Physicists at the ForWind Center for Wind Energy Research at the University of Oldenburg in Germany have developed a real-time monitoring technique that they claim could be used to analyze the structural health of wind turbines more effectively than existing methods.
Until now, standard methods have relied on so-called spectral analysis, which looks at the different frequency response. But these measurements are distorted by the turbulent working conditions. As a result, these detection methods often only detect really major damages in turbines, like a crack that covers more than 50 percent of a blade.
The challenge for the team was to find a method for detecting fatigue in the wind turbines’ parts without having to remove each of the components and while the turbine is in operation. The new technique combines the use of strain-gauge force sensors with a novel modeling approach based on Stochastic equations. The team tested it on an experimental set-up of undamaged and damaged beam structures, which were exposed to excitations, or noise, made by different turbulent wind conditions.
The analytical method allowed the team to distinguish between dynamics attributed to mechanical properties such as stiffness of the blade and those attributed to interfering noise, such as turbulence. The authors say they could detect precisely the changing mechanical properties of the beam material, based on an analysis of the mechanical vibrations.
When the method is further refined, the researchers believe it could be used to identify material fatigue or untightened screws, for example, and be applied to more complex structures, such as automotive or airplane parts.