Keeping Those Wind Turbines Turning

E-mail Melanie Martella

Fiber-optic sensors, by which I mean the ones used for distributed temperature and strain sensing, are interesting technologies in their ability to take lots of measurements in difficult environments. They've found utility in such applications as monitoring pipelines for leaks and damage, taking measurements in oil and gas drill holes, and monitoring the health of a variety of civil structures. One of the more recent ones involves using fiber-optic sensors on the blades of wind turbines to give a heads up on how much stress the blades are experiencing in response to the high winds.

Essentially, when wind speeds are high, the turbine's rotor blades can experience stresses sufficient to break them, and when you're talking about a structure that's very tall (here's an eye-opening graphic that contrasts the height of a proposed wind turbine in Hempnall, U.K., with Norwich cathedral and a person who's six feet high. The group who created the graphic are, in case you're wondering, not in favor of this wind turbine project), and thus one that will cause serious damage to anyone or anything unlucky enough to be below—as well as seriously impacting the turbine's ability to generate power—one is justifiably enthusiastic about keeping the turbine and its blades as happy and healthy as is possible with an inanimate object.

The Fiber Bragg grating-based sensing technology was originally developed to measure high-frequency vibrations experienced by the Ariane rocket during take-off. Now, four researchers from Technische Universitaet Muenchen (TUM)—Dr. Mathias Mueller, physicist Thorbjoern Buck, software engineer Rolf Wojtech, and industrial engineer Dr. Lars Hoffmann—are founding a company to commercialize the technology and apply it to real-time monitoring of the stresses on the turbine rotor blades.

When high winds are experienced, turbine operators can tilt the blades so that they're edge-on to the wind, lessening the induced strain on the turbine. Because a turbine with blades oriented in this manner isn't generating power, the aim is to monitor the stress in real-time so that the turbine is producing power as often as it is safe to do so.

Germany has a long history of supporting and encouraging renewable energy sources and, over the last ten years, the proportion of its power generated from wind has grown to about 7%, with variation among the regions. The Saxony-Anhalt region of Germany, for instance, generates a whopping 47% of its power from wind.

Because the turbines are, relatively speaking, new creations their use engenders the need for new, robust sensing and monitoring technologies. Any new technology is going to spark the growth of supporting industries, either from the repurposing of existing technologies or by generating new materials, new sensors, new monitoring methods, specialized maintenance and installation providers, and the list goes on

Speaking of future instrumentation needs, I'd recommend the Future of Instrumentation Workshop that will be happening next week, November 8 and 9, at Oak Ridge National Laboratory in Oak Ridge, TN. More information is available here.