This Futuristic Boat Just Circumnavigated the Globe on Solar Power

For the past 19 months, the Turanor PlanetSolar has been on a voyage around the world powered only by 38,000 SunPower solar cells. On May 4, the boat will return to Monaco, completing a trip that it began in September of 2010. The 537 square meters of solar panels power six banks of lithium-ion batteries. On a good day towards the end of the trip, they could charge up the batteries by a full 50 percent. On a bad day, they might only get 10 percent more juice before dusk.
The trip was not intended to prove that solar-powered ships are ready for the commercial primetime, but like many first-time journeys, to prove to future engineers that the feat could be accomplished and now need only to be optimized. Perhaps they also provided new (and green!) inspiration.