If you assume a future where a higher percentage of sources are unreliable then obviously there is more value in a reliable source. But if you look at thermal storage, no one has been able to make that economical and how do you lower the cost of salt to improve that?

But Ivanpah has one trick up its sleeve: they cleverly sited themselves right next to a large natural gas pipeline. If the utilities have a need for more on-demand power, Ivanpah simply needs to install a natural gas burning boiler and they will be able to make steam and turn the generators any time needed.

Another future possibility would see Ivanpah converted to a hybrid facility called an integrated solar combined-cycle plant. On the generation side, it would be a two stage turbine like any other combined cycle plant: first a high temperature gas turbine whose exhaust goes into a boiler for a steam turbine.

On the hot side, the working fluid would first run through the solar tower for preheating and then into the gas fed “boiler” for superheating.

GE is working with eSolar to develop this kind of technology.

http://www.technologyreview.com/news/425012/ge-invests-in-solar-thermal-company/

1. Bringing multiple band-gap PV materials to the point of mass production and reliability that single band-gap PV has right now. I know some people working on this, but it’s still very much in the experimental stage with the panels costing multiple thousands of dollars per square inch.

2. A totally unexpected way of storing solar energy; maybe something along the lines of a high-efficiency artificial photosynthesis or an unforseeable materials science advance.