You know, you're right. I had previously thought that was infeasible due to transmission losses, but I ran the numbers (which I should have done before posting the above), and it would only require a worst case of 50% losses, and ~4000 of today's HVDC cables going around the world. And probably quite a bit better, since that assumes that half the world is getting its power from the other half all the time.
I still think everyone owning an electric car for storage is probably a more realistic plan, but it's definitely not impossible to create a world energy grid and run the world even just from solar.
Your comment is exactly right; a blend is what's needed. Though in the case of solar, a blend still requires very long, very high capacity HDVC cables.
On the other hand, Tesla is busy getting luxury car buyers to help subsidize the capital investment in building storage on a bigger scale, and nobody has figured out how to get luxury car buyers to subsidize grid improvements.
In the long term, since the grid is a monopoly that is not eager to drop its price, whereas solar and batteries are likely to keep dropping in price, in part due to competition and in part due to appealing to early adopters, I expect that a few decades from now, the typical homeowner will use mostly solar and batteries instead of paying the monopolies' higher prices.
I find that a reasonable expectation, but it will not make any difference in the ability of European homeowners to benefit form Africa's surplus of sunlight. Storage only helps when you have a sufficiently high average power in one spot, and just need to spread out the peaks and valleys in production. Fantastic storage does not help if you can't gather enough energy to store in the first place. That may not turn out to be a problem for the average European homeowner if photovoltaics get good enough, but it is the problem that kijin was addressing by suggesting sunny countries sell power to cloudy countries.
One might use excellent storage technology to, e.g., charge batteries in the Sahara and ship them to Switzerland (or, more realistically, synthesize oil in the Sahara and ship it Switzerland), but that's just a slightly more indirect way of addressing the problem of transportation- moving the energy from the place where it can be produced to the place where it is needed to be used.
I still think everyone owning an electric car for storage is probably a more realistic plan, but it's definitely not impossible to create a world energy grid and run the world even just from solar.
Your comment is exactly right; a blend is what's needed. Though in the case of solar, a blend still requires very long, very high capacity HDVC cables.