Yes, even helicopter design is getting in on the solar power boom. Enter the Solarcopter, the world's first solar-powered quadcopter.
The Solarcopter is also proof that professional-level solar design has entered the realm of DIY; the project has been built entirely by students at Queen Mary University in London. Though it is not designed for passenger flight, its inventors think it could be the future of drone technology.
The prototype can only sustain short flights, but future versions could be used for surveillance, search and rescue, or perhaps for tracking animal migrations. You can follow the progress of the Solarcopter at its Facebook page here.