You can't just connect 20 cable's from Africa to the European grid and expect it to work, that's not how the grid works. And I'm truly surprised that many people on HN seem to think it would.
Source: I work in utilities and one of my current focus area's is creating software to help expand the net to cope with the addition of new renewable sources and EV charging stations. And even that is posing a massive challenge on a relatively small and local scale. I couldn't imagine the impact of this fantasy of just plugging in some cables from Africa somewhere.
Edit: This incident is an example of how sensitive all this stuff is:
https://www.bloomberg.com/news/articles/2021-01-27/green-shi...
But if you want a carbon-free grid, then you can't ship the light or the wind. You either massively overbuild generation and throw most of the power away, build huge amounts of very expensive storage, or you ship the power.
Currently the world is headed towards overbuilding, but thats only because typically private companies build power generation, whereas power transport is mostly in the realm of governments, and governments are slower to act on market forces (and often aren't great at capital efficiency).
The end result will clearly be a mixture of all 3, but we're going to see a lot more power movement in the next 50 years than we saw in the last 50 years.