What would happen when we cover all the deserts with solar panels? 

Lots of good answers about the energy. Let’s think out loud a bit about the climate effects.

When you cover a huge area of the desert as so wonderfully illustrated by Jeff Barry

then “interesting” things happen. This particular heat island would cause a huge vertical draft of hot air each day. That draft would in turn suck moist air from the Mediterranean Sea southward and into the heat chimney. The northern parts of Libya and Tunisia would get greener and their wadi’s would become full time rivers. Similarly the green part of the mountains of Morocco would expand.

The moister air would provide for plants—trees especially—to grow. These in turn produce more moisture downwind. Israel has been doing this kind of climate-forming and terraforming since the 1960’s.

At night all the moist air in that big hot column would condense out. Every night you’d have thunderstorms all over the area. Your solar factory would be covered in water daily and fog each morning for an hour or two. This would cause more maintenance for your factory.

It would also make all kinds of things grow under the solar panels, in the shade. Enterprising people would find good things to plant and harvest, to feed all the people coming to the now more-hospitable area of the world to live.

Most of the excess moisture would follow the jet stream. I don’t know where that is in that area. It might shift because of the solar factory.

Anyway, just out-loud musings on secondary effects. No judgement as to good or bad, but it would indeed change things.

Edit: 19 August, 2019

It occurred to me last night that southern California might actually already be a test bed for this. They have requirements for new solar PV on the roofs of all new home (and business, IIRC) construction. Together with retrofits and solar farms in the nearby desert we could easily get enough of a hot-air chimney to start on-shore airflow.

When/if I get time I’ll see about digging into the climate records in places like Palm Springs and Borrego Springs.