Laser Guidance Adds Power to Wind Turbines

www.wired.com
March 25, 2010

The wind industry may soon be dependent on a different kind of environmental awareness that has more to do with lasers than ecology. A new laser system that can be mounted on wind turbines allows them to prepare for the wind rushing toward their blades. The lasers act like sonar for the wind, bouncing off microscopically small particulates and back to a fiber optic detector. That data is fed to an on-board processor that generates a three-dimensional view of the wind speed and direction. Subtle adjustments in the turbine blade's angle to the window allows it to capture more energy and protect itself in case of strong gusts.

The startup company that developed the Vindicator system, Catch the Wind, recently deployed a wind unit on a Nebraska Public Power District turbine. It increased the production of the unit by more than 10%, according to the company's white paper. If those numbers held across the nations' 35 GWs of installed wind capacity, the LIDAR (Light Detection and Ranging) sensors could add more than 3.5 GWs of wind capacity without adding a single additional turbine. "This is what they call disruptive technology," said William Fetzer, vice president of business development for Catch the Wind. "There are roughly 80,000 to 90,000 wind turbines out in the world, and they don't have this technology."

Wind farms are only as good as their data. There have been revolutions in assessing wind resources over long time-scales, but the short-term gustiness of the wind has remained a problem. Current wind turbines rely on wind-measuring instruments known as anemometers that are mounted to the back of the turbine's gear-housing unit, called a nacelle. The data from the wind is fed to a computer that optimizes the blades' configuration to capture the most energy from the wind.

In many cases, cup anemometers, which took their current form in the 1930s, are still used. They work well enough, but have to be positioned behind the blades, which subjects them to turbulence. And, importantly, they can only tell you how fast the wind was blowing after it passed. That doesn't help you with a freak gust of wind or any of the odd behavior that renewable energy developers have caught the wind exhibiting.

Fort Felker, director of the National Renewable Energy Laboratory's National Wind Technology Center, said he saw great potential in LIDAR and similar sound-wave-based systems generally. "Once you have a detailed knowledge of the coming wind, there are a lot of opportunities," said Felker told Wired.com. While he estimates the amount of energy that could be captured is below Catch the Wind's 10%, he said the systems could really help reduce the wear-and-tear on machines caused by strong winds hitting improperly positioned blades. "Researchers have already demonstrated that substantial reduction of loads is certainly possible," Felker said.

LIDAR, despite first being demonstrated for wind measurement in the 1970s, has been slow to catch on. The systems have been too expensive. "Widespread deployment of the technique has so far been hampered by the expense and complexity of LIDAR systems," a 2005 NREL research report found. "However, the recent development of LIDAR systems based on optical fiber and components from the telecommunications industry promises large improvements in cost, compactness, and reliability so that it becomes viable to consider the deployment of such systems on large wind turbines."

Now, even the most venerable R&D testing group in the world, the Danish National Laboratory for Sustainable Energy's Risøe wind outfit, is working on a turbine-mounted LIDAR system, though they only claim a 5% increase in electricity production. Catch the Wind grew out of a small-business grant that the company's predecessor, Optical Air Data Systems, received from the U.S, military. They developed a LIDAR system for helicopters working in the dusty Iraq and Afghanistan terrain. The company developed their rugged and relatively lightweight LIDAR systems by marrying aerospace knowledge with emerging telecommunications tech like better fiber optic cables and laser diodes.

Still, Catch the Wind may have a tough road ahead. The energy industry is notoriously risk averse. Besides, wind electricity in many places is already cheaper than wholesale electricity prices. Erin Edholm, a representative for National Wind, a wind-farm developer that's put in more than 4,000 MWs of turbines, said that the company's wind resource assessment team "has not used [LIDAR] or considered using it to date." But that doesn't dim the hopes of Catch the Wind's Fetzer for the company's ultimate success. "When you do disruptive technologies, it takes time," Fetzer said. "People don't believe that things are as bad as they are until they can see what we can do."

It helps that they don't need the wind turbine manufacturers to incorporate their technology to jump start their business. They've got what's known as a "bolt-on" solution, meaning it can be attached to existing turbines. They don't need manufacturers to incorporate their product to sell it to wind farms. Still, some wind farmers may worry that the warranties they have on their turbines would be voided by adding a LIDAR system. Fetzer said Catch the Wind is working out the warranty issues. General Electric, which is the largest wind turbine manufacturer in the United States, is not using or developing LIDAR specifically, either. Catch the Wind did recently sell one of their machines to a large, unnamed turbine manufacturer.

Though Catch the Wind is not discussing pricing for their products, Fetzer maintains that their customers will make their money back in the three-to-five year range that he says wind developers are looking for. The 2005 NREL report calculated a preliminary cost for a generic LIDAR system of less than $95,000, once production was up and running. The development of controls for capturing the most energy from the wind has been a constant theme in wind energy research. But it's not always the company that develops the technology that reaps the rewards from its commercialization. Wind turbines in the 1980s struggled mightily to convert the wind's gusty capriciousness into steady rotary power.

At the time, the turbine's rotor had to turn at a constant rate. Researchers realized that their machines could operate over a larger range of speeds if the rotor could speed up or slow down in response to the wind, but they would need power electronics to translate the power into electricity suitable for the grid. A multimillion dollar R&D program launched by U.S. Windpower and the Electric Power Research Institute to commercialize a variable-speed rotor resulted in a mostly defective turbine design that helped push U.S. Windpower out of business. The variable-speed rotor went on to become a standard part of wind turbine designs.

Catch the Wind obviously is hoping not to suffer the same fate. They are exploring a variety of business models including sharing the revenue from the extra power they say their systems can generate. If they don't generate any more electricity, the wind turbine owner doesn't pay anything. If they do, Catch the Wind gets half the take. "It's a good value proposition," Fetzer concluded.