Fastblade: A Technological Facility for Full-Scale Tidal Blade Fatigue Testing

Fatigue testing of tidal turbine blades requires the cyclical application of loads without matching the natural frequency of the blade due to their high stiffness and associated thermal issues of composite materials at those frequencies (i.e., 18Hz cycles). To solve this, loading the blades with an auxiliary system is necessary; in most cases, a hydraulic system tends to be highly energy demanding and inefficient. Using real on-site collected data, a series of equivalent target loads were defined and used in FastBlade to prove an efficient way to perform fatigue. They used a regenerative digital displacement hydraulic pump system and saved up to 75% compared to a standard hydraulic system. During the test, a series of measurements were performed on the blade response and Fastblade itself, showing exciting results on the mechanical behaviour of a blade and best testing practice for FastBlade. The blade withstood 20 years (equivalent) of accelerated fatigue loading without catastrophic failure. FastBlade identifies possible improvements to the testing procedures, i.e., control strategies, load introduction, instrumentation layout, instrument calibration, and test design.