PlanetSolar is the largest solar-powered boat and sailed around the world only using solar power. As you can see, this was achieved by covering every square inch with solar panels, and then some more, just to get as much power from the sun as possible. The successful circumnavigation of Planet Solar has shown the possibilities of using solar power, but the project has shown as well that it is not yet feasible, especially when you are a bit removed from the equator.
PlanetSolar is a trimaran and has sailed around the world to promote renewable energy. Have a look at the earlier post about PlanetSolar.
The results of PlanetSolar are impressive. It would be great to see a Plant Solar 2.0 at some point in the future and find out what the progress is we have made with solar power.