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Going Up: How the Unsung Elevator Makes Urban Efficiency Possible

Why don’t we appreciate the elevator as modern society’s most efficient mode of urban transportation?

Why don’t we appreciate the elevator as modern society’s most efficient mode of urban transportation?

America adores the car, respects the subway, dreads the bus, and ignores the elevator. But it is that final stretch of the urban journey, the confined ascent, that is the most energy-efficient portion of any commute. As far as green living goes, the elevator is an unsung hero denied the credit it deserves. Let’s fix that.

Without the elevator, we would not have experienced the rise of cities. As crucial to the process of urbanization as sewage systems, streetlights, and steel, the elevator enables dense vertical living. Without height, our cities would sprawl out over suburbia and farmland in a blanket of pavement and a noose of traffic.

Not only did the elevator help shape our modern cities, it also offers an object lesson in ecologically sound technology. “It takes about as much energy to run the light inside as it does to run the elevator,” says Don Vollrath, a principal engineer at Magnetek, an energy-efficient elevator-drive manufacturer. According to the laws of physics, Vollrath says, “in the long run, because whatever goes up in an elevator usually comes down at a later time, the overall energy it takes to operate an elevator should be [close to] zero.” It’s more complicated, of course, but still admirable. An elevator uses about one quarter of the energy that a car requires to move passengers the same distance. This may seem like a contrived comparison, but elevators are no afterthought of mobility: Elevators in the United States take 18 billion passenger trips each year, moving people 1.36 billion miles, according to the National Elevator Industry. Those 1.36 billion miles are the cleanest of any American transportation method today, save bikes and feet. The reason isn’t fancy science, but elegant design.

Elevators of some sort have been around since ancient times. Greeks and Romans used water- or animal-powered crane-like hoists for freight and people. Victorian blue bloods used a crude system attaching a chair to a pulley outside a window so the bravest members of the privileged class could avoid stairs. These early elevators harnessed the same central principle as today’s most modern lifts: counterweight.

Jay Popp is an elevator-design consultant. He says that in the United States, “the counterweight is typically 40 percent of what the car weighs at capacity. People in North America will only allow a certain number of people in before they’ll wait for the next elevator, unlike, say, Asia, where people will go to full capacity because they don’t have a ‘no touch’ area around them.” So when a U.S. elevator is 40-percent full, then the car and counterweight are in perfect balance. It shouldn’t consume any energy at all; moving the car then is essentially a free ride, like a seesaw.

But not so fast, Vollrath cautions. “We use an electric motor with cables, sheaves, rollers, and bearings. We must ask about the efficiency of those components.” Those components are pretty efficient, though—only 10 percent of energy is lost to friction and resistance.

While great minds struggle to make a cleaner car engine, there’s just not that much more to improve in elevator design. The frontier of vertical transportation, like everything else, is in computers. New algorithms are employed on “destination-dispatch” systems that try to cluster passengers going to nearby floors into the same elevator, reducing the distance each cab must go. You punch in your floor at a central panel, then a computer tells you which elevator to wait for.

These faster, destination-dispatch elevators will eventually become the standard in new towers, saving even more energy (and money) on the often overlooked leg of a commute. Subways are the arteries of modern cities, but the remarkably efficient capillaries deserve their due as well.

photo (cc) by Flickr user Steve Snodgrass

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