| ▲ | svantana 16 hours ago |
| I never understood why wind turbine towers are built as hollow, tapered cylinders. Isn't the best mass-to-strength ratio acheived with truss/grid type structures, like in construction cranes? |
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| ▲ | wizardOfScience 15 hours ago | parent | next [-] |
| A wind turbine tower is essentially a cantilevered beam resisting the bending moment from lateral wind loads. The loads can come from any direction.
Bending induces stresses in any beam that increase with distance from the centre.
A thin walled hollow tube is the most material efficient design theoretically as it concentrates the load bearing materials along the perimeter of the beam.
Any deviation from this incurs material that is not fully utilised. |
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| ▲ | adwn 15 hours ago | parent | next [-] | | Your explanation raises the follow-up question, which svantana already hinted at: Why don't construction cranes use hollow tubes instead of their typical truss structures? | | |
| ▲ | wizardOfScience 15 hours ago | parent | next [-] | | The crane manufacturing business case is not driven by material efficiency to the same degree. It is a tool that needs to be reliable and have performance in operations. Limit the need for man hours through ease of use etc. It should also be able to take many assembly/disassembly cycles. Thus does the amount of material not matter as much in a crane. For wind turbine towers the material cost can be >>50% of the installed cost. | | |
| ▲ | majoe 8 hours ago | parent [-] | | Working for a crane manufacturing company. While raw material costs are maybe not that drastic, we consider material efficiency the most important metric for cost and a lot of brain power was spent to optimise the amount of steel used. There are multiple reasons for this. The ones I can think of are: * The margins for cranes are thin and steel is expensive.
* Thicker steel is harder to work with, increasing manufacturing cost.
* Each kg of dead weight may decrease the performance of your product, e.g. max. Live load. This is especially true for the jib.
* More weight at the top of the crane may necessitate a sturdier structure below, amplifying cost even more.
* More weight may require more ballast blocks, which are costly (especially transport)
* More weight means higher transport costs
* More weight means more wind area, which is the critical factor for high constructions.
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| ▲ | Aldipower 13 hours ago | parent | prev | next [-] | | Because at cranes the force is not the wind that comes from any direction, but the directed payload hanging at the crane arm. Almost all cranes I now moving also the pole around. | |
| ▲ | IsTom 15 hours ago | parent | prev | next [-] | | Certainly makes them easier to disassemble and move elsewhere. | | | |
| ▲ | carlosjobim 14 hours ago | parent | prev [-] | | My guess: They want the wind to pass through the crane, while they want wind turbines to capture the wind. | | |
| ▲ | majoe 7 hours ago | parent [-] | | This is the answer. Interestingly, wind/storm loads are oftentimes the limiting factor for the configuration height of a crane. This is because, when adding another tower segment, not only the total area increases but also the wind forces. The other loads stay roughly the same This is the reason why bottom-slewing cranes, which are commonly used for small buildings, sometimes are built with solid walls.
Top-slewing cranes, which are used for high buildings, always use a steel framework. |
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| ▲ | Onavo 15 hours ago | parent | prev | next [-] | | This is what I come to HN for, kudos | |
| ▲ | potato3732842 7 hours ago | parent | prev [-] | | This is almost a "spherical cows" level gross over simplification. If you weren't defending it in other replies I'd think you were satirizing people who only have book learning and no real world experience. At the limit the failure of your statement obvious. If instead of a thick walled wood tube hundreds of feet tall this structure were an orders of magnitude wider cylinder of thin plies the same height it wouldn't even be able to hold itself up, it would flop over, tear and all fall down under its own weight if not from manufacturing variances then from the wind and differential expansion/contraction from the sun and if by some miracle it survived that it would flop over The material has to support itself and tolerate undefined small (relative to the main load) loads in other directions as well as point loads from fastening it to whatever you are using it to bear the loads of, going all in on "large and thin" fails to optimize for this for more or less the opposite reasons that going all in on "solid" does. | | |
| ▲ | pinkmuffinere 3 hours ago | parent [-] | | The parent is explaining why it’s hollow instead of being a truss. They accurately explain that the hollow tube is optimal to counter the wind loads. Your criticism is that they didn’t discuss gravity loads, but that wasn’t “in the prompt” — the gravity load doesn’t explain why they’re a hollow cylinder. There are a wealth of other irrelevant things that could be discussed, but have been neglected because they are irrelevant to the question. Frankly your comment disappoints me. wizardOfScience gave a _great_ answer, that would make any solid mechanics professor proud. | | |
| ▲ | potato3732842 3 hours ago | parent [-] | | You're strawmanning bot me and the comment I'm replying to. Whether you're using a truss design or a solid material wall what I'm saying holds true. You can't just go all in on "put the material at the perimeter" because it'll have other problem. Gravity is just one of those problems. |
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| ▲ | cluckindan 16 hours ago | parent | prev | next [-] |
| The forces acting on the wind turbine tower are mostly perpendicular, i.e. the wind hitting the blades and the structure. Ideally, the blades have maximum wind resistance (up to a point). The construction crane rarely experiences that kind of wind load, because the truss structure is hollow and allows air to pass through. Ideally, the structure has zero wind resistance (down to a point). |
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| ▲ | looofooo0 16 hours ago | parent | prev | next [-] |
| https://gicon-hoehenwindrad.de/ They test-building a 380m wind turbine in such a style now. |
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| ▲ | patall 16 hours ago | parent [-] | | I know it's a test project and one shouldn't be to stoked about a test project, but for the last year I have again and again searched for updates about it. Unfortunately, they keep it (understandably) low. Let alone the story of the 90+ year old engineer that envisioned such a project (and they are only implementing 20% of it) is so awesome. Looking forward to when it finishes and hopefully changes our view on wind power for good! |
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| ▲ | flir 15 hours ago | parent | prev | next [-] |
| UK has moved from open grid style to a cylinder style for electricity pylons. Presumably there's an advantage to it, but I don't know what it is: https://www.nationalgrid.com/national-grid-energise-worlds-f... |
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| ▲ | potato3732842 7 hours ago | parent | next [-] | | I can't speak to the UK but in the US things like electrical towers and highway signs mostly go to tubular construction for labor cost reasons. Tube gets manufactured in a facility specializing in doing it in a low labor way (rolling or whatever). Flanges get welded on, they get slapped on cribbing and trucked to you and then assembled with minimal labor. Contrast with the lattice. Cheaper material inputs, a whole bunch of cheap channel with holes punched as needed, but all that punching, and then all that bolting, takes way more labor, a lot of it can be done cheaply, but it adds up, and when it does get to site there's more pieces to pick and connect, etc. Basically the more expensive material saves you quite a bit of human labor at each step. Same reason huge rolled steel and welded tubes displaced riveted construction. | |
| ▲ | scrlk 15 hours ago | parent | prev [-] | | Ostensibly for aesthetics. However, the new T-pylon design has been discontinued for cost reasons, and there were complaints about noise in high winds: https://eandt.theiet.org/2025/01/06/national-grid-abandons-c... |
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| ▲ | mkj 14 hours ago | parent | prev | next [-] |
| Nabrawind have something like that. It's still a column at the top for blade clearance, but the rest is a grid structure so it doesn't need huge external cranes. https://www.nabrawind.com/our-solutions/nabralift/ |
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| ▲ | impossiblefork 14 hours ago | parent | prev | next [-] |
| No, the optimal shape is a thin dense shell with a stiff low-density interior. Optimization only leads to trusses if you constrain the design to have no low-density elements. In practice this leads to things like a thing CFRP surface wrapped around balsa or stiff foam. |
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| ▲ | lostlogin 16 hours ago | parent | prev | next [-] |
| I’d be interested to hear the answer to this, but don’t really want to see it. Wouldn’t it look terrible? |
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| ▲ | metalman 14 hours ago | parent | prev [-] |
| It is likely that ,while a truss would be lighter and stronger, to counteract the forces encountered by a turbine it would also require a cross section so large, as to interfere with the blade travel, rendering the proposal, impossible.
There are small wind turbines useing truss style towers, but they all have a "stub" tower on top, and they are under 10kw......10-15'blades.
the wooden tower under discussion, is also "small" by todays standards, and unlike steel towers that can be made by any half respecting medium sized fabricator, will require a specialised industrial facility that cant make anything else usefull, and so the one that is doing this, is funded at great expense from government grant funding.
kinda cool,kinda cringe |
