The reason we don’t have mile-high skyscrapers isn’t because we can’t build them. It’s because you can’t get to the top. The biggest limiting factor in skyscraper design is the elevators. The cables that carry them are limited in length, and to have enough cars to service ever-taller buildings, and with the extra people that use them, you need to fill most of the tower’s interior with elevator shafts.
ThyssenKrupp's Twin elevators solve one part of this problem, by putting two elevator cars into one shaft. The cars share not only the shaft, but everything else—the hoistway, the "landing doors" (what you and I just call "doors"), and the guide rails. ThyssenKrupp says that the Twin can shift 40% more passengers than a single-car shaft.
Energy-wise, the savings are big. First, the building needs fewer shafts, saving on building materials and costs. And second, the elevators can be fitted with energy-recovery systems that recycle the energy from braking, putting around 30% of that energy back into the building’s own grid.
But perhaps the best part of the Twin is ThyssenKrupp’s routing system (which is also available on its regular elevators). Instead of hitting a call button and then selecting your floor when you get inside the elevator, you tap your destination floor on a panel in the hallway, and you’re directed to the correct car. This means you wait less, the trips are faster (because the optimum route can be calculated by the system), and the cars run empty far less often. This last saves energy.
There are other benefits to having a two-car system. For instance, one can be kept in service while the other is down for maintenance.
The Twin has been around for a little while, but is about to make its debut in the U.S., in Atlanta’s Coda development, says Treehugger’s Muriel Vega, beginning in 2018. Until then, why not take the stairs?