For years, one argument has dominated the debate around renewables: they are intermittent, and therefore require large-scale, dispatchable backup—usually in the form of gas-fired power plants. It is a compelling argument. It is also becoming increasingly outdated. Because while much of the discussion still treats batteries as a marginal technology, real-world systems are starting to show something very different. Storage is not just filling small gaps. It is beginning to replace the role traditionally played by large, flexible fossil generation.…