Pumped storage has a serious problem: you can’t build it just about anywhere. There is very limited number of sites, and the most practical ones are already built out. This also ignores the issue of environmentalists being almost certain to block destroying entire valleys or mountain ranges.
There are hundreds or thousands of times as many places to store pumped hydro as there are places to put hydroelectric dams. The latter needs a river valley and a watershed. The former only needs an elevated basin. An elevated box canyon would do; you just build a dam across the end. Sometimes, you dig a pit, or build a dam all around a flat hilltop.
Furthermore, underground reservoirs have been demonstrated, in both natural and abandoned mining cavities.
A hollow sphere anchored to the sea bed can have the water pumped out with surplus power, and allowed back in to generate power.
Draining water from an elevated reservoir to a deep underground cavern can multiply the energy storage capacity. Height is strictly limited to hill height, but underground cavities may have any depth, to the limits of drilling.
what you can do is retrofit existing hydro dams, add more generation capacity (penstocks/turbines) and then let them fill when the sun shines/wind blows and empty when it doesn't, this is actually more efficient than pumping water uphill
