California can't use all its solar power. That's a huge problem. CA's solar plants don't even operate at full capacity

[BubbaJoe]

13. Other forms of energy storage are possible for CA

Given the proximity to the mountains, there are gravity storage methods, either hoisting weight to a high level with excess energy then letting it descend to generate power when the sun goes down, or using pumps and resevoirs to pump water up hill with excess energy to drive turbines at night. efficiency is around 80 to 85% usingf these methods.

Although the video is using electrolysis and water to generate Hydrogen (no fossil fuels are used) efficiency is not as good (70 to 80%) but since you are using excess electricity produced by sunlight maybe that is OK. I like the idea of using fuel cells to generate the power from the hydrogen.

We need to remember although solar cells have been around for a while, how to store that energy is relatively new. There will be progress in this area (epecially if there is profit to be made). It will take time, but it will come.