Just as Americans adjust to getting more renewable energy, the military steps in and makes wind farms compete with national security.
Last month, Gen. Gene Renuart, soon-to-depart commander of Northern Command and the North American Aerospace Defense Command, told the House Armed Services Committee that wind farms pose problems for the radar that keeps America safe from air and space threats.
"Comprehensive air domain awareness will not be attained unless we can resolve the growing issue of radar interference," Renuart said in prepared testimony. "A formal vetting process is required with the necessary authorities to prevent projects from interfering with the defense of North America, while supporting the expansion of alternative energy sources, such as wind farms."
Hence, he said, NORAD has set up a special team to vet wind projects close to its radars.
But the Peterson Air Force Base command won't elaborate about how close the projects have to be or how big. Nor will it say when the team will report, or to whom, or whether the findings will be made public. Officials say only that the command works with the Federal Aviation Administration.
FAA spokesperson Laura J. Brown, asked how wind farms interfere with national security, says, "I'm not in a position to answer, because we don't evaluate national security. We're partners with NORAD on a lot of things, but ... that's not our role."
Brown says that wind farms' proliferation has caused the FAA to fall behind in evaluating projects. It had taken 30 days to declare a hazard or give clearance; now projects must wait up to three months.
"The number of wind turbine [projects] that have been put in over the past few years has just skyrocketed," she says. "Within a matter of years, it quadrupled."
The agency can't block a project, but local zoning boards often approve or reject projects based on FAA findings.
Technology Review, a journal published by the Massachusetts Institute of Technology, says turbines create a shadow that makes airplanes disappear from radar screens. They also clutter the screens with the turbines' "signature," which changes as blades accelerate and slow with the wind.
"Aviation safety and military authorities insist that the potential for confusion and accidents is real," the journal reports.
Those concerns prompted a Department of Homeland Security study, which determined no obvious problem with accurate detection of aircraft and weather patterns around wind farms. Still, the study showed, authorities had held up development of several gigawatts of wind energy due to the radar issue.
NORAD says it hasn't questioned any wind farms in Colorado, such as ones near Lamar and Greeley, but it's unclear whether Renuart's concerns will hinder future plans. Two turbine proposals currently are under FAA consideration, one east of Falcon and another near Fort Carson, according to an FAA database.
Brown says wind farm owners have satisfied FAA concerns by moving turbines, making them shorter or eliminating them.
Despite all that, the industry is going strong. The American Wind Energy Association last week reported that more than 10 gigawatts of wind power capacity were installed last year, enough to power the equivalent of 2.4 million homes or generate as much electricity as three large nuclear power plants.
"The wind industry has and will continue to work with government agencies ... to mitigate concerns," Debra Preitkis-Jones, spokeswoman for the association, says in an e-mail.
The AWEA study showed Colorado ranks ninth in the nation with a generating capacity of roughly 1.2 gigawatts.