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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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@ enemy: kites are extremely light structures, and so are the cables. the damage that can occur by a kite crashing is truly minimal. The entanglement, instead, is something to be careful about, and so is the interference with aviation. All that has been studied in detail: kites and aviation can live together, but there will be the need of precautions, protocols, etcetera...
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.
Recreational kites are light and can fall on one's head. A kite capable of generating power is another story.
These CANNOT be flown where people are underneath.
Alan
Airplanes CANNOT be flown where people are underneath!!!....Ugh, the discourse is ABSOLUTELY declining here....
We have a century of experience with airplanes (and many do NOT want to live in the flight path of airports).
We have NO experience with kite gen.
I stand by my statement.
Alan
And I stand by the intent of mine....which is to show your statement and counterstatement are silly
It does seem that we forget that there are very heavy and very flammable large objects flying over us all the time...I live near a military base and the amount of aircraft traffic overhead is astounding, and this is over an area where tens of thousands of people live! The placement of the kitegen can be much more limited we can assume.
This post came at an interesting time for, as I have been studying trimaran hydrofoil boats to see what can be learned from them (I have recently posted a YouTube clip of the French hydrofoil that did 47 knots). All indications are that the physical possibilities implied in wind power are HUGE, it is the logistical issues that are the problem. If you had told someone 30 years ago that 50 miles per hour could be done with a sailboat, they would have told you it was absolutley physically not possible.
The strenth to weight of the materials involved in any kite system would be of great importance in determining it's success, but time is on our side on this...nano materials are in the pipeline that will be stunning in their strenth to weight ratio, and there are already various composites that have incredible strenth to weight ratio.
This absolutely has possibilities, but one must be concerned about local opposition. The current cost of wind is being driven back upwards by lawsuits and local laws and zoning rules to effectively ban current generation turbines in many places. The NIMBY and BANANA issues are very real and very daunting in an already risky industry.
RC
Your dismissive acronyms suggest that you don't care what goes into your back yard or perhaps anywhere?
People should be much more concerned about what is in their area and in others' too. The problem with "NIMBY" isn't that people care too much, it's that they don't care enough to see that if they want to use and waste energy at the rates we do in modern society, generation (and transmission...) has to happen somewhere.
But very good lifestyles can be maintained with far lower energy needs and overall lower impacts, locally or elsewhere. And this is where the emphasis needs to be--on reducing demand, and only secondarily (or tertiarily...) on new generation.
Good luck convincing the entire world to follow you back into the stone age there, doboi. Even the laywers you depend on for your tactical manoeuvers should eventually abandon it.
"Good luck convincing the entire world to follow you back into the stone age there, doboi."
Hey, now, cave living is way underrated ;-}
Really, could you have come up with a more cliched response? When anyone questions our mad rush into techno-oblivion they are always immediately equated with the stone age.
Presumably much learning, music, art...could be preserved and enjoyed at a far lower cost to the living world. But if that vision is to frightening to you, please do resort to more cliches.
That is a good start but it should also include things like space telescopes and generation after generation of researchers grinding away at understanding big things like how the universe looks and advancing small things with vast areas of possible knowledge like biology and understanding ourselves.
There is so much that can be possible in the long term if we dont fuck up too much. Some day we can have biotechnology and nanotechnology as understood and usefull tools making todays problems seem easy in hindsight if such tools are used wisely.
But I do not long for infinite generations of people in a static low tech culture telling the same kind of stories around a campfire. If I could choose between that and divergent surprises while figuring out the universe and doing stuff I would choose the later without hesitation but you wont get that if the developments trashes its own ecosystem.
So that we can kill them better when they show up. The aliens. The link is to "Blindsight" by Peter Watts - maybe the best sci-fi novel I've ever read. Derrick Jensen meets The Swarm.
Biology, understanding ourselves. GMO trees. The toxic food chain, etc.... Yeah, we need to study that more.
cfm in Gray, ME
"understanding ourselves"
That's the main project. But the fact that you seem to be willing to broach a mass extinction event to avoid getting bored suggests that you might be a candidate for a bit more self-reflection and self-understanding?
dohboi,
To your reply, I can only say that I was not intended to be dismissive, but it is possible that it came across that way.
Contrary to your remark, I do care very much what is built in my backyard and "anywhere". Remember that here in Kentucky we live in the shadow of "mountaintop removal mining" to extract coal. This is real "in our backyard" catastrophic activity that is virtually ignored by the mass media and even by those folks here on TOD.
I just believe we should play fair: I can come up with objection after objection against every alternative proposed because it will have some kind of "impact" while ignoring impacts that are absolutely catastrophic and that are already occuring.
I ask: Does any of the renewable alternatives to coal production and use(the kite gen, concentrating solar mirror, PV solar, conventional 3 blade wind turbines,ocean wave power...or do ALL of them combined have even the remotest possibility of causing the catastrophic "impacts" that coal extraction and use is already causing?
I am going to be very forthright here, dohboi: I ask, why is that if a PV solar plant opens, there are repeated stories in the news about the fact that it uses "heavy metals" while no mention is made of he micro chip plants just up the road that have used thousands of tons of heavy metals since the 1970's? Why is it that the birds killed by a windmill make headlines, while no one talks about the hundreds of thousands of birds that die every year flying into open oil tanks that look to birds like lakes? Why is not the destruction of rivers and the catch basins for coal sludge ignored, and it makes the back page of a newspaper in the hill country of Kentucky and West Virginia when a cheaply made damm breaks and the slop buries a town killing a few locals, and no where else in the U.S. covered?
Do you want to see massive destruction of birds, plants, animals, eco-structure, soil and rivers, hundreds of thousands of acres of the most diverse eco-structure on the face of the earth turned into lunar landscape? I challange you to put "mountaintop removal mining" into a google search engine and sit back and enjoy the slaughter. But if only the carbon from the coal can be sequestered, all will be okay and we won't need solar or wind or renewable energy the mining and utility companies tell us! But of course, the coal will still have to be extracted and the catastrophic almost unbelievable damage will continue.
It is all too easy to fire up a few local activists groups to the alternatives and create opposition to any alternative based on the most marginal of impacts while the the opponents to mountaintop removal which can be seen from SPACE can get no press coverage. Al Gore screams about a glacier in the arctic while ignoring a catastrophic destruction that is going on in his own backyard in border states of Tennessee. Why?
All the supporters of the alternatives are asking for is a little fairness. Do we need to reduce energy consumption? ABSOLUTELY, we waste energy that goes up the smokestack and out the tailpipe while producing no benefit for anyone except the energy producers.
You say, "People should be much more concerned about what is in their area and in others' too." ABSOLUTELY, but where are the "not in my backyard will I risk being struck on the head by a flying windmill or put up with a small sound from it" instigators to talk about WHAT IS ALREADY HAPPENING? People are willing to attack any change with a bit of instigation and ignore the destruction that has been underway for years. Perhaps we accept the current destruction simply because it is already "well-established". Parhaps we know that we can attack a new start up company much more easily than we can take on a fight with Peabody Coal or Duke Energy.
By thinking that any alternative that brings with it any impact, no matter how slight it may be in comparison to the catastrophic impacts of the entrenched fossil fuel industry, we are supporting our own kind of destruction: The destruction of any path forward except poverty, decline and loss of our intellectual leadership in the world. The alternatives should be questioned and examined closely: But we must do this examination in the context of the damage that is already being done on a much more massive scale than the alternatives have shown any potential to do. We cannot become propaganda pieces for the fossil fuel extraction industry by throwing out meandering attacks on every possible alternative to them.
Thank you for the opportunity to discuss these issues,
RC
Well said, Roger.
Alan and aviator--I suggest the truth lies somewhere between your positions. No way would this be located over a regularly used area such as urban or a village, because as you say these things are (possibly) going to crash down occasionally. But on the other hand the land below could reasonably be used for farming or fishing or a solar thermal farm, with a negligible probability of any significant harm from a crash.
And meanwhile sometimes the precarious can be made unexpectedly reliable. Planes, even helicopters, very rarely fall from the sky. Six people were killed in a major uk tower block fire this week, but hundreds of such blocks have remained consistently unfired for over 40 years (even Ronan Point which was one-quarter demolished by a gas explosion), giving an outstandingly higher safety record than standard height houses with wooden floors.
PS--My thought before working through 201 comments is that this article really does warrant the "excellent" word unlike some recently that it has been dubiously endowed on. Excellent presentation of what looks at firstish sight like excellent engineering (with fine developments of a general concept I was thinking along myself between more pressing chores).
"Yes but don't forget that 20 years back in 2009 people were saying then that we were energy-doomed, and they completely failed to see the kitegen era coming; they were wrong then and they're wrong now."(?!)
the precarious can be made unexpectedly reliable
But only over a considerable period of time. Long term experience is required, unexpected failure modes will be revealed as the experience base expands, equipment near the end of it's service life will have different failures than brand new equipment, operators with differing levels of expertise and maintenance, etc.
In my SWAG, a minimum of ten years, in the best case, to even remotely approach aviation safety standards.
Alan
Actually not even with time and experience. This kite is fundamentally different from an aircraft, in that it inherently can only be a flap on the end of a cable loop. It can't have engines or steering gear. So there's little scope for self-corrective techs. For this reason I'd agree with my reckoning that it couldn't be acceptable within falling distance of urban or villages, but could be acceptable in land for farming, hiking etc, where any crashes would only rarely hit anyone.
It's not the kite that's the problem. It's the cable it drags. Keep that out of the rigging, please.
A farmer, with his wife and children, might disagree that their lives and home are somehow more expendable than those of the townspeople in the nearest town.
The risk to each individual person is about the same, regardless of location & density, of living under a KiteGen (those that work outside, such as farmers, likely have greater individual risk). It is just that towns have all those individual risks clustered together.
And said farmer owns the air rights over his farm.
Alan
Alan, any crash will take a fixed amount of space, the odds of it actually hitting a person relate directly to the odds of a person being in that space.
The farm family is just as likely as any other to be in that space, but since there are fewer farm families per km^2 than village or urban families there is less of a chance that anyone at all will be there.
It isn't a matter of relative value, it is simply a matter of the odds of anyone at all being there.
There is simply no place on earth where you can count on nobody ever being on the ground or water perpetually, there is no completely abandoned space. All you can do is set relative limits.
This applies equally to this technology as to conventional wind, planes, satellites, transmission lines, and myriad other above-ground-level constructions and craft.
And furthermore I wasn't envisaging that the farmers or hikers would be actually living under the thing, just they would have their sparsely-visited fields thereunder. You wander in the country and in a square mile more often than not you never meet anyone anyway. So lower probs all round.
The current standard for wind turbines (ground based) is no permanent human habitation can be within the "falling radius" of a wind turbine.
It appears that the falling radius for KiteGen is a minimum of a mile/1.6 km. Applying the same rule to KiteGen as is currently used for other wind turbines severely reduces the # of sites.
Farmland with a couple of farm houses/mile2 is far too dense. Ranchland, with one ranch house/ 30 miles2 (77 km2) seems to be close to the maximum density *IF* the falling radius is only 1 mile.
Alan
This increases transmission problems.
The big problem isn't the kite falling out of the air, despite it's weight it will be moving relatively slowly due to aerodynamics. Any shelter at all should be sufficient. Additionally, since it is only the rigid portions of the kite that are likely to cause damage from impact, the design should minimise rigid kite components (a paraglider style kite would be ideal from a safety perspective).
The big issue is line springback. That would involve a danger area around half the line length in radius. That sort of clearance is available in many more areas.
It is really curious that the main issue emerging here about the KiteGen technology is the falling of the kite hypothesis. I beg your pardon, but from the TODers I was expecting more pregnant commentary.
Let me divide in three main situations, all already experienced in the real tests of the prototype:
a)
If the machine is fully operative the kite cannot fall. Even in the case that the wind stop or suddenly change of direction. The base drums and winches are able to reel in the ropes at various speeds reestablishing the traction that stabilize the flight speed, the lift and the maneuverability of the kite. The control can choose to bring back the kite and stop the machine or move in the new downwind sector
b)
If the KiteGen Stem has one side in mechanical trouble, and only one rope cannot be recovered, with the other rope is easy to start the sideslip procedure and bring back the kite, up to it will be hanged under the arm top, the drawback is that a double rope in half length extension should be recovered from the ground.
c)
The KiteGen Stem is in total default:
If it is an electronic control failure the machine has typically enough time before the falling event to restart the program, or switch the active controller and recover the normal operation, but raising the maintenance alerter flag;
If it is an hardware failure the kite will fall, but an indipendent watchdog automatically cut one of the two rope in order to let flagging the kite avoiding dangerous forces on ropes during the fall.
In my humble opinion and after some machine refining, the latter cases could happen likely with a frequency as the civil aviation, airplanes disasters frequency.
From a technical standpoint there are 3 issues:
1. Will it work at all: I am satisfied from the information that you have made available that it will.
2. Will it be cost effective: Looks promising, but more data is needed. You have plans to collect that data with more tests.
3. Will it be safe: all signs look good there. The safety issue that most concerns me is a break in the line close to the ground. A top of line break has plenty of time for air resistance to slow it down before the line hits the ground.
I realize that the sort of line part that is the most dangerous is also one of the least likely, but if you can show that it has been adequately considered and appropriate precautions taken then it will make siting and permitting that much easier.
The main consideration with a line part is how far the broken end needs to travel for air resistance to slow it down to a safe speed. The actual safety radius for this failure mode will be where a cylinder of that diameter centered on the lines intersects with ground+2m or so. Half the line length on the ground is a very conservative estimate for this, I'm sure that well considered calculations will reveal the actual safe radius to be less than that.
As for the kite itself falling, I see little risk there. In the event of a double line break it appears that you will have a free-gliding/falling mass of cloth. It might get tangled in something...
[Edit]
I see from your comment below that you have considered at least some portion of this in your design. I note that sand can get into almost anything and cause mechanical jams which would impair your tensioner's ability to adjust. If you plan for this sort of failure and nothing happens it still makes people feel better about having one "in their backyard".
[Edit 2] The actual safety radius is even smaller than my original estimate due to the forces being under tension. The actual vector of force is going to be very nearly aligned with the line itself. I suspect that the safety radius will be small enough to be satisfied by the enclosure. Still, calculate it out to be safe.
You overlook downdrafts. Those that you can see (thunderstorms) and those that you cannot (clear air turbulence).
These will force a kite down in seconds. Perhaps to the ground, perhaps just 1 km.
I suspect that after a sudden downdraft, the droop in the cables will hit the ground and become entangled before the kite itself hits the ground.
You fail to understand the over half century of extreme effort (many billions of $ and millions of man-hours) required to get to current civil aviation safety record. I found your statement "...after some machine refining, the latter cases could happen likely with a frequency as the civil aviation, airplanes disasters frequency" quite naive.
Boring (I know) and Airbus (I suspect) hold safety in both deadly seriousness and as the highest priority (*FAR* more important than profits or whether a/c fly or are grounded). Does KiteGen have the same emphasis ?
In any case, it will take a decade of experience, with thousands of KiteGens, in a very wide range of climates, and many different operators (some of whom have tight budgets, and unskilled personnel), to get an inkling of what the risks really are.
I have some other, more esoteric concerns about KiteGen, but safety appears to be the primary one.
The grid must accept whatever KiteGen produces. Conventional wind turbines have large amounts of rotational inertia to even out the variations in wind for short time periods (sub-second to multi-minute) although there is still a pulse (drop) whenever a blade on the down side passes in front of the tower. Large #s of turbines are used to even out this relatively small pulse statistically.
It seems that every time there is an inflection in the path of KiteGen, power production would vary.
Alan
Alan--Your second point, about rapidly varying output, looks like a significant problem unless there is an adequate flywheel system built into the base; hopefully someone can turn up to respond here.
As for danger from downdraughts, the suggestion has already been made that the kite can be very rapidly switched to reel-in mode, and perhaps thereby it would escape from the downdraught zone and or promptly re-establish its "flying" mode. It may not take many years to clarify this. Over a non-populated area any crash would be of low risk importance anyway.
To: Alan and other "Kite-crashing"-folks -
This crash-issue is the last challenge this concept will ever face - before this alot of hurdles of functionality shall be checked. And if Kite-Gen so do - then the "crash"-issue will also become ckecked - Why ? Because that one is the easy part ... and I have "10 working proposals ready" already.
The "rope" will become the major-problem, therafter controlling randomness and efficiency...
As a street fighter from the 60's, we used kites to interfere with helicopter blades during riot conditions, with some success.
That said, I love kites, and in the proper environment, why not explore the possibilities?