Cranes are a familiar fixture of practically any city skyline, but one in the Swiss City of Ticino, near the Italian border, would stand out anywhere: It has six arms. This 110-meter-high starfish of the skyline isn’t intended for construction. It’s meant to prove that renewable energy can be stored by hefting heavy loads and dispatched by releasing them.
Energy Vault, the Swiss company that built the structure, has already begun a test program that will lead to its first commercial deployments in 2021. At least one competitor, Gravitricity, in Scotland, is nearing the same point. And there are at least two companies with similar ideas, New Energy Let’s Go and Gravity Power, that are searching for the funding to push forward.
To be sure, nearly all the world’s currently operational energy-storage facilities, which can generate a total of 174 gigawatts, rely on gravity. Pumped hydro storage, where water is pumped to a higher elevation and then run back through a turbine to generate electricity, has long dominated the energy-storage landscape. But pumped hydro requires some very specific geography—two big reservoirs of water at elevations with a vertical separation that’s large, but not too large. So building new sites is difficult.
Energy Vault, Gravity Power, and their competitors seek to use the same basic principle—lifting a mass and letting it drop—while making an energy-storage facility that can fit almost anywhere. At the same time they hope to best batteries—the new darling of renewable-energy storage—by offering lower long-term costs and fewer environmental issues.