LEEUWARDEN, Netherlands — Ladies and gentlemen, start your engines — and pray for sunny skies.

The Frisian Nuon Solar Challenge race for boats powered exclusively by solar panels got off to a challenging start yesterday, under cloud cover and a light drizzle.

More than 20 teams from Europe and the United States have converged on the Netherlands' rainy northwest to navigate a 140-mile course of lakes, rivers and creeks.

A favorite is from Delft University of Technology, which won a solar-powered road race three times in Australia. Last year, the team's wing-shaped car averaged more than 60 mph on land, besting challengers from the U.S., Japan and Australia.

The top speed in this week's race heats will be much slower, because of the greater force required to propel a boat through water.

Organizer Andries van Weperen said conditions yesterday were "less than ideal" — but that's part of the point.

"It's going to be a very different kind of race, with wind, currents and navigation all playing a role," Van Weperen said. "Since this is the first time, experience will have to be our teacher."

He said that with teams operating at the frontier of what's technologically possible, mishaps are inevitable.

During a qualifying race for the pole position Saturday, a boat from the Northern College of Leeuwarden pulled out after its main battery exploded. There were no injuries but "it was pretty dramatic," Van Weperen said.

"The whole boat was on fire," he said.

The team from Cedarville University in Ohio averaged a respectable 5.8 mph, finishing at the top of their boat's class for the first of six days of racing.

The Delft team's vessel seeks to maximize the surface carrying solar panels. It curves sharply at the waterline to minimize drag. "I guess you could say it looks a little like an aircraft carrier," said spokesman Martijn Hoornaert. The boat is 25 feet long; others in the competition are as short as 8 feet.

Hoornaert said his team believes their boat will be fastest, but might break down: "Our boat has simply not undergone enough testing. It's never been in the water for more than half an hour at a time."

Several teams are trying a catamaran approach, with panels stretched between the two hulls. Other entries appear to be regular boats with solar panels strapped to the deck.

"There's no need to reinvent the wheel," said Faduma Yusser of Drenthe College.