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Accredited Testing

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. Small and large wind turbines are given a suite of tests that test acoustic noise emissions, duration, load, power performance, power quality, and safety and function. Each of the tests is briefly described below. Tests are performed to International Electrotechnical Commission (IEC) standards and in compliance with NREL's A2LA-accredited Quality Assurance (QA) system. Duration, load, power performance, and safety and function test data are collected using a National Instruments-based data acquisition system and compiled through custom LabVIEW software.

Acoustic Noise Emissions

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 downwind from the tower base) and processed using Noiselab software. Noise testing is performed according to IEC Standard 61400-11.


Duration testing is performed to summarize the turbine's performance over long time periods. Test data are sorted monthly into time classes specified by the standard and submitted to the client in an informal report. Duration testing is performed according to IEC Standard 61400-2.

Mechanical Loads

Mechanical loads testing is performed in accordance with the IEC TS 61400-13. The objective of mechanical loads testing is to measure data which is then used to validate the simulation models of the turbine. Turbine loads are measured in conjunction with inflow parameters and turbine operational signals. Loads are measured on the blade root, main shaft and tower. Loads are measured under normal operation, during transients and during faulted conditions.

Power Performance

Power performance testing produces a power vs. wind speed graph to summarize the turbine's power generation performance at different wind speeds. This test is performed according to IEC Standard 61400-12-1, referencing Appendix H for small 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.

Power Quality

Power quality testing is performed 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.

Safety and Function

Safety and function testing is performed to verify that the turbine displays its designed behavior as represented by the manufacturer. Features tested are drawn from the wind turbine documentation and may possibly include additional NREL-specified features. The testing is conducted in accordance with IEC Standard 61400-2.

For more information, contact Dave Simms at 303-384-6942