Laser Sensors for Wind Turbines

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Catch the Wind has adapted LIDAR so that it can be mounted on wind turbines and used to measure wind changes in time to make adjustments to the turbine. It pulses three invisible laser beams in front of the turbine that can simultaneously measure both vertical and horizontal wind speeds at different distances, as well as sudden changes in direction. Like conventional LIDAR, it does this using the Doppler principle: when the laser bounces off small dust particles carried in the wind, it changes color. The color of the laser is directly proportional to the speed of the particle. The device uses proprietary algorithms to convert this data into measurements of wind speed and direction before communicating a course of action to the turbine's control system. The device provides 20 seconds' advance notice--enough to turn the nacelle and angle the blades so that the turbine can catch more of the wind energy while reducing strain on its parts.

Conventional LIDAR isn't suited for mounting on wind turbines because these devices rely on mirrors, which must be precisely positioned, to project a single beam as a three-dimensional cone, says company president Philip Rogers. Changes in temperature or sudden movement can knock the mirrors out of alignment. Rogers's company's device replaces mirrors with fiber optics that project three separate beams. This design makes it rugged, small, and lightweight enough to be permanently mounted onto a turbine nacelle and integrated into its control system. "It's very much akin to solid-state electronics," Rogers explains. "It makes for a very compact and robust system that's not susceptible to shock, temperature change, and other things caused by movement."

Catch the Wind's system is currently being field-tested at the Wind Energy Institute of Canada on the windy shoreline of Prince Edward Island. Paul Dockrill, director of technology at the institute, says that the device performed well under initial ground tests atop a tripod. It will soon be mounted onto the nacelle of a turbine as part of a more in-depth study.

Rogers envisions the fiber-optic system being integrated directly into new turbines at the point of manufacture, and also being retrofitted to the thousands of turbines already in operation today. "We are in discussions with a number of manufacturers, and we've seen significant interest," he says, adding that beta versions of the device will come next spring, and commercial production is targeted for late 2010.