One of the more interesting methods I have seen is power turbines that run on compressed air, with the solar or wind pumping in air increasing the pressure, storing the energy in the potential of the expansion of the compressed air.
Another is use of a MONSTROUS flywheel, storing the energy as kinetic rotation. Same idea, energy in spins it, power takeoff siphons energy off to turn generator.
I think it will all come down to efficiency and more importantly cost.
Great stuff to ponder, a better world might be the result of few more good minds left to wander around such dilemmas..