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Device and Component Testing

NREL houses the nation's premier laboratory facilities for testing offshore wind and water power devices and maintains a staff of offshore-trained test engineers and technicians that conduct a wide range of field measurements to verify system performance and dynamic responses. Applying 35 years of wind turbine testing expertise, NREL has the capabilities to obtain high-resolution measurements in the laboratory and open water test sites.

With the support of the U.S. Department of Energy, NREL has helped the wind industry advance by introducing customized sensors and instrumentation; conducting landmark experiments, such as the National Aeronautics and Space Administration, Ames, unsteady aerodynamics experiment; and leading industry research groups such as the wind Gearbox Reliability Collaborative. NREL is now taking its past successes and applying it years of experience and testing capabilities to advance the water power industry. Capabilities directly applicable to water power technologies include:

To read more about NREL's wind testing capabilities, see Testing.

Instrumentation

As the newest member in our nation's renewable energy portfolio, the marine and hydrokinetics (MHK) industry is developing concepts for dozens of devices that can turn the kinetic energy in ocean waves and currents into clean electricity.  For these new technologies to mature to commercial readiness, research and testing are essential to mitigate technical, environmental, and financial risks.

To advance the MHK technology and provide necessary data to feed future designs and field expansion, NREL is developing a Modular Ocean Instrumentation System (MOISyT) that will provide device companies with the field measurements they need to better understand system operation and performance. In addition to system performance, NREL's MOISyT provides the measurements needed for resource assessment, siting, testing, evaluation, monitoring, demonstration, and eventual certification for a broad range of offshore renewable energy devices, resources, and locations.

NREL's MOISyT is built with a commercial off-the-shelf, modular, and scalable infrastructure and LabVIEW software with individual software modules developed for separate functions and measurements. The reusable code can implement new features as needed and enables the MOIS to be rapidly customized to meet the unique measurement needs of individual deployments.

For more information contact Eric Nelson.

Structural Testing

A metal rotor blade from a water current turbine is clamped in a test stand. Small test sensors are attached to the blade from its tip to its base and are connected to the blade by cables.

Test setup for an edgewise fatigue test on an MHK blade.
NREL/PIX 19530

NREL facilities at the National Wind Technology Center (NWTC) support the testing of water power devices and components needed to simulate operational performance of designs from concept to production machine. NREL staff engineers and technicians provide water power industry manufacturers, developers, and operators with the turbine and component test expertise needed to validate designs and quantify performance. Component and full-scale structural testing is a valuable and necessary means of demonstrating system reliability. Conducting tests on components in the laboratory environment provide the data required to validate in-water designs. At the NWTC, laboratory test rigs are designed and configured to apply realistic boundary conditions and the forces, moments, and torques needed to properly simulate in-water loading in a laboratory environment.  Test articles can be heavily instrumented to measure key design parameters including stress, strain and displacement.  Designers need to measure key values to validate models and ensure their designs will meet the criteria for a full lifetime of operation.  Typical component structural testing needed to validate models and includes:

  • Property testing
  • Dynamic Characterization
  • Strength testing
  • Fatigue testing

Property testing evaluates inherent structural properties, including mass and center of gravity. Precise measurements of these parameters are critical to ensure compliance with design goals.

Dynamic characterization of a component or complex structure is accomplished through modal testing. Modal testing provides designers with the natural frequencies, damping values, and mode shapes of the component or system. These data are used to validate distributed system parameters including mass and stiffness. The parameters are critical inputs to dynamics models. Parameter tuning plays an important role in designing structures by minimizing dynamic loads and increasing lifetime. A typical modal test is conducted by installing an array of accelerometers on the structure, then measuring the response to a known input from impulse and random excitations.

Static strength testing validates design parameters and demonstrates the ability of a component or system to handle extreme design load cases. These load cases simulate the response of the structure while operating and parked to extreme conditions such as inflow direction changes, 50 or 100-year flow conditions, and loss of grid connection. These events can be simulated in the laboratory by properly constructing representative boundary conditions then applying loads simulating the flow or forcing function through hydraulic actuators, cranes, or winches. Multi-axial loading at independent locations is sometimes needed to properly simulate a given load case. Loads are applied while measuring specific data, including strain and displacement. Strain is used to evaluate the stress on a component, and displacement measurements quantify the stiffness of a component.

Fatigue Testing demonstrates the durability of a component or system. Typically fatigue tests will load a component with millions of load cycles applied over several weeks or months. Fatigue testing reveals design and manufacturing problems at an early stage of development and leads to overall improvements in design, performance, and reliability while reducing the risks inherent when commercializing new designs.

Fatigue loads are introduced to the structure through hydraulic actuators. Specialized component testing of blades may be accomplished by applying loads at the system's natural frequency to decrease the test duration. Displacement and strains are typically measured during the fatigue test. Structural health monitoring and nondestructive evaluation techniques, including acoustic emission and thermography, are employed to further assess the test article's health.

NREL is accredited by the American Association of Laboratory Accreditation (A2LA) to perform testing to the IEC 61400-23 wind turbine blade test standard. NREL has operated wind turbine blade structural testing facilities since 1990 and during this time has tested hundreds of wind blades. The NWTC has pioneered the development of innovative test systems that improve test accuracy and decrease the time of a typical test program. This expertise is being applied to the development of test methods and protocols for marine and hydrokinetic devices.

See our Blade Test Facility Specifications.

Drivetrain Testing

Dynamometers are an effective means for validating new drivetrain designs. NREL has dynamometer testing facilities that can test drivetrains and components with capacity ratings of less than 10 kW up to 5 MW. NREL's dynamometer test facilities can test a variety of components and subsystems, including generators, gearboxes, mechanical or electro-dynamic brakes, power electronics, control systems, and software.

Illustration of an underwater current turbine with a transparent nacelle that shows the turbine's gearbox and drivetrain. An arrow connects the turbine's gearbox to an enlarged illustration of the turbine's gearbox and drivetrain connected to a dynamometer for testing. Text boxes and arrows show the movement of electrical power, mechanical power, and control signals through the test system.

Test objectives of manufacturers and design engineers may include performance, system integration (generator, power electronics, and grid), software development, or accelerated life testing.

Controllable Grid Interface

NREL is developing a new controllable grid interface (CGI) test system at the NWTC that will significantly reduce the time to conduct and cost of conducting certification testing for renewable technologies. The CGI will be the first test facility in the United States to have fault simulation capabilities and that allows manufacturers and system operators to conduct certification tests in a controlled laboratory environment. When commissioned in 2013, it will be the only system in the world that is fully integrated with two dynamometers and has the capacity to extend that integration to renewable energy devices in the field and to a matrix of electronic and mechanical storage devices, all of which are located within close proximity on the same site.  The CGI's capabilities include:

  • Voltage fault ride-through
  • Frequency response
  • Continuous operation under unbalanced voltage conditions
  • Grid condition simulation (strong and weak)
  • Grid voltage distortions simulation
  • Reactive power, power factor, voltage control testing
  • Protection system testing (over and under voltage and frequency limits)
  • Islanding operation
  • Sub-synchronous resonance conditions
  • 50 Hz tests

Read more about NREL's CGI test system.