[edarchis]

Relying on a salinity differential, even between salted and unsalted, seems like a terribly small amount of energy. There are projects to put large spheres at the feet of offshore windmills to pump water in and out. That has some pressure challenges but store a lot more.

The advantage I see for the salinity difference is that you can make them a lot larger than the pumped water ones. But is worth it, I'm skeptical.