The approach most cities take toward electric car charging can charitably be described as helter-skelter. With little data on where and when people need to juice their jalopies, local governments and businesses have spent millions of dollars to install chargers in the hope that if they build it, drivers will come.
And so in California, where Tesla Motors' Model S electric sports sedan outsells high-end Mercedes and BMWs, you might find chargers at a random Whole Foods in Berkeley, a cluster of them in San Francisco's financial district, or in places scattered around Santa Monica. Deploying charging stations typically involves navigating layers of bureaucratic red tape, dealing with the local utility company, and persuading business owners to hand over a piece of their real estate. It's a tough business — witness the bankruptcy last year of Ecotality, one of the biggest electric charging companies in the United States.
But what if instead of luring drivers to chargers, you could bring the chargers to the drivers? And make them solar-powered to boot?
That's the idea behind the portable solar-powered parking space invented by Envision Solar out of San Diego. Called the EV ARC, the 9-by-16-foot structure fits on the back of a flatbed truck for delivery. It consists of a parking pad and a canopy of solar panels that charge a 21.6 kilowatt-hour battery. No power grid, construction, or permits needed. The big idea: Municipalities and businesses will buy the solar chargers and set them in parking spaces on city streets, parking lots and at retailers, moving them around as needed.
"You can deploy this thing in five minutes," says Desmond Wheatley, Envision's chief executive, standing by an EV ARC he brought to an electric car conference in Palo Alto, California, in April. "There's zero environmental impact, and you pick this thing up and move it and you'll never know it's been there. At the end of the day, is it better to drive on sunshine or grid-powered electricity?"
Envision's vision of a network of off-the-grid solar charging stations taps into a nascent trend. Installations of solar panels are exploding — the U.S. brought online 4,751 megawatts of photovoltaic power in 2013 alone, which accounted for nearly a third of new electricity capacity that year. For homeowners, using their solar arrays to charge their battery-powered cars with carbon-free electricity maximizes their investment in both. (Envision also makes "solar trees" with grid-connected chargers built into their trunks, which have been deployed around the U.S.)
"We know from the studies we've done that people really link together solar charging and electric vehicles," says Daniel Sperling, director of the Institute of Transportation Studies at the University of California, Davis. "You couple electric cars with solar and it's really a very compelling combination that sends all the right signals about the environment and energy independence."
"Economically it doesn't pencil out, given the high price of solar," he adds. "But if you put a standalone solar charger in a parking lot, a retail establishment or a workplace or somewhere it's going to be used during the day, it probably makes sense insofar as solar charging makes sense."
The EV ARC itself costs as much as an electric car — $40,000, according to Wheatley — though subsidies can cut the price in half.
But as the cost of solar-generated electricity continues to fall, companies like SolarCity, one of the largest U.S. residential solar installers, have been putting electric chargers in customers' garages. And now SolarCity is offering some customers a Tesla Motors 10-kilowatt-hour lithium battery pack along with solar panels for their roof. The battery — a smaller version of the one that powers the Model S — stores electricity generated by the rooftop array to charge a car or provide for power the house at night or during a blackout.
In March, Honda unveiled the Honda Smart Home, a prototype of a dwelling with an oversized solar array that stores electricity in a version of the lithium-ion battery that powers the Honda Fit electric car that's parked in the garage.
And in January Ford took the wraps off a prototype of its own off-the-grid solar charging system that could be deployed at homes, corporate campuses, or in cities. A cheap and lightweight solar canopy features a roof made of plastic Fresnel lenses. The lenses concentrate sunlight on 16-square-feet of solar panels that are built into the roof of Ford's C-Max Energi plug-in hybrid hatchback. That boosts electricity production to charge the car's lithium-ion battery.
Still, solar street charging has its limitations.
Depending on the configuration, Envision's EV ARCs solar panels will generate 2.3 kilowatt-hours or 3.1 kilowatt-hours of electricity to charge the battery. That's enough energy to add 60 to 90 miles a day to a battery's capacity — as long as the sun's shining. A conventional grid-connected charger, of course, can supply electricity 24/7.
But portability may be solar charging's biggest advantage as electric car technology evolves. The way grid-connected chargers have been deployed reflects the fact that most electric cars currently can travel only about 75 miles on a charge, and that drivers need to charge frequently. But as that range inevitably grow with improvements in batteries in the years ahead, many of those fixed charging stations will probably be rendered as superfluous as a pay phone. A portable solar charger like the EV ARC, on the other hand, can be redeployed as charging habits change and drivers increasingly just need to top off their batteries.
So far Envision has sold the EV ARC to corporate customers and for trial runs in places like the San Diego airport. "We want to create the first ubiquitous urban electric charging infrastructure powered by solar, so people can drive around a city on nothing but sunshine," says Wheatley.
Images courtesy Envision Solar.