Gravity Could Solve Renewable Energy's Biggest Problem

In the Swiss municipality of Arbedo-Castione, a 70-meter crane stands tall. Six arms protrude from the top, hoisting giant blocks into the sky. But these aren't building blocks, and the crane isn't being used for construction. From a report: The steel tower is a giant mechanical energy storage system, designed by American-Swiss startup Energy Vault, that relies on gravity and 35-ton bricks to store and release energy. When power demand is low, the crane uses surplus electricity from the Swiss grid to raise the bricks and stack them at the top. When power demand rises, the bricks are lowered, releasing kinetic energy back to the grid. It might sound like a school science project, but this form of energy storage could be vital as the world transitions to clean energy. "There's a big push to get renewables deployed," Robert Piconi, founder of Energy Vault, tells CNN Business, adding that companies are under increasing pressure from governments, investors and employees to decarbonize. But relying on renewables for consistent power is impossible without energy storage, he says. Unlike a fossil fuel power station, which can operate night and day, wind and solar power are intermittent, meaning that if a cloud blocks the sun or there's a lull in the wind, electricity generation drops. To compete with fossil fuels, you need to "make renewables predictable," says Piconi, which means storing excess energy and being able to dispatch it when required. [...] Instead, Energy Vault decided to base its technology on a method developed over 100 years ago, which is widely used to store renewable energy: pumped storage hydropower. During off-peak periods, a turbine pumps water from a reservoir on low ground to one on higher ground, and during periods of peak demand, the water is allowed to flow down through the turbine, generating electrical energy. Piconi says Energy Vault relies on gravity in the same way, but "instead of using water, we're using these composite blocks." By doing it this way, he says the company is not dependent on topography and doesn't have to dig out reservoirs or create dams, which can have negative effects on the environment.

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