[Old Professer]

Truck in seawater to the desert, electrolyze it and then truck it back to civilization; sort of like marching camels to the oasis, filling up their water tanks and marching them back to the next water hole?

[cogitator]

With the exception of the Gobi, parts of all of those desert regions are pretty close to the ocean. I'd send the power from the photovoltaics to the coast, rather than send the water inland (which would usually be an uphill gradient requiring pumping, anyway).

The method isn't that far-fetched; the hurdles are efficiency and scale. But there was recent news (posted here, I'm pretty sure) that focusing the sunlight on the photovoltaics significantly increases their energy conversion efficiency.

Schatz Solar Hydrogen Project