⇒ Now the volatile supply line has valleys between the peaks. If you integrate over time and place, the supply line covers about 40% of demand in this situation.
That is /very rough/ and depends on a lot of factors, but my point is the same if it were 30% or 60%: where does the rest come from?
- Transmission: as already mentioned, we know how to transmit electric energy, it’s just material and effort. This smoothes out the »place« dimension.
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⇒ - Storage: obviously, we’d want to smoothen out the time dimension as well. This means adding storage that can meet 100% of demand as well (volatile sources frequently drop to 0), and feeding it with enough additional clean sources that it can fill every expected gap (and gap accumulation).
And here I’d like to repeat my point from before: the best (most effective) storage we have right now is pumped hydro, by far. And pumped hydro is not enough, by far.
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⇒ - Backup. Of course, anything inherently CO₂-producing is out for this, and this includes gas, obviously, and biomass (maybe less obviously, but think about it). And that leaves?
So, this is my plan: keep building solar and wind till peak demand is sometimes met, build nuclear to replace all the fossil »backup«.