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Tethered Turbines

Here's a fascinating bit of alt-energy technology: tethered wind turbines.

Professor Bryan Roberts, an Australian engineer with sought after expertise in helicopter technology, has long realized the potential of high altitude wind energy and has refused to abandon pursuing it. [...] He has now designed a Flying Electric Generator, classified as a rotorcraft, using a single tether, designed to operate at an altitude of 15,000 feet and higher where only average winds are sufficient to generate power.

And it is clear now that FEGs rated in the tens of megawatts may operate at higher altitudes with rotor diameters not exceeding those used today on the largest helicopters.

Sky Wind Power imagines clusters of 600 units, each producing 20 megawatts, together putting out more power than a nuclear power plant, and taking up a 10x20 mile rectangle of airspace.

Roberts claims to have built a prototype able to generate power at a lower altitude, and the website has an abundance of pages detailing available winds at different heights, global power consumption, the long-range economics of the design, even how the FEGs could be used to generate hydrogen. The intensity of the prose AND THE OVERUSE OF ALL-CAPS gives the site a distinctly "crank" feeling, as does the Gernsbackian vision of tethered autogyros supplying power to us all. But the engineering & science aren't outrageous; in principle, such a thing should be possible (if not necessarily feasible). Safety is the biggest concern -- tethered vehicles at 15,000 feet and higher can pose a bit of a problem for non-tethered aircraft, and there's the perennial "what happens if the line snaps?" problem. Perhaps the design should be altered to include a lighter-than-air element -- who can say no to autogyros and dirigibles?

(Via Treehugger)


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Comments (9)

So, is the idea to make the airspace covered by these things to be closed to all aircraft at 15,000 feet or below?

Are there any pilots here to tell us if this is feasible?

Ben Wendt:

It is certainly possible to close off the airspace from small airplanes; there are many places small aircraft are not allowed to fly.
I think there is a major engineering stubling block here though. 15000 feet of tether, plus the weight of transmission wires would be immensely heavy.
As to the concern about the tether breaking, the thing could have a wing and a computerized piloting system to guide it back to the ground, but the dangerous thing would be that huge wire falling from the sky.

I doubt the economics of such a field of contraptions could make economic sense. From the scale and complexity of the rendering of one unit, I would guess $10 million (think helicopter complexity & therefore pricing) x 600 units = $6 billion, and that doesn't include land rights, maintence, etc. You could build a helluva lot less expensive, lower impact, electricity-generating solutions for the same amount of coin at this power output level.

Seems like waaaay to much engineering for a problem to which there are other, easier to execute alternative solutions in the pipeline. Interesting idea....

I'm kind of interested in who's the poor person with the job of servicing and maintaining the thing.

I've been playing around with this idea myself for a while. I'm very much surprised at the scale they adopt. The height and size they aim at does not seem practicle.
Smaller tethered turbines seem to me to be excelently suited for nomadic people, providing them with lite, portable power generation. I'd suggest a much simpler design with simpler materials though. I was thinking of a prototype using some standard bicycle dynamo's and easily replaceble rotor structure (kites inspired me to think of this).
Concerning maintenance, if the rotors could be remotely decoupled from the dynamo, the whole contraption would slowly descend. Applying a little tension to the tether would insure the thing lands near the ground station allowing for easy maintenance. Like a kite, a little tension combined with an extended teher would get the thing back up.
Another adaptation is use in "kite-powered" ships (which have featured earlier on Worldchanging).

Jon Abel:

To get around the weight of the power lines and tether, a blimp might be used to help it keep aloft.

Power lines can be eliminated by microwaving power down to a collector site. Or it can be a high flying factory producing something requiring lots of cheap power...say hydrides or aluminum fuel. Blimps would not be needed because the kite will provide plenty of lift. Heavy tow line can be supported at intervals by box kites. Alexander Graham Bell had great hopes for box kites until those upstarts enjoyed some success at Kitty Hawk, thereby putting most Angle of Attack lift bodies (fancy name for kites...) on hold, perhaps like many of his ideas, they need to be re-visited.
Personally, I think the idea is over-engineered. You could do more with the thermal gradient between 15000 feet and ground level, do it cheaper, and with no moving parts.

Big problem in one word: weather.

I note the engineer is Australian. Most of Australia is desert, with rather stable weather patterns, and high freezing levels. Anything tethered above the freezing level would face serious threat from icing. Turbulence and sharp wind shifts could imperil tethered generators too. Whether or not they used helium for lift, such devices would require exotic materials or excessive weight to handle stress loads. I doubt very much they would be commerically viable.


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