Wind turbines may soon be getting smarter, as an emerging technology promises to endow them with the ability to "see" oncoming wind and react to it before it arrives at the turbine's spinning blades.
If the technology catches on, it could have a profound effect on the worldwide power generation industry's 80,000 wind turbines. Engineers from Catch The Wind Inc., makers of the new technology, say their laser-based sensors can boost energy efficiency and reduce wear and tear on wind farm assemblies, thus improving the bottom line for utilities on two separate fronts.
"If you're going to make money from the wind, you ought to know what it's doing," says William Fetzer, vice president of business development for Catch The Wind. "And for the first time, there's a technology that allows you to do that."
Known as the Vindicator Laser Wind Sensor, the device is an egg-shaped capsule weighing about 55 lb and containing a fiber-optic-based laser module, processor, control system and lens assemblies. In practice, it provides turbines with a dose of intelligence by sending out beams of laser light and then measuring the infinitesimal changes in the color of airborne particles as they move along the beams. Then, the device works with the turbine's motors to change blade pitch or even re-orient the entire nacelle in an effort to maintain efficiency.
"We're going to change the way the (wind) industry designs its controls," Fetzer says. "They've never had smart controls before."
Inventors of the technology, however, didn't originally foresee it being used for power generation. Phillip Rogers, CEO and president of Catch The Wind, initially worked with the technology almost 20 years ago, while serving as an engineer at the famed Lockheed Martin "Skunk Works" (an alias for Lockheed's Advanced Development Programs) during the 1990s. At the time, engineers saw it as a better wind sensor for automated flight controls. Its bulkiness — back then it was approximately the size of a large conference table — and its lack of maturity, however, prevented it from taking off in a big way.
Still, Rogers saw other applications for it. As laser diodes in the telecommunications industry matured and the technology shrank, he put together a group of scientists and engineers who re-targeted it for the power-generation industry. The technology, developed at Optical Air Data Systems LLC, appeared to be the answer to a dire industry need.
"For a rotor to be most effective, the wind needs to be coming right down its axis — perpendicular to its face," Fetzer says.
Wind turbines, however, were notoriously incapable of "knowing" the direction of oncoming wind. Up to now, turbines have employed anemometers behind the spinning blades, at the back of the so-called nacelle (the structure that houses the generating components).
"With wind vanes and anemometers on the back of the nacelle, you're measuring a very disturbed flow of wind," Fetzer says. "It's already been chopped up by the blades and aerodynamically it's very unstable."
Fetzer says the inability to recognize wind direction and speed has resulted in a serious drop in the generating efficiency of such turbines. He says experts estimate that for each degree the yaw angle is out of optimum, the turbine loses about one percent in power efficiency.
"We've found that wind turbines are typically 10 to 15 degrees out of yaw all year long," Fetzer says. "That's why we decided to go after this market."
Using the Vindicator, utilities can predict the direction of wind gusts as far as 300m away. Even with a fast-moving 30 m/s wind approaching, it still gives the wind turbine about 10 seconds to compensate. That's sufficient, Fetzer says, because yaw motors typically move the turbine at a rate of about one degree per second.
That ability can be critical, Fetzer says, because wind gusts can change dramatically when pressure fronts roll in.
Capitalizing on the Boom
Field trials are proving that the wind sensing strategy works. Nebraska Public Power District implemented the technology on a Vestas V-82 wind turbine in Ainsworth, NE during August 2009, resulting in a power production increase of 12.3 percent on the one turbine where it was employed.
Scientists at the National Renewable Energy Lab. (NREL) say they're aware of the concept, but have not yet taken a position on it. "There's not enough data in the field to give a definitive answer," says David Glickson, a spokesman for NREL. "Obviously, getting the wind turbine pointed in the right direction and maximizing the efficiency is going to be beneficial, but we still need more data."
Catch The Wind says that when utilities begin to implement the technology, they're very likely to save on maintenance costs, too.
"With any asymmetric loading on a spinning body as large as a wind turbine, you're going to have all kinds of stresses going right down that axis," Fetzer says. "Even if you're three or four percent out of yaw, it adds big loads."
Catch The Wind is also counting on modern wind turbines adding pitch control to their current capabilities (most already have yaw control). "Variable pitch control appeals to us because when we get pitch and yaw, the turbine will be able to do more in response to big wind gusts," Fetzer says.
In the meantime, the company has also branched into sport sailing, where the laser measurement technology provides instant, accurate wind measurements, especially in competitions. Using a smaller unit with two lenses — instead of the three employed on the Vindicator — the Racer's Edge Laser Wind Sensor weighs 18 lb and can be held by a racer using a neck strap. The device has already been employed by racers in the America's Cup competitions.
The company says it sees a niche for its technologies, especially as countries gear up for the move toward alternative energies. The American Wind Energy Assn. estimates there are now 30,000 wind turbines in the U.S. alone, and some experts have predicted that the number could go to 100,000 in the next few years, ultimately enabling suppliers such as Catch The Wind to capitalize on the boom.
"Today, wind turbines are fundamentally inefficient because they don't know which way the wind is blowing," Fetzer says. "We can put this laser sensor on the back of a wind turbine and measure between 200 and 300 meters in front of the turbine, so we have time to provide control inputs to the turbine and proactively catch the wind."