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269 comments on High altitude wind power: an era of abundance?
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269 comments on High altitude wind power: an era of abundance?
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Without making much effort to study the concept, I suspect that your comment is not likely to be correct. The drag force on an object also increases as the square of the speed and the area. Larger devices capable of producing MWs of wind poser would also be expected to result in large drag forces which would be transferred to the support structure. The typical kite string would be transformed into a rather heavy rope or cable. Also, the drag force on the tether itself would be rather large, as the drag coefficient on a circular cross section is large.
There's no free lunch in engineering.
E. Swanson
Of course not, an analysis would require a bit of thought and effort...You would rather toss out offhand comments....
OK, looking at Kitegen's multi stem idea, I see a version of a vertical axis wind turbine It has the usual problem of a vertical axis machine, which is, at any one time, half of the kites are moving into the wind and the forces on the ends of those stems result in torques which oppose the rotation of the base. Look at the first image in the linked graphic. What happens on the left side as the kite changes direction, which is actually outside the frame of the graphic? It would appear that the kite would need to make a fast climb to nearly vertical, then dive back down, a situation similar to "jibing" a sail boat, IMHO.
The graphic which shows a comparison of the intercepted area with that of a horizontal axis machine grossly overstates the effective area of the turbine and thus overstates the possible efficiency of energy conversion. The effective area should be the area of the kite(s). Also, the claim that only the tips of a horizontal axis turbine are efficient ignores the effects of both pitch control and proper twist along the blade.
Given the large size and slow rotational speed, it looks to be little more than a drag turbine. And, should the positioning mechanism fail on one kite, the whole thing would crash as the lines would become entangled after one revolution...
E. Swanson
BlackDog, Your points look sound but they apply only to the vertical axis fairground roundabout embodiment which I never much warmed to. The separate yoyo thingys illustrated above seem much the more promising way forward, apart from looking too much like an array of howitzers to ever appear as (relatively!) beautiful as turbines.
Free lunches are getting harder and harder to come by in any area. Average wind around the globe has decreased by about 10% over the last few decades and is likely to decrease more as the temperature differential between the poles and the equator weakens.
Whoa. Send me some links or background on that dohboi. Climate change renders windfarms inoperable. That's poetic.
As long as there is day and night, land and sea, and a spinning globe there will be usable winds.
All climate change will do is change some of the details.
http://www.marketwatch.com/story/study-tracks-loss-of-wind-strength-in-us
"A third possibility for slower winds is climate change, he said.
"It's simple meteorology that the wind is driven by differences in temperature between the poles and the equator, and those differences have been narrowed by climate change," Takle said."
Yes there are other sources for wind, but this is a major one. In general, also, CC means unpredictability. Some places that had experienced reliably high winds will see much less wind, others will see more. As the article says, the temp differential between land and sea will probably always generate good wind speeds. But then the placement of the coast/depth of the sea will be changing too.
CC makes it harder to plan pretty much anything with the certainty we had before.
I suspect you are in error regarding sources of wind. The primary cause of wind on earth is movement of air from hot equatorial areas to cooler temperate zones, which is, agreed, due to deltaT, but the velocity and thus energy contained in those winds is due to earth surface velocity differences as spherical section diameters on the rotational axis reduce from equator to those temperate zones. It will matter little how much air moves at high altitude from equatorial areas to temperate zones, still the sectional rotational velocity difference remains unchanged and therefore likely the wind velocities (west to east).
I imagine these things fighting it out, buckyball single-molecule threaded cables - the sort that would slice through a body that walked through them unaware. Diamond crusted cables to saw away the other kites from the other corporations competing in the free market.
I can't help but think the emergy of the power delivered by a system like this is an order of magnitude greater than that of a coal plant. Just a gut feeling; these machines will be subject to all sorts of shocks - people, maybe entire city blocks - getting sawed in half by these cables dropping and tightening.
Wouldn't it be easier to take drugs and pretend it worked?
cfm in Gray, ME
No diamond-encrusted saw cables will ever be used to tether a wind-gen kite, nor any single-molecule-wide invisible saws such as you may have seen on some science-fiction kung-fu-figher video game. Even if comprised of the most futuristic single-wall-nanotube composites, any cable capable of holding these kites will be too large to cut, and in order to reduce wind resistance, will be sufficiently smooth surfaced, to be any greater threat than a child's skip-rope.
Drag in energy kite systems in some energy harvesting methods being explored becomes useful. The family of methods using the ground-based lever includes wafting levers, rocker arms, oscillating lifting levers, TipBooms (counter-weighted), stems, carousels, tree trunks, piezo-electric booms, ratchet booms, and tugged-hydro-turbined rafts. Kite-tugging a hydro-turbined-saturated ocean barge could transport freight while making electricity; the electricity could make hydrogen from the available water; at destination ports, the hydrogen could be off-loaded for work-use points night or day.
http://EnergyKiteSystems.net
The KiteGen stem method is a member of a family of lever systems; some members combine reel-in-and-out and others do not use that cycling. The near-vertical TipBoom method oscillates without the reel-in-and-out, especially in always-up formats (some of which involve lifter kites along with oscillating kites or wing-mills). Some working test scale systems are occurring in Ilwaco, Washington, at KiteLab with passive controls.