Structural Research Facilities
NREL's structural research 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 validated in one of three facilities at the National Wind Technology Center (NWTC). Facilities are capable of validating blades and components smaller than 1 meter (m) to more than 50 m in length.
Structural research facilities are equipped with state-of-the-art servo-hydraulic equipment and data acquisition systems tailored for researching composite blades and components. NREL's structural blade research validation is performed to the International Electrotechnical Commission 61400-23 standard. General types of rotor blade research performed at the NWTC includes:
- Property validation—Evaluates inherent structural properties, including shape and mass, and dynamic characterization of inertial and stiffness properties
- Static strength research validation—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 research—Application of millions of cycles of accelerated fatigue loads to demonstrate the durability and lifetime of a blade or component. Capabilities include single-axis validating by direct load application from servo-hydraulic actuators, up to biaxial loading by validating flapwise and lead-lag directions simultaneously using resonant research systems.
Research Equipment and Facilities
Structural research facilities share modular servo-hydraulic control and actuation equipment and data acquisition systems. The NWTC maintains hydraulic research 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 research validation. NWTC measurement capabilities include:
- Basic load
- Strain (foil and optical fiber) sensing
- Many types of nondestructive research systems.
Modal, acoustic emission, thermography, and surface characterization systems are available.
Building 251 and A-60
These two facilities are capable of validating blades and systems up to 19 m. Facilities are equipped with research stands with overturning moment capacities to 1.4 millinewtons per meter (MN-m). Research facilities also include coupon and component research validation load frames with force capacities of up to 500 kN.
Structural Test Laboratory
Designed and equipped to validate blades greater than 50 m, the Structural Test Laboratory (STL) is used for researching large structural components and blades. The STL has validation stands rated at 5.4 millinewton-meters (MN-m) and 16.7 MN-m. Both indoor and outdoor research configurations are possible. The high bay of the SRL includes a structural floor for reacting MN-scale forces for applying research validation loads.
To learn more about structural research validation, see the NWTC Structural Research 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.