They could be put on top of the massive surface area of oil sands deposits that are currently being treated as ecologically unimportant. A lot of oil extraction isn't as 'punctiform' as it used to be.

Much oil sands extraction occurs in regions poorly suited to large-scale reliable solar generation.

Alberta has wind though.

I'd say that Sahara is an ecological disaster already, the result of ancient deforestation. Even if we might considering preservation of its ecosystem, we likely won't plan to preserve all of it.

While some ecological disasters are definitely man-made, the Sahara has been mostly the way it is today for the last 10,000 years (source: https://en.wikipedia.org/wiki/Sahara#Desertification_and_pre...). Of course the current climate change will influence whether it will expand in the future, but the "core" Sahara has been there before human influence...

> I'd say that Sahara is an ecological disaster already, the result of ancient deforestation.

There is literally zero scientific evidence I’ve seen to back up that claim, unless by “deforestation” you mean natural “deforestation” by glaciars.