Couple examples: You put a line to cities in the south of Europe. But existing lines from there are nowhere large enough to take all that power, you will have to build lines from Milan and others all the way inside Europe. You can’t build a line to Gibraltar and call it a day, it has to go all the way up to Norway (albeit with tapering)
You also overestimate the efficiency of aluminium power lines, don’t take into account the amount of towers and/or plastic material that would be needed to wrap the lines if you make them underground.
We are talking about years of production, and that’s just for Europe, if you want to replicate this to other continents you quickly get a supply challenge, even if you spread this over 30years, at which point it will be too late, regarding global warming. Not to mention that m the CO2 emissions associated with building such massive lines would take decades (if ever) to be offset with the gains from the use of Solar, which was the point of the thing in the first place...
But in the end my point was not that this is impossible, but that efficiency is not the largest limiting factor here. Material supply is the largest problem. It is not insurmountable but it is a real challenge.
