Skip to Content

World Solar Challenge returns after a four-year hiatus

World Solar Challenge returns after a four-year hiatus

13 Oct 2023

World Solar Challenge returns after a four-year hiatus

By Matthew Ward Agius | Cosmos

University and industry teams from around the world will converge on Darwin in the north of Australia this week for the Bridgestone World Solar Challenge

In the three decades since the first event in 1987, hundreds of institutions, entrepreneurs and auto manufacturers have entered an array of unusually shaped vehicles into this 3,000km ‘race’ through the arid heart of Australia. 

Yet in 2023, the event finds itself in a new age. No more are electric vehicles a prototyping exercise – they’re available in showrooms across the planet. But the Darwin-to-Adelaide challenge remains, positioning itself as a testbed for innovation and a training ground for tech workers of the future.

At its heart, the event is a design challenge that pitches teams mainly staffed by undergraduate students against one another. The most successful teams typically combine a mix of state-of-the-art aerodynamics, battery packs and efficient solar array design with clever on-road management. And all require a little luck. 

In 2019, the world-leading Brunel team from the Netherlands was neck-and-neck with Belgian rivals Innoptus when its battery pack overheated, burst into flames and melted the car to the ground as its crew stood helpless to end the thermal runaway.  

Days earlier, brutal crosswinds blowing across the Great Victoria Desert in far north South Australia sent several cars off the road. The event can be brutal. 

But it’s worth it when the technology flows through into industry and, eventually, consumer products. 

Solar cars are a rarity on the roads, but not unheard of. Lightyear One is a Dutch car company spun out of the Eindhoven University solar team – a previous participant in the event. Toyota’s ev-bz4x SUV has a solar roof, and so too does Mercedes-Benz’s Vision EQXX.  

Solar Challenge winning Innoptus team (formerly Agoria) car. Credit: Mark Evans/Getty Images for SATC

Solar challenge alumni include Google founder Larry Page (who crewed the University of Michigan team), and Tesla co-founder JB Straubel (a former Stanford University team member). Nasdaq-listed fast-charger company Tritium and renewable tech manufacturer Prohelion both emerged from Australian teams. 

That, ultimately, is the modern-day pitch of the event – and the appeal drawing new teams during each edition, including the first competitors from Eastern European nations Estonia and Romania this year.  

“The point of this challenge has always been to bring sustainable mobility to market,” says the event’s director Chris Selwood. 

“The value of this event extends well beyond solar cars and the 3,000 kilometres they travel. The value lies in its people and the lessons they learn [and] our alumni are a cohort of high-achieving changemakers, from global highflyers to garage start-ups.” 

It’s not as simple as just building a car. 

A class battle 

Traditionally, the Bridgestone World Solar Challenge was a single event with small, single-occupant vehicles designed to be as aerodynamically and electrically efficient as possible.   

That has changed and now there are two categories.  

The Challenger Class: solar rockets speeding to the finish 

Leading the way from Darwin to Adelaide will be entries in the “Challenger Class”.  Single occupant and often described as having the aerodynamic drag of your daily drive’s rear-view mirror, these machines will zip from Darwin to Adelaide in 4-5 days, weather permitting.  

They’re designed for maximum efficiency – consuming the same amount of power as a washing machine. This year’s regulations have seen a revamp in the interests of driver and environmental safety.  

Challenger Class specifications 

  • A maximum solar array area of 4 square metres.  
  • A maximum vehicle length of 5 metres and width of 2.2 metres – about the average dimensions of a large SUV or pick-up, though many will be far smaller than this. 
  • A single driver who can be switched out at any of the nine control points between Darwin and Adelaide. 
  • At least 3 wheels.  

In developing a Challenger, a team needs to make trade-offs in search of strategy – three wheels provide one fewer contact point with the road, reducing friction, but four might improve stability.  

This year, many teams have opted for a ‘bullet’ monohull intended to punch a hole through the air. The Brunel team – which draws its team from Delft Technical University in the Netherlands – has a long history of building a catamaran-style car which it describes as ‘sailing on the wind’.  


Solar array placement and design are also important. Does a team construct a ‘flat array’ or opt for something curved? How does it consider the driver’s cockpit and the risk – no matter how small – of it casting a shadow over the array as the sun moves through the sky? 

Although the record average speed for the event is 102km/h (posted in 2005), regulation changes designed to minimise solar cell use and increase safety in recent years will see this year’s average time closer to the 80-90km/h speeds registered in recent events. 

The Cruiser class elevates real-world relevance 

You can’t drive a rocket on the roads. 

So where the practicality of the Challenger class as a commuter vehicle falls over, the “Cruiser” class rises in its place. Cruiser cars are intended to emulate a production passenger car and their specifications are naturally different. 

Cruiser Class specifications: 

  • A maximum solar array area of 5 square metres.  
  • A maximum vehicle length of 5 metres and width of 2.2 metres – as with the Challenger class. 
  • At least two vehicle occupants – a driver and one passenger.  
  • At least 4 wheels.  

The Cruiser Class is also staged like a ‘regularity rally’ – rather than simply being the fastest, cars are intended to complete three stages within a set time limit, arriving at three control stops in Tennant Creek, Coober Pedy and Adelaide between certain hours.  

Arrival during these time windows is essential. Lateness incurs a penalty when calculating a team’s final score. Indeed, the winner of this category will be judged on ‘score’ not ‘time’.  

Final points will be calculated based on an equation that accounts for the total person-km distance travelled, divided by the product of external energy use of the car (in kWH), a practicality score (between 0 and 1) and penalties.  

Plus, a team needs to reach all three control stops under their own power – no towing.  

Passing muster: scrutineering, towing and non-competitive entries 

Car in the competition will cost anywhere from tens of thousands to millions of dollars.  

And that doesn’t even include the unpaid labour costs, with teams of anywhere from a dozen to more than 100 volunteers spending over a year designing, building and testing their machines for competition.  

As part of this process, teams will spend a week undergoing scrutineering in Darwin before the race starts.  

Kaohsiung University of Applied Sciences have their entry reviewed during scrutineering. Credit: Scott Barbour/Getty Images for SATC

Experienced scrutineers led by Dr John Ward, research director of the energy systems research program at Australia’s science agency, the CSIRO, ensure cars are compliant with the event design and safety regulations.  

Failure to be declared compliant with the event regulations or roadworthy to use public roads from Darwin to Adelaide will strike a car from the start. Roadworthy cars that fail to meet competition regulations are placed into a non-competitive ‘Adventure’ class enabling them to still participate in the voyage south. 

It’s not a race (though everyone treats it as such) 

Officially, the Bridgestone World Solar Challenge isn’t a race. After all, it would be inappropriate to race 40 cars on public roads from Darwin to Adelaide in road-registered vehicles, let alone specialised cars powered by the sun.  

That being said, the glory of being first to the finish line is what spurs these teams to build the most efficient vehicles and to be tactically superior in managing them.  

And the feel of the challenge being a race is aided by the shootout-style qualifying day – dubbed “dynamic scrutineering” – at the Hidden Valley motorsport circuit.  

Come Sunday morning, teams will make their final tweaks for the official start in Darwin’s State Square, beginning the first metres of their 3,000km journey south to Adelaide along the Stuart Highway.  

Scrutineering for the Bridgestone World Solar Challenge opens on October 16 ahead of the official event start on October 22.