The World Solar Challenge. It's the biggest event on the solar car-racing calendar.
SOLAR CAR TEAM MEMBER: There are six teams that are competing that are really close together. It will be an exciting race, the differences are small. But in the end of the day, we're gonna cross first.
The cars have to get from Darwin to Adelaide — more than 3000 kilometres! And they have to do it using only the power of the sun.
AMY GUNNELL, SOLAR CAR DRIVER, TEAM ARROW AUSTRALIA: We're super excited, happy to have clear roads ahead of us, which means we'll get out of town really quickly and be on our way to Adelaide.
The goal of the race is to help improve solar car technology. So a lot of teams come from universities or massive tech companies but not all of them.
CAMERON MUTIS, LIBERTY SOLAR TEAM USA: So we're a high school team, which definitely puts us at a bit of a disadvantage, not having all the funding that these college teams have. So for us to have a car that's able to compete with these immaculate teams is such a cool experience for us!
The event's been running since the 1980s and over that time the cars have become faster and more sophisticated. But after almost 30 years are we any closer to actually seeing these things driving around town? Well, to help answer that question we need to understand how they actually work.
Solar cars use solar panels to convert the sun's energy into electricity. Running on electricity also means solar cars need electric engines instead of petrol ones and they need battery packs to store all of that electricity too. The technology for each of those parts has improved a lot in recent years. Batteries are now smaller, cheaper and can hold more power. Solar panels now convert more of the sun's energy than they used to and they're also cheaper.
Electric engines have improved too and lots of companies have even released electric cars that can just be plugged in to recharge at home!
But combining all of that new technology together in a solar car is still a big challenge. Even though the parts are cheaper than they used to be, they're still pretty expensive. Some of these cars cost millions of dollars to create!
It's also hard to collect enough energy to move a car using just a few small solar panels on the roof.
That's why these solar cars are often odd shapes, to catch as much light as possible. And despite the big roofs these cars still have to be very light to travel at a decent speed.
SOLAR CAR TEAM MEMBER: We can hit speeds of about 120 kilometres per hour, the highest speed we've ever hit is 132 but we tend to cruise at about 70 or 80, that's kind of the efficient point of the car.
Another problem is night time, or cloudy days, when there isn't enough sun around to power them! And then there's the issue of space. There's barely enough room for one person in some of these cars, let alone a whole family or a load of shopping!
But over time these scientists and engineers hope to keep improving their solar cars. And one day you might even be able to drive one to school!
In the meantime though, seeing a solar car in your neighbourhood will probably only happen during special events like this.
CAMERON MUTIS, LIBERTY SOLAR TEAM USA: Just being here halfway across the world getting to race against all these countries it's just incredible for us, we're so excited to be here!