It's hard to feel completely virtuous using an electric vehicle when there's a high probability that at least some of the power going into your car comes from a coal-fired power plant or other dirty energy source.
Not so with Ford's new solar-powered concept vehicle, a version of the C-MAX plug-in hybrid that's outfitted with 16 square feet of photovoltaic panels on its roof. The vehicle, which takes six to seven hours to charge fully, can run on solar energy for 21 miles before switching to gasoline.
The panels on the roof, made by solar panel manufacturer SunPower, are high-efficiency—but not efficient enough to keep the vehicle running for any significant amount of time. In order to get enough power to operate, the C-MAX Solar Energy Concept has to park under a solar canopy outfitted with a solar concentrator that, like the name suggests, concentrates the sun's power. There are four aluminum posts and 20 square meters of acrylic—just enough general structure to brave the elements without raising the cost too high.
Teaming up with the Georgia Institute of Technology, Ford designed its concentrator with Fresnel lenses, which are "similar to a magnifying glass without the bulk," according to Mike Tinskey, director of global vehicle electrification and infrastructure at Ford. In order to allow the car to get optimal sunlight, it moves forward autonomously across its parking space while charging, using a combination of onboard sensors and software. "You use the vehicle as a tracking mechanism," says Tinskey.
In theory, there are a few advantages compared to traditional plug-in electric vehicles. Solar-powered cars are cheaper, since they don't require costly power from utilities, and they are guaranteed to be powered by 100% renewable energy.
But right now, they aren't entirely practical. Leaving a vehicle charging for an entire day doesn't make sense for many drivers, and a widespread infrastructure of solar canopies would have to be installed outside of drivers' homes—comparable to the ongoing process for plug-in electric vehicles that is taking many, many years.
Ford also has to work on safety. "If you stand under a concentrator that's multiplying [the sun] by seven or eight times—if you stand there for a few seconds, it will burn you. It's one of the things we have to work through. We have some low-cost ideas for how to make that happen," explains Tinskey.
Still, Tinskey says he's "cautiously optimistic" about the business case for solar-powered cars. It just might take time for technology to catch up to the concept.