High Altitude Wind Turbine Tower Design

Engineering System Design
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About guy tension:
https://www.researchgate.net/publication/272151204_Guy_tension_influence_on_the_structural_behavior_of_a_guyed_mast

Guy tension influence on the structural behavior of a guyed mast

Abstract and figures
Guyed masts are a specialized type of structure commonly used in the broadcasting industry to support equipment at substantial heights. The stability of these structures is based on prestressed guy cables. The level of prestressing is specified by the designer and should be rectified periodically. Excessive relaxation can make the guys sensitive to galloping, while high tensions can produce vibrations of the cables; for these reasons it is recommended that the cable tension values should be within a certain range. This work investigates the effects of changes in the cable tensions on the displacements of a mast, the axial forces of the members and the dynamic characteristics of a mast. The results show that an increase of the cables tension in the studied range produces a decrease of up to 33% of the axial forces in the legs under extreme wind load, and produces a significant increment in the natural frequency of the mast.

1 Like
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I’d say this is heading into “Professor Crackpot” territory. :slight_smile:

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More long-established beginner information for the “Professor Crackpot” know-nothings… :slight_smile:

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I’m seeing many “inventions” here, not necessarily needing to be combined, not necessarily even related:

  1. Inflating wind turbine towers with air to allow thinner walls.
  2. Adding guy wires to utility-scale towers to facilitate higher heights
  3. Adding a sealed piston to support a turbine at the top of a tower on compressed air below (why???)
  4. Drastically decreasing the size of turbines, in spite of the supposed higher height of the inflated towers, to facilitate easier blade transport;
  5. Using steel for the blades;
  6. using helicopters to install the blades;

This is just the list that pops into my mind after hearing the video while doing something else.
If I were to read and listen more closely, there are probably many more showstopper aspects I would notice.
In my humble opinion. none of these “inventions”, or let’s say “ideas”, seems even promising, on its face, as an isolated “improvement”, let alone in combination.
What is presented smacks of what I keep calling “all-ya-gotta-do-is” proposals, based on what I call “bumper-sticker-level reasoning”.

It’s just a big pile of “all-ya-gotta-do-is” suggestions, none of which seem to be sufficiently analyzed in their pros and cons as basic concepts, let alone filled in with all the “nitty-gritty details” of exactly how they would work, what inherent problems would need to be solved, or what smaller steps would need to be employed to make them work.

In short, this amounts to just one more of thousands of half-baked (or less) concepts floated about by people with little or no experience in wind energy, which, like so many of these stories, might sound great to similarly-inexperienced-in-wind-energy minds, but which, for those of us with decades of reviewing such proposals, read like some sort of comedy, or an exaggeration of itself.

Always glad to be proven wrong, I don’t wish to squelch anyone’s creativity here, or declare that there is nothing noteworthy in the proposal, however, raw creativity is just a start. It needs to be tempered with knowledge and logic, not to mention way more acknowledgement of what problems it introduces and doesn’t solve, in addition to addressing all those details that would need to be addressed for the “all-ya-gotta-do-is” proposals to work out. In other words, it needs a much more thorough analysis before even being proposed.

Combining so many off-beat ideas into one design multiplies the chances it will not work as a whole. As it is, I’m not sure this even rises to the level of a “Professor Crackpot” proposal.

Oh well, maybe not bad for a first try. Have some renderings done, and maybe some online magazine like “Interesting Engineering” can write a favorable article with a start date of how many million homes it “will power” on some remote island that will quickly be forgotten by readers, as it slowly never happens, and is replaced by the next series of false, “press-release breakthrough”, articles.

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Some questions to @ChristophePochari1:
By increasing the pressure in the cylindrical tower the piston will tend to rise and, in addition to supporting the load (wind turbine) with compressed air, will stretch the guys from above, is not it?

On the other hand, the pressure may impose the need for a resistant and therefore quite heavy cylinder. What do you think?

Perhaps a small proof-of-concept could be achieved by using a pump like the one below but thinner and narrower, blocking outings while adapting said pump with its piston to the shape of the guyed cylinder supporting a load.

https://www.amazon.co.uk/SPYMINNPOO-Inflatable-Inflating-Original-Cylinder/dp/B09T6PNWVL

We can get an idea of ​​the force of pressure exerted by a bottle of champagne when the cork is thrown violently.

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Another question to @ChristophePochari1 :
Are you considering implementing an air compressor?

I think yes but I am not sure, because without compressor the load on the piston could have the effect of making it slide downwards (a bit like the pump I illustrated), which would have the effect of compressing the air contained in the cylinder and therefore making it possible to resist the load, without however allowing to tension the guy cables due to the descent of the piston under the load of the wind turbine until stabilization.

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A sealed upper surface to the tube, supporting the turbine, would similarly enjoy an upward force = pressure x area, just like a sliding cylinder, without any need to slide up and down, so I’m not seeing how the sliding cylinder accomplishes anything, except making things way more complicated, more expensive, and introducing severe failure modes. Such a piston would be moving up and down with every revolution, since the rotor would never be perfectly balanced. If a blade was thrown, the piston would likely jump out of the top, hitting all the surrounding guy wires, taking down the whole windfarm of closely-spaced, guyed towers supporting extra-small turbines, in a cascade of falling turbines taking out neighboring turbines. Temperature changes would change the height of the cylinder. The doors at the bottom of the extra-tall tower, as well as the hatch at the top, would each need to be an airlock, and you might need to keep a special high-pressure chamber handy at the bottom, so workers could decompress without getting the bends after being inside the high-pressure tower.
Pierre suggested a small model using a bicycle pump. How about a smaller model using a hypodermic syringe? Maybe that could be a model for installing turbines by dropping them from a giant helicopter, the way tree seedlings are planted by dropping them from planes. The needle would imbed itself into the ground. Worry about all the details later - who cares about details, we’re on a roll here! Not sure how you would install the guy wires, but with all those towers supporting teeny turbines, you’d need a way to install them all without using too much manpower. If the tower needed the compressed air to support the turbine, it would have to be pressurized somehow during installation. If the tower could support the turbine without compressed air, then the piston would be unnecessary. If word got around that a single bullet hole in the tower would cause the piston to drop, slacking the guy wires and causing the whole windfarm to cascade-collapse, as just one way that the cylinder could lose pressure, a lot of rural people are always looking for fun things to shoot at. OK I’m gonna place my hand on you guys’ foreheads now and ask if you are feeling OK, because I’m sensing maybe you might be in need of hospitalization.

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I will try to translate this information to identify the available elements of a reduced physical realization.

The proportions are approximated. We will therefore be very far from the wide bicycle pump.

The cylindrical tower:

The piston is a 6 mm diameter rod to match the inside diameter of the tube after light sanding. We can cut the rod by 1 m to have a shorter piston. We add a cap which will support the load:

Adding anchored cables as guys.

Now you introduce air in the anchored tube with a pump or a compressor. The piston should rise and tighten the cables.

Then test to see if the load can be higher with this means compared to the same material but without compressed air, the cables being stretched by another means at theirs respective anchors on ground.

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Hi Christophe,
Thanks for the precision.

For another use of a part of the concept: could an aluminum wing or blade containing air or another gas under high pressure then be more rigid, which would allow it to scale more in wingspan, and with a higher aspect ratio?

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The 2 handle pump @PierreB suggested also will indicate what happens to the thin shaft when loaded asymmetrically.
Pushing just one of the handles down is like a very mild simulation of the torque reaction or the rotor thrust which the piston rod will have to counteract.
I’ve seen kids break even those small pumps

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OK, so how much upward force would be generated by the same 4MPa of gas pressure on a steel cap attached to the tower top?

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Generally speaking my question is if we can increase the rigidity of a tube or any structure made of non-expanding material (like a compressed gas cylinder) by filling it with compressed air, say at a pressure of 4 MPa (so 40 bars) you suggest, or more. If yes @dougselsam would be happy for the shaft of SuperTurbine ™.

https://www.highpressure.com/products/valves-fittings-tubing/ultra-high-pressure-valves-fittings-and-tubing/ultra-high-pressure-tubing/

Tubes and valves. Far above 40 bars.

I agree with @aokholm 's comment: I don’t see the use of the piston which adds complexity and risks that @Rodread explains when using a thin shaft.

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These bad boys take 20 MPa. I would be hard convinced that a HAWT tower could withstand 4 MPa, considering dimensions and other stress on the tower, in particular if it was not a welded shut system [like you have previously shown, a moving piston mechanism].

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So I don’t see anyone answering this basic question, so i will try to answer my own question here:
Unless I’m missing something, (which is always possible), it seems to me that the upward force from the 4 MPa of gas pressure on a steel cap fixed to, say, “A 750mm diameter constant diameter tube”, would be the same amount of upward force on a moveable, vertically-sliding piston inside such a tube.

This brings me to ask what would then seem to be the obvious question: What is the point of having a moveable piston in the first place? What advantage is there in avoiding a firm attachment of the top mounting surface for the turbine?

This brings me to a comment I often find applies to newly-proposed inventions: “This is a great idea, except for its main features!”

Now don’t get me wrong - the sliding pistons sounds “cool” - maybe even “sexy”. In fact, it has a lot of characteristics reminiscent of a sexual situation, where the tower turns into an inflated “erection”, with the sliding piston imitating “intercourse”.

I can just imagine that piston, humping and pumping up and down, as the slightly-unbalanced rotor turns… But how does that do anything for “performance”" - in wind energy that is?

So, like I say, maybe I’m just not seeing something that others are, which would not be the first time, but I’m still wondering “why the piston”? :slight_smile:

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:laughing:
You definitely seem to be seeing something the rest of us hadn’t @dougselsam
What an insight

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It seems to me that when a gas is compressed in a bottle, it tends to want to spread in all directions, not just upwards. And since the piston is supposed to be waterproof, that doesn’t change anything.

If by chance the bottle were pierced in a stroke, the compressed gas would rush into the opening, wherever it was. And also the bottle could explode.

Experiment with a balloon: if you hold the opening downward then let go, the balloon will fly upward by reaction. Now you pierce without it bursting: the air will try to escape through the hole, wherever it is.

Many have asked the question of the piston. But in your eyes “why the piston” suddenly takes a singular turn.

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Hello Pierre:
Once again, I’m trying to make any sense of what you wrote.
Yes compressed gasses push in all directions equally. Including upwards, which would support a cap at the top just as much as if it were a sliding piston. You don’t say whether you are questioning that fact.

Whether the piston is “waterproof” seems a bit strange to mention. Obviously, it would need an airtight seal, which at 40 atmospheres pressure, would be a challenge.

When you talk about “the bottle pierced in a stroke”, I have no idea what you mean.
By “bottle” do you mean the inflated tower? How would a sliding piston “pierce” a bottle?

If you say compressed gas would rush “into the opening”, I think compressed gas would rush “out of” any opening.

The rest of what you say about the ballon also seems off-target and irrelevant. A closer analogy would be a compressed-air cylinder tank, such as that attached to my air compressor, which I used yesterday to top off my tires.

Ironically, the tank consists of a vertical, cylindrical, steel tube about 750 mm in diameter, and as I was using it yesterday at about 6 atmospheres pressure, I wondered how thick the walls would need to be to hold 40 atmospheres safely, as well as the low likelihood it could support a modern wind turbine, and also how big of a turbine such a comparatively small-diameter tube could realistically be expected to support.

So, I’m sorry to have to note that you, Pierre, are still making no sense whatsoever, which seems weird since you are usually so astute and accurate in your posts. Well, we all have our moments. Hopefully you get better soon.

I’m still hoping someone, of all the “really smart people” in this group, even comprehends my point that compressed air in a vertical cylinder would apply the same exact upward force to a sealed lid on top of that cylinder, whether the lid was firmly attached to the top of that cylinder, or able to slide up and down within that cylinder.

So far, I have no indication anyone here even knows what I am talking about, let alone getting any reasonable response to my point about the main feature (piston supporting a wind turbine) of this topic of conversation.

Has anyone else here had any engineering education? Any coverage of forces and how they work? Any study of standard Newtonian mechanics? I’m asking an extremely straightforward and direct engineering question, and the responses seem more emotional than mechanical, almost like what I’d expect in a mental hospital, rather than an engineering discussion. Sad to see.

I guess it’s like Warren Buffet says about when interest rates go up: as the water level goes down, “you can tell who is swimming naked”.

In an engineering discussion, when you bring up simple forces, you can tell who has any background in basic engineering. And the point I’m making is very basic. High school-level stuff…

Is anybody out there? :slight_smile:

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It’s not worth it, it’s understandable. I have given some very simple examples (balloons) for your special attention, to show you that compressed air does not necessarily go upwards when it is released.

I suppose that the others will yawn when reading my previous message because, unlike you, they understand what it is about. :grinning:

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OK Pierre, well I am, again, sorry to say, I believe this discussion is way over your head, and I don’t think you are tuned into the relevant aspects. I don’t think you’ve ever sat in a college class about forces and mechanics. Apparently, a simple analysis of static forces is beyond your current capabilities.

Nobody is talking about which way compressed air would escape if released. It would escape in whatever direction the hole pointed, but we’re NOT talking about any such thing. Remember, in this case, we’re talking about air that is contained, not released. Your comments are not meaningful in the context of a discussion of whether compressed air in a cylinder has the same upward force, whether the lid is attached or sliding.

So I’m going to explain this using what Einstein called a “thought experiment”.
The idea is that some experiments are so simple, you don’t even need to DO the experiment, just THINK about it:

Let’s start with a vertical cylinder, filled with compressed air, supporting a sliding internal sealed piston with a weight above.

Let’s treat this as a static problem, since no significant up-and-down movement is part of the original idea.

The force of the compressed air on the piston is equal to the pressure (pounds per square inch) times the area of the bottom surface of the piston. The piston is held at one height by the air pressure below.

In other words, the system is in equilibrium.

The advantage of the compressed air would be removing the downward compressive stresses on the walls of the cylinder, and opposing any buckling forces on the walls of the cylinder. All good so far.

(Bear in mind, that compressive stress has been transferred to what is known as “hoop strength” (horizontal tension) of the cylinder walls, so let’s hope the steel can handle that tension)

NOW, let’s say we drill holes around periphery of the cylinder, through the edges of the piston, and insert bolts through the holes, and tighten all the bolts securely. How does the inclusion of the bolts change the forces? Answer: it does not change any of the forces. The compressed air is STILL pushing upward on the piston with the exact same amount of force, the bolts do nothing, and tightening the bolts does not change the amount of vertical compressive forces on the walls of the cylinder, which should be about zero, since the piston and its weight were already supported by the air pressure alone, no bolts needed.

So by this simple thought experiment we can see there is no difference between the amount of upward force applied to a sliding piston versus a simple attached lid. This makes the piston unnecessary. So, like I say, unless I’m missing some major point, which is always possible, there is nothing to be gained by a piston versus a lid.

And it has nothing to do with air escaping a bottle or balloon.

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Unlike you, I understand this very simple, high-school-level engineering problem.