Solar-powered Ford C-Max Energi chases the sun by itself

It’s strange enough to ride around in a self-driving car. But it may be even weirder seeing a car drive itself around with no one inside. That’s what Ford is proposing with its C-Max Solar Energi concept.

Originally previewed at the 2014 CES show, the car recently reappeared at the Washington Auto Show, along with Mike Tinskey, Ford’s global director of vehicle electrification and infrastructure, who was there to explain it all. The C-Max Solar Energi concept comes with its own car port, with transparent solar collectors for the roof that effectively act as a bunch of magnifying glasses. Tinskey says the car port can be assembled with common tools by any owner and transported, as necessary.

The purpose for the car port is to charge the car’s batteries with solar power. That way, the owner wouldn’t necessarily need an electrical outlet to plug in. (Read our complete Ford C-Max road test.)

But the problem with solar-powered cars is that conventional cars don’t offer sufficient surface area to collect enough solar radiation to charge their large batteries. (Tiny dedicated competition solar cars are much more efficient, because they carry only one person, usually lying on their back, and run on bicycle tires. Even the small batteries they use require the entire surface of the car to face up toward the sun and be covered with solar panels—something a traditional car shape, with its vertical sides, wouldn’t allow.)

The C-Max Solar Energi carries a small, 8-kW solar array on its roof that by itself could charge the car in a day, provided there were no clouds and the sun stayed perfectly centered over the car. Any other weather variable would significantly lengthen the charge time. Ford says it has a patent-pending system to deal with that problem.