If you’ve ever seen a solar powered car, it was probably a SunRaycer or something like it - a sleek vehicle that carries a driver with no passengers. Ford hopes to change that with their new concept car: the C-MAX Energi. A car powered entirely by the sun is the ultimate zero-emission vehicle, and while Ford’s new model serves as a proof of concept, it would require optimal conditions for it to be a practical zero-emission car.
First, let’s clarify something: the C-MAX Energi is a hybrid vehicle with a 300 Watt solar array on its roof. By itself, the panels won’t provide nearly enough energy to move the car. Instead, the solar panels help recharge the CMAX Energi’s 7.6 kWh Li-ion battery bank. Running only on electricity, the car has a feeble range of 21 miles (34 km). Now you know why they included a gasoline engine. Let’s do the math. On a bright sunny day, between 10AM and 2PM (peak sun), the solar array will generate about one kWh, less than one-seventh of the total battery capacity. In other words, in one day the panels will charge the batteries enough to provide about 3 miles of driving range. To recharge the car in a more reasonable timespan, you can plug it into a standard 120V outlet for 7 hours, or use a 240V charging station to charge it in 3 hours.
In order to improve the solar charging time, Ford proposes a canopy made of Fresnel lenses. The lens concentrates the sunlight onto the panel, allowing it to produce much more energy. Watch the video to see how it will work:
I’m not sure how they intend to make the car move during the charging process, but movement requires energy, even though the distance is small. A bigger issue to me is the fact that concentrating sunlight also concentrates heat. I’d hate to be an ant on the roof of that car.
Like I said, it’s a proof of concept more than a pragmatic solution. In my opinion, a more practical vehicle would be fully electric. Dump the gasoline engine and replace its weight and cost with a much larger battery bank, increasing the range. Instead of a Fresnel lens canopy with panels on the roof, use a solar canopy to charge the car and keep it cool at the same time. Newer batteries can be quick charged, eliminating the need for a gasoline engine in most applications.
On the positive side, the CMAX Energi offers better fuel economy (about 100 mpg, or 160 km/gal) than a Toyota Prius, so it does have that going for it. Essentially it’s a hybrid vehicle that gets really good gas mileage. It’ll need that improved fuel efficiency, since the electric motor and batteries won’t give it much additional distance.
Putting photovoltaic panels on a car won’t provide a significant amount of energy until panels are much more efficient than they are today. I think we’d be better off developing an electric vehicle charging infrastructure and more PV farms to generate the electricity. The CMAX Energi sounds like a good idea, but unfortunately it doesn't go the distance.
Image and video: Ford