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Meet Stella, the world's first solar-powered family car

Katharine Byrne
17 Jul 2014
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We go hands on with Stella and NXP's brand new Car-2-Car communication technology

Stella, the world's first solar-powered family car, has made its debut appearance in London. Designed by students at Eindhoven University, Stella took first place at the World Solar Challenge race in Australia in 2013, which tasked solar cars from all over the world to travel 3,000km in six days. It seats four passengers and weighs just 380kg thanks to a lightweight carbon fiber exterior. More importantly, it's 100 per cent road legal. 

We were there to see the car in action, as well as get a hands on demo with NXP's (one of Stella's main sponsors) brand new Car-2-Car communication technology, which uses 802.11p Wi-Fi signals to warn road users of upcoming obstacles so they know in advance when to change lanes, for example, or apply the brakes.  

Stella sits very low to the ground, making it as tricky to get in and out of as a modern supercar. The doors open upwards, but once you're inside, Stella is surprisingly comfortable. The whole of the top of the car is covered in solar panels, and the rear slopes down to help create less air resistance.

Of course, the unusual design is bound to raise a few eyebrows from the general public, but Stella's Juliette van der Lof explained that this was all part of the team's plan to win the World Solar Challenge. 

"As we were participating in the Challenge, we had to make decisions about the optimal design to be able to win the race. Therefore, we chose in the end to have the shape it has now, but our previous designs also included something more like a sedan, like a BMW. But in the end, it wasn't that optimal."

Her team mate André Snoeck agreed. "Stella looks different because Stella's a solar car. A solar car has to be very efficient and very lightweight. It's only 380kg, which is almost as heavy as the four people in it. Compare it to a small car, which is already 1,000kg, and one that's the size of Stella and it would normally be 2,500kg." 

But the team behind Stella wanted the car to be more than just efficient. "We wanted to prove that our car is sustainable and reliable," said van der Lof, "and we wanted to build the family car of the future."

For instance, as well as solar panels which let Stella run for 700km on a full charge, there's also a battery pack which adds an extra 430km to the car's overall range. This means you can drive Stella at night when there's no solar energy left to charge the car.

On cloudy days you can also charge the battery from the national grid, which takes roughly 7-10 hours, but van der Lof was keen to point out that cloudy conditions are just as good as bright sunshine. 

"Most people were laughing at us when we told them that we're from The Netherlands and that we're going to build a solar powered family car," she said. "Everyone was saying, 'You're absolutely crazy, because it's always cloudy and raining in the Netherlands.' So we said, 'Well, it is cloudy, but actually when it's cloudy, we are producing more energy from the light because when it's cloudy the light goes in waves in the clouds and then comes on the roof at different spots, so it's better divided.'" 

Fortunately, Stella's engineers have made sure its energy consumption is just as ruthlessly efficient as the rest of the vehicle.

"We took some numbers from the Dutch National Statistics Centre and we discovered that out of 12 months in the year, in 10 months the car produces more energy than it uses," said van der Lof. "We calculated this with twice the average distance people drive on a normal day, which is 70km a day, and still our car is producing more energy than it uses."

The team were also keen to include NXP's Car-2-Car communication technology, which can warn drivers of upcoming accidents and give real-time information about general traffic congestion and road conditions to help road users drive more safely.

"We were looking at technologies which could be interesting for us and also for the future," said van der Lof, "and one of these things was the Car-2-Car communication from NXP. NXP is one of the biggest companies in the region of Eindhoven where we were based. We knew what they were doing so we came to them with our idea, we explained what we were going to do and what we wanted to achieve and they were really enthusiastic about it. That's the way everything started with all the companies we've worked with."

In our assisted test drive, a separate screen showed the position of the car on the map as well as an upcoming road works sign. About 40m away from the obstruction, a warning popped up on the screen telling us how far away it was and that it was on our side of the road. In theory, this would mean drivers would know to switch lanes earlier, thereby creating less congestion as they're kept up to date with what's happening around them.

Of course, it's not just Stella that uses this technology; it's also inside the road works sign itself and communicates with Stella via a new Wi-Fi standard (802.11p), which is faster and more secure than the ordinary Wi-Fi we use for our smartphones.

NXP hopes this kind of technology will become commonplace in all future cars and city infrastructure, but since NXP only make the initial chips, it will be a big challenge getting all the car manufacturers and relevant roadside infrastructure authorities on board before the company's vision can become reality.

Still, Snoeck was confident that NXP's Car-2-Car chips wouldn't be hard to implement once car manufacturers decided to adopt the technology. "The Car-2-Car technology was easy to include as we built the car from scratch," he said. "Compared to building a whole car, putting in NXP's technology was not difficult."

As for Stella, the car will remain a prototype, according to van der Lof, so it can continue to be used to test new technology. 

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