World solar challenge shakes up 2025 agenda

The world’s longest running solar car race is to overhaul its rulebook and increase the difficulty of the challenge.

The World Solar Challenge is a two-yearly event that pitches custom made solar cars against each other in a ‘race’ over more than 3,000km between Darwin and Adelaide in Australia, with only solar energy to power the vehicles.

The event is an early pioneer of alternative fuel transport and marks its 17th edition in 2025.

Chief among the changes is a decision to bring the event forward to the end of August – Australia’s winter – where solar exposure from the Darwin start line will be about three-quarters of the October average, and even less when they arrive in Adelaide.

It’s a change that will almost certainly result in slower competition times.

Event organisers have confirmed specifications for the flagship ‘Challenger’ category – where designers aim for single-seater, ultralight vehicles, will be afforded a greater solar capture opportunity at the expense of lower battery capacity.

“This change encourages strategic energy management aligning with real-world challenges facing everyday providers who juggle supply and demand gaps between power availability versus power use,” says the event’s director Chris Selwood.

The ‘Cruiser’ class, which was designed to attract showroom-style designs that could carry multiple passengers, will also have its rules relaxed after all competitors failed to reach the finish line in 2023 due to strong headwinds.

It will be treated as a ‘single stage’ race between Darwin and Adelaide (the class had previously been broken up into compulsory time points). The event will continue to award points for design and sustainability to determine the overall category winner.

A new demonstration class will also be introduced in 2025 for designers to consider other forms of solar-based transportation. It’s a response to the availability of other emerging technologies in transport and to “showcase prospective ideas, technology, and renewables”.

It’s also a category that may help encourage leading teams to stick with the event. The Netherlands-based Eindhoven University of Technology team won the Cruiser class three times before opting out of the most recent event, instead building an off-road solar vehicle to drive through the Sahara Desert.

The UNSW team ‘Sunswift Racing’ had also indicated it was likely to step away from solar car racing unless regulations were freed up. It plans to build a hybrid solar-hydrogen car to be raced at Le Mans.

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