Windmills in the sky, "Flying Windmills," have been demonstrated by Australian professor Bryan Roberts to be practical.
"When the United States realizes that high altitude wind energy is capable of being its most economical energy source, market forces will lead to its gradually supplanting oil and to energy independence - as well as end the debate on global warming - because its most economical energy source will produce no greenhouse gases."
What a wonderful promise that is. My first thought was that a tethered high altitude "windmill," actually a kind of four-rotor helicopter, would interfere with airplane flights. However, the amount of restricted air space required is not that vast. Balloons are already tethered as high as 15,000 feet to detect drug flights, according to David Shephard, president of Sky WindPower Corporation, based in San Diego.
Wind farms exist now. There's an American Wind Energy Association, a National Renewable Energy Laboratory, a Department of Energy project called Wind Powering America.
A couple of years ago, I heard a spokesman for a tribe in the Dakotas that was building a wind farm to make electricity for themselves, and to sell. He said, "The federal government was generous enough 100 years ago to set aside for us land that has a great deal of the natural resource, wind."