Conditions were fierce for competitors in this year’s Bridgestone World Solar Challenge (BWSC), with 34 teams from around the world battling blazing sun, a potential tornado and the perilous Australian outback.

The biennial BWSC is an incredible race, designed to inspire young people and bring awareness and innovation to sustainability and transportation. It’s a battle of endurance, testing teams to navigate more than 3000km from Darwin to Adelaide in hand-built vehicles powered by the sun.

Among 2025’s competitors were 44 German students from RWTH Aachen University and FH Aachen University making up Team Sonnenwagen Aachen, supported by Mercedes-Benz.

During the BWSC in 2023, Team Sonnenwagen suffered a devastating blow when side winds from an oncoming road train pushed their vehicle off the road, resulting in disqualification 300km from the finish line.

The team’s mission for the 2025 race was to place in the top five in their new Covestro Æthon, which underwent rigorous stability testing at the Mercedes-Benz Testing and Technology Centre and the Stuttgart wind tunnel.

In the heady post-race comedown, we caught up with Team Sonnenwagen Aachen to debrief about the highs and lows of the gruelling journey.

The race for pole position

“The first highlight of the race was the qualifying, which gave us pole position,” says team manager Leonie Brandt. The team clocked the fastest circuit at 1.52.51 minutes in the time trials at the Northern Territory’s Hidden Valley Raceway.

Then came the race. Amid cheers and in high spirits, first driver Moritz Mitzel proudly led the field, but on the outskirts of Darwin, disaster struck. The car had an electrical fault – a broken cable and malfunctioning main board, which stopped the solar panels from working.

“We were not getting any solar energy, and for a solar race, that’s kind of a problem,” says the team’s head of driving strategy and optimisation Dennis Eckerdt. “The electrical department had to find out what the problem was and that took about 20 minutes, and 13 teams overtook us in that time.”
 
It was a massive blow as the team watched their lead vanish.
 
A stunning comeback
 
After the electrical department performed some fast repairs, the drivers sprang into action, determined to regain the team’s strong position.
 
For cars to overtake in the solar race, communicators must signal ahead to vehicles, letting them know another team is approaching. At one point, says Leonie, they had six people in the Mercedes V-Class lead car simultaneously communicating with six different teams.
 
In an extraordinary effort, Team Sonnenwagen’s drivers managed to overtake nine teams, sometimes at speeds of 110km/h. At the end of day one, the team was within 30 minutes of the lead group and fourth overall, a strong position after such a potentially damaging start.
 
“After the repair, everyone was a bit down but overtaking all the cars really cheered everyone up,” says Leonie. “The top teams were still in reach.”

Maintaining the position

At the end of day two, when Team Sonnenwagen pulled up at Barrow Creek, around 1200km south of Darwin, the team was about 50km behind the lead group. By day three, their position as fourth in the overall field was solid.

This gave the team the chance to follow their racing strategy in the bubble of fourth position, behind the top three and far enough in front of the field to feel safe.

“For us, we were in a quite comfortable spot,” says Leonie. “The top three teams overtook each other multiple times in a day, and the section behind us was similar.”

Innovation and design yield positive results

Heading towards Adelaide, strong head winds and cross gusts put the Covestro Æthon to the test. Driver Felix Nupnau Perez, who also drove the Covestro Adelie in 2023, says the innovations put in place to increase stability hugely improved the car's performance.

“It’s much more enjoyable to drive the new car and it is great to see what the team built and developed in the last two years,” he says. “The steering was much more enjoyable, so you don’t have to hold onto the steering wheel and try to keep it on the road all the time. You can even let one hand go and drive with one hand sometimes.”

Battling wild weather on the way to Adelaide
 
On day five, the team was greeted in Adelaide by torrential rain, intense traffic and tornado warnings. This was a critical leg for Team Sonnenwagen and Felix felt the honour keenly when the team chose him to drive the final 500km. This time, at the exact spot of the accident in 2023, there were roadworks.
 
As one of the communicators in the lead vehicle, it was Leonie’s job to radio Felix whenever there were significant bumps or potholes. “After some testing, we figured out that we’d have to be really sensitive to bumps,” says Leonie, “because in the Mercedes, we didn’t really feel them. It was almost too comfortable!”
 
With a clearance of only 7.5cm from the ground, a 10cm pothole full of water makes a big difference to the Covestro Æthon. “Sometimes it was like a solar boat,” says Felix with a laugh. “Like a submarine!”
 
They’d taped the vehicle to make it more waterproof, but Felix says he was still soaking wet in the cabin. Crawling along at about 30km/h, he oriented himself by following the lights of the Mercedes-Benz support vehicle.
 
“It was very special,” says Felix. “The highlight for me was driving the last 300km. It was really fun to drive with the wind and the traffic. It was still tricky, but I enjoyed it.”
 
“We were really happy we finished the race in five days,” says Leonie, “because there were some teams still out on the sixth day and the whole event was paused for 45 minutes because there was a tornado warning. So we were lucky. We just made it before the really bad weather.”
 
The result saw two teams from the Netherlands, Brunel and Twente, claim first and second place respectively, with Belgian team Innoptus coming in third, and Team Sonnenwagen Aachen maintaining fourth position throughout the race.
 
“The main aspect this year was getting the car stable and making it to the finish line,” says Leonie. “That was a really big goal, and we achieved it.”