[SoftTalker]

Renewable (solar for example) needs enough battery to cover the 12-18 hours a day where the sun isn't shining or is at too low an angle to effectively capture by solar panels. This is far more than covering a few hours of load peak. Solar might actually be a decent peaking power source, as it tends to peak at the same time as demand. But it's not a good base load source; it needs far too much battery buffer.

[cauch]

My point is that to follow the demand, you need ~12 hours of capacity: the trough is during the night around 1-4 am, the peak is mainly in the afternoon around 5pm. So if you have a battery for nuclear, you will charge it during the night and discharge it ~12 hours later.

Not sure about your 12-18 hours, it looks like you want to use the energy during the night, while it is the trough and does not require energy.