HILL AIR FORCE BASE, Utah -- The Air Force this week commenced its most sophisticated study to date that will for the first time look into the impact power-generating wind turbines have on long-range radar platforms, researchers tell Inside the Air Force.
A team comprised of Air Force, Energy Department and Federal Aviation Administration officials began gathering data on Sept. 3 from a King Mountain, TX, FAA radar located near a large wind farm, John Yarman, flight chief of radar optimization for the 84th Radar Evaluation Squadron, said during a Sept. 5 interview at the unit’s headquarters here.
The squadron, also called the RADES, records data from all long-range U.S. radar systems. Officials also analyze that data and can reconstruct aircraft mishaps and flight information.
"It is our job to bring as much reality into this radar coverage as we can," Yarman said.
Hundreds of wind turbines near the King Mountain radar site are nearly 500 feet tall while their blades themselves stretch out several hundred feet horizontally, he said.
"It’s a great test site because there are three groups of wind turbines out there and the hundreds that give us different aspects . . . on the radar," Yarman said.
Typically, controllers track aircraft through a plane-mounted transponder, however, small aircraft without this capability, a malfunctioning aircraft or potential adversaries wanting to avoid detection are observed by search-only radar systems that paint a picture of objects in the sky. The wind turbines affect this type of radar system, some of which have a 250-mile radius.
The turbines create "clutter" that appear like airplanes on a radar screen making it nearly impossible for processors to decipher the clutter from aircraft, he said. This creates a blip on the radar screen similar to a Boeing 747 jet on final approach. The clutter also prevents radar from picking up aircraft flying over the turbines.
"They’re generating a nasty cone of silence out there," Yarman said. "Our job is to clearly define how severe that detection loss is, then experiment with our radars and see if we have some built-in characteristics that we can adjust to help mitigate the problems of wind turbines.
"If we don’t, then we’ll take some initiatives to see if we can get the joint program office and industry to put together something for the radar systems that will help us mitigate the wind turbines," he added.
With the Energy Department pushing for alternate forms of power generation -- such as wind turbines -- on one side and the Pentagon on the other claiming they will not tolerate any reduction in radar sensitivity, Yarman believes a solution will be "in the middle. They are an issue, but it’s not the end of the world either."
The RADES’ mission is to "remain absolutely neutral and let the data do the talking," Yarman said.
Wind turbines generate 2 percent of U.S. energy production, however, government officials want that number increased to 20 percent, he said.
Observations from a Minnesota radar site near wind turbines show the structures knocked out the search-only radar for about 25 miles, making any aircraft flying overhead undetectable up to 100,000 feet, Yarman said.
"Aircraft flying over the top of wind turbine farms disappear from coverage if they’re unfriendly," he said.
Early data from the ongoing King Mountain testing -- presented to ITAF -- showed a plane flying near the wind turbines was detectable only through its tracking beacon. Officials are flying aircraft near the turbines to determine just how severe a blackout area the turbines create, Yarman said.
"If these wind turbines are very close to the radar and very dense, they put up a horizon screen, so we have a harder time seeing behind them," he said. "Our radars don’t have advanced signal processing that’s been designed to specifically mitigate these wind turbines, so they’re a nasty thing for us," he said.
The radars, however, are designed to eliminate stationary objects, such as buildings, Dallas Stone, a senior member of the RADES team, said during the same interview.
In an initial attempt to address the issue, the RADES along with the FAA have created a Web site that shows potential wind farm contractors the locations of radar systems and areas that are poor construction sites. Industry currently is asked not to build wind turbines withing a 20-mile radius of radar systems, Yarman said. The unit analyzes roughly 200 wind turbine proposals per month.
However some wind farms, such as the one at King Mountain, were built prior to these guidelines and are closer to the radar stations, he said.
The international community, particularly the United Kingdom Ministry of Defence, has spent much more time studying the effects of wind turbines, according to Yarman. Germany does not allow wind turbine construction within 60 miles of their defense radar systems.
One possible solution could be advanced signal processing in future radar systems.
"There’s no doubt in my mind that advanced signal processing can largely mitigate the wind turbine issue if the country puts some money" into development, Yarman said.
The results from the $100,000 Air Combat Command-funded King Mountain test will most likely lead to future tests of different types of radar, Stone said. The research is expected to conclude on Sept. 14.
