Gravity-Based Batteries Try to Beat Their Chemical Cousins
Alongside the chilly, steel-gray water of the docks here stands what looks like a naked, four-story elevator shaft—except in place of the elevator is a green, 50-ton iron weight, suspended by steel cables. Little by little, electric motors hoist the weight halfway up the shaft; it is now a giant, gravity-powered battery, storing potential energy that can be released when needed. Reversing direction, the motors become electric generators, sending up to 250 kilowatts of power back to the grid. For peak power, the weight can descend in 11 seconds—but for testing purposes, it moves just a few meters at “creep speed,” says Douglas Hitchcock, project engineer at Scottish startup Gravitricity. The company announced this week that its small-scale demonstrator is now operational, capable of switching between drawing energy from the grid and sending it back in a matter of seconds. The design offers an alternative to the chemical batteries that dominate the global energy storage market—a market that is growing hand in hand with renewable power, which needs to bank energy when the Sun shines or the wind blows, and release it when the grid faces high demand. Gravitricity is one of a handful of gravity-based energy storage companies attempting to improve on an old idea: pumped hydroelectric power storage. Engineers would dam up a reservoir on a hill, pump water to it at times of low demand, and release it to generate electricity. But the systems require specific terrain, expensive infrastructure, and planning approval that is increasingly hard to come by. These days, banking energy usually means hooking up renewable power to giant batteries.
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