Solar and wind energy are renewable, but rely on the weather. Energy Vault’s EVx Gravity Energy Storage System instead employs massive blocks, which, after being raised, store the energy that went into lifting them, and when lowered, release that energy when it’s needed. The ever-present pull of gravity amounts to a natural battery that can provide short-, medium-, or long-term storage, says CEO Rob Piconi. "It's resilient to harsh weather conditions and high temperatures, and since the energy is produced inside the structure, there is no risk of chemical fires,” he says. In May, the company connected its first commercial project to a grid in China, and announced a partnership with architecture firm Skidmore, Owings & Merrill to design skyscrapers that incorporate the system, potentially providing a way buildings can act as their own emergency generators.