But even a breakthrough gave us 100% efficient solar cells it would only marginally add to the range. We're never going to see a 50x improvement in solar cells

But even a breakthrough gave us 100% efficient solar cells it would only marginally add to the range. We're never going to see a 50x improvement in solar cells, that would violate thermodynamics. If you want a futuristic range-enhancing technology to dream about, look at in-road inductive charging (in-road discussion starts around 5:00): http://www.youtube.com/watch?v=b71wC4z8its http://www.youtube.com/watch?v=b71wC4z8its Infrastructure costs would probably be massive though.