The Defense Department warned in late September that a report showed that giant wind turbines with rotors rising 450 feet can interfere with radar used by the military and commercial airlines.

The report said the dangers are at present potential and not actual and will remain so as long as wind farms do not proliferate in the line of a radar's sight.

The 62-page study, which was called for by Congress in a defense authorization bill earlier this year, said each wind turbine proposal must be studied on a case-by-case basis by federal agencies like the defense department, the Federal Aviation Administration and the Department of Energy.

How much this impacts missile defense systems and military and commercial aircraft depends mainly on how effective the FAA and other federal agencies are in keeping the wind turbines away from radar sites, the military study says.

"(Should wind farms) degrade the ability of the radar to unambiguously detect and track objects of interest by primary radar alone, this will negatively impact the readiness of US forces to perform the air defense mission," said US Army Lt. Col. Brian Maka, spokesman for the Defense Department.

Already, the concerns held up development of wind farms in the upper Midwest. Ten to 15 wind farm projects for 614 turbines that will produce more than 1000 megawatts were put on hold until the defense department released its study.

"This was a big concern and something they were not suspecting," Jodziewicz said.

But the projects were recently approved, showing that the added scrutiny does not have to curb wind farm growth, she said.

"Decades of experience tell us that wind and radar can coexist," AWEA Executive Director Randall Swisher said. "The American wind energy industry will continue to work collaboratively with government and others."

Lt. Col. Maka said the Department of Defense supports wind power and other forms of renewable energy and wants to work with the industry to allow wind farms to flourish.

The defense department gets new proposals for wind turbines almost daily and thus far has not rejected any proposals as being in the line of sight of radar, Maka said.

The turbines are already sprouting up across the United States and with 46 of 50 states having enough wind to make significant amounts of electricity, the issue of placing wind farms in the sight of radar surely will be faced more often, both the AWEA and the defense department agree.

The Earth Policy Institute, a private organization advocating sustainable energy, said that wind power has had an annual growth rate of 29 percent in the past decade.