Distributed generation seems like it would make sense (with current tech). Italy and Spain could help here.

Maybe you could go from Tunisia to Europe, but supplying African countries seems more attainable.

It'd be nice if you could turn the energy into a gas like methane, pull CO2 out of the atmosphere in the process. Good for the atmosphere and you could transport gas over long distances.

https://en.wikipedia.org/wiki/Power-to-gas

I wonder if hydrogen is practical to transport in large quantities. My guess is no.

Your idea of methane, if it could be done efficiently, seems more likely.

Ammonia might be a better way. Easy to produce, store and transport and contains higher hydrogen density than compressed hydrogen (I think).

http://www.ammoniaenergy.org/

The biosphere can't handle ammonia accidents at anything resembling the scale of crude oil and natural gas accidents. Methane is the better choice.

I saw that very recently an Australian company had worked out a way of transporting hydrogen in large quantities by converting it into something else which I conveniently can't remember.

It was the CSIRO converting hydrogen to ammonia for transport, and then back to hydrogen again: http://www.abc.net.au/news/2018-08-08/hydrogen-fuel-breakthr...

Standard 800 kV DC line from Algeria to Berlin (2400 km) would incur less than 10% transmission loss.

What's the maximum current carrying capability for this standard 800 kV DC line?

Not sure for a standard line but the record is "1100 kV voltage, a 3,000 km (1,900 mi) length and 12 GW of power". So presumably 11,000 amps or so for that one. I guess you can have as much current as you want by making the cable thicker.

Being built in China here approx https://www.google.co.uk/maps/dir/Guquan,+Putuo,+Zhoushan,+C...

It's quite an impressive looking thing (vid) https://www.youtube.com/watch?v=VZ2KfrP_R3s

so transporting 1 TW would be a hundred of those in parallel

Yeah, but the average EU power consumption today is 0.35 TW, so with only a hundred of those in parallel (more likely spread around the Europe) you could literally satisfy 100% of EU power demand, and still have plenty of spare capacity.

I guess something like that. Probably beefier pylons and more cable on them.

could submarine power cables in the Medeterranian sea be thinner since the water keeps the cable cool?

Dunno - bit beyond me that one.

I suppose that a lot of such transmission lines should be superconductive, if only to help put enough electricity through physically more narrow channels.

Even with modern high-temp superconductors, it's a lot of expensive infrastructure, a lot of protective redundancy, and a lot of maintenance.

> Even with modern high-temp superconductors, it's a lot of expensive infrastructure, a lot of protective redundancy, and a lot of maintenance.

Which means lots of local jobs, which may not turn out so bad in the short term.