A new lightweight lift cable will let buildings soar ever upward

http://www.economist.com/news/science-and-technology/21579437-new-lightweight-lift-cable-will-let-buildings-soar-ever-upward-other

by sethbannon • 13 years ago

79 71 13 years ago

economist.com

PufferBuffer• 13 years ago

I wonder how many technologies out there exist, which would allow us to go far beyond our current state of the world, but we simply don't know about them. In a such an interconnected world, it sure feels that innovations are not very well combined to move us forward. Good article, btw.

chiph• 13 years ago

What's the minimum bending radius for carbon-fiber?

durkie2• 13 years ago

it depends entirely on the matrix material, and then after that the mechanics of whatever structure you're building.

Pure carbon fiber is far too delicate to be used on its own without a matrix, but the fibers themselves behave very much like a lock of hair.

akkartik• 13 years ago

Are elevators really the limiting factor? Why can't we setup two staggered half-kilometer shafts?

jacobparker• 13 years ago

I can't comment on the first part (seems weird to me?) but they briefly mention "staged" elevators towards the end of the article (although it does not answer the first question.)

gaadd33• 13 years ago

I assume the people who spend a large amount on the top floors of a very tall skyscraper don't want to have to change elevators halfway there.

hboon• 13 years ago

There are already many buildings that segregate elevator systems into multiple stacked towers such as the Petronas Towers in Malaysia [1]. But in Petronas' case, it can become too complex that even the staff don't always get it right.

[1] http://en.wikipedia.org/wiki/Petronas_Towers#Lift_system (note, lift means the same thing here)

jordanb• 13 years ago

I went to a talk by an SOM architect a few years ago, while Tapei 101 was under construction.

He said the principal limiting factor for the height of a super-tall structure is economics.

In fact buildings over sixty stories or so don't make much sense in any real-estate market -- not even Manhattan or Hong Kong -- if viewed from the perspective of real estate as a commodity. Where supertalls make economic sense is if they can be turned into a prestige address when the building becomes a landmark.

With respect to wire rope, there is already synthetic rope with dramatically better tensile strength, and it's displacing wire rope in many applications. Synthetics have a lot less hardness than steel though, and are subject to abrasion. I don't know if a carbon fiber rope would be harder than a steel rope or not, but I know from experience that CFRP panels are not nearly as hard as steel plate.

durkie2• 13 years ago

There are a wide variety of coatings out there that could address this -- especially for an application requiring some flexibility like this, there are a wide variety of polyurethanes that have super high abrasion resistance compared to steel.

It would probably also be practical to simply modify the bearing surfaces as well.

ars3• 13 years ago

The abrasion problem is more internal than external. The individual fibers run against each other when the bend (since some bend more than others).

Without some elasticity the internal forces will destroy the cable. Not sure how elastic CF is compared to steel.

They may be able to help with some clever rope making techniques.

contingencies8• 13 years ago

I too saw Taipei 101 under construction... incredible to think it's in a serious earthquake zone.

there is already synthetic rope with dramatically better tensile strength, and it's displacing wire rope in many applications

The article did mention the use of a dual layer anti-abrasian coating for durability.

Honestly though, why increase height and density still further? There are stupendous issues here with efficiency with regards to food, water, and HVAC - if nothing else. My personal view is that cities of the present are essentially anachronisms spawned from 20th century post-industrialism intertia: artifacts of outmoded labour markets, planning laws and now-quaint geospatial efficiencies.

As the cost of living in cities rises due to the shortage of land, the requirement for importing food and water, and the artificiality of maintaining a reasonable healthy lifestyle in high density urban environment, my bet is that, broadly speaking, emerging labour markets (our type of industry, for example) based on new technologies for communications and a reformed education system will cause a mass migration of professionals away from cities, back to a more sustainable, decentralized model. Sort of like the green banker-belt outside of London, but on a far larger scale.

In short, I believe that while the city will not disappear, its face will change .. and certainly not primarily through ever-taller buildings.

wisty3• 13 years ago

I think GDP was shown to grow almost quadratically with density. It wasn't so much about efficiences, as omnipresent services. If you can walk past 10 hotdog vendors on the way to work, you'll probably buy one.

btilly2• 13 years ago

Honestly though, why increase height and density still further? There are stupendous issues here with efficiency with regards to food, water, and HVAC - if nothing else.

Can you back up your impression that there are stupendous efficiency issues with numbers?

In the USA multiple studies have been done on the question. They find that the per capita carbon footprint of people living in major metropolitan areas is lower than those living in smaller cities and the country. And NYC, that concrete jungle that epitomizes a disconnect from anything natural, is actually per capita the one of the 10 most ecologically friendly cities in the nation!

It may be unbelievable to you that it is environmentally friendly to pack people densely enough that walking and public transit become favored options. So I point you to http://www.brookings.edu/~/media/research/files/reports/2008... for a citation.

kiba• 13 years ago

my bet is that, broadly speaking, emerging labour markets (our type of industry, for example) based on new technologies for communications and a reformed education system will cause a mass migration of professionals away from cities, back to a more sustainable, decentralized model.

You never heard of the economy of scale that comes with urban density? How would lower density makes the environment more "sustainable"?

jzwinck• 13 years ago

My personal view is that cities of the present are essentially serving the same purposes they have served since the 19th century: meeting places for like-minded participants in labour markets, social and cultural gatherings, and sex.

As the cost of living in cities rises due to the shortage of land and the requirement for importing food and water, those seeking life partners can increase not only their number of prospective mates, but the feasibility of finding one who makes a lot of money. Not to mention the availability and acceptability of almost any persuasion, hobby, or kink. Those souls most interested in health will have no problem finding a vegan delicacy at any mealtime, no worry of being stuck with some "salad" at McDonald's as the only option being any points A and B, and they can always hop a train to commune with nature.

Broadly speaking, the desire of people to live near thousands of their peers after graduation will cause young professionals to keep moving to cities, eschewing a life more connected with nature for one with a greater diversity of local work opportunities, events, and beautiful bodies. Just like London.

paddy_m• 13 years ago

The biggest reason that cities are expensive to live in isn't so much a lack of land, it's a lack of properly zoned land. Even in limited areas like Manhattan, we have imposed extra artificial limitations on ourselves in the form of zoning laws. Remove those laws, and there will be much more housing built, and it will be cheaper to live in cities. Forced low income housing is another restriction, by only giving developers reasonable exceptions to draconian laws like minimum parking requirements if they set aside a certain portion of the units to low income housing, the government again restricts density. Better to remove ridiculous zoning laws in general, and housing will become more affordable for everyone.

versk2• 13 years ago

It seems like you have a lot of misconceptions about cities and there health and environmental impacts, which have been proven multiple times to be lower in per capita then suburban and rural communities, often by great amounts. I'd like to understand why you think the decentralized model is more sustainable, It requires cars and roads to live outside the M25. Other comments have dealt with these numbers already.

Anyway, to my point. I see no reason why new technology and interconnectedness is going to lead to the decline of the western city. My Experience suggests its more likely to lead to a greater desire among young adults to move to the urban cores (as they always habe), for Sex/Marriage, Culture and Nightlife as they see there own friends partake, so to speak. At the end of the day, extremely few people would find the internet an acceptable replacement to living amongst ones peers

dylangs1030• 13 years ago

I love when scientific interest articles pop up on the front page like this.

It's really amazing to me that one of the things that holds skyscraper maximum height back is the practical concern of lift height. That's simply not the first thing I would think of if someone asked me the question.

But while that's cool, I don't think we necessarily should be building taller skyscrapers. They're not very practical. If they were, we'd have quasi-Coruscant cities where all the buildings were as tall as the Empire State Building or Willis Tower.

Instead, what tends to actually happen is the buildings become landmarks that attract a lot of attention but comparatively little real estate. Furthermore, when cities expand they generally need to build upwards quickly and forsake extravagance for practicality. If it takes 10 years to build a monolithic structure higher than the skyline, that's a project that's burning money for a long time until it's profitable.

WalterBright• 13 years ago

Maybe I should patent the idea of putting the motor in the car and doing away with the ropes altogether. I.e. imagine a vertical electric train.

rogerbinns• 13 years ago

The ropes provide energy efficiency. On one end is the lift car, but on the other and going in the opposite direction is a counterweight of similar mass. The lift motor only needs to move the difference in mass.

If you put the motor in the car without ropes then it has to be powerful enough to lift the whole car and all occupants. And if you want any hope of energy efficiency you'd need regenerative braking for when going down. This would make the lift car a lot heavier and the electrical system a lot more complicated.

Sometimes simpler is better!

Someone• 13 years ago

Yes, but in either case, energy is lost in accelerating and decelerating mass. If your cable is a mile long, accelerating and decelerating it costs quite some energy, too. Long cable also have problems with swaying and elasticity.

Also, a main problem with high rise buildings is loss of floor space at lower heights (the water, electricity, waste, and person traffic of floors 2 to N all have to pass though floor 1)

Ropeless elevators can have a huge advantage there, as they allow one to hang multiple elevators in a single shaft that both service the full range of floors. Yes, that requires sophisticated software to prevent lift cars from having to pass through each other too often (some designs allow cabines to do that by making it possible for the cars to move horizontally, too), but it is an active research area.

"ropeless elevator" is not on Wikipedia yet; the best (but tangential and possibly slightly commercial) I could find Googling it is http://www.barkermohandas.com/images/Integrated%20Vertical%2..., which is about a system with wires that allows one to move cars horizontally by sliding them from one car frame to another using linear motors.

ars3• 13 years ago

Is it really that impractical to put the motor in the car? The elevator anyway needs rails on the side, if for nothing else to provide something for the emergency brakes.

Use regenerative braking on the way down so you don't need a counter weight - although that does mean you need a much large motor, you might save on energy, but power requirements would still be high.

dmckeon• 13 years ago

Assuming that the weights of the lift car and the passenger load remain about the same, moving the motor to the car saves the weight of the cable, but adds the motor, power contacts, and whatever traction device (cog?) moves the car.

edit: completely overlooked counter-weight balance, see: https://news.ycombinator.com/item?id=5887522

Adding regenerative braking adds some form of energy storage - batteries, flywheel, compressed air, or whatever. A flywheel might be lighter than batteries, but torque I/O might affect passenger comfort.

It would be interesting to see how CF holds up over time. ISTR that Kevlar rope is very strong, but turned out to have unexpected issues with repeated jerky load/unload cycles. Presumably the CF elevator cable would have adequate testing before commercial use.

ars3• 13 years ago

For regenerative I would just dump it back into the grid. There are plenty of other consumers in a skyscraper, the meter would not even flow backward.

I'm also wondering this about CF - my understanding is it's strong, but has very poor abrasion resistance.

Even if you avoid external abrasion you can't avoid internal as the fibers rub against each other when they bend.

aaron6952• 13 years ago

It seems to be missing the real issue that you generally don't want lifts that go all the way to the top in one run because it uses up to much real estate.

You have to have multi-stage lifts else the whole building becomes full of lifts rather than offices etc

Much more exciting for projects like loon I would have thought.

ampersandy• 13 years ago

I don't see why that would be a real-estate issue, wouldn't the other stages of the lifts take up just as much space?

zalzane• 13 years ago

Lifts on the ground floor have to service the entire tower, where a lift that started half way up the tower would only have to serve half as much traffic as the ground floor lift, so you could have like a dozen lifts that go from ground->50%, and 6 lifts that go from 50% to top.

aaron6952• 13 years ago

Because when you stack lifts on top of each other in different parts of the shaft you can have multiple lifts running at once, hence multiple time the efficiency per m2. (High latency though)

Lifts are also limited by speeds, if they go too fast they make some people queasy. This is also an issue to contend with since express elevator are limited in the 'express' bit.

Edit: to be a bit clearer if you split up a shaft into 4 sections with fours lifts you can have four lifts full of people being moved, hence your bandwidth is 4 times as much. Taken to extreme you have one for every floor http://en.wikipedia.org/wiki/Paternoster

s0rce• 13 years ago

edit: I take it back, my memory is failing me. Some intermediate-modulus high-strength PAN based carbon fibers have strengths exceeding most synthetic polymers. Here is a comparison I put together a few years back for some research on fibers.

https://dl.dropboxusercontent.com/u/3730003/fiber%20strength...

This is quite surprising as many synthetic polymers (zylon, spectra/dyneema, kevlar) are much stronger than carbon fiber. There is even a competition to make the strongest rope for potential space elevators:

http://www.isec.org/sec/index.php/technical-program/strong-t...

jlgreco2• 13 years ago

How tall does a building have to get before all the other "utility" stuff becomes a limiting factor for any reasonable floor-space/building footprint? I imagine the space you need to dedicate on each floor to water/sewage, electrical, ventilation, etc goes up approximately linearly with the addition of floors. You also need to add more elevators as you add more floors, just to service the additional people each floor implies. Add too many floors and eventually some of the floors become little more than shafts running to other floors.

I don't really know anything about architecture so maybe my intuition is off. Maybe these concerns are never realized with the number of floors that are practical for other reasons?

ics2• 13 years ago

The Burj received some pretty unflattering coverage a year or two ago for their "poop trucks", which were necessary for moving however many tons of feces 30,000+ people produce per day. However in many cases the building "cheats", i.e. the floor area shrinks rapidly the higher you go up and so the strain is better distributed throughout the system. I say cheat only because it's much more challenging to manage a uniform (or close to it) floor area from base to top such as the old WTC. The GE Building at 30 Rock is a good example of a building that used the building code (NYC setbacks, a good topic in itself if you're interested) to its advantage in planning the elevators and ventilation. It was mentioned in another comment above I think but in reality the economics are a much more controlling factor than hard engineering, and most of the engineering problems are about doing X for $YYY rather than XYZ for glory and innovation.

Edit: This link might be of interest... http://www.bloomberg.com/news/2013-01-02/double-deck-elevato...

crazytony• 13 years ago

The problem has more to do with Dubai than with the building. Many buildings in Dubai employ similar schemes because the sewerage system wasn't scaled as the city grew.

This is like a lot of things in Dubai: roads, public transport and the airport which is currently being more than doubled.

mikhailfranco• 13 years ago

The Burj is a joke. It also seems to be mostly empty, because it priced itself out of the real estate market after the receession. It is so 'prestigious', no one can afford to use it. There are miles of empty lots starting just a few hundred yards away. If the Burj toppled over to the east, the top of it would land on empty ground. It is a temple to the vanity of the rulers of Dubai and their property developer lackeys. It is also an embarrassment, because Sheikh Khalifa of Abu Dhabi (the one with all the oil) had to bail them out to get it completed after the property bust of 2008 - that's why it's called Burj Khalifa, not Burj Dubai, as originally planned. And not to cap it all, the observation deck is only half way up!

benpbenp• 13 years ago

One idea I keep returning to is a "laned" system for elevators/lifts. Two shafts for going up, and two for going down. One of the two in each direction is the "passing lane"-- and you fit dozens of elevator "cars" in the whole system. For very high altitudes it may even make sense to have a third, high-speed lane.

Obviously this would require a completely different mechanism as you can no longer have cables attaching each car to the roof. In fact I have no clue how it could work! This is what I keep pondering...

jlgreco2• 13 years ago

You might be able to do it with linear motors. The problem there would be the reliance on the safety brakes in the event of power outages (not really a problem with counterweight elevators).

joe_the_user• 13 years ago

I've had exactly the same thought.

I remember hearing that elevators took up a quarter of the floor space of the old World Trade Center - only because they used express and local elevators, it would have otherwise been half the floor space. So it would seem a "vertical train" system could be quite valuable for saving real estate.

Pitarou2• 13 years ago

Check out this plan for the (pre-9/11) World Trade Center:

http://en.wikipedia.org/wiki/File:World_Trade_Center_Buildin...

Roughly 1/4 of the area is taken up with elevators, stairwells, and so on. So here's a back of the envelope calculation:

Elevator to office ratio: 1 : 3.

Proportion of floor area that is usable: 3 / (1 + 3) = 3/4.

To join the mile-high club, you need a building that's about 4 times higher. I will make the very crude assumption that, for a building that is 4 times higher, you will need 4 times as many elevators.

Elevator to office ratio: 4 : 3

Proportion of floor area that is usable: 3 / (4 + 3) = 3/7

Usable floor area compared to floor area of the old World Trade Center, occupying the same site:

4 * (3 / 7) ÷ (3 / 4) = 16 / 7; or about 2.3

So it's doable, but it's ridiculously inefficient. Where you draw the line is an interesting question. 100 stories is already pushing the limits, but you can alleviate this problem by tapering the building, like the Burj Khalifa. This is remarkably similar to how the pyramid builders solved their problems.

But what the pyramid builders really needed was the arch. And what modern engineers really need is an efficient vertical transport system. The obvious thing to do is have more elevators per shaft. Maybe something like a vertical cable car would work. Or even ditch the cables and make each elevator independently mobile within a network of interconnected shafts, like a vertical train system.

JoachimSchipper• 13 years ago

One high-throughput system is the http://en.wikipedia.org/wiki/Paternoster. Unfortunately, it looks extremely dangerous, and in fact has caused a large enough number of accidents that it's banned in most modern countries.

JoeAltmaier• 13 years ago

On the same note, in the last century brick buildings were limited in height by the thickness of the walls. If you went much beyond 20 stories, the ground floor walls filled the entire floor, making a sort of pedestal. So further height got zero further floor space. Steel buildings got around this. Hanging each floor from a steel skeleton means the walls don't get thicker at all.

As you calculate, elevators are the new brick. The number needed to serve higher floors increase to the point the ground floor is nothing but elevators. So further height is pointless.

Its exacerbated by the need to fill/empty the building in bursts - people want to work regular hours, and everybody works the same hours. So you need enough elevators to essentially evacuate the building in under an hour.

Ways to work around this? Well, a pyramid structure would help I imagine. Elevators to server higher levels could be distributed evenly about the ground level, more in the center and fewer around the lower edges. That also increases windows-per-volume.

And of course if people lived and worked in the building and rarely left it, then the need to 'evacuate' from the ground floor goes away.

I imagine an arcology where people live, work and entertain in alternating levels. Fire and services can be located internally in strategic volumes. Air can be drafted up through the building using thermal gradients instead of fans.

Need to write a storey involving this kind of structure sometime I guess.

marcosscriven• 13 years ago

This reminds me of a book back from the nineties called "Faster" by James Gleick. There was a chapter on lifts being the limit to building height, although I seem to recall it was more down to shaft space rather than cable strength.

thornjm• 13 years ago

There are a number of suggestions to remove the cables altogether and have the car power itself, but would it not be easier to have the cables removed and still power it through the building?

Something like electromagnets, rail gun style?

OnionChamp• 13 years ago

"The other mile-high club"? Together with the brokeback mountain cover, this is pretty pathetic.

spIrr• 13 years ago

Promo page for the new technology (called "Ultrarope"): http://download.kone.com/ultrarope/index.htm

Sami_Lehtinen• 13 years ago

I have been wondering why elevators aren't just vertical trains. No limit to distance, and several cars could use same tracks. Currently elevator shafts can reserve huge part of floor space. Down going cars could run motors in regenerative mode. So there's no need for heavy counterweights or heavy ropes. Another effeciency trick is trying to get people going to same destination into same car, reducing number of required stops. Might add some latency, but makes overall throughput better.

ams61102• 13 years ago

Why do tall elevators use cables at all? Why not a system with a motor driven gear wheel on the car engaged with toothed rails on the sides of the shaft. You would not have counterweights but you could recover energy used in lifting on the next descent, and store it in supercapacitors for use on the next lift, which would achieve the same ends.

paul_f2• 13 years ago

Lots of discussion here about ratios of usable space in tall structures. Why don't we solve that by putting the elevators on the outside of the building?

ams61102• 13 years ago

If for no other reason, it would reduce available windows, and offices with windows are high-rent items.

That said I have seen a few buildings with exterior "glass elevators" but it seems to be mostly a novelty.

paul_f2• 13 years ago

It's always a novelty before it becomes mainstream. Have the elevators run in tracks of some sort, rather than in a shaft. Elevator won't block the view until it goes by.

A new lightweight lift cable will let buildings soar ever upward

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