Thanks for this excellent summary of storage technologies. I can't wait to read the sequel on redox flow storage with new chemistry.

May I ask, out of interest, what do you think of building larger grids connected through UHVDC lines, perhaps even global grids? It may not be an approach attractive to the USA, but certainly Europe and China. Would be great if there was a grid that spans the globe and is able to shift solar power around the clock, literally.