Citigroup has put out some pretty bullish predictions on the future of energy storage. Personally, I see a huge opportunity here for utilities and other grid-level players to get in this space. The obvious problem is getting the technology to an affordable and efficient level. Less obvious is coming up with a software/hardware infrastructure that can dispatch thousands of what are effectively power generators in response to demand and grid stresses. I think we'll see these types of technologies proven on smaller microgrids, but eventually storage will be a grid-level asset, just as large power stations are now. Certainly having storage options would alleviate the main issue with renewables, namely that they're not dispatchable and don't line up with demand.