In the early 90s you could generate H2 from water with and get 80% of the energy required to do that in a power cell. H2 is easy to store. And if ness could be compressed and used in fuel cells in cars.
And I dare say you could use the O2 produced as well to increase the thermal efficiency of Combined Cycle systems to near 90% so saving massive amounts of gas too.
And as for another form of storage - imagine heating your hot water and storage heaters on the almost free electricity generated when the sun is shining.