"If solar energy is eventually going to matter— that is, generate a significant portion of the nation’s electricity — the industry must overcome a major stumbling block, experts say: finding a way to store it for use when the sun isn’t shining.
That challenge seems to be creating an opening for a different form of power, solar thermal, which makes electricity by using the sun’s heat to boil water. The water can be used to heat salt that stores the energy until later, when the sun dips and households power up their appliances and air-conditioning at peak demand hours in the summer.
January 3, 2012
This approach seems sensible and likely to succeed because energy storage has always been the problem with renewable sources like the wind and the sun.
However, it's probably only viable for those portions of the grid served by very high sunlight locations, i.e., the Southwest. Unlikely that this technology would ever be viable in the northeast U.S. or the Pacific Northwest where cloudiness rules.