I wonder if the name has been trademarked...

It's not a Mind-Machine Interface; it's a Brain-Machine Interface. If you're a physicalist, then there is no such thing as a Mind-Machine Interface, because there are no minds, only brains. If you're a dualist, then the technological goal described in the article is no more a Mind-Machine Interface than the laptop on which I'm typing this comment. In both cases, the brain mediates between the mind and the machine -- the only difference is the presence or absence of additional mediators (fingers, a keyboard, etc.). The term "Mind-Machine Interface" is either misleading, or it unnecessarily takes a side in the physicalism vs. dualism debate (by implying that "mind" is just another word for "brain"). "Brain-Machine Interface", by contrast, is a term that both philosophical positions agree is accurate.

- Raw silica (SiO2, approximately sand) can't be used to build solar cells. Converting silica into silicon (Si, the actual material used in solar cells) requires a high temperature (1900 C) reaction with a carbonaceous fuel like coal. Are they proposing to bring in a steady stream of fossil fuels (oil?) to the Sahara?

- Also, depending on the type of solar cell they are proposing, the crude silicon produced by the above process would have to be refined and possibly crystallized (also a high-temperature process).

- Finally, when talking about superconductors, "high-temperature" does not mean what we would consider hot (the Sahara, for instance), or even warm (e.g. room temp.), but rather "above the boiling point of liquid nitrogen (77 K)". Feasible high-temp. superconductors would still have to be cooled to ~80 K with liquid nitrogen. What is their plan for producing/transporting a steady stream of liquid N2 in the desert?

Others have mentioned problems with transmission grids. Not saying it's impossible, just that there are real scientific and engineering issues. It's not just a matter of some yen and cooperation.