With a proper energy grid and pumped hydro, couldn't they focus on situations like these for dumping excess energy?

For example, some places will even pay customers to use power at night so that they don't need to shut down the plant when demand is low. If that energy were sent to a pumped hydro plant, it would move water back up into the reservoir. With large enough reserve pools, a lot of energy could be stored this way, even years' worth.