Here is an article that provides an interesting summary of different approaches to storying energy:
https://arstechnica.com/information-technology/2017/10/a-world-tour-of-some-of-the-biggest-energy-storage-schemes/ One of the drawbacks of existing green energy sources is that they do not necessarily produce energy during convenient hours. These energy storage mechanisms are intended to help out with that. I had forgotten about pumped storage — pumping water uphill from one reservoir to another. The pumped storage stations in the article can deliver orders of magnitude greater power than the alternatives, and they presumably have a lot more storage capacity as well. Eric
