The efficiency of solar panels and electric drivetrains has reached the point where the Sun can easily send cars across Australia. But fully solar-powered vehicles involve a lot of compromises in terms of performance, carrying capacity, and driver comfort. Such vehicles are not something you could use for your daily commute, while commuter cars simply don't have enough surface area to host the panels it would take to run them. But Ford has come up with some clever compromises that will let solar panels partially power one of its concept cars.

The design is based on its C-MAX Energi plug-in hybrid, which has enough battery capacity to cut into its use of an internal combustion engine on shorter trips. The result is a car that the EPA rates at roughly 100MPG. To that, Ford has added an array of solar panels on the roof, enough to generate about 300W of power—nice, but not enough to fully recharge the car's batteries during the daytime.

To get there, Ford added an additional part: a canopy you park the car under. The roof of the canopy is a Fresnel lens, a compact, thin lens that can be manufactured out of inexpensive and light materials; in this case, Ford will use acrylics. The lens will focus light from a broad area onto the roof of the C-MAX Solar Energi, boosting the amount of power it generates.

The most clever bit, however, is how the system deals with the fact that the focus changes with the position of the Sun in the sky. The car will actually move itself under the canopy in order to stay in the focus and optimize its charging. Presumably, that means that the canopies will have to be oriented relative to the east-west axis, and the parking spot will have to include some additional space beyond that normally needed for a car.

Ford will be showing off the concept car at CES, so we might have the opportunity to take a closer look at it.