Cable-Free Elevators Will Soar to New Heights, and Move Sideways
I live in one of the few buildings in New York that still has a manual elevator. When I ask the operator on the morning shift how he's doing, his well-oiled response is "up and down." For the last 160 years, elevators have travelled a predictably vertical path. That will soon change when the German manufacturer ThyssenKrupp introduces the first fleet of cable-free cars that can also move sideways.
The system, dubbed MULTI, will allow multiple cabs to motor along a single, looping shaft. The cars move by magnetic levitation (the same technology behind some high-speed trains), rather than being pulled by the heavy steel ropes that limit how high skyscrapers can stretch. With MULTI, architects will be able to build spindly towers on small plots formerly deemed untenable for high-rises.
That will become increasingly important in cities such as New York, where demand for real estate will continue to grow but available land is scarce. “From an industry standpoint, elevators have been a detractor to slender, tall buildings going to the heights that are technically feasible,” says Patrick Bass, ThyssenKrupp’s senior vice president for research and development. The ropeless MULTI takes up half the shaft space to move the same number of people, albeit in more cabs. And because the elevators aren’t weighted down by hefty rope, there's no limit to how far up they can ascend.
“Until very recently, it was very difficult to get an elevator to go more than about 800 meters in a single rise,” says Julian Olley, director of vertical transportation at the British engineering firm Arup. “The reason is that the longer the ropes holding an elevator get, the more their ability to support weight is taken with just supporting themselves.” MULTI runs like a train on rails. “If you put down more track,” Olley says, “it just keeps going vertically upwards, as opposed to horizontally along.”
ThyssenKrupp is coy about how much MULTI will cost but claims that the upfront expense will be offset by income generated from rentable space the system will free up. For towers over 300 meters tall, Bass says the system should pay for itself in under 10 years. Not only does the shaft take up less room, but the multiple cabins reduce the need for large lobbies to accommodate queuing passengers.
The company estimates wait times for MULTI to be 15 seconds to 30 seconds, even though the cars will be traveling only 5 meters per second, or 11 miles per hour. By contrast, the elevators at One World Trade Center, also from ThyssenKrupp, are twice as fast, but the high speed can cause discomfort for people whose ears are sensitive to pressure changes. “Per year, New York City office workers spend a cumulative amount of 16.6 years waiting for elevators, and 5.9 years in the elevators,” said Andreas Schierenbeck, chief executive officer of ThyssenKrupp Elevator, in a company press release. “This data provides how imperative it is to increase the availability of elevators.” And MULTI can do that by adding more cars without more hoistways.
For architects and builders, the revolutionary elevator technology opens up opportunities to experiment with unconventional shapes and groundbreaking heights. “The mile-high building is easily achievable—as would be a two-and-a-half-mile building,” Olley says. But he’ll have to wait until at least 2016, when ThyssenKrupp will finish building a test tower in Rottweil, Germany.