I can confirm for certain that during the summer there are...

I can confirm for certain that during the summer there are thumping great pumps running during the off-peak period pumping water back up into the dams (and swimming pools on towers) to re-run when the demand (and the price) is high.

Energy banking is going to be increasingly important as grids get more and more renewable energy. It's not just because it's renewable, or even just because it comes and goes without any control (although that is important). But it's because with wind and solar the generation isn't done by crashing great heavy whirligigs spinning away. Those whirligigs have so much weight that when the demand balance on the network changes suddenly the weight of them helps to keep everything steady.

Without the whirligigs you need banks of batteries that can instantly either absorb or release power onto the grid.

If we're going to keep adding renewable energy to the grid (and I absolutely think we should) then we're going to have to stop throwing our hands in the air and weeping about how terribly unstable it is, and just do... something... about it!

With Zinc Bromide batteries!