>use them as the basis of the grid and use wind and solar that are more prone to fluctuations to fill up the demand when necessary
Er, how does this work? You can't control when wind and solar produce power, so how can you use them to "fill up the demand when necessary"? If anything, using a fluctuating source on top of already fluctuating demand just increases the amount of power storage you need.
A power source that ramps up and down quickly is more convenient than one that ramps up and down slowly, but both are miles more convenient than one which ramps up and down uncontrollably.
At least with solar you know when it won't produce power. You could have enough nuclear for nighttime demand, and build enough solar for the extra daytime demand. You'd have some remaining discrepancies to make up but relatively small ones.
Er, how does this work? You can't control when wind and solar produce power, so how can you use them to "fill up the demand when necessary"? If anything, using a fluctuating source on top of already fluctuating demand just increases the amount of power storage you need.
A power source that ramps up and down quickly is more convenient than one that ramps up and down slowly, but both are miles more convenient than one which ramps up and down uncontrollably.