[wrycoder]

This may be the right place to mention that the comment in the article, "But the photovoltaic cells we use today need pure silicon, and nanoscale manufacturing — essentially the same technology as microchips used in a computer — so actually making solar panels would be incredibly difficult." is incorrect.

One needs only modestly pure silicon and no nanoscale tech at all. You can make photovoltaic cells with a small furnace and a couple of rather basic inorganic chemicals. Patterning for diffusion masking can be done with wax applied by hand.

You do need some electricity, so steam power or biodiesel would be necessary at first. You will need to run scavenged vacuum pumps and induction heaters to create the silicon ingots and zone refine them. You will need to conduct some basic inorganic chemistry and be able to produce the key industrial acids and bases.

Edit: you will need to recreate Pyrex glass and be able to form it into tubes and chemical glassware.