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DOE Pulse
  • Number 405  |
  • January 20, 2014

New test facility to improve wind turbines

NREL engineer Scott Lambert (left) and Project Manager Mark McDade discuss calibrations being done on the new dynamometer at the 5-MW Dynamometer Test Facility at NREL's National Wind Technology Center.

NREL engineer Scott Lambert (left) and
Project Manager Mark McDade discuss
calibrations being done on the new
dynamometer at the 5-MW Dynamometer
Test Facility at NREL's National Wind
Technology Center.

Premature failures of mechanical systems significantly impact the cost of wind turbine operations and thus the total cost of wind energy. Recently, DOE's National Renewable Energy Laboratory (NREL) took a step forward toward more reliable, lower-cost wind power with the addition of the new 5-megawatt (MW) Dynamometer Test Facility at its National Wind Technology Center (NWTC). The new facility expands the capability of NWTC engineers and industry partners to verify the performance and reliability of wind turbine drivetrain prototypes and commercial machines.

The facility is capable of testing drivetrains up to 5 MW—large enough to test virtually any land-based turbine—and employs dynamically variable loading capabilities that will allow researchers to better simulate conditions a turbine might experience in the field.

"These new capabilities make this a very special facility, one of the largest of its kind in
the world," NWTC Director Fort Felker said. "It gives NREL an enhanced ability to do comprehensive testing of modern multi-megawatt wind turbine systems in a laboratory environment to verify their performance before they are deployed."

A dynamometer replaces the rotor and blades of a wind turbine and allows researchers to control the turbine drivetrain's systems while simulating normal and extreme operating conditions. Historically, this testing has been done under torque (rotating) loads only. The new state-of-the-art facility at the NWTC incorporates a non-torque loading system into the testing regimen, a hydraulic device that enables simulation of both the rotational and bending loads that a wind turbine rotor places on a drivetrain.

"The non-torque loading system is what really sets this facility apart from other test sites," NWTC Dynamometer Project Manager Mark McDade said. "This allows us to test the drivetrain system with the types of loads that it will see in a real-world application. It's a very important feature for a test apparatus because the adverse impacts these types of loads can have on a system are significant."

The system features a 6-MW motor, providing power to a turbine during testing. The motor turns at very high speed and low torque. The motor drives a gearbox, which transforms that output to the high torque and low speed that is appropriate for a wind turbine drivetrain. This provides the rotating loads on the test article.

Add to this motorized torque testing the non-torque loading capability unique to the NWTC, and NREL is able to put a wind turbine drivetrain through the most realistic loading tests possible in a laboratory.

Dynamometer testing is used by industry to confirm proper operation and reduce the risk of deploying wind turbine prototypes before they are put into service. Conducting these tests in a laboratory environment before deployment is important because unanticipated failures can be detected and corrected early in the development process, leading to a lower cost of ownership for wind farm operators—and ultimately lower-cost wind energy for the consumer.

"These machines are expected to operate reliably in the field, often in harsh conditions, for 20 years or more," Felker said. "The ability to comprehensively test these systems in the lab, to verify their reliability and performance before they go into service, is an important capability for the wind industry."

Another important capability that enhances the value of the work being done at NREL's 5-MW Dynamometer Test Facility is the Controllable Grid Interface (CGI), a powerful energy systems integration tool that allows engineers to control the electrical grid conditions that a test article will see.

The CGI simulates various grid disturbances, such as over-voltage or under-voltage events, allowing engineers and industry partners to determine how grid-connected systems will react to these events in a controlled environment. This type of testing—performed offline from the grid, but simulating a real-world grid environment—enables users to verify performance, assure standards compliance, and understand failures in a fraction of the time and cost that it takes to perform similar tests in the field.

The CGI will also help engineers determine how these systems will be able to provide ancillary services to the grid, as well as test and optimize the grid-integration-related performance of a unit before it is deployed.

"This is a significant capability for NREL, and it is very complementary to the work that will be done in the dynamometer," McDade said. "As more and more renewable energy generation and storage are added to our electricity mix, it is critical that we understand how systems will perform on the larger grid, how they will react to disturbances, and how they will be able to provide benefit to the grid from a systems integration standpoint."

The CGI can test not only the integration performance of wind turbines, but also that of a wide variety of grid-integrated energy systems, such as utility-scale solar photovoltaic (PV) generation, PV inverters, and energy storage systems.

In addition to enabling deployment-readiness testing, the new NREL test facility will examine future technology innovations, such as advanced drivetrain systems, that promise to usher in the next generation of higher-performance, lower-cost wind turbines.

Research at the facility will accelerate the development of new wind energy technologies, providing opportunities to verify concept and performance of prototype technology improvements at the pilot level before moving them into the marketplace.

"Important R&D will be done in this facility to answer the engineering questions that will allow us to develop the next generation of wind turbine technology," Felker said. "We need to continue to push the cost of energy down while at the same time improving the performance and reliability of these systems. A laboratory environment such as this, where we can seek the answers to these questions is an important step toward meeting those goals."

Learn more about NREL's National Wind Technology Center.David Glickson.

[David Glickson, 303.275.4097,
David.Glickson@nrel.gov]