True! I just wonder how much energy they'd realistically be able to store for a given amount of resources. I just wonder if this has the same issues as Lifted Weight Storage, where the energy density just doesn't really make sense once you get right down to it. I don't know the relevant math to determine how much water and at what pressures might be required to scale this up to the 500MWh/1GWh range. It might be perfectly fine.