The World Solar Challenge has been held every two years since 1987, and for many engineering students, competing has become as much a right of passage as spring break in Daytona Beach or a road trip to Bonnaroo.
To claim victory in this grueling, Mad Max-style marathon across the Australian outback, teams must create innovative vehicles that push solar technology to new heights. Beyond just speed records, judges are increasingly looking for cars that are practical and marketable. When winning Dutch university team Eindhoven crossed the finish line in 2017, its car included an app to recommend sunny parking spaces, an upholstered interior with room for five, and even the ability to install a rear-facing child seat.
Team Eindhoven’s work builds upon a grand tradition of student-made solar cars, which have been steadily progressing solar technology since the mid 1980s. In the American Solar Challenge, happening this month, competitors are increasingly building cars that people might actually want to buy. These kinds of hands-on solar projects can act as an incubator for future tech talent—Google co-founder Larry Page is a former student solar car competitor—even if they don’t participate in international competitions. Children as young as 10 are building cars with just pizza boxes and pieces of aluminum foil, while an all-female team from India and a duo from Palestine have recently made headlines for their resourcefulness in building effective cars under adverse conditions.
So if solar-powered vehicles have become such a common sight in classrooms around the world, why aren't we seeing them on our city streets?
Despite student successes on the race circuit, many analysts, car manufacturers, and industry titans have written off solar technology as impractical for consumer vehicles. Panels are expensive to produce, vehicles can require heavy batteries to store excess power, and the systems simply aren’t as efficient as those of other renewable energy sources.
There’s also the issue of access to sunlight: Vehicles that can speed across the Australian outback would screech to a halt in the Pacific Northwest. Even in the sunniest of climates, vehicles are often shaded by high buildings, and we tend to park in covered areas—limiting the cars’ effectiveness.
As engineer Tom Lombardo calculated in his famous takedown “Your Next Car Will NOT Be Solar Powered,” a conventional solar-roofed car operating under perfect weather conditions and 100 percent motor efficiency still could only expect to generate 6.4 horsepower. “For comparison, my riding lawnmower has an 18 hp engine,” writes Lombardo. “I've never measured it, but I'd guess that its top speed is about 10 mph.”
Solar’s drawbacks have led commercial car companies to focus their efforts on other sustainable sources, such as electricity or biofuels. Toyota’s Prius Prime is one of the few available consumer vehicles that draws upon solar power, but the car is only available for purchase in Japan, and it isn’t fully solar-powered—its rooftop panel is intended to be supplemental to the vehicle’s electric battery.
A more practical approach is using solar energy as a stationary charging source for electric vehicles. Just six to eight 300-watt solar panels installed on a garage roof or carport can produce enough electricity to drive an electric car more than 1,500 kilometers per month, and according to Clean Technica’s 2017 EV driver report, between 28-40 percent of electric car drivers already have solar panels in their homes. In June, China began testing solar-paneled highways that can heat themselves to melt snow, provide illuminated signage, and generate energy for nearby buildings. China’s eventual goal is to transform its roads into a wireless power source that can actually charge EVs as they drive.
The dream of a solar-powered car isn’t all lost. Significant student-led breakthroughs are also driving solar panel design. In April 2018, University of Michigan student Xiaozhou Che discovered a new method of solar panel design that increased panel efficiency to 15 percent—up from 11-12 percent. Discoveries like Che’s could pave the way for a completely solar-powered car. But just like solar power itself, it’ll likely be a slow and steady race to the finish line.