Automobiles powered by electricity or EVs — including plug–in hybrid gasoline–electric cars like the Ford C-MAX Energi and fully electric cars like the Nissan Leaf — are still a tiny fraction of the automobiles now on roads in the U.S. and around the world, and they are expected to remain such for a long time. But as their numbers grow and their owners plug them in, keeping EVs fully charged with power from “the grid” (power plants and their distribution infrastructures) could pose a challenge to electricity suppliers.
So, Ford Motor Co. and its research partners have devised a new way to fully charge an EV without tapping the grid: using a parking spot setup that mates a special sunlight–enhancing canopy with both a solar panel on the vehicle’s roof and the vehicle’s built–in automated driving capability. It’s the first setup of its kind in the world, Ford says, and it will be on display for the first time this week, at Ford’s booth at the International CES technology trade show in Las Vegas.
The display will include Ford’s solar–panel–equipped C–MAX Energi plug–in hybrid research car — formally named C–MAX Solar Energi Concept — and a miniature version of the canopy, because the full–sized canopy is too large to fit in the booth, said David McCreadie, manager of electrical vehicle infrastructure and smart grid at Ford in Dearborn, Mich.
However, the Solar Energi Concept and its accompanying technologies are still in the early stages of development, requiring more testing, and are not likely to be commercialized any time soon, McCreadie said.
The Challenge of EV Charging
According to Polk, a global market intelligence firm based in Southfield, Mich., as of last July, fully electric vehicles composed just 0.3 percent of the total U.S. automobile market. Hybrid gasoline–electric vehicles, counted separately, held a three percent market share. Meanwhile, traditional gasoline powered vehicles accounted for 74 percent of the U.S. auto market.
By comparison, the car shopping website Edmunds.com forecast last year that EV sales would total just 0.4 percent of the U.S. auto market (only 55,000 vehicles) at the close of 2013, and predicted an increase to just 1.5 percent market share (250,000 vehicles) in 2017.
Yet, though the market share expectations remain low, electricity market analysts are paying close attention to the possible impact of EVs on the U.S. power grid.
“EVs represent the largest new electric load to appear in homes in a generation,” said Brewster McCracken, CEO of the Austin, Texas–based energy research firm Pecan Street Research Institute, in a report issued by the firm last October.
From June 1 through August 31, 2013, — peak summer demand months when air conditioners usually stress electric grids — Pecan Street analyzed data from more than 2,500 EV “vehicle charge events” by a random group of 30 participating households in Austin, where the firm believes EV ownership is the most concentrated in the nation. Their EVs comprised 21 Chevrolet Volts, nine Nissan Leafs and one Tesla Model S.
While the analysis showed that most of the households charged their vehicles during hours when overall electricity demand (and cost) was lowest, and therefore didn’t strain the grid, EVs still could pose a challenge to utilities elsewhere in the U.S., Pecan Street concluded in the report. “These findings suggest that this new load is not only manageable, but movable,” McCracken said. Nevertheless, the report found, “Even with these surprising findings, EVs’ impacts could prove more challenging for utilities in regions without significant air conditioning use. In those regions, utility distribution systems are frequently sized for homes with flatter and smaller electric use patterns. These systems could be stressed over a broader range of hours each day by new consumer products like EVs with high instantaneous electric draws.”
How Ford’s Solar Charging System Works
Ford’s C-MAX Solar Energi Concept takes EV charging off the grid, and was crafted to work in Raleigh, N.C., which Ford determined is an average U.S. city in terms of daily sunlight exposure. It should therefore also work fine in cloudy locales like Seattle, Wash., and sunny climes like Phoenix, Ariz., McCreadie said.
In place of the C–MAX Energi’s optional panoramic glass roof, Ford installed a 1.5 square meter solar panel that normally would not generate enough energy to fill the car’s 8 kilowatt–hour (kW–h) battery. But the accompanying acrylic canopy contains lenses that capture and funnel the equivalent of 15 to 20 square meters of solar energy to the car’s panel, McCreadie explained. “We have sized [it] appropriately so that the average U.S. area would be able to recharge the C-MAX Solar Energi battery over the course of a day,” he added.
To get that full charge, the car must remain parked under the canopy for six to eight hours. And during that time, of course, the rotation of the earth will change the position of the sun relative to the canopy and the car, moving the focal point of the sunlight. Therefore, a third element in the C–MAX Solar Energi Concept is autonomous driving technology built into the car. It keeps the car lined up with the sun by continuously repositioning the vehicle under the canopy throughout the day.
“We’ve charted out for different locations in the country and the different seasons what it would take to keep the car under the concentrator, and the vehicle is going to creep ever so slowly as time passes…to follow a path under the concentrator…on the order of several feet,” McCreadie said. And to accommodate all this movement, he said, the canopy is sized larger than a typical parking spot — approximately 14 feet wide by 17 feet long and 15 feet tall.
A “World’s First” Innovation
Ford is not the first automaker to install a solar panel on the roof of a car. Earlier, for example, boutique car maker Fisker Automotive featured the world’s largest automotive solar panel on the roof of its Karma extended–range EV (“EVer”), used to power the vehicle’s low–voltage electrical system.
Yet the C–MAX Solar Energi is the world’s first application of an automotive rooftop solar panel to fully charge a vehicle’s battery pack for propulsion, McCreadie said. He also said that Ford’s solar panel does not significantly add to the weight of the car, so its mileage is not degraded. Same as the C–MAX Energi plug–in hybrid, the C–MAX Solar Energi will go for 21 miles on battery power alone, have a total driving range of 620 miles, and match the plug–in hybrid’s 108 MPGe (miles per gallon equivalent) city and 92 MPGe highway EPA fuel economy ratings, he said.
In addition, Ford said its internal data show that up to 75 percent of all trips made by an average driver are within a 21 mile range, and thus the C–MAX Solar Energi would allow him to almost always drive solely on solar–generated power and rarely juice the car with power from the grid. (The C–MAX Solar Energi also has a charge port and can be charged by connecting it to a charging station with a power cord and plug.)
Not Ready for Commercialization
The solar panel used on the car was supplied by SunPower Corp., with which Ford has partnered on solar technology since 2011, and the Solar Energi Concept’s solar concentrator canopy was developed in collaboration with researchers at the Georgia Institute of Technology, but the intellectual property for the concept belongs entirely to Ford, McCreadie said.
Research began about a year ago, but much work remains to be done, and the concept is still a long way from coming to market in a production vehicle.
“We’ve not physically tested the concept yet. That will be happening after CES [and] details are still being developed,” McCreadie said, adding the work is now more an intellectual pursuit aimed at “advancing the public dialogue about how we can get to a greener transportation base off grid” than it is a commercial enterprise.