That's nice, but there is a long way to go, also it would probably be better to see batteries as a part of the 'storage' bracket, after all the batteries don't generate electricity, they store it. It's a bit like lumping fields of grain in with bags for grain. The one is useful all by itself, the other can't function without some other generator doing its job first. Typically the use for storage in the form of batter…
Not in a power-grid context; it'll over-volt the grid sometimes and under-volt it other times.
In the specific context of "understanding generation supply to a grid", working in terms of "load supplied by a system of solar & batteries" makes the math drastically simpler.