There aren't many tried and tested solutions for grid energy storage. Pumped hydro is probably the best known and longest used. It's reliable and low risk. It'

There aren't many tried and tested solutions for grid energy storage. Pumped hydro is probably the best known and longest used. It's reliable and low risk. It's only practical if geography includes two adjacent large bodies of water with significant altitude differential. This isn't exactly rare but it's unusual, so pumped hydro isn't often a solution. Other than p.h.? Thermal (molten salt)? flywheels? These are rare and early in development. Each has its own reliability issues. If grid-scale storage is needed, it seems like Li batteries are the best understood, lowest technical risk option for now.