kitegen - Google Image Search. Some prototypes have large circular ground stations, all with arches built in - very Italianate. The footprint was what I was chiefly concerned with; ostensibly the kites would be invisible, or barely visible, at 800m. Trying to find out more about that I find this Wired piece: High-Altitude Wind Machines Could Power New York City | Wired Science | Wired.com.

The Department of Energy had a very small high-altitude wind program, which produced some of the first good data about the qualities of the wind up there, but it got axed as energy prices dropped in the 1980s and Reagan-era DOE officials directed funds elsewhere.

The program hasn’t been restarted, despite growing attention to renewables, but that’s not because it’s considered a bad idea. Rather, it is seen as just a little too far out on the horizon.

“We’re very much aimed these days at things that we can fairly quickly commercialize, like in the next 10 years or so,” said National Renewable Energy Laboratory spokesperson George Douglas.

Startups like KiteGen, Sky Windpower, Magenn, and Makani (Google’s secretive fundee) have come into the space over the last several years, and they seem to be working on much shorter timelines.

“We are not that far from working prototypes,” Archer said, though she noted that the companies are all incredibly secretive about the data from their testing.

Drake, for several details I have to refer to Massimo Ippolito, who knows these things better than me. Anyway, for what I can answer.

1. Cost. It depends on the size and the type of the machine. There are several estimations of the pure cost of building a Stem. But the one planned in Italy is the first one of its kind, so its cost doesn't reflect what the cost could be once it is mass produced. So, personally I think it is too early to speak of costs; but, of course, since the machine is lighter and simpler than an equivalent wind turbine of the conventional kind, the energy it produces would cost much less.

2. Duration. As I say in the post, kites and cables should last at least 6 months in normal conditions of operation. Ippolito says that he plans to change them every 4 months.

3. The first full scale model of a stem is planned for a maximum power of 3 MW. The average power is expected to correspond to about 5000 working hours per year.

4 and 5 . A 1-3 MW stem will require a hemisphere of about one km radius. It is not necessary that the land is completely empty. It can be farmland - it could even be suburbs, but for the time being it is not planned. The airspace within the hemisphere must be reserved for the kite(s). It is possible and it is allowed by present regulations.

6. The first working kitegen is planned in an agricultural area in Piedmont, Italy. Ippolito tells me that all the necessary authorizations have been obtained and that construction should start very soon.

Drake, and all interested in exploring rapid development of various AWE methods for small wind and large wind are invited to explore the opportunities at
http://EnergyKiteSystems.net
with its adjoined AirborneWindEnergy
discussion group. There are scores of distinct methods being explored. Several kite labs are perfecting in the small before scaling. Proofs of concepts are announced.
The Kitegen "Stem" is a hybrid "reel-out and reel-in" energy kite system. There are some neat variations in that family. Differently are stems and booms that do not involve reel-in and reel-out cycles that hold promise.
There are identified over 100 energy kite systems researchers shown on one of the public pages. Our net list for special notices is over 70 persons at the moment. The AWE discussion open-to-all group is at 38 members. Let me know of your interests: Notes@EnergyKiteSystems.net
The web is aiming for rapid development in both open and closed source tech.

Lift,
Joe