Since 1987, the World Solar Challenge has been a biennial race for solar-powered cars through 1,877 miles of the Australian Outback. It was originally dominated by incredibly aerodynamic, single-seat vehicles that were efficient, but never stood a chance of going into production. In the interest of promoting practicality, the organizers introduced the Cruiser class in 2013. Vehicles that competed in the Cruiser class were judged based on how many passengers they could carry, how practical the judges considered them to be, and how much electricity was needed to supplement the amount produced by the car’s on-board solar panels.
The winner of the 2013 Cruiser class competition was Solar Team Eindhoven from the Netherlands’ Eindhoven University of Technology. The winning car was called the Stella, and it could seat four passengers, had a range of 373 miles, and even offered a trunk.
For 2015, Solar Team Eindhoven is back with an improved version of the Stella called the Stella Lux. With 381 solar cells on its roof charging a 15 kWh battery pack, a full charge gives it a range of up to 621 miles. It also has a top speed of just over 77 miles per hour.
Compared to other solar-powered cars, the Stella Lux actually looks a lot like a conventional vehicle. Its design channels a bit of the Dymaxion, and its tires are much skinnier than anything currently on a production car, but it doesn’t look like the worst way to travel across Australia. Compared to solar-powered cars outside of the Cruiser class, it actually looks downright comfortable.
The biggest claim coming from Solar Team Eindhoven, though, is that the Stella Lux is an energy-positive solar-powered car. How that claim is worded might have you believe the solar cells are efficient enough to produce more than enough energy to power the car, effectively giving it an unlimited range as long as the sun is out. Digging deeper, though, you see that the Stella Lux is only energy positive if you drive it a short distance every day.
If you think about it, all solar-powered cars are energy positive if they set the number of miles driven per day low enough. For someone who only drives 30 miles or so per day, the energy to power their car would be free, but Solar Team Eindhoven won’t exactly be cruising through the Australian Outback on an endless supply of solar power.
While the achievements of the teams competing in the World Solar Challenge are impressive, you have to question how practical it is to put a solar array on a car in the first place. The idea of a car that can run on its own power forever is nice, but it’s not exactly practical.
Instead of trying to fit solar arrays on top of cars, surely it would be more efficient to put much larger solar arrays on rooftops that could then, in turn, charge electric cars. In fact, electric car owners can already do exactly that. A Tesla Model S doesn’t have a 600 mile range on a full charge like the Stella Lux, but it has a comfortable, luxurious interior, excellent acceleration, and an attractive design.
You also never have to worry about how much sun your Tesla is parked in, which direction it’s facing, how hot the interior is going to get while it (hopefully) sits in the sun, or the damage that random road debris might do to the cells on your car. A rooftop solar array, on the other hand, can be set up to maximize sun exposure and then generally left alone. It will sit there producing electricity without you having to worry about anything.
The other advantage of rooftop solar power is that most power companies will pay you more for your electricity during the day than you’ll pay to charge your electric car at night. Solar Team Eindhoven claims you can sell any additional electricity it produces back to the power company, which will offset what you have to pay to charge the Stella Lux when drive more than a short distance in a day, but that’s really only mitigating the inefficiency that comes with mounting a solar array on the roof of a moving car.
Where solar panels on production cars probably have the most potential, though, is as a way to offset the drain of accessories like air conditioning. Fisker tried that approach with the Karma before it went bankrupt, as have a few other automakers. Its adoption hasn’t exactly been widespread, but as more automakers search for ways to extend the ranges of their battery electric cars and improve the fuel efficiency of their hybrids, you may start to see solar panels on mainstream cars becoming more common.