Student-built EV covers 1,864 miles in 44 hours to win solar race
The Sophie 8X, a student-built solar-powered EV from the Vocational Training Council (VTC) in Hong Kong, has claimed victory in the Cruiser class of the 2025 Bridgestone World Solar Challenge.
The event took competitors on a 3,000-kilometer (around 1,864-mile) journey across the Australian outback, from Darwin to Adelaide.
Preliminary records show Sophie 8X completed the route in 44 hours, covering 3,021.5 kilometers (1,877.5 miles) at an average speed of 68.7 kilometers per hour (42.7 mph). It was a demanding test of engineering skill, racing strategy, and renewable energy innovation.
The World Solar Challenge, held every two years since 1987, has become the ultimate proving ground for solar-powered cars. Its mix of extreme heat, long distances, and unpredictable terrain requires cars to perform at the highest level of efficiency.
Lightweight design shows what EVs can be
One of the biggest takeaways from the competition is how different these student-built EVs are compared to mainstream consumer models. Many popular EVs, like the Tesla Model Y, are heavy and energy-hungry.
At 1,900 kilograms (4,200 pounds), the Tesla weighs more than twice the Cruiser-class competitors, which fall between 400 and 800 kilograms (880 and 1,760 pounds).
Sophie 8X’s battery pack is a perfect example of this efficiency-driven design. Its 15.2 kWh pack weighs just 40 kilograms (88 pounds). By contrast, the Tesla Y relies on a 60+ kWh battery pack weighing more than 770 kilograms (1,700 pounds).
The Sophie 8X roof is fitted with six square meters of solar cells. These not only keep the battery charged but also directly power the vehicle. The team used advanced 400 Wh/kg lithium battery pouches, conserving weight and space while maintaining energy density.
Advanced motors and aerodynamics deliver results
The Hong Kong team made major upgrades in the 2025 design. They collaborated with Guangdong-based partners to build in-wheel permanent magnet synchronous motors that are 18 percent lighter than those used in the 2023 version.
These motors are paired with a third-generation silicon carbide semiconductor controller, boosting efficiency in energy conversion.
Team members explained that the custom-designed SiC motors can reduce energy consumption by 30 percent at cruising speeds of 100 kilometers per hour (62 mph). This gave Sophie 8X a crucial edge in long stretches of open road where efficiency is everything.
Aerodynamics also played a key role. The lightweight carbon fiber body was shaped with the help of computational fluid dynamics (CFD) modeling to minimize drag. The team also rebuilt weather and road condition models to better optimize energy usage and plan strategy.
These improvements paid off in a close race to the finish line. Sophie 8X crossed first, followed just four minutes later by Estonia’s Solaride III Enefit. Italy’s Onda Solare from the University of Bologna trailed in third place, while Taiwan’s Apollo IX Plus and Australia’s Sunswift team pushed to finish before the evening cut-off.
A step closer to real-world EVs
Perhaps the most significant milestone for Sophie 8X is not just its win, but the fact that it is legally authorized to drive on public roads in Hong Kong. This marks a first for such a student-built solar EV and shows that it meets recognized automotive safety standards.
Event Ambassador Chris Selwood praised the achievement, saying, “What a credit to this team. In 2023, they finished in the non-competitive class. Now in 2025, they’ve returned to win the Cruiser Cup.”
Since its launch in 1987, the Bridgestone World Solar Challenge has seen more than 10,000 participants from leading universities and research groups.
Teams from Cambridge University, Stanford University, and Tokai University have all contributed to advancing solar technology. Each edition pushes the boundaries of what solar power can achieve in road vehicles.