There are already lots of projects around the globe using pumped hydro as a storage strategy. Probably right now is the only method technologically mature enough for storing big quantities of energy. China and US are the countries with biggest installed capacity, but many way smaller european countries have developed many projects and are among the 10 biggest installed capacity..
Probably the size of the infrastructure and its environmental and local impact will be a limiting factor. I hope we can see soon new methods like the hydrogen or compressed gas based technologies.
Nice article @mauromar , although pumped hydro looks like a technology from the past, storage itself is a very present debate.