Clever concept that relies on elevators to move heavy loads up and down could store energy for lower cost than batteries.
Gravity is hard to escape. So why not put it to good use? Researchers propose to store energy using gravity that could turn skyscrapers into giant batteries.
The idea piggybacks on existing elevators and empty spaces in high-rise buildings. Renewable energy, the researchers suggest, would be used to carry a heavy solid mass up to the top of a building, effectively storing it as potential energy. As the mass comes down, it would drive a generator that produces electricity. Given the stock of tall buildings around the world, such systems could store up to 300 gigawatt-hours of energy, they report in the journal Energy.
As renewable energy surges globally, the need for low-cost, long-lasting energy storage as an alternative to batteries is increasing. Gravity energy storage is one such novel concept that is being tested around the world.
The elevator system has a key benefit that the storage capacity is already out there, and situated exactly where the stored energy is needed. There are over 18 million elevators in operation around the world, and many spend a significant amount of time sitting empty and idle. During this time, and when extra renewable energy is available, the researchers propose, elevators can lift heavy objects like large containers of wet sand up to the top.
Then, when power is needed, the heavy containers can be dropped down, and the kinetic energy harvested using a regenerative braking system. Regenerative braking recovers some kinetic energy from a moving vehicle or object that would otherwise become heat and instead turns it into electricity. It is used commonly in electric and hybrid-electric vehicles.
“It's a realistic alternative because it utilizes existing infrastructure to provide a secondary service, energy storage,” says Julian Hunt of the International Institute of Applied Systems Analysis in Austria and lead author of the paper. “The technology is important because it allows energy to be stored in a decentralized way close to where the electricity is consumed in an urban setting.”