That's what grid energy storage is for. Traditionally this is often implemented with hydro (sometimes even by pumping water up to a high-altitude reservoir during periods of excess power generation). There are many more exotic methods as well - e.g. the crane that stacks concrete blocks, or the train with concrete that goes up and down the hill.

More recently, grid-scale batteries are being installed at increasing scale (e.g. Tesla's Megapack), and the cost efficiency of that solution seems to be improving rapidly.