I don't have a lot of information about the scale required; however, I will note that grid-attached energy storage is a big field that is not limited to batteri

I don't have a lot of information about the scale required; however, I will note that grid-attached energy storage is a big field that is not limited to batteries. Batteries are generally more energy-efficient, but relatively expensive per unit energy and power. Cheaper options tend to use physical phenomena (pumping water up a gravity gradient, compressing air in caves, &c).