If you don't want to read the article: "Battery" in its name implies that it has got electrodes in it and that's all. It's neither an energy generator nor an energy storage device -- if you were wondering.
Also here's the catch/
"The desalinated water that comes from the battery still contains too much salt for drinking, La Mantia says: “We removed up to 50% of the original salt, but we need to arrive at 98%."
It's rather interesting how the word battery came to mean chemical storage of electricity, since the original meaning of the word has to do with beating. (For example with military weapons, or with a hammer to make forged metal.)
Military weapons are indeed likely the source of the term 'battery'. Ben Franklin coined the term in reference to arrays of Leyden jars. Presumably, this was for experiments where he would 'load' the capacitors, and then quickly 'fire' (discharge) them, resulting in a spark of some kind (which probably is what led him to suspect that lightning was electrical in nature).
I think the problem for such power plants is to make the membranes efficient enough, and given that they have problem to remove all salt in this "battery", I guess that they have the same problem. For reverse osmosis I'm pretty sure it is more efficient with lower gradient, so these techniques could be combined.
Since osmotic power is better with larger salt gradients, a power plant that use the gradient between the ocean and the Dead Sea would be perfect. The Dead Sea sinks one meter per year because of excessive use of water for irrigation. There is probably not the right political climate in the area to achieve such things however.
The dead sea idea is interesting. The political climate is fine actually - Israel and Jordan have a pretty good relationship.
There are already plans to collect energy from the elevation drop - adding the salinity change too could be pretty nice. This seems like a rare environmental win - get free energy, and replenish the water level at the same time.
Also here's the catch/
"The desalinated water that comes from the battery still contains too much salt for drinking, La Mantia says: “We removed up to 50% of the original salt, but we need to arrive at 98%."