Pumped hydro storage is the gold standard for large scale storage, but it is only cost effective in certain geographic areas. Many of the prime areas for pumped

Pumped hydro storage is the gold standard for large scale storage, but it is only cost effective in certain geographic areas. Many of the prime areas for pumped hydro are already being utilized in developed countries. So, we can't really implement a ton more pumped hydro. Melting and re-solidifying salt or water is done at smaller scale, but has not been used for large scale storage. Some grocery stores use systems like this to shift cooling loads a few hours, but nothing at grid scale. To make a serious impact we need big scalable solutions. Batteries are in the lead here since the price keeps coming down. They also have the advantage of being able to discharge at both high power and low power.