Vecna CTO Builds Solar-Powered Volkswagen Bus—And it Actually Works

Xconomy Boston — 

Trying to run an electric car from solar cells on the car’s roof makes no sense—or so I thought. Earlier this week, I met with Daniel Theobald, the CTO of healthcare company Vecna, who has been driving a solar-powered Volkswagen bus for a year.

His project won’t transform the auto industry overnight. But by taking on what most engineers would consider foolishly ambitious—a solar-powered car—he’s created a proof of concept that could lead to commercial solar vehicles, at least for some uses. In the process, he and his colleagues have created power electronics technology that could be applied to other products for Cambridge, MA-based Vecna, including its delivery robots for hospitals.

Certainly, combining solar power and electric vehicles isn’t new. Many EV owners have rooftop panels on the homes. And some Toyota Prius models are equipped with solar cells embedded into the roof, which power a fan to cool the car. But making car-attached panels serve as the primary energy source is very hard. The big challenge is that on-board panels put out a tiny amount of juice compared to the power a car needs to run.

Theobald was also under the impression that a solar-powered car was essentially impossible. But he wanted an electric or hybrid car that could transport his large family, so he decided to challenge his assumptions and see where it would lead. He bought a 1966 Volkswagen minibus off Craigslist, converted it to electric power (in an afternoon), and started reengineering the vehicle for solar.

His conclusion: “You can have a practical vehicle that runs completely on solar.”

Vecna1-1

Photos: Martin LaMonica

To be sure, the VW bus looks funny—there are ten solar panels affixed to its roof, some of which hang over the front and back. The cost of the vehicle and equipment, including very efficient, but pricey, solar panels is about $30,000. Driving on solar also restricts his range to about 20 miles if there’s no sun.

But in taking on the challenge, Theobald and other Vecna engineers working on the project have created technology they’re seeking to patent, which could lead to new business opportunities. For example, airport service vehicles are outside for long periods of time and don’t need to go long distances. This is a situation in which having a solar-powered vehicle—one that wouldn’t necessarily need to be charged by plugging in—could make sense, Theobold says.

“Making practical solar vehicles is something most people wrote off so in many ways, it’s a fairly unexplored problem,” he says. “But there are a lot of applications where solar-powered vehicles make a ton of sense.”

There’s some crossover with Vecna’s current business, too. Engineers are now working to outfit the bus with a lithium-ion battery, which will be used in Vecna’s healthcare robots.

Vecna1-1-2

Optimizing for the Solar+Mobility

Engineering-wise, Theobald’s project uncovered some conventions that make solar-powered passenger cars such a tough challenge. For example, the electronic components normally used in electric cars, such as the battery packs, are not optimized for the voltage that solar panels put out. Also, a significant portion of energy is lost in charging and discharging a battery, but that can be minimized.

In early tests, Vecna engineers tried to have the bus run directly off the solar panels, rather than charge the battery and run off the stored energy. Powering a car largely from solar panels limits the acceleration significantly, but it can be done in city driving, they found. Driving the car at highway speeds (it can go 80 miles per hour) requires much more power than what the panels can generate in full sun.

Vecna1Theobald also found that the topography of a given route makes a huge difference. Driving up a big hill to bring his kids to school would kill his battery, but taking a slightly longer yet flatter route used about one-quarter of the energy. “This idea of being aware of the energy as we travel is going to become much more relevant as we start using electric vehicles,” he says.

The solar-powered bus also uses a number of tricks to lighten the weight and reduce aerodynamic drag, such as using thin tires and lightweight wheels and bumpers.

With more tinkering, the energy use and efficiency can be optimized further, Theobald says. For example, the lithium-ion batteries are lighter and last longer than their lead-acid cousins now installed.

Another possibility is to use batteries in conjunction with ultracapacitors, a type of storage device that can very quickly discharge power to accelerate a car, for example. Engineers are also trying to find lighter-weight versions of some of the electrical components, such as the motor and battery charger, by converting products used in other industries.

Theobald’s ride certainly won’t work for everyone—even with solar charging, the car has a range of about 30 miles. But he’s made something that electric car enthusiasts could only dream about: an electric car that rarely needs to be plugged in.

“Given my normal driving, I don’t need to charge it all—the sun gives me all the energy. It’s incredibly convenient. As long as I’m not parking under a tree, I’m covered,” he says.

Updated on December 18 with a new price figure based on new information from Theobald. 

Vecna1-1-4

By posting a comment, you agree to our terms and conditions.

  • Z3grinch

    What a joke! This guy is a total hack. watch for a rebuttal comment from one of his minions to my post.

    • anytime

      I’d like to fight you, meet me at your girl friends house in the morning, I will be there overnight. Sincerely, your Dad

      • Guest

        I’ll bring the Champagne you bring the strawberries and chocolate.

    • yup

      Oxygen thief!

    • Troy Sparticus

      Nope. I guarantee he is no hack.

      He did this for fun.

  • Z3grinch

    This thing isn’t to code and not road safe. Watch out citizens of MA!

    • Minion1

      Bus passed all inspections, is completely up to code, and is totally
      road safe…but thanks for your concern! I hope this eases your
      anxiety.

    • Helicoptermike

      Shhhhut it! ;)

  • disqus_Lzp2BYTDVb

    another of the many things that just make the hard working employees shake our heads, sigh, image above all always

    • Troy Sparticus

      This ended up a side project with a few people at work involved just to see if they could make it work.

      There were no employees involved.

    • se51937

      hahahahahaha that’s hilarious.anybody who knows him knows that image is the last thing hes worrying about.

  • Ron Winton

    Here’s an advanced solar technology will change the way that EV owners will charge their vehicles. It’s called Hyper X 2 and it uses bifacial (double sided solar cells) for extra power production and a very high, up to 21.5% module efficiency.

    This advanced technology has been around for the past 6 years but it was always considered to be far too expensive to install. Now because of new technological advances Hyper X 2 Bifacial solar panels can be purchased at a much lower cost than many standard single sided solar panels.

    Instead of boxy looking 1 1/2 to 2 inch thick framed Gen 1 solar panels, these new higher performance Gen 2 solar panels are only 1/4 inch thin and are made with a stronger, see through, glass on glass, frameless, construction that allows sunlight to pass through and reflect off the roof’s surface, thus illuminating the backside of the double sided solar cells, producing additional power.

    The new 300 Watt, 60 cell solar panels that are used in Hyper X 2 solar systems offers a better PTC to STC ratio “Real World” performance according to the California Energy Commission’s performance rating listings than over 119 of SunPower’s solar panel models.

    And they offer a very high 94.3% PTC to STC performance ratio. They also offer a heat resistant -0.31%/degree C temperature coefficient for better performance in warm/hot climates. And when it comes to aesthetics, nothing even comes close to Hyper X 2’s panel’s glass on glass, see through, frameless construction.

    With N-type mono-crystalline bifacial cells for double sided power production, up to a 21.5% efficiency rating, superior aesthetics, and a price that outcompetes the solar lease and PPA company’s offerings, very few products on the market compares to Hyper X 2 Solar. http://vimeo.com/111960877

  • Guest

    Bus passed all inspections, is completely up to code, and is totally road safe…but thanks for your concern! I hope this eases your anxiety.

  • se51937

    hahahahahaha that’s hilarious.anybody who knows him knows that image is the last thing hes worrying about.

  • Max Rosenblum

    Those mags look custom milled. Gorges

  • Helicoptermike

    I absolutely love it ! Thanks ! :)