Belgian Agoria Solar Team members are seen at the finish line of the 2019 World Solar Challenge at Victoria Square in Adelaide, Australia, October 17, 2019. AAP Image/David Mariuz/via REUTERS

(Refile changes to biennial from biannual in paragraph 2)

MELBOURNE (Reuters) - More than 40 racing teams from 21 countries left Darwin on Sunday to race across Australia to the southern city of Adelaide in the world’s fastest solar powered cars.

The 3,000 kilometer (1,864 mile) Bridgestone World Solar Challenge is one of the most prestigious solar car races. The biennial event first began in 1987 and is based on a notion that a 1000 watt car would complete the trip from Darwin to Adelaide in 50 hours.

The teams are expected to complete the race by Thursday, with speeds of 90-100kmh (55-62 mph) powered only by the sun. In the week preceding the event, teams had to pass a series of practical safety and compliance tests to qualify for the start line.

Top Dutch Solar Racing team car ‘Green Lightning’ led off the competitors from Darwin’s State Square after earning pole position with the fastest lap at Hidden Valley Raceway on Saturday.

The teams, comprising of secondary and tertiary students form countries ranging from Australia through Sweden, Netherlands and Japan to the United States, must be self-sufficient, traveling each day as far as they can until 5 p.m. and making camps to stay overnight along the route through the desert. The solar vehicles are categorized to compete in three different classes: challenger, cruiser and adventure.

“The 15th edition Bridgestone World Solar