The Rise of the Multi
A New Breed Of Elevators Will Alter The Urban Skyscape As We Know It
The year is 2028. George Jones runs into the lobby of a Manhattan skyscraper, late for his first day of work.
Floor 57? Not a problem. A conference room at the furthest edge of the newest, biggest, star-shaped building in the world? Kind of a problem.
Ding! Ding! sounds the sliding door as George races toward the elevator and shouts,Going up?! A hand suddenly juts out from between the doors and keeps it from closing. Actually, it’s going diagonal, a woman grins and replies. Even better, says George with a smile.
When the doors close, the elevator lifts up for a moment and then shifts crosswise joining nine other cars in a shaft shaped like an octagon. Inside, George watches the digital display of his journey through the building and thinks back to his childhood when it was perfectly normal for elevators to only go up and down. We’re not in such a convenient future yet. But what if elevators could move any which way, up, down, left, right, and diagonally? Such is the promise of the new MULTI elevator system, announced in 2014 by the German engineering and design firm ThyssenKrupp, and currently under construction at the company’s new 800-foot test tower in Rottweil, Germany.
The city as we know it could be transformed into an ultra-efficient people-moving machine, not only underground but into the air as well — to the great relief of our hypothetical and tardy Mr. Jones.
Dense cities have always been built to reach up toward the heavens. This verticality boom means that the elevator is as much an element of city travel as a taxi cab; you’re likely to spend more time waiting for one, too. Office workers in New York City wasted a grand total of 16.6 years waiting for elevators over the course of 2009. In a city with 840 famous miles of subway track, there are also a staggering 1,570 miles of elevator shaft space that can only support one car moving up and down at a time, as opposed to the cadre of trains that show up every few minutes.
“Urbanization leads to the need of higher buildings,” says ThyssenKrupp’s CEO Heinrich Hiesinger. But, “over the last decades elevators became the bottleneck in the evolution of architecture.” In other words, the old rope-and-pulley system has been holding us paradoxically down. With its use of high-powered magnets, ultralight materials, and a track-flipping exchange mechanism, MULTI “will enable new sizes, shapes, and forms of buildings,” Hiesinger says. The city as we know it could be transformed into an ultra-efficient people-moving machine, not only underground but into the air as well — to the great relief of our hypothetical and tardy Mr. Jones.
FROM THE GROUND FLOOR UP
While architects race ahead with new facade materials and building designs, elevators present something of an historic barrier. The problem is they haven’t changed much over the past century. The MULTI goes against “everything we knew about elevators in the last 150 years,” says Dario Trabucco, an Italian research manager at the Council on Tall Buildings and Urban Habitat, which is currently launching a study on how the MULTI system could change skyscrapers. “This will enable architects to get rid of one of the most stringent constraints in the design of a tall building.”
The city sky of the future can be more than just tall monoliths, perhaps even Tetris blocks of buildings that extend into sky bridges and interconnecting linkages. Such horizontal architectures would be the minimum of what is enabled by MULTI, when going sideways within a building is as easy as going straight up.
the green plains of Rottweil, Germany.
Since 236 B.C. when Archimedes built a hemp pulley system to raise and lower a platform, elevators have been propelled by cables. By 1743, Louis XV commissioned what he called “flying chairs” for Versailles. New York’s Equitable Life Building had the first office passenger elevators installed in 1870, and the German Werner von Siemens built the first electric elevator in 1880. Most elevators then and now are made up of two parts: one car in one shaft.
There was one type of multi-car lift, however, that presages the MULTI. “Paternoster” refers to an elevator system in which open compartments circulate on a loop one after another without stopping, allowing passengers to step on and off at whatever floor they choose without having to wait for a car to go up and come back down.
The paternoster system saw popularity for the most part in Eastern Europe until the 1970s due to major liabilities. The fact that the cars were always moving meant that passengers old and young were at risk of falling into the shaft or getting a limb caught. Nevertheless, multiple-car elevator systems remained a dream for engineers. “The whole elevator industry always thought about how we could have more than one cabin in one single shaft,” says Markus Jetter, the head of research and development for MULTI.
TOP FLOOR TECHNOLOGY
The dream started to become a reality in the 1990s as ThyssenKrupp researched what would become its TWIN system, which put two cars in the same shaft. Double-deck elevators had existed previously, but with TWIN, one car could be docked while the other continued to move. The system allowed for up to 40% more passengers. But to truly have multiple cars traveling along the same track, technology had to advance much further.
MULTI depends on three things, Jetter explains. The first is a new linear drive mechanism that propels elevator cars without the need of a central rope. Second, the cars themselves need to be much lighter — traditional cars can weigh as much as six tons — to propel themselves more easily. Finally, there’s the exchange, a component that shifts an elevator car from a vertical to a horizontal trajectory.
The propulsion system works like a maglev train pointed straight up into the air instead of along the ground. There are electromagnetic coils strung along the entire length of the elevator shaft, and the elevator car is outfitted with “a linear arrangement of permanent magnets” according to Jetter, called “magnet yolks.” This means that while the elevator car magnets are always on, the coils in the shaft can be turned on and off according to where the car is at the moment to propel it along.
“We might have to get used to the new sensation of traveling sideways in an elevator, but other than that, from the inside the experience will remain remarkably similar to what we’re used to today.”
ThyssenKrupp isn’t the first to create self-propelled elevator cars. In 1996, the Finnish engineering firm Kone created the MonoSpace, which hoists itself on a track installed in the shaft and doesn’t require a bulky machine room. But that system was designed only for low-rise buildings. MULTI can go as high as it needs to. Rather than hefty stainless steel, the MULTI cars are made of carbon composite and aluminum. Some of the new materials were developed by ThyssenKrupp in-house. The result is a car that’s 50% lighter.
The final component is the exchange, a segment of elevator shaft that can rotate to place the elevator car onto a horizontal track without changing its orientation. “The car itself stays in the exchanger in an upright position, locked in to make sure that the people will not fall over,” Jetter says. We might have to get used to the new sensation of traveling sideways in an elevator, but other than that, from the inside the experience will remain remarkably similar to what we’re used to today.
THE DOORS ARE WIDE OPEN
Now that ThyssenKrupp has created the technology to drive a multi-car elevator, it’s up to architects to run with it. “New forms of internal mobility, from conveyor belts to high-speed elevators, always open up possibilities for rethinking how architecture can be designed,” says Geoff Manaugh, creator of the popular speculative architecture website BLDGBLOG.
With current ropes, elevators can’t travel more than 500 meters in height. Without such limitations, the upper limit to a building’s height could hew to human comfort rather than technological limits. “If you are not going to have a cable anymore, you’ll be allowed to have endless height in verticality,” says Dario Trabucco.
Likewise, architects will also gain in floorspace. The elevator and service core usually takes up a large part of any skyscraper design. Since MULTI can use fewer shafts to transport more people, the core can occupy less space. Trabucco suggests that developers might compensate for the MULTI’s higher cost by leasing out the added square footage. And even if the shafts occupy the same amount of space, MULTI could double the handling capacity, according to Jetter.
That means never wasting time waiting for an elevator again. Buildings could become more dynamic systems rather than static, vertical hierarchies. Rather than standing around while a car ascends and descends, new cars will appear every 15 to 30 seconds. “When we manage to have the right number of cars in the system, we will always have the next car available as soon as one is leaving,” Jetter says.
There’s a utopian tinge to the MULTI innovation, that it will solve all of our elevator woes. But Manaugh suggests that perfect elevators could also create something like the situation in Amazon warehouses, where products are scattered at random and workers left to seek them out. Randomness turns out to be the most efficient distribution solution. Extrapolate that to a skyscraper: If an elevator can deliver you directly anywhere in a building, there won’t be any need to just stack one floor on top of the next.
Randomness turns out to be the most efficient distribution solution. Extrapolate that to a skyscraper: If an elevator can deliver you directly anywhere in a building, there won’t be any need to just stack one floor on top of the next.
POTENTIAL CHALLENGES
The MULTI technology is advanced, and obviously aimed at ambitious new architecture. “Super mega tall buildings above 300 meters, that’s our target,” Jetter says. But ThyssenKrupp’s CEO has also stated that the system is just as applicable to older buildings. It will just require some significant adaptations in design and expectation.
“They will have to come up with some solutions to allow the passenger to withstand the horizontal or diagonal forces that MULTI will create,” Trabucco says. “It will be a different way of traveling that we aren’t used to in elevators right now.”
Trabucco also points out a larger problem. If skyscrapers will increasingly be connected by horizontal bridges for elevator travel, structural engineering will have to change. “Buildings move and sway differently from each other,” he says. “The final structure will have to allow the various parts of the building to move independently.” Structural technology might have to catch up with elevators rather than the other way around. ThyssenKrupp has anticipated as much, installing a massive pendulum prototype in the same test tower that holds the MULTI system to potentially counteract the natural sway that affects super tall structures.
GOING UP IN THE FUTURE
Like anything that moves human bodies through space, elevators are a fundamentally dramatic technology. As the technology evolves further, it will be important to keep considering the human experience of traveling in a metal box. If our own comfort and spatial logic isn’t emphasized enough, it could be that we won’t like the next generation of elevators very much. Manaugh finishes his imagined scenario of a world where elevators move any which way: “We could end up just looking at another generation of people-movers humming away inside cavernous megastructures — as anticlimactic as airports.”
In that imagined future with Mr. Jones, different floors may not be so important any more. People in elevator cars will get used to the sensation of new movements, not unlike traveling in an airplane. The entire elevator system will be pushed toward the outside of the building so passengers can see the city speeding by. Buildings won’t be static towers that stand alone, but churning hives of movement through interconnected structures. The destination won’t be as important as the journey. The buildings that we’re in won’t even really matter: we’ll be in another one soon enough anyway when the next elevator arrives.
