The only other grid scale tech I'm aware of is pumped hydro which is very effective BUT severely limited to areas with existing good topography where you have two large enough basins separated by substantial height.
well, there are batteries of all kinds, there is green gas, and many other systems which can in one way or another support the grid - each with their respective advantages and disadvantages, such as capacity, controllability, cost, space requirements, topography requirements, ...
ALL BES currently installed have 4 hour capacity or less. It is far too expensive to have multiple day grid scale BES. I'm so tired of having to repeat this basic fact. WTF is green gas?