We are not building much storage because it would be stupid to spend on storage that we have not spare renewable generating capacity to charge up. After we have plenty, then we will need storage, and will build it then.
For Japan, many pumped storages have been built to store energy generated by nuclear plant mainly at night. Now few nuclear plants running but many PVs are deployed, so it stores energy at noon. It's reversed but anyway it's useful!
For nuclear era, it was easier to pay cost for storage because same operator built both nuclear plant and pumped storage. Even if operator isn't same, there are only few nuclear operator in the grid so easier to talk. For PV (or say electricity deregulation) era, it will be a bit difficult since PVs are deployed by small operators or individuals. Great market mechanism or govt regulation is needed.
California quietly added 3GW of batteries in the last three years to shift mid day solar to the evening. I think part of the quietly bit is locating them at mothballed natural gas peaking plants. Advantage the power infrastructure is there and no use change permits needed.
Before that, they attached pumps and ponds at the bottom of penstocks leading to reservoirs in the Sierra Nevada mountains that were built decades ago.
