The first Aptera was an extremely efficient three wheeled car that didn't make it to production. Years later it's been rethought and now Sandy Munro - one of the serious gurus on automotive production - is involved. It's radically different from anything else and would be very interesting if it catches on.
Since it began in the mid 80s solar car racing has become very sophisticated. It isn't about engineering future cars as much as developing new technologies. Here's Derek Muller (Vertasium) on a recent race (there are several in a series)