Let the Sunshine In: The Rise of Solar EV Charging

By · November 27, 2012

Westport solar charging

Pulling up to the solar pumps at the Westport, Connecticut railroad station. It's electric! And solar-powered, too. (Jim Motavalli photo)

If there’s such a thing as a plug-in paradise, it’s something like what I encountered at the the train station in Westport, Connecticut on a recent frosty Saturday morning. Not only was the parking lot abuzz with electric cars, including Teslas, Fiskers and Volts, but they were availing themselves of free electricity from a 27-kilowatt solar display mounted on the station’s roof.

The Solar Connection

Three years in the making, Westport’s solar solution is a model for other American towns and cities to follow. Charging takes four to eight hours at 240 volts, so it makes sense to plug cars in where they’re going to be parked for a while. And it also helps if that location is “intermodal,” meaning connected to another form of travel. Bikes to train stations make sense, and so do electric cars.

According to John Rountree, the solar architect who designed the system, "Though electric cars are clean and don’t emit carbon dioxide, if the energy being used to charge them is being produced by a dirty coal plant, then the environmental side effects are not really being eliminated,” Rountree said. “Solar makes sense because it emits no emissions."

Westport is a wealthy town, the home of man-in-a-gray-flannel-suit New York commuters. But in straitened times it didn’t want to simply buy the rooftop system. And so when a large state grant fell through it turned to a new and popular alternative—solar leasing. A company, in this case Encon/ECI, installs the system at its own cost, and reaps the benefits down the line.

According to town building official Stephen Smith, the driving force behind the plan, “We put out a request for proposals and Encon had the best response. They agreed to install the system and maintain it for 15 years, and in exchange the town agreed to purchase the electricity generated at a 30 percent discount.”

VIP Passes for EV Owners

There are four chargers now, but there will eventually be up to 20 well-located EV spots, set up to accommodate smaller commuter cars. The town is issuing special VIP passes for residents with battery vehicles, and snagging a prime parking space is bound to be an incentive for some people to go electric. It helps that both towns on either side of Westport also have EV charging convenient to the rail line. Though neither is solar yet, at least one of those towns is contemplating adding that component.

Solar charging for electric cars is an idea that just makes so much sense, and the leasing model is a way for cash-strapped communities to avoid out-of-pocket expenses. One big player SolarCity (headed by Elon Musk’s cousin, and with Elon heading the board), has recently not only added EV charging to its leasing model, but expanded operations to the East Coast. It’s great that there’s competition in this field.

SolarCity has installed more than 2,500 EV charging stations so far, including home units. "A rooftop solar energy system can enable you to drive completely emissions free while dramatically reducing your energy bills," the company says, adding that many utilities have special EV rates "that can help you pile on the savings."

Charging the Parking Lot

A company I watch closely is Envision Solar, which has made a specialty of solar charging in corporate parking lots and garages. Dell’s Texas headquarters is a big customer, and so are colleges such as the University of California at San Diego. I’ve visited the latter, and seen solar arrays smartly incorporated into the very accommodating structure of the garage’s flat roof. The system will work even better if it includes battery backup, so power generated during the day can be released at night.

GM's Solar Tracking Tree

GM's Solar Tracking Tree rotates with the sun to capture 25 percent more energy for charging EVs like these Volts. (GM photo)

General Motors is a big believer in charging its Volts on solar, and in September installed what Envision calls a Solar Tracking Tree at its Milford Proving Ground in Michigan. The “tree,” GM’s second, turns to track the sun during the day, increasing its efficiency by 25 percent. The new installation should generate 30,000 kilowatt hours of solar electricity annually, enough to charge six electric cars a day.

GM said it will double its global solar use by 2015, and increase renewable energy use to 125 megawatts by 2020.

High Energi, plus Solar Charging

Also preaching the gospel of solar EV charging is General Electric, which earlier this month announced that it is buying an additional 2,000 Ford C-Max Energi plug-in hybrids to complement its existing orders for 12,000 Volts. At its offices in Plainville, Connecticut, GE not only installed a huge 100-kilowatt solar array with charging for 13 EVs simultaneously, but also said it was getting into the business of selling such charging systems.

GE is partnering with Inovateus to offer complete solar EV chargers, scalable to different needs (from universities to office buildings and sports complexes). I’ve been to Plainville, and trust me on this—solar installations that can charge that many cars at once aren’t small. It’s not surprising they can double as carports. But GE thinks the business case is there.

Selling Cars With Sun Power

In Westport, I ran into a Connecticut Chevy dealer, Leo Karl, who has sold a very respectable 55 to 60 Chevrolet Volts—three of which were circling the parking lot giving test rides. “We’re continuing to see increasing sales momentum,” he said, pointing out lures like Westport’s solar charging (free so far) as incentives. He’s selling more Volts than Corvettes. Volt sales even top the Chevy Malibu, he said.

Greg Taylor, representing another high-toned local dealer that also sells Aston Martins, said that the Fisker Karma is moving briskly. “It’s such a fun car to drive, and a great environmental story,” he said, pointing to dashboard wood salvaged from California wildfires.

State Representative Jonathan Steinberg, whose brother was BMW’s electric vehicle guru, said that Westport’s solar installation is “in the vanguard of renewable energy innovation.” I’d agree with that. Let the sunshine in.


· · 5 years ago

I think I have convinced our landlord to do one of those solar leases on our house. The house has a really nice large gently sloped south facing roof with no trees blocking the sunlight. Since it is a rental, we can't install them and our landlord won't want to dump a lot of money into something which doesn't really help him save money. But the lease route works well, he can put in the lease and just add the lease cost to the price of rent. The cost of the lease is less than the electricity it saves, so renters come out ahead too... Win win!

· · 5 years ago

I also think any covered parking lot is a good candidate for solar. Lots of apartment complexes and whatnot have covered parking via simple carports. Those are nice surfaces which could have solar panels easily. In the southwest there are a good number of parking lots with carports to shade cars - they could also charge cars if set up to do so! Not only is juice generated by the solar but cars need less AC when kept in the shade - saving more energy...

· Jesse Gurr (not verified) · 5 years ago

What happened to the CNN fuel cell story?

· Anonymous (not verified) · 5 years ago

Jesse: CNN fuel cell story is here: http://plugincars.com/cnn-says-fuel-cells-will-compete-battery-powered-c...

· · 5 years ago

I'm guessing that standard 120 volt outlets are optimal for commuter rail systems since I can't imagine anyone driving a car to the station farther than can be charged in a normal day at 1.2 kW.
Assuming someone is parked for 8 hours, at 120volts, 15 Amps, one can get at least 30 miles of charge (lots of knockdowns for battery thermal control, cold weather, etc.). I suspect this is much farther than anyone drives to this commuter station.
It is a lot cheaper to install a lot of standard 120v outlets than Level 2 charging stations.

· Tom (not verified) · 5 years ago

Win win win

I love it also why not solar trickle or 240 v chargers
where one spends a few hours

Tesla is smart to partner with Solar city and offer the
Whole package so to speak

Ideally Ford GM would offer a $7500 option
You want lifetime fuel with that EV??

Go Solar

· · 5 years ago

Yeah, you could serve a lot more cars if they were all slow charging at 120 volts.

One nitpick I had for this otherwise nice story is this statement, "Charging takes four to eight hours at 240 volts, so it makes sense to plug cars in where they’re going to be parked for a while." My Nissan Leaf takes just three hours to charge at Level 2 for my average 30 miles per day, not four to eight hours. I think it only takes six hours on my Leaf to go from empty to 100%. I would think it rare for intermodal commuters to need anywhere near that much charging while away at work all day. Level 1 makes a lot more sense.

We have been solar charging our Leaf for the last two months and it does make me feel better about driving with truly zero emissions.

· · 5 years ago

I would think that old used batteries from leafs, etc could be used for storage with solar applications. Once those batteries get to 65-70% of useful life owners will want to change them but they will still have 16 kw of storage left in them.

· Spec (not verified) · 5 years ago

In California, the PV & EV mix works really well in-part because of the tiered rate structure. You start paying pretty high electricity rates after you hit the 3rd tier and those high rates make PV quite attractive.

· · 5 years ago

I remember an article here this past summer, showing the Solar Tree. Perhaps the fact eluded me at the time - or that particular article didn't clearly point it out - but I didn't realize then it was a dual axis tracker. Very neat.

Not directly pertaining to this article on solar EV charging, but somewhat "breaking" EV news that occurred today: Chevy has now officially taken the wraps off the dedicated Spark EV, with a very nicely cleaned-up front end . . .


Price appears to be somewhere between the Mitsubishi i and the Nissan Leaf: around $25K, assuming the full federal rebate is applicable.

I couldn't find anything in this particular article but most of the recent press releases I've read seem to indicate that liquid thermal management will be featured on the battery pack. Regular readers here already know that neither the i or the Leaf have this.

The Spark EV is also going to have the SAE AC-DC Combo plug. While the Smart ED will also have both liquid thermal management on the pack and the Combo plug, it will have just 2 seats for about the same price as the Spark EV's 4 seats.

· · 5 years ago

I did a rough calculation of how much solar PV it would take to run an EV 15,000 miles per year (the number of miles the EPA uses for it's annual cost estimates) and I compared it to the amount of land it would take to grow enough corn to make enough corn ethanol to fuel an E-85 vehicle. It takes about two acres of corn for the E-85 car and 24 square meters of PV for the EV. That's a ratio of about 350 to 1. This is just a ballpark number but.... WOW!!!

If we take into account the fertilizer used as well as fuel to plant and harvest the corn plus the energy to transport the corn and ferment the corn and distill etc... corn ethanol seems downright ridiculous compared to solar energy + EVs.

· David Martin (not verified) · 5 years ago

valkraider has it right.
People insist on installing solar where it ain't sunny.
A dual purpose sunshade/charger in hot places makes sense, and would prevent or reduce battery damage as well as, in those hot areas, reducing load on the grid when it is highest.
Use solar where it is sunny. Doh!

· · 5 years ago

@smithjim1961: that's because plants are roughly 1% efficient at converting light to energy, vs above-10% for PV cells; and then the corn to ethanol conversion loses a whole lot more (in fact, even in the best case it loses at least half the available energy, and most of the time it loses most of it).

At one point I was considering building a house in southern Arizona, and solar PV there makes so much sense it's weird that not everyone has it.

· · 5 years ago

It's great to see this Westport, Conn. solar EV setup is now online :-) Others have already pointed it out, but it's worth re-noting:

-- Solar + EV makes a ton of sense in so many different situations and for so many different people (though not for all of them)

-- Nowhere does solar + EV make more sense than the vast blacktop parking areas of the U.S. where: a) cars cluster; b) where people fight like crazy for shaded spots; c) where EVs could fill up on sun in a place that they're going to sit for hours and hours at a time anyway.

Wish more people got the latter point. Even the solar industry and solar advocates don't seem to really truly get this point, preferring, in many cases, to build giant solar farms in often ecological delicate places far away from urban centers to covering America's parking lots with solar-EV canopies. I guess the latter approach just makes too much sense for it to make sense to the big guys...

· · 5 years ago

I've often wondered why not give the option to integrate solar directly on the entirety of the car's roof and hood. Sure it's a trickle even compared to level 1 charging, but it's not meant to replace regular charging, only to supplement the charge. Besides it would trickle all the daylight hours provided the car is outdoors, whether the car is parked or moving.

· · 5 years ago


Wow indeed! I knew it was a big difference, but those are some telling numbers.

You are, however, forgetting about a key component which makes it all the more compelling - the ethanol requires 2 acres of arable land. The PV, on the other hand, can be installed over parking lots (and Christof points out) or, more commonly, on rooftops of existing buildings. In either case, the PV requires "zero" land area (because that land is already claimed - you're just increasing its utility). The ethanol now requires infinitely more land than the PV, and the land subtracts from open spaces and/or farm land.

· · 5 years ago

@Jose G,

Short answer - PVs aren't cheap. You get a much better bang for your buck by simply installing them on your garage and using a grid-tied system. Covering an entire car with PVs will only net you a mile or two on an average day, so it doesn't meaningfully contribute to your "autonomous range".

· · 5 years ago

I do realize PV isn't cheap, I was suggesting it as an option, let run some numbers:
My calculations are closer to 3-4 miles / day, which adds up to 1200 miles / year:

Using: 20kwh / sq.ft per year
= 0.05 kwh / sq ft per day
@3.5 miles / kwh
= 0.175 miles / sq ft per day

I have to measure the exact number here, but assuming:
20 sq ft available = 3.5 miles / day

Back to 20kwh per year * 20 sq ft = 400kwh per year ... or about $40 / year @ $0.10 / kwh.

Ok, for an option that would likely be $2000 or more, probably doesn't make financial sense to integrate (yet).

But there is a cool "you're never completely stranded" factor to it.

· · 5 years ago

Jose G,
You're probably assuming an optimal pointing toward the sun so you probably need to knock down another 50% for sub-optimal pointing unless you have a wedge shaped car (or tilted parking space) that you'll always point at the sun.
$2K is a bit low for the panels since you'll need to integrate them into the body or the aero drag will be a big hit. I'd guess 4 to 5K extra at a minimum.
1 or 2 miles per day might be right.
I've seen golf carts as several military bases with solar canopies on them that do allow them to do daily errands around the flightline without having to plug in regularly so it does work. Golf carts don't have to worry about aero drag so their costs probably come closer to your estimates.
I guess it will work but I'm not sure it is worth it.

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