Structural Testing Laboratory
NREL's structural test facilities enable the characterization and validation of wind turbine blades and components.
The extreme operating loads experienced by blades during field operation and accelerated fatigue lifetime loading can be simulated and tested in one of three laboratories at the National Wind Technology Center (NWTC). Facilities are capable of testing blades and components smaller than 1 meter (m) to more than 50 m in length.
Structural test facilities are equipped with state-of-the-art servo-hydraulic test equipment and data acquisition systems tailored for testing composite blades and components. NREL's structural blade tests are performed to the International Electrotechnical Commission 61400-23 standard. General types of rotor blade testing performed at the NWTC include:
- Property validation — Evaluates inherent structural properties, including shape and mass, and dynamic characterization of inertial and stiffness properties
- Static strength testing — Application of quasi-static bending moments to validate design parameters and demonstrate the ability of a blade or component to handle extreme design load cases. Extreme and ultimate (failure) static loads are applied by cranes, hydraulic actuators, or servo-electric winches at multiple stations along the blade.
- Fatigue testing — Application of millions of cycles of accelerated fatigue loads to demonstrate the durability and lifetime of a blade or component. Capabilities include single-axis testing by direct load application from servo-hydraulic actuators, up to biaxial loading by testing flapwise and lead-lag directions simultaneously using resonant test systems.
Test Equipment and Laboratories
Structural test facilities share modular servo-hydraulic control and actuation equipment and data acquisition systems. The NWTC maintains hydraulic test systems capable of displacements to 1.5 m and force capacities to 500 kilonewtons (kN). Hundreds of channels of data acquisition are available using custom-designed software specific to structural testing. NWTC measurement capabilities include:
- Basic load
- Strain (foil and optical fiber) sensing
- Many types of nondestructive test systems.
Modal, acoustic emission, thermography, and surface characterization systems are available.
Building 251 and A-60
These two facilities are capable of testing blades and systems up to 19 m. Facilities are equipped with test stands with overturning moment capacities to 1.4 millinewtons per meter (MN-m). Test facilities also include coupon and component test load frames with force capacities of up to 500 kN.
Structural Testing Laboratory
Designed and equipped to test blades greater than 50 m, the Structural Testing Laboratory (STL) is used for testing large structural components and blades. The STL has test stands rated at 5.4 millinewton-meters (MN-m) and 16.7 MN-m. Both indoor and outdoor test configurations are possible. The high bay of the STL includes a structural floor for reacting MN-scale forces for applying test loads.
To learn more about structural testing, see the NWTC Structural Testing fact sheet.
Satellite Facility: Wind Technology Testing Center
With wind blades now exceeding the 50-m maximum that the on-site STL can safely manage, NREL formed a cooperative research and development agreement with the Massachusetts Clean Energy Center to develop the nation's newest blade testing facility, the Wind Technology Testing Center.