Efficient allocation is one big problem. Given the assumption that solar panel production will lag the optimum demand for a good while, the panels we do produce

Efficient allocation is one big problem. Given the assumption that solar panel production will lag the optimum demand for a good while, the panels we do produce should be installed in places which maximize their output, modulo efficiency of transmission to a population centre. So, Sahara desert is out of the question, but Northern Europe is not ideal either. Arizona, Nevada and Texas should be blanketed.