In case you weren't impressed with the fire-breathing CSP, which will someday use molten glass as a storage fluid (still cool), how about an air-breathing battery?
The thing with solar is that when the sun is shining full-blast, solar power plants go like gangbusters. They can put out so much energy the grid doesn't even know what to do with it. Then a big cloud comes by, and it's game over. So everyone is looking for a way to hold on to the energy created in the good times to release during the dark times. Literal dark times, not metaphorical.
So now there's an iron-air battery that can use the rusting process to store energy. No, you may not bring your crappy old Pontiac Grand Am to the local solar facility and park it in their front lawn as a favor. Iron-air batteries have been around for decades, but they were crazy inefficient. However, by adding a wee-bit of bismuth (the pink part of Pepto-Bismol), these new iron-air batteries are ten times more efficient. And cheaper. And safer. And environmentally friendlier.