Wind farms, along with solar power and other alternative energy sources, are supposed to produce the energy of tomorrow. Evidence indicates that their countless whirring fan blades produce something else: “blank spots” that distort radar readings.

Now government agencies that depend on radar — such as the Department of Defense and the National Weather Service — are spending millions in a scramble to preserve their detection capabilities. A four-star Air Force general recently spelled out the problem to Dave Beloite, the director of the Department of Defense’s Energy Siting Clearinghouse.

“Look there’s a radar here — one of our network of Homeland surveillance radars — and [if you build this wind farm] you essentially are going to put my eyes out in the Northwestern corner of the United States,” Beloite related during a web conference in April.