It seems to me that the molten salts make the most sense and seems to be the farthest along: https://www.solar-reserve.com https://www.solar-reserve.com The c

It seems to me that the molten salts make the most sense and seems to be the farthest along: https://www.solar-reserve.com https://www.solar-reserve.com The case for small scale electric storage seems less obvious to me https://en.wikipedia.org/wiki/Molten_salt_battery#Vehicles https://en.wikipedia.org/wiki/Molten_salt_battery#Vehicles but lithium ion seems to be working for now.