A high voltage DC line should have less losses than the energy gained by moving south. Furthermore, one can pretty much rely on the Sahara sky not being clouded

A high voltage DC line should have less losses than the energy gained by moving south. Furthermore, one can pretty much rely on the Sahara sky not being clouded, which is probably more important as you then can rely on having the same energy output every day. The let-down is that it would cost billions to put the necessary lines in place. Putting the solar farms into the south of Spain is likely to be more cost-effective. The nice thing about photovoltaics though is, that there is no minimum size for a plant. This means, we could do both in parallel - extend European solar plants and set up some in Africa.