If we have excess nuclear capacity at night, we could use it to split water into hydrogen and oxygen. The hydrogen could be used as a non-carbon based fuel for vehicles.
The “we can use the excess energy for...” argument has been used several times on this thread. A big question come to mind when anyone gets all Jules Verne on me. Why aren't we already doing it? I usually get a sense after a little research that the reason is that its either not economically feasible or logistically possible. The “lets go hydrogen” is a bit of both don't you think?