Then you moved the goalposts rather far from supplying electricity to the Ruhr area industry :-)

electrifying nearly all energy use

As JakeS said, such electrifying can improve energy efficiency greatly, lowering the generating capacity needed. I add that solar thermal (which is spreading rapidly in Germany) and geothermal (which I see as significant by 2030) can give heat energy without electrifying.

Yield per-square-of panel is not the same as yield per - square of plant.

Correct, you need North-South separation (for Sun-following plants, East-West too). However, just because that, not all the surface you contemplated is 'covered'. For rooftop plants, separation is provided by North-facing roof sides, courtyards, gardens and streets (the latter also for plants installed on highway noise barriers).

_{*Lunatic*, n.
One whose delusions are out of fashion.}