Ford C-Max Solar Energi Concept shows why we’re not driving on sunlight

Those of us who were children in the Reagan years may remember the science-project awe of the first solar-car race — the 1987 contest won by a General Motors project that looked like a one-eyed insect. Since then, despite advances in solar panel tech, solar-powered vehicles still resemble devices for cooking drivers rather than real vehicles.

In the latest bid to use the sun to drive our cars, Ford will show off the vehicle above later this month at the annual Consumer Electronics Show. Labeled the Ford C-Max Solar Energi Concept, Ford says it shows how sunlight could replace the plug for electric vehicles — but only with a carport-sized magnifying glass.

A few automakers have dabbled with solar-powered production; the Toyota Prius offers an optional $3,820 solar-roof package that powers a ventilation fan, and the late Fisker Karma had solar cells that could offer a slight recharge of the car's batteries. But the science of solar cells has yet to overcome their low efficiency — turning less than 25 percent of the light that shines on them into energy — making them impractical for cars so far.

Ford and its partners, solar-cell builder SunPower and the Georgia Institute of Technology, say they've come up with a way around such issues for the C-Max Solar Energi. In its sun-chasing form, the C-Max can get a full recharge of its 8 kWh battery with a day's worth of sunlight — enough to drive 21 miles on electricity only, the range of the standard plug-in hybrid C-Max. The trick to doing so isn't in the solar panels themselves, but a special canopy/treadmill that parks an array of Fresnel lenses above the C-Max Solar. The lenses concentrate sunlight on the solar panels, and the canopy shifts the car and lenses to keep the solar panels on target throughout the day.

Ford says after CES, the team will test how well the Solar Energi concept performs in the real world, but it immediately faces the question of why putting tiny panels on the car makes more sense than building big, stationary solar panels to make electricity that the car can then gather through a wall plug. The race for sun-powered cars looks to be a long, slow one.