They're not dealing with a pressure differential. Or at least I don't think so.
I don't think the Journalist who wrote the article understood the technical details, but from digging a little at their website I think what's going on is they're moving heavy brine up and down, all of it equalized with local pressure.
Despite them describing it as pumped hydro, I think its better framed as a cousin of the "chunk of concrete suspended over a mine shaft" style gravity battery. Replace the mineshaft with water and the concrete with salt.
I don't think the Journalist who wrote the article understood the technical details, but from digging a little at their website I think what's going on is they're moving heavy brine up and down, all of it equalized with local pressure.
Despite them describing it as pumped hydro, I think its better framed as a cousin of the "chunk of concrete suspended over a mine shaft" style gravity battery. Replace the mineshaft with water and the concrete with salt.