Technology

To put it simply, the sun doesn't shine and the wind doesn't blow precisely when you need electricity, at least not all the time. You need to store solar generated energy from midday so that people can turn their lights on in the evening, and you need to store power from windy days to use on still days. Otherwise the electricity is wasted in the moment and non-existent when you need it.

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.