Do i right understand You are searching for the water energy system we call "Pumpspeicher-Kraftwerk" in german?
https://en.wikipedia.org/wiki/Pumped-st ... lectricityBecause this sort of energy "transforming for saving" system could be "closed", which is important when using saltwater!
It has to be guaranteed that no saltwater comes out, contaminating the surrounding soil, natural rivers and groundwater aquifers!
One more expensive fact using saltwater is the need of very resistant materials because of stronger corrosion.
A useful landscape for such a project could be the Atacama Desert along the chilean westcoast.
Here there is the effect of mountains wringing out water from soaked air-masses extremely small:
Because along the chilean westcoast is a very cold maritime stream called "Humboldt-Stream", coming from the extreme cold antarctic continent to the warmer north.
The cold air masses above him are not able to contain and transport much air water.
In the moment, when they reach the hot land, they expand their capability of taking up water so much, that they would dry the land more if it would not already be the most dry site on earth.
There is only a very small stripe along high mountains, where this heated air is going colder again and condense a little fog stripe.
But this is very few water.
So this region has no sweet water to move electric power stations.
It would be possible to pump saltwater in a bassin between high mountains in a short distance to the coast,
powered by windmills and solar power plants (photovoltaic panels or parabol rin or mirror concentrating power plants).
(Maybe it would be more effective to solar-heat saltwater to steam, earning the salt, leading the demineralised steam by steam pipeline upon the mountains and condense it there as demineralisied water in a bassin, for dual-use for storing power, fresh water and irrigation.)
But is a need in this region for the storage of renewable energy?
This region is nearly not habitable despite of some mining, fishing and space monitoring activities.
The distance to the next agglomerations is not very short and needs long expensive wires.
I guess the energy needed there could be produced just in time.
Not only by wind and solar, but maybe using the sea streaming, wave power or flood changing.
The need would increase if the chileans decide to colonise the Atacama Desert and for this produce big masses of fresh water, which needs much energy.
But this is a sort of production that could follow the just-in-time energy potential.
The risk of salt-contamination maybe in this area is not as bad as in more sensible areas, because there is not much nature which could be damaged on the short way to coast.
There are already areas where natural salt mineral depots exist.
But one big risk has to be mentioned for the whole west coast of both americas:
The risk of extremely strong earth-quakes which can damage a water storage bassin and causes a giant flood which will destroy and salt-contamine everything on its way to coast!