Lasers Can Remotely Monitor Oscillations of Wind Turbines

Illustration: Fraunhofer IOSB

Wind turbines, like any machine with moving parts, can fail. They have a useful life span, after which the loading on the various pieces including turbine blades and tower could cause decreases in efficiency or, in very rare cases, outright collapse. That loading comes during normal operation, but the oscillations the turbine undergoes play an important role in just how long a turbine will survive. Heretofore, sensors placed physically on the turbine have been the method of choice for measuring the oscillations. But lasers might work better.

A new system, to be demonstrated at an IT conference called CeBIT in Hanover, Germany, in March, combines a low-power laser with a camera to comprehensively assess oscillations of a wind turbine. Unlike the sensors-on-the-turbine technique, with which the oscillations are really only recorded at the specific points where the sensors sit, the laser-based method captures the entire oscillatory pattern—on the blades, tower, all of it—and paints a more complete picture.

Researchers at the Fraunhofer Institute in Germany created the new system. From a press release:

"The centerpiece of the system responsible for this is an IT-based tracking system combining a camera and a laser. These are mounted on a head that can pan and tilt to follow the rotor blades. The camera records images of the installation and forwards these along to software that processes the images and builds a model of the rotary motion from the data. With the help of this information, the pan and tilt head is positioned so that the laser automatically follows the rotor blades. The camera simultaneously collects data about the exact position of the roughly two-to-three centimeter laser spot on the rotor blade in order to stabilize it on the revolving surface."

The researchers, led by Ilja Kaufmann, say that the system is easily transportable, and can work from hundreds of meters away from the turbine itself. Assuming it's possible to correct for the laser's motion, even monitoring offshore turbines from a boat should be feasible. As many wind farms near the ends of their prescribed operating lives, systems like this can help operators make choices regarding when to decommission a turbine. "Operators can use our technology to [evaluate] their installations," Kauffman said. "We can provide decision-making assistance for questions like 'Is it in good enough shape that I can continue to operate it, or should I sell it and build a new one at the same site?'"

This idea seems to solve a few issues with turbine monitoring: keeping track of the full turbine rather than just individual points, and making the process easier. The new tool and technique make it simple to monitor one turbine, move the system to the next one, and so on. And it seems that idea is gaining steam: below is a video of another method for remotely monitoring a wind turbine using interferometric radar from up to a kilometer away. The days of sensors on turbine blades may be on the way out.

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