I calculated the costs of covering the needs of Germany for a 2 days low production event (as it happened between 6-9 december) and you would need about a trillion dollar.
That's for something that cannot even garantee you more than 48h of runtime for half the country's needs.
You would need at least 4 times that to be safe.
Even if batteries price are divided by 2 (very unlikely, there are large fixed costs) you would need trillions of dollar for a single country.
That's just not happening any time soon and even in 30 years time, I doubt it will be that prevalent of a solution.
I did a conservative calculation if you started around 2000 in Germany and went full nuclear like France did. Not using any fancy new nuclear or anything. Literally just mass production of standard nuclear plants. Plus all the updates of the grid, including domestic fuel enrichment and 'waste' storage. Plus all the investment necessary to great a fully modern grid to electrify the economy.
We are talking in the order of 500 billion Euro and this is very conservative assumption on nuclear construction cost. Much worse cost then what France actually achieved in their build-out. Also much of that is actually the grid, grids are really expensive it turns out. But building nuclear in central location next to places where there used to be coal plants, makes grid cost much cheaper because most of the grid is already there perfectly positioned to feed the population clusters. And that accounts for actually increasing overall production of energy, not decreasing as Germany is actually doing.
On the other-hand for the renewable path that Germany is going since 2000, just the grid alone is going to cost more then 500 billion euro, some estimation suggest that 2000-2045 total gird investment requirement is above significantly above that. Sadly today where everything is in this different private organization, this information is all over the place and 'semi'-private organization doing different parts of the infrastructure.
In total, between all the renewables, the grid and the storage, we are talking 1.5 trillion euro and that still includes gas peakers. If you want to go beyond and really go all in, it would be even more then that, as you suggest.
Turns out, if you plan includes trying to gather solar energy in Greece and Spain (or even Egypt), transporting it to Germany and then storing it into batteries there, well yeah, that's going to be expensive. And the solar panels you import from China aren't the expensive part.
France did the exact right think in the 70/80s build reliable long term energy generation, sadly since the 90s the newer generation of French politicians done literally anything they can to handle the situation as a badly and as incompetently as possible but that's a different story.
I calculated the costs of covering the needs of Germany for a 2 days low production event (as it happened between 6-9 december) and you would need about a trillion dollar. That's for something that cannot even garantee you more than 48h of runtime for half the country's needs.
You would need at least 4 times that to be safe. Even if batteries price are divided by 2 (very unlikely, there are large fixed costs) you would need trillions of dollar for a single country. That's just not happening any time soon and even in 30 years time, I doubt it will be that prevalent of a solution.