If you're travelling any part of the 3000km stretch between Darwin and Adelaide in the next few days, don't be alarmed if you see what appears to be alien reconnaissance craft cruising the roads.

An array of futuristic vehicles with the sunlight dancing upon their saucer-like tops are taking part in the Bridgestone World Solar Challenge, a marathon north-south trek across the red heart of Australia undertaken by 40 teams.

As the name suggests, all of the cars involved in the race must be powered by electricity generated from the sun. Organisers say they welcome "lateral thinking" in designs, hence the car that has a coating so aerodynamic that dirt doesn't stick to it, thereby avoiding that perilous moment when you have to guide what looks like a shiny door wedge on wheels through the car wash.

"One of the unique aspects of the event is that we don't prejudge people's ability, we have a class of cars where the only expectation is that you bring your enthusiasm," Chris Selwood, the event director, told Guardian Australia.

The enthusiasm will be provided by competitors from 23 countries, including a team of native Americans from a tribal reservation in Mississippi, which excelled in a similar race in the US before heading to Australia.

"The on-road component is a big adventure and it's exciting," Selwood said. "But essentially this is a design competition to find the world's most efficient electric car."

The race component, which lasts for four days, has strict rules. The harsh Australian sun could, theoretically, keep the cars running 24 hours a day so a timeframe of 8am to 5pm is set for driving hours.

To ensure that the vehicles run on energy derived from the sun throughout the journey, solar cars are allowed a nominal 5kW of stored energy to run off, around 10% of normal total capacity. They then get as far as they can in the available time, often 600km to 700km, before setting up camp in the outback for the night.

"Early in the morning they'll run off stored energy, mid-morning there will be a balance point of stored energy and energy from the sun and then the middle of the day they will be storing energy as well as using it," Selwood said.

"It's a unique position to go down the Stuart highway in these cars. There are 140-tonne road trains but it's a lightly populated road with straight lines of 40km at a time. Australia's the best place to come out and play with solar car."

Selwood admits the cars aren't built with "the comfort of the driver in mind" but adds the "real heroes" are the people who devise the energy capture and storage.

Long term, this unusual vehicular challenge aims to demonstrate the viability of solar energy as an option for transport. While the popularity of rooftop solar panels has soared among Australian households in recent years, cars, buses and trains are yet to make the switch to solar-powered electricity in large numbers.

"Of course, if you are travelling from Brunswick to the CBD of Melbourne, you probably wouldn't want a huge solar panel on your roof – you'd generally have them on your garage," Selwood said. "If there was the political will, we'd be driving solar cars around our cities now because of the benefits in maintenance. But politicians are too wedded to the status quo.

"At some point, society will have to make the choice between being powered by brown coal or being powered by solar."