The most advanced solar cars from around the world compete in a race from Darwin to Adelaide.
Around 40 teams from 20 countries are racing in this year's Bridgestone World Solar Challenge in Australia.
The rules of the road permit vehicles only five kilowatt hours of stored energy. The remaining energy must come from the sun or be recovered from the kinetic energy of the vehicle.
At the end of day one, the Nuon Solar Team from the Netherlands was in the lead, traveling 394 miles, followed by another Dutch team - Solar Team Twente in second place and team Tokai University from Japan were in third place.
(SOUNDBITE) Coach Wobbo Ockels from the Netherlands saying (English):
"We've been going really well. I mean, initially was very hectic and we had to overtake many people, I think we did more than 20 overtakes. Then we were just getting quiet and we're just running fast, that's part of our tactics. And now we're here, you know, with a happy smile, being ahead of a lot of the other teams, number one with about 30 minutes, it feels really good."
But this is just the beginning. The race is nearly 1,900 miles through the desert - so when the sun sets tomorrow there may be a new challenger in pole position.