BOSTON – The U.S. military has noticed a problem with the wind turbines environmentalists are fond of installing across the nation's landscape: They jam military radar and create the possibility that an airplane could be hidden in the sky because of the bounce from the waving blades.

The solution, however, may be soon to arrive. A proposal from Vestas Technologies is offering hope.

Ian Chatting, an official with Vestas, says the material is being modified.

"What we've done is modify some of the glass fiber using a process that is confidential to Vestas and we spent quite a lot of research and time creating. So we modified the materials that are actually in the blade and used in the blade in normal circumstances," Chatting said.

"The actual details of that are quite sensitive, and that's what we spent several years researching," Chatting said.

Technical problems were highlighted during military tests near Barstow, Calif., and earlier were the subject of hearings in the U.S. House Armed Services Committee.

Lt. Cmdr. Wendy Snyder, a spokeswoman for the Navy, said the technical issues caused by the bounce in radar waves forced the military to design unidirectional radar tests.

"Because of the hundreds to thousands of turbines on the Tehachapi Ridge to the west of Edwards/China Lake, those tests can only be conducted flying from west to east. We also need a certain volume of electromagnetically 'quiet' space going east," Snyder said.

Snyder said that Defense Department officials didn't remain idle once the radar jamming problems were discovered. The DoD has done studies to determine how and why the interference takes place.

"Air Force and Navy officials are currently developing a test plan to quantify the impact of turbines on flight tests over the Mojave to determine how much 'quiet' space is necessary," Snyder explained.

The problem isn't limited to military aviation. Chatting says that wind turbines also have caused problems with civilian radar in Europe. He adds that the greater the number of turbines in an area, the greater the complications.

"What happens is that you get interference from the radar and the combination of moving blades and the tower creates a radar signal that bounces around between the structures and the blades," Chatting explained.

"You get a kind of cloud of points on a radar around the wind farm. It can be difficult to distinguish individual turbines and or individual aircraft that fly behind or around those turbines," he said.

Chatting says that his company recognized the problem and wanted to find a solution.

"What we've done is to take some of the technology that's used in defense and things like the stealth bomber, make it a much lower cost, downgrade it if you like. That allows us to put it in a civil structure like a wind turbine," Chatting said.

"We've taken the composite of materials used in aircraft and submarines and chips and embed layers of material into the blade structure so that we can absorb the radar signals and reduce the reflected radar signal by about 99 percent," he added.

A military technology expert who spoke on condition of anonymity says that the military is moving from analog to digital radar. The expert suggested that the problem could be as simple as a software adjustment.

Snyder disagreed, saying that the problem in the U. S. requires more than a software adjustment.

"Because these tests are designed to baseline a radar's performance, software adjustments won't work – engineers have to have raw performance data to be able to write the software adjustments. It's not a question of analog vs. digital, it's a question of assessing new technology in a clean environment," Snyder said.

Snyder says the military supports clean energy, but "clean energy" technology can also adversely impact other military functions.

"In some cases, renewable energy projects can impact homeland defense capabilities, test capabilities, or training capabilities, and the mitigation possibilities vary with each case," Snyder explained.

The wind turbine developed by Vestas Technology is the result of a five-year process that drew on the stealth technologies used in aircraft and submarines.

Chatting says that the challenge is to refine the technology so that it is affordable.

"The task is to make it cheap enough and affordable to put on wind turbines, obviously many of these materials are very specialized and developed in small laboratories and are used in relatively small quantities," Chatting said.

"They're certainly not available in a commercial and industrial scale, so it's quite a journey to make this affordable. Also we want to put it in our products and make it reliable," Chatting said.

Wind turbine experts have said that the turbines can be expensive to operate and maintain. Chatting says his company is attempting to address this concern.

"Most people would like their wind turbines to stay relatively unmaintained for a period of 25 years, and so, it's not an easy thing to achieve that level of reliability," Chatting observed.

Chatting says that his company is actively working to show European and American defense officials that the Vestas technology works.

"We've put up a demonstrator system in the U.K. last year and brought in some military radar equipment and did a series of tests on an airfield. The technology worked very well.

"The challenge is going to be to get the general acceptance of the radar operating community that actually this technology is solving their problem," Chatting said.

"There are people like the federal aviation authorities, the Joint Air Worthiness authorities, various Department of Defense communities, the Air Force, who all have different opinions and different levels of acceptance," he said.

While testing continues in the U.K., the U.S. military also is attempting to solve the problem. Snyder says that the Navy is working with other groups for a solution.

"We're [setting] up a clearinghouse to give industry and government entities a single point of contact to vet proposals, and working with the interagency to balance energy security with military testing, training, and operations. The process is in its infancy – we're working to involve all stakeholders in our solution, but don't have an approved plan yet," Snyder said.

Chatting says that one of the stakeholders in the solution is his company.

"Actually the U.K. Ministry of Defense and the United States Department of Defense have been extremely helpful in this and they're very keen to solve the problem," Chatting stated.

Chatting believes it will be several years before the radar-friendly turbines will go to mass production.

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