There are a few ways to store excess energy generated during the day. Usually batteries are the obvious answer.

One of the great things about batteries is that the metal used in them is recyclable and can be repurposed to make new batteries. So, at some point, we’ll barely need to be mining the metals used in those.

Compare that to petroleum products which, if not for green energy, would always needs to be extracting more and more to be able to satisfy an increasing demand of energy.