I'm not an expert, but I expect that a lot of that seemingly free space to the sides of runways is kept deliberately clear in case of emergency landings and wha

I'm not an expert, but I expect that a lot of that seemingly free space to the sides of runways is kept deliberately clear in case of emergency landings and whatnot. Cluttering it with solar panels would probably be a no-go; imagine a plane crash-landing into the middle of a huge electrical installation not easily accessible for firefighters.