Technology

Power usage is not consistent throughout the day, but power plants are optimized to make a consistent amount of power. You don't just turn a knob at the plant and make more or less power. You're stuck with all the electricity that's coming out of the plant, like it or not. So when plants are making too much power, you have to store that electricity somehow, and when plants aren't making enough to you need to have reserves. That's what a 'battery park' like this is does. In America, we call this storage 'the power grid'.

And yes, it gets more complex still when you start adding renewables like wind & solar, as now the power being generated is also not consistent. And although they generate 'enough' power, they tend to generate power at the wrong times. So the ability to store power & distribute it later becomes even more important.