The plane employs 17,248 solar cells to harness the sun's energy. As the sun sets, the plane switches over to the energy stored in its batteries. Solar Impulse can, in theory, perpetually stay aloft for as long as a pilot wants to fly.
This is a project dreamed up by Bertrand Piccard, a Swiss who co-piloted a non-stop balloon flight around the world in 1999, and André Borschberg, a Swiss businessman.
Piccard has a family history of exploring - his father was a noted undersea explorer and his grandfather was a prominent balloonist too. Borschberg leads the technical team that actually builds the systems that make Solar Impulse work. The two undertook the project as a means of demonstrating that "pioneering spirit, innovation, and clean technologies can change the world."