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

~~~
contingencies
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.

~~~
btilly
_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...](http://www.brookings.edu/~/media/research/files/reports/2008/5/carbon%20footprint%20sarzynski/carbonfootprint_brief)
for a citation.

~~~
contingencies
_Can you back up your impression that there are stupendous efficiency issues
with numbers?_

I would have thought that the cost of hauling food and water up 60 floors was
self-evident? While I could go invest time finding numbers, to be honest I
find it a bit rich that you ask me to provide sources while making equally
unreferenced, sweeping and IMHO dicier claims in response.

For example, claiming the carbon footprint of city dwellers is low might be
possible if it doesn't consider the cost of hauling the products they
routinely use and throw away at rates far higher than other people on the
planet... but that doesn't make it a realistic or truthful stance on the
matter.

I am not surprised that NYC is low on obvious evils when considering this form
of skin-deep environmental statistic, because it produces very little of...
well, anything. As the center of finance, NY derives a great amount of wealth
from achieving effectively zero of utility to the rest of the world.

For something more concrete, let's try measuring garbage. (I'm not going to
get in to the interesting question of Wall St.'s facilitatory role in greater
evils.)
[https://en.wikipedia.org/wiki/Environmental_issues_in_New_Yo...](https://en.wikipedia.org/wiki/Environmental_issues_in_New_York_City#Garbage_disposal)
_In September 2012, Travel+Leisure named New York City the #1 "America's
Dirtiest City," from the results of a readership survey rating 35 "Favorite
Cities" in the United States._ It continues: _In 2006 Mayor Michael Bloomberg
signed legislation establishing a new solid waste management plan, which will
use barges and trains to export 90% of the city’s 12,000 daily tons of
residential trash_. I can tell you that country people don't generate that
much trash, and they can often dispose of it in a decentralized fashion (eg.
via compost). Even Mexico City only produces 10,000 tons per day (random stat
online), and its population is far higher and they probably _actually make
some tangible goods_. But I'm not going to go build a well-referenced
numerology of truth here. I hope you might be motivated to research further
yourself.

The bottom line is that nature loves decentralization, and 'taxes'
centralization. Cities are unnatural conglomerations that abhor nature. While
we can sustain them, it's not the smartest thing to do in a finite world.
Society is just beginning to learn from and invest in this with concessions to
green architecture, urban design, public transportation, public communications
infrastructure projects (Australia, China, France, New Zealand...),
decentralized energy generation, etc.

~~~
tekacs
Up 60 floors perhaps, but getting it there required only bringing it a few
miles from the nearest depot (having been brought there en-masse) rather than
a giant star (or worse) network, replicating the same effort 1000 times to
transport said food and commodities and to provide infrastructure to every one
of the many parties in the decentralised model you propose as more efficient.
:/

------
jlgreco
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?

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

[http://en.wikipedia.org/wiki/File:World_Trade_Center_Buildin...](http://en.wikipedia.org/wiki/File:World_Trade_Center_Building_Design_with_Floor_and_Elevator_Arrangment.svg)

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
One high-throughput system is the
[http://en.wikipedia.org/wiki/Paternoster](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.

~~~
Pitarou
That's pretty much what I had in mind as a "vertical cable car". Looks like
somebody actually built one in ... um ... 1884!

------
ars
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
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](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.

~~~
ars
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.

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

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

------
PufferBuffer
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.

------
marcosscriven
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.

------
Sami_Lehtinen
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.

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

~~~
durkie
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.

------
thornjm
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?

------
paul_f
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?

~~~
ams6110
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_f
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.

------
ams6110
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.

------
s0rce
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...](https://dl.dropboxusercontent.com/u/3730003/fiber%20strength%20to%20weight%20ratio.pdf)

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...](http://www.isec.org/sec/index.php/technical-
program/strong-tether-comp)

------
aaron695
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
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?

~~~
aaron695
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](http://en.wikipedia.org/wiki/Paternoster)

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

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

------
dylangs1030
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
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
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
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...](http://www.barkermohandas.com/images/Integrated%20Vertical%20&%20Horizontal%20Transport.pdf),
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.

~~~
versk
Not everything is a software problem, I think you are hugely underestimating
how much more power is required for an elevator to self propel vertically
upwards compared to a counterweight system. I'm not an expert but I'd have to
guess its at least 10x if not potentially much more

