Impedance-based structural health monitoring of wind turbine blades

Abstract

Wind power is a fast-growing source of non-polluting, renewable energy with vast potential. However, current wind technology must be improved before the potential of wind power can be fully realized. One of the key components in improving wind turbines is their blades. Blade failure is very costly because blade failure can damage other blades, the wind turbine itself, and possibly other wind turbines. A successful structural health monitoring (SHM) system incorporated into wind turbines could extend blade life and allow for less conservative designs.Impedance-based SHM is a method which has shown promise on a wide variety of structures. The technique utilizes small piezoceramic (PZT) patches attached to a structure as self-sensing actuators to both excite the structure with high-frequency excitations, and monitor any changes in structural mechanical impedance. By monitoring the electrical impedance of the PZT, assessments can be made about the integrity of the mechanical structure. Recent advances in hardware systems with onboard computing, including actuation and sensing, computational algorithms, and wireless telemetry, have improved the accessibility of the impedance method for in-field measurements.The feasibility of implementing impedance-based SHM on wind turbine blades is investigated in this work. Experimentation was performed to determine the capability of the method to detect damage on blades. First, tests were run to detect both indirect and actual forms of damage on a section of an actual wind turbine blade provided by Sandia National Laboratories.Additional tests were run on the same blade section using a high-frequency response function method of SHM for comparison. Finally, based on the results of the initial testing, the impedance method was utilized in an attempt to detect damage during a fatigue test of an experimental wind turbine blade at the National Renewable Energy Laboratory's National Wind Technology Center.iii ACKNOWLEDGEMENTS

Structural health monitoring of offshore wind turbines: A review through the Statistical Pattern Recognition Paradigm

“…According to [83], only local response of the structure will be transmitted to the sensor in case the excitation frequency is big enough. Damage detection using this monitoring technique has been proven to be effective in different types of structures, including composite structures [84,85].…”

Performance optimization of a dual-rotor wind turbine system

“…One of the key components in improving wind turbines is their blades. Blade failure is very costly because blade failure can damage other blades, the wind turbine itself, and possibly other wind turbines [5]. Wind turbine rotor blades with embedded sensors are a potential technology for the substantial improvement in wind turbine efficiency.…”

Wind turbine blade health monitoring with piezoceramic-based wireless sensor network

“…It is important to perform structural health monitoring (SHM) to detect damage before structural failure of wind turbine blades occurs. Traditional SHM methods for wind turbine blade include the following: (1) visual inspection; (2) tap test; (3) acoustic emission (AE) [2][3][4][5][6][7]; (4) infrared thermography [8][9][10]; (5) electro-mechanical impedance-based method [11]; (6) optical fiber-based approach [12][13][14][15][16][17][18],); and (7) piezoelectric transducers [19,20]. Unfortunately, visual inspection cannot detect cracks inside blades and is not suitable for automated and real-time applications.…”