Wing Wind Power

Thanks for that; both the calculations and the "other observation"

Not too impressive overall is it

There was always going to be pairs, or triples, of these, so the 'farm' output is constant.

But even so - not too impressive

But maybe it could be viable at "bad" ground based wind sites, or be cheaper than oceanic 'floating farms'.

A few random thoughts:

The pull rate could easily be ten times higher, 2000 fpm being an easy-to-control rate, via an autopilot.

Two units could be separated enough to avoid collisions, line entangling, etc. (while connected to allow reciprocation). This would permit constant pulling with one or the other, doubling the output.

Lift/drag ratio affects the angle of pull (high l/d makes the rope angle more vertical) but has less effect on the total pull. There is not a huge disadvantage in using the whole range of high-lift devices (which add loads of drag) although achieving the same altitude would then required more rope. The wing on the 747 has a pretty full load of very effective high lift devices, and so can land at reasonable speeds, meaning that it could stay aloft in (relatively) low wind speeds. That speed could be as low at perhaps 50 mph, if the 747 were completely gutted and shortened by perhaps 50% (long enough to keep the flight dynamics from becoming twitchy).

The double wing version would have the disadvantage that both wings would have to be reeled in at the same time, if the wind died altogether. (I don't know if this ever happens at 30,000 feet.) Like a kite when the wind dies, you need to start running to keep the thing flying.

150,000 psi would be achievable with a unidirectional carbon fiber bundle (wrapped in perhaps Kevlar). A 4" dia cable wold provide 1,900,00 lb breaking strength. The natural catenery would act as a shock absorber.

You might look into the space elevator concepts. Maybe these units could slide up and down the space elevator cable?

I noticed you asked what a sprag clutch is. It is a toothless ratchet. Transmits torque in one direction, freewheels in the other.

The wing bit is, or can be quite different to the 747 engineering, as that is cantilevered off a centralised stress of payload mass and undercarriage loadings.

The Air Wing can have a 'fan' of tethers to spread along the span. Its a bit more drag, but a huge advantage in structural mass.

I have often thought, but never done the sums: If you made a carbon fiber wing-skin, with the lowered structural needs, the 'end weight' might 'sufficiently insignificant' to remain flying on a 'breath of air'.

However; the wind side of this is a lot trickier than most realize. It's all very well to say there will be some at some altitude, and probably 99% true. The trick is getting from one 'failing stream', up through the turbulent separating layer, into the next productive stream, against the weight [and windage] of the tether.

One really needs 'on-board thrust'. So now we start on PV and motors, plus batteries for night moves, and the weight creeps back. You could send motor power up the string, but even at high voltage and using aluminium, it gets self defeating.

E.g. I don't think the helicopter boys have calculated the tether weight for output to the ground, but maybe the plan is to generate/drive at a gazillion volts [and have high tensile zero mass insulation?]

However; I think we could indeed 'overcome' all the problems and get close to 24/7 significant power out of this system [bar pull downs for 1000 hourly inspections - but you could have spare wings]

So, it would be quite expensive power, but maybe the economics will 'catch up', when finally the word "finite" sinks into the 'fossil heads', because there ain't no cheap stuff left. Then all are casting about for Hobbit Miracles .... Oh ... we are there.

Question in my economic brain is why wouldn't you invest in stuff you can basically ignore, sitting on the ground and spend the money on re-pump storage?

E.g, if you covered the land allocated to this flying exercise with PV or regular turbines, dug the hole deeper, built a nice pond, you need a guy with a spanner - not a team of air-traffic controllers, back up pilots, ground maintenance staff, radar, com's in triplicate, interlinks with airfields and airborne craft, and a "chase the lost private pilot off" stand by interceptor.

Or all the things Tcmtech kept rightfully yelling, then add a staff/MW 'unrivaled' by any other power generation technology.

It's this 'uncounted infrastructure support overhead' that will bring the 'altitude wind' idea competitively 'down to earth' - not so much R&D cost or technical hurdles.

We could 'solve the technical', as a fun exercise, but I doubt we could obviate the operational overheads.

The basic attraction of Airborne Wind Energy is that it uses tension structure almost exclusively, which is the proper way to approach a diffuse mechanical energy source. Foundations tend to be an inordinate percentage of the price of current windmills. The other compelling reason for kites is the increasing consistency, as well as strength, of the upper winds.

While layers of doldrums are not usually a problem, a wing-mill can be much more versatile if a rigid wing such as the one proposed here can launch and retrieve a train of air-inflated foil kites to maintain output in reduced wind. The vigor with which the kites are flown across the wind gives a wide range of adjustment, too.

In general, kite trains are inherently stable, while individual kites are not reliable in turbulence. Airborne generators are sometimes proposed, but don't seem to scale up well or safely. The world's biggest kites are towing ships, and they are pure tension structures, with automatic launch and retrieval.

Indeed it may will soon be more than just "saving some fuel".

The Royal Clipper, the world's largest sailing ship is the first five masted sailing ship to be built in nearly 100 years and the first since the German five- master Preussen, on which the new ship is modeled. Her masts tower to 58.5 meters. She will carry 228 passengers, have a crew of 106 and fly 5.200 square meters of canvas on 42 sails. There are 1.950 square meters of deck space offering each passenger 8.50 square meters for sunbathing and three pools for swimming.

Except it will be cargo rather than passengers.

Neat! But whats the cost per hour of 106 skilled old school sailors and what would the cargo capacity be when compared to a common sized modern freighter?

Somehow me thinks that the wages of 106 skilled sailors buys a lot of 30 cent a gallon ship fuel.

106 reformed Somali pirates might come fairly cheap....

But why not have one sail per mast that extends upward from a large "window shade" coil at the bottom? Reefing and mast rotation could be done by semiautomatic hydraulics.

(Well, maybe...just an idea.)

Here's a promo about 3:59 in - I don't many are sailors

Haven't found the core crew complement - not that I've looked hard

From

Advanced technology

Under sail, the 133 meter-long Royal Clipper can achieve a speed of 18 knots. Although at first glance the ship appears entirely traditional, she is equipped with the very latest in advanced technology and materials. As a result, operation is simple, and the vessel requires relatively little maintenance. The masts and rigging were specially developed for the ship. The masts are made from tapering steel tubes, to which the entire rigging is attached. The complete rigging is hydraulic remote controlled from several control stations on deck. The Royal Clipper has an ultramodern navigation and control system, including an Autopilot system and GPS.

Oh here we go, something slightly informative

extract;

"Size of crew: 105, of whom only 20 are needed to handle all sails. The remaining 85 crew serve passenger needs or are on support duty, such as in engine room"

There are 1.950 square meters of deck space offering each passenger 8.50 square meters for sunbathing and three pools for swimming.

Impressive. If each passenger has three swimming polls, that would mean there are 684 pools on board.

The wing bit is, or can be quite different to the 747 engineering, as that is cantilevered off a centralised stress of payload mass and undercarriage loadings.

However, I think that when you take into account the need to operate at very high lift coefficients (for lowish wind speeds) and also very low lift coefficients (for high wind speeds and for times when the wing is intended to move earthward), then the wing of a 747 is pretty good, at least for prototyping purposes.

To be able to maneuver adequately under the wildly varying conditions (as compared to those in a typical airplane, where airspeed is near constant) requires at least the flying ability of an airplane, (including the ability to yaw on command) which then means that multiple load takeoff points along the length of the span is too limiting for maneuvering ability, I think. If that's true, then the structural issues become much like the classic airplane issues (cantilevered or braced, monocoque or frame-and-skin, etc.) and it is likely that the issues would resolve as they have for airplanes. Although there is not the economic need for high l/d ratios (as there is in an airplane, where better aero efficiency means less fuel cost), there could be survival needs requiring low drag.

In short, I think that to get the stability, maneuvering ability, and structural integrity required, the design would end up looking a lot like an airplane.

E.g, if you covered the land allocated to this flying exercise with PV or regular turbines, dug the hole deeper, built a nice pond, you need a guy with a spanner - not a team of air-traffic controllers, back up pilots, ground maintenance staff, radar, com's in triplicate, interlinks with airfields and airborne craft, and a "chase the lost private pilot off" stand by interceptor.

I agree that it would be hard to get enough bang for the buck.

The lost pilot issue is one that also popped for me. Airplanes, when piloted by someone who is lost, seem to have an uncanny ability to find things to fly into. You could calculate the probability that a small airplane and a tether could occupy the same space at the same time, and conclude that the likelihood of collision is impossibly small. That calculation, however, ignores the fact that lost airplanes are drawn by magnets to such stuff.

They used to say: An autopilot is a device used to accurately place the wreckage at the crash site.

Well I had to go and have a little think on "(including the ability to yaw on command)" so thanks for that. You also raise 'progressive stall' which a 'infinite wing' approach wouldn't exhibit. But I could do Airy points through a pulley

Main point of the previous - no humungus main spar, the GRP skin becomes 'structural' and not quite so much need to 'dismantle half the wing' with flaps and L.E. slots.

PP's are magnetic - no doubt.

Kramerat, I have worked out that the tower would have to have a ratchet from top to bottom so that it was secure at any stage of the journey upwards. My device could be made to lift a one million tonne weight over a distance of ---whatever the size of the tower that we built. Any idea of the calculations from a 400 ft tower with this weight attached. It would be possible to have two of these towers for my device .Anyone know how many Kwh this would kick out? When you have worked that one out can you please tell me what thickness the steel rope will need to be.Or would it be possible to have several smaller ropes.?? UK Joe

You are rude, undereducated and all over the place, like a crazy persons poo. Your grandstanding on other peoples shoulders is starting to be an embarrassment for this site. Well, maybe not starting because from the word go you have been polluting any attempt to come up with a solution on anything.

Sit back and study and when you have something to present, present it in a normal acceptable way. Study, that is the stuff one does before one starts anything. Your half baked mind and attitude is not helping you. You will find out one day but that day seems a long time away.

UK Joe my lovely behind. Get a life and stop interrupting people at work.

Ky, it just shows how far a person can go without education. Pollution or no pollution i have got my problem solved. I do not need to present anything now. Goodbye I,m off for a poo.UK Joe.

If you have been paying attention , you would notice that the various figures have been posted, to allow you to do your own home work

It is rude to hijack a thread, why don't you start your own or at the very least post a link so we know which thread to ignore...

Hi Garthh, I have been paying attention but as you may be aware figures are not my fortay. I am new to this blogging business and am quite devoid of etticate. I am not computer literate and am unable to post a link myself. Sorry for cutting in to Anonymous person#1. However Garthh, you was mesmerised with my posts and I do not think for one moment you will ignore my thread if I ever do learn how to set one up.UK joe.Perhaps you would instruct me how I can start one.

Not mesmerized, annoyed is more like it

As TCM said, you already started a thread about some fantasy device

I don't imagine personal interactions go much better for you in person, the internet is no different, arsehole is arsehole

In the last 30 years I have been quite interested by this type of wind generator.

But it has an enormous amount of design problems.

The ladder tipe with many slats going up and down has the very serious problem that if we need to orient it to the wind, then the necessary mechanism on the ground becomes too heavy, complex and expensive. All the other drawbacks can be solved.

The solution of a single wing moving up and down seems to be the best solution. BUT:

1º-If we want to make it orientable to the wind wihtout the use of monstruous mechanisms, we need to hook it in the center.

2º-But by doing this, we have to use a Cantiliver wing (As in a 747) and then the necessry reinforcing o the wing, make it as heavy and expensive as a real 747 wing.

2º The best solution to this is to try a wing with multiple hanging ropes but that still is attached to only one point. These are the Parapente wings.

3º But their strongly curved shape yields a very low aerodynamical efficiency. Also the angle of attack cannot be controlled easily.

4º- So the best thing would be to concentrate in inventing a high peformance lightweight wing. I have some ideas.

5º- As for the length of he stroke, please realize that making a 10 meter stroke every 30 seconds is the same as making a 100 meter stroke every 300 seconds.

6º-The rope can be tied to the center of the wing and to one 10m diameter crank, that does not need to be orientable. A flywheel would keep this crank rotating.

7º- The wing needs a tail rudder and a tail elevator in order to be oriented and controlled.

8º- The power stroke is only up. the stroke down is with the rope loose.

9º- The tail elevon control would keep a slight tension on the rope downstroke.

We do not have all the problems posted by the people in the forum.The elevation of the wing needs only to be of 100/200 meters. (Or less)

BTW. THe system would NOT use the wing as a kite. Kites are extremely inefficient, but as real aircarft wing with he proper angle of attack.

chorete

kramarat,Your'e not as full of that stuff as you are claiming. I am so glad that your brain is still ticking even at that time of night. I have mulled this idea over in the past and now you have confirmed what I was thinking. I think this is the path I shall follow. UK Joe.

tcmtech, Will you talk to me then????

Sorry but I just took a poo earlier myself and now I am out of troll food for a while.

You may want to ponder on what my signature quote means too. It could prove to be immensely valuable to you in your quest.

Tcmtech, I have just bid you all fairwell but I can't leave without knowing what your title is. Well??????

Tcmtech, I have been signed out by CR4-me thinks. What does it stand for then ?????I won't sleep if I don't find out.

Seems as you have ALL sent me to Coventry.Watch the News in a couple of months. BYYYEEEE-Love Joe.

Dear CR4 members: a footnote.

I have off and on, been involved in assessing the viability of these 'energy' schemes over a decade or two.

The input on this was so remarkable, I was quite frightened there for a bit, it might actually prove viable.

I think that 'solution mix' actually turned out the closest to making the concept viable I've ever encountered.

To underline that; compare the 4.5 MW result and complexity level with the 1.6 MW helicopter apparently 'astounding all' in this altitude wind 'competition'.

To me it makes as stronger case as one is likely to be able to make, for the Competition Assessment folk to bring the 'final 30 odd' to CR4 for 'engineering mix' and viability evaluation.

With luck, they might read this thread and this comment.

It may have started out as an 'exercise in something else', but I found it both fascinating and very 'engineering-ly' productive.

Thanks to All.

There is a huge archive of material pertaining to kite power available through http://tech.groups.yahoo.com/group/AirborneWindEnergy/ and a trade association at http://www.aweia.org/

Perhaps the easiest way to build a whole system on this general principle is to use the kite tether to haul a big skip of water uphill to a hydro-power reservoir, to produce power on demand without major investments in silicon, etc.

Are you guys aware of the substantial de ratings that air density will play at 35,000+ feet!

feet meter inches Hg mm Hg psia kg/cm² kPa

0¹⁾ 0 29.92 760.0 14.696 1.0333 101.33

35,000 10,679 7.06 179.3 3.47 0.244 23.93

50,000 15,255 3.444 87.5 1.69 0.119 11.65

http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html

Yes

Density altitude has been mentioned and was again in the link I posted on boundary layer.

I also alluded to it in the observations on the helicopter concept.

It's also why i dropped the 'pull' from 500 - 750 tons to 250, as up till now no one 'pulled me up on that' wee bit of physics.

So well done you - again.

The Missing Link Between Air Density And Wind Power Production

Heeeheeee Tcmtech beat you to it

But cool research -

One hopes though that is not the formula he actually used

For those of you who care, it actually directly derives from ½ mv² x Betz, where m is the mass of a m³ of air at the prevailing density, moving at U (initial velocity) m/s.

As does Bernoulli with a few tans and sines thrown in.

Sir Issac is everywhere.

Betz seems to lose some of its meaning when applied to a wing translating through space, because the reference area is less clear. If taken as the span times the stroke (translation) distance, then it seems that as the stroke distance increases, the "Betz" number would drop: in other words, a wing traversing a large space will extract less energy as a portion of the total available.

The 747 wing cruises with a Cl of about .4. With full flaps and slats, its Cl is about 3, I'd guess. (Cl gets as high as about 4 in C-class catamaran wings.)

Obviously, 747s fly quite well at 35,000 feet. Halving the cruise speed (from say 400 knots to 200 knots) would require quadrupling the Cl from .4 to 1.6. Dropping back to 144 knots would require a doubling of that to 3.2. So in the range of windspeeds from 144 on up, you'd expect full lift of about 400 tons to be available. The "plane" would weigh perhaps 50 tons, for a net of 350 tons.

I think that a wing (used as a kite) has an advantage over a windmill in permitting simpler adjustment of Cl, but more particularly, in suffering no large disadvantage from the large increase in drag that accompanies an increase in lift. The angle of pull would change with increased drag, but the magnitude of pull would remain high. In a standard, land- based windmill, drag does not increase output, but adds to the moment at the base of the structure.

It is a rare location that has 20 knot winds consistently. (The average wind speed across the US as a whole is 8 knots.) At 35,000 feet, air density is 1/4 that at sea level (potentially meaning a reduction of energy to 1/4 of sea level energy.) But winds can be 100 knots*, 5 times as great for 25/4 times the energy: about 6 times the energy per chunk of airspace.

I suppose the answer to the lost pilot syndrome is to ignore it (other than putting cable locations on charts. We don't have a precedent of moving mountains or power lines out of the way of such pilots, after all. (I used to know a private pilot who lost his undercarriage to a set of power lines, survived the incident, and subsequently landed gearless at an airport.)

* I just looked this up -- and it is a pretty rough estimate. Winds at 35,000 feet are lower than I would have guessed. When I've flown small planes, it always appears that winds at even 10,000 feet are just slightly less than my indicated airspeed... and they change direction to always come from my destination. The same effect is seen in sailing. The wind is invariably coming directly from my destination. This makes me think that sailors should worry less about navigation: just sail to windward all the time, and you'll find interesting places.

Re: But winds can be 100 knots*, 5 times as great for 25/4 times the energy: about 6 times the energy per chunk of airspace.

I'm not sure where you got the 25 from the 5 times greater (I didn't try very hard to figure it out)--generally, power output from the wind is proportional to the cube of the wind speed, which would make the numerator 125.

But, maybe there is another factor I'm not thinking of that would make it proportional to only the square of the wind speed--maybe because it's a wing instead of a windmill?

But, maybe there is another factor I'm not thinking of that would make it proportional to only the square of the wind speed--maybe because it's a wing instead of a windmill?

No, I think the cube still applies. I was ball-parking lift, and incorrectly calling it energy.

I kinda blended aspects of my response to you with Tcmtech, above.

On the 'wing' side, it's pretty low airspeed. More 'glider' territory.

I think if this got $ for a 'cut and shut' R&D exercise, I'd be looking about for something like a U2

_{(not U2 though it might be, and has planes in it)}

If you are referring to me I used no formula but my common sense was tingling when I saw that at 35,000 feet the air pressure is about 23% of that at typical sea level. I suspect that its density ratio is similar as well.

Google with a cut and paste is about as complex as my math gets these days hence the link I posted to show where things came from.

I was referring to you in raising density altitude

And referring to the author of Sue's link [not Sue] in math aspects. I.e the way the formula for the power of a turbine was expressed, sans Betz, or I'm again 'marveling' at journalism doing 'science'.

Taking a quick look at your "common sense" by way of demonstrating the underlying math for others.

I think 23% air pressure, so density, is quite a reasonable proposition on a PV basis (ignoring T)

Say this is the case at some near altitude, it would alter the 1.225 kg/m³ at sea level to 0.28 kg/m³ at that nominal altitude

So P would be (0.59 x .5 x 1.225) x U³ x A, vs, (0.59 x .5 x 0.28) x U³ x A

Or, respectively; 0.36 U³ A, vs, 0.08 U³A.

One obviously needs more U (wind speed) and/or A (area) for the same P (power) out.

Given the 'wing' is fixed to ground speed, not airspeed as an aircraft, more U has to come from wind, not engine thrust.

Given A for the device is physically set; and using a nominal U = 10 m/s, P = 361 W/m² [at sea level]: and P = 83 W/m² [at our altitude density] .

To equal 361 W; U [at altitude] would need to increase to 16.3 m/s.

Or, 163% sea level velocity to 'break even'.

To do it by A, you'd need ~ 4.4 times, to 'break even'.

These [area & mass per unit volume] are often the 'overlooked factors' by those assuming 'higher speed numbers at high altitudes', translates directly into 'vast power'.

I.e. they lack your "common sense" that says there must be an 'm' involved in a mass flow equation

Perhaps because 'm' isn't 'blatantly obvious' in the script

Thanks 34point5! Nice to know my high school physics was at least worth the effort I put into staying awake for most days!

Here is one more bullet hole in this concept of using the higher altitude air currents related to the jet stream. By gosh wouldn't you know it that dam thing wanders all over the place and changes speeds like panicked old lady on the interstate!

http://www.weatherimages.org/data/imag192.html

No you wouldn't want to be designing for 150 knots and expecting that consistent yield - not even if you had a "pass the kite string" system, running the length of the US.

But 60 knots = ~31 m/s might be 'reasonable' given the wing is not "committed" to 'jet-stream' operation.

In watts density, that translates to U about 18 m/s at sea level (35 knots, 40 mph, 64.8 km/h)

It might do better in the southern hemisphere - a little less 'old lady'.

Maybe of interest

I don't think any of this 'rules it out' - just puts the viability into perspective.

As said I think there are more sensible things that the power industry could put the money into - that actually also address the big hurdle of alternate generation - storage.

I am constantly amazed that no one seems to be able to grasp "quixotic" in one camp and "finite" in the other.

I just found this site, with lots of practical experience well distilled:

http://peterlynnhimself.com/Kites_For_Yachts.php