This is a very interesting article, but they fail to provide the information which I consider to be the most significant; what are the energy loss percentages for each form of storage? If any of them approach 50% energy out, versus energy in, I would be surprised.
Here are humanity’s best ideas on how to store energy
The plans, the prototypes, the power-pumping: These batteries are hints of the future.
Molten salt tank at the thermal solar solana plant in Gila Bend, Arizona -- the first US plant to use molten salt storage.
https://arstechnica.com/information-tec … e-schemes/