Researchers at Georgia Tech and Emory University have built an energy-recycling set of stairs that store a user’s energy during descent and return the energy during ascent.
The spring-loaded stairs compress when a user comes down the stairs, saving energy through impact and braking forces at the ankle by 26 percent. When going up the stairs, users get a boost of the stored energy making it 37 percent easier on the knee than using conventional stairs. Researchers say the device can be placed on existing staircases and doesn’t have to be permanently installed.
"Unlike normal walking where each heel-strike dissipates energy that can be potentially restored, stair ascent is actually very energy efficient; most energy you put in goes into potential energy to lift you up," says Karen Liu, an associate professor in Georgia Tech's School of Interactive Computing. "But then I realized that going downstairs is quite wasteful. You dissipate energy to stop yourself from falling, and I thought it would be great if we could store the energy wasted during descent and return it to the user during ascent."
Each stair is tethered by springs and equipped with pressure sensors. When a person walks downstairs, each step slowly sinks until it is level with the next step, where it locks in place. When someone goes up the stairs, the spring is released, lifting up the back leg.
"The spring in the stairs, instead of the ankle, acts as a cushion and brake," says Yun Seong Song, a postdoctoral researcher at Georgia Tech. "The gentle downward movement alleviates work by the trailing ankle, which is what keeps you balanced and prevents you from falling too fast on normal stairs.
The project could be used to help the elderly, pregnant women or those suffering from leg injuries to get up and down stairs easier. Current solutions such as elevators or stair-lifts are not often practical to install in the home and are not very affordable. Researchers say this is an inexpensive option that can be used for short periods of time and so users don’t need to permanently alter their homes.
The complete research can be found in the journal PLOS ONE.