The guiding rule of this race is that the boats can be powered by only solar energy. Assistance from wind, humans or animals is strictly forbidden.
The race starts and ends in the Frisian capital of Leeuwarden in the Netherlands. This year's race began with a major obstacle--note the sky.
Solar energy is also the power behind the North American Solar Challenge for solar race cars.
Four-person teams compete in the FNSC Solar Challenge, and they must meet two conditions. Each team member must take a turn riding in the boat--and they must all be able to swim.
A solar boat navigates through a small canal. Racers finish a leg of the course each day--then camp out and prepare for the next day's race. The Friday leg of the race is called "Hell of the North" by speedskaters, as competitors will have to take their boats out of the water twice and walk. There are two dams they will have to surmount.
A solar racer corners in a canal.
Here, organizers get the solar boats ready for the start.