The thought of vehicle-integrated solar cells taking an active role in powering an electric car remains a tantalizing prospect. In fact, the use of solar panels on the roof of a vehicle is not a new idea. It’s been shown that ultra-lightweight solar race cars with solar-packed body shells can actually drive exclusively on the power of the sun. In real life, though, this doesn’t work with production cars weighing thousands of pounds that need to carry varying numbers of passengers and weight, provide the acceleration needed for safe motoring, and in general perform all the functions required of a modern car.
Disappointing to some, car-mounted solar panels typically generate just enough electricity to operate a fan to keep the interior of a parked car cool on a hot day, falling fall far short of providing the kind of energy needed for drive motors. Lowering cabin temperatures in a parked EV does serve a purpose since less energy is needed to cool the passenger space during the early part of a drive. That means less of a drain on batteries needed to power an electric vehicle. In this case, every little bit helps.
There are other answers and solar charging does take different forms. Plenty of EV owners offset their car’s use of electricity through large solar panels on their homes. Many public charging stations also make use of solar arrays to provide at least part of the power needed for charging electric vehicles. These have been the most logical examples of solar charging to date. Still, efforts toward creating the true solar car continue.
The latest example comes from Ford. Working in a collaborative project with long-time solar technology partner SunPower and Georgia Institute of Technology, Ford’s C-MAX Solar Energi Concept embraces an innovative approach that could potentially deliver the same amount of electrical power as plugging a C-MAX Energi PHEV into the electrical grid. The goal is no less than creating a logical stepping stone toward making a solar-powered hybrid feasible for daily use.
Ford’s C-MAX Solar Energi Concept benefits from amplifying the sunlight that enables the car’s already-efficient SunPower solar cells to create electricity. A huge jump in solar energy conversion is accomplished with a special solar concentrator lens that directs intense solar rays to the solar panels on the vehicle's roof. The off-vehicle solar concentrator uses a special Fresnel lens of the type originally invented for use in lighthouses, boosting the impact of sunlight by a factor of eight. Similar in concept to a magnifying glass, the patent-pending system tracks the sun as it moves from east to west.
With the aid of the concentrator, the system can collect enough energy from the sun each day to equal a four-hour battery charge for the C-MAX Energi, about 8 kilowatt-hours. Ford says this is sufficient to deliver the same performance as a conventional C-MAX Energi plugged into the electrical grid. The Ford C-MAX Solar Energi Concept would also have the same total range as a conventional C-MAX Energi of up to 620 miles, including up to 21 electric-only miles. Since the sun isn't always shining, there is still a charge port so this solar Energi variant t can be charged conventionally from the grid.
The special solar concentrator carport used with the C-MAX Solar Energi is conceptualized in a way that maximizes capturing solar energy as the sun moves throughout the day. This requires an east-west carport orientation and also the ability for the car to autonomously move forward and backward beneath the canopy during daylight hours, thus enabling its solar cells to make the most of sunlight directed by the concentrator. As Consumer Reports posits, not only does this require buying into the concept of an unattended car moving all by itself during the day, but also the potential liability issues that could come with it.
Ford studies suggest that the sun could power up to 75 percent of all trips made by an average driver in a solar hybrid vehicle. Solar charging could be especially valuable in places where the electric grid is underdeveloped, unreliable, or expensive to use. In addition, use of a C-MAX Solar Energi could reduce yearly CO2 and other greenhouse gas emissions from the average U.S. car owner by as much as four metric tons – the equivalent of what a U.S. home produces in four months. If all light-duty vehicles in the United States were to adopt Ford C-MAX Solar Energi Concept technology, annual greenhouse gas emissions could be reduced by approximately 1 billion metric tons.
Next up: Ford and Georgia Tech will be testing the concept under real-world conditions. The outcome of those tests will help determine if the concept is feasible as a production vehicle.