[cupofpython]

it is the most efficient in terms of energy transfer. I think it is lacking in terms of actual storage capacity. the upfront costs are also extreme.

ideally, every green energy farm would have a gravity well storage system nearby (like pumped storage) for the purposes of keeping discharge steady. Energy would be transferred into and out of this system pretty quickly, and stored in a more cost/size efficient storage option that could act as the true "battery" on dark days / longer periods of energy production downtime