with the standard. Turbines with a UL 1741 

compliant inverter will not undergo power quality testing. 

Accomplishments of the Project to Date 

After the four turbines were selected, two data-shed sites were developed, one existing 

and the other a new installation. With a possible second solicitation on the horizon, the 

data sheds, turbine sites, and data acquisition software were all designed to be nonturbine specific. The data sheds were outfitted with wire ways to allow easy installation 

and removal of data and power cables. Conduit was laid and buried from the data shed to 

the individual metrology tower sites to allow for future removal and new installation of 

power and data cables. In the case of future turbine installations, metrology tower 

locations will remain constant while turbine locations will vary depending on turbine 

sizing. 

Custom data-acquisition software was developed in LabVIEW for duration, power 

performance, and safety and function tests. The software has built-in flexibility to allow 

for a varying number of data channels and signal types. This allows for minimal codeuser interaction while setting up the software for new turbines. 

Foundation kits for the four turbines were received ahead of the turbine system itself to 

allow time for foundation pouring and curing. NREL used a subcontractor for the 

foundation installations for the Gaia-Wind 11-kW turbine, ARE 442, and Entegrity 

EW50. The Windspire foundation was installed by NREL site operations crew. 

The installation and commissioning of the Mariah Windspire was completed during the 

week of May 5, 2008; this was the first installation in the Independent Testing Project. 

The Gaia-Wind 11-kW turbine was installed and commissioned during the week of May 

6 
7 

12, 2008. Installation and commissioning of the ARE 442 was completed the week of 

June 9, 2008. 

Instrument calibration and laboratory check out (a process of validating that all systems 

are working as designed) to A2LA requirements and IEC recommendations have been 

completed for three of the turbine sites. NREL staff have completed the safety review and 

documentation that permit operation of the three installed turbines in an “unattended” 

mode. This permits the turbines to operate continuously as required for some of the test 

protocols. Data have been collected for several items in the safety and function test for 

the Gaia-Wind 11-kW turbine. Data are currently being collected for the duration and 

power performance tests for both the Windspire and the Gaia-Wind 11-kW turbines. 

Plans to Expand with Second Solicitation 

DOE is planning a second competitive solicitation to test additional SWTs in the FY 

2010 timeframe. It is anticipated that the second round RFP will be released in fall 2009. 

In addition, DOE/NREL may consider expanding this project to support testing additional 

SWT systems at the NREL site with funding from non-DOE sources. 

For More Information

For progress on DOE/NREL’s Independent Testing Project, go to NREL’s web page 

under a section titled Small Wind Turbine Independent Testing at: 

http://nrel.gov/wind/technical_support.html Test reports will be posted as they become 

available. 
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Testing Small Wind Turbines at the National Renewable Energy 

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K. Sinclair and A. Bowen 

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