I'm not able to find it now, but a few years ago I read about an idea to have a massive solar plant grid in the SW of America. It would transmit to the rest of the country. Every so often there would be storage plants.

On good days the plants would compress air into man made caves. After the cave reached a certain pressure, the generator would distribute energy as a pass through. If there were bad generation days out SW, the compressed gas would spin turbines at the plant. I believe that each plant was to have 3-5 days worth of common load production. After that, I think there were fallback generators like gas.

The reason I bring this up, is that battery/storage can be more than what we normally think about. In the case of the caves, there are several states that have natural formations. Investment in this idea, or others could reap great returns for the future.