This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Solar-powered cars have been little more than a novelty to date, experimental vehicles resembling photovoltaic-laden surfboards designed mostly for racing across deserts. Expensive batteries, relatively inefficient PV energy conversion and the lack of intense sunlight in many places have made sun-powered passenger vehicles impractical.
Ford is looking to change that with a version of its plug-in hybrid C-MAX Energi that would allow drivers to charge the hatchback’s lithium-ion battery via PV panels mounted on the roof. Other carmakers already sell models that use solar cells to power cabin ventilation (Toyota) or accessories (Nissan). The C-MAX Solar Energi Concept—which Ford will showcase at next week’s International Consumer Electronics Show (CES) in Las Vegas—would be the first mass-produced, commercially available automobile to offer drivers the ability to recharge a depleted battery via solar power or by plugging into an outlet.
The recharging process gets a boost when the solar C-MAX is parked under an accompanying 20-square meter acrylic canopy equipped with 20 Fresnel compact lenses—the kind used in lighthouses—that act as a giant magnifying glass, directing intense rays to the car’s solar panels. Used in tandem over the course of six to eight hours, the rooftop solar cells and concentrator canopy would fully recharge the car’s battery, which can power the car for up to 34 kilometers before the hybrid’s gasoline engine needs to kick in.
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Further improving solar-charging efficiency, the new C-MAX would use sensors and cameras to track the sun’s position and autonomously reposition the car for optimal sunlight exposure. Ford already offers this technology to help drivers maintain a pre-set distance from the vehicle in front of them (via adaptive cruise control), stay in their lane and avoid vehicles in their blind spots. The C-MAX Solar would use these capabilities when parked under its canopy to automatically roll up to 2.5 meters forward or backward as the sun shifts in the sky. The combined canopy and tracking system will enable the car to charge up to eight times faster than simply parking the solar-powered car in the sun, says Mike Tinskey, Ford global director of vehicle electrification and infrastructure.
“What we’re trying to do here is essentially replace the plug,” Tinskey says. “We’ve been calling this the world’s first plug-in vehicle that doesn’t need to be plugged in.”
The C-MAX Solar Energi Concept is a collaborative effort, with SunPower Corp. in San Jose, Calif., supplying the roof’s high-efficiency solar cells and Georgia Institute of Technology helping Ford develop ways to speed up the charging process so that it would be practical for commuters.
Ford obviously has some kinks to work out if its C-MAX Solar Energi is to ever see the light of day, much less a sales floor. The cost of the solar cells, tracking system and canopy are an open question. Ford would have to deliver the technology at a reasonable cost to compete with other hybrids.
The vehicle’s proposed system of rolling back and forth could likewise pose logistical and safety problems. Would there be enough space in the average driveway to park and robotically roll a C-MAX Solar? What’s to stop it from inadvertently running over an object in its path—such as a driver’s wallet or foot? Questions also arise as to whether such a vehicle would ever be practical in places without much direct sunlight, such as a shade-covered driveway or parking space.
Despite these challenges, it’s an automotive move in directions we’d all like to explore—wireless, energy independent and off the grid.