My Exploration Of The C-Max Solar Energi

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Originally published on Kompulsa.

At the North American International Auto Show (NAIAS/Detroit Auto Show), I saw many cars. However, I was curious about the Ford C-Max Solar Energi, due to the fact that it’s solar-powered and especially the fact that it seats a family.

Ford C-Max.
Ford C-Max.
Image Credit: Nicholas Brown / Kompulsa.

You may have seen solar-powered cars in the past, but they often seated only one person, and were very unusually shaped. To be fair to those cars, they were built for racing, and they traveled thousands of miles using only solar power. The C-Max Solar Energi got my attention because it can seat a family and has ample interior capacity. I sat in the front, stretched out my legs, and did the same in the back.

The concept of solar-powered cars has long been belittled due to the fact that solar panels only generate 100 to 443 watts per square meter (normally 100-200 watts). This, combined with the predominantly curved shape of cars makes it difficult to install enough solar panels in an aesthetically pleasing manner.

Ford equipped the C-Max with 300 watts of slightly curved solar panels on the roof. The solar panels follow the curves of the roof, and are dark, so they didn’t look much different from a sunroof until I peered closely at them. That’s good, considering the fact that some people have an issue with the appearance of solar panels.

Ford says that the solar panels actually cover a considerable portion of the vehicle’s power requirements. Is this possible? Let’s find out:

If the vehicle consumes an average of 250 Wh of electricity per mile, that translates to a daily power consumption of 7,500 Wh (7.5 kWh), based on the fact that the average American drives less than 30 miles per day.

Assuming a solar panel capacity factor of 30%, the solar panels would generate an average of 2.16 kWh per day, which is 28.8% of of the car’s power consumption. So this is a very helpful, lightweight range extender that isn’t affected by electricity prices, power outages, or the lack of charging infrastructure. If there is a shortage of range in a plugless region, the car can be parked and charged by the solar panel while the passengers shop or dine.

Sound off with your thoughts about the Ford C-Max Solar Energi in the comment section!

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Nicholas Brown

Has a keen interest in physics-intensive topics such as electricity generation, refrigeration and air conditioning technology, energy storage, and geography. His website is:

Nicholas Brown has 594 posts and counting. See all posts by Nicholas Brown

20 thoughts on “My Exploration Of The C-Max Solar Energi

  • The electric only range is 21 miles, and 28.8% of that is 6 miles. If I am going to be incentivized to park in the sun (and I am not going to enjoy a hot interior when I return), why not develop some quick-setup, flexible, photovoltaic canopy/car cover that could give the range more than a six mile boost? Or at least make it an option. On the flip side, what is the dollar value of those 6 miles? That would add up quickly over time, and I’ll bet the solar panels outlive the car by quite a few years.

    • Your math is off. 28.8% of 30 miles is 8.64 miles, which is the range the author is purporting can be 100% solar-powered per day. 8.64/21 = 41% of the 21 mile range being fully powered by the sun.
      Secondly, the car will not be as hot when parking in the sun, since a large portion of sunlight hitting it is now turned into potential energy in the battery, rather than heat in the car.

  • I think your 30% is a mite bit optimistic. Maybe if you park on the south side of a large white wall?

    In any case, this is a change I hope plugins are headed towards, a few extra E range miles (on sunny days), for those who can’t recharge. But, the economics will have to be made to work (i.e. it can’t cost much), a couple of more KWhr battery capacity would probably help more (but be much less sexy).

  • The concept may be a bit premature but would still be good PR for electric vehicles on the street. If in the future, ongoing research into harnessing the presently inaccessible infrared spectrum for solar cells bears out, then such a vehicle could see the majority of its local trip energy coming direct from the sun. Also, why not more solar panels on the hood? Wouldn’t this double the car’s solar PV?

  • While the technology has not matured to the point of being practical, I like the idea of having more than one energy source for powering a vehicle. Even the first ‘practical’ versions of solar powered vehicles will have limited use cases. Heck, when I return from a weekend snowboarding trip, traffic moves so slowly on the way back that a 30 minute drive there can take 3 hours on the return. And it’s dark, so the solar panels would not help. That is just one example where solar power would not work.

    This is a concept vehicle to show the promise of a technology, so I would not expect it to be something that could be used in the real world today, anyway.

  • Completely different vehicular category I realize . . . but the ELF pedal electric tricycle sports an enclosed driver’s cabin with a small solar panel on top. 8hrs in the sun fills the battery for a 20M trip with combined human power. This one’s actually on the market and doing fairly well in its niche.

  • Put it in production!

  • Some clarification on this that was left out of the article . . .

    The system was described in FAR greater detail here on CleanTechnica just a few weeks ago . . .

    Note that an automobile rooftop panel of this size would produce a paltry amount of electricity on it’s own. The rest of this C-MAX Solar Energi system (not even mentioned in this current article!) is a Fresnel lens concentrating system approximately 8 times the size of the panel on top of the car (think something along the lines of a carport-sized structure) to concentrate the light . . . and, unfortunately, a great deal of heat as well (which would not only make the interior of the car murderously hot, but completely kill the efficiency of the car’s rooftop PV panel in the process.)

    Further . . . for this thing to function as advertised, the car has to slowly move forwards or backwards underneath that lens structure to allow optimal solar exposure throughout the day. So, yeah, it’s another excuse to shoehorn a self-driving system into a vehicle that wouldn’t otherwise need one (I know that some people absolutely love the whole autonomous car thing, but I hope it never becomes a requirement for an automobile to be street legal.)

    Also . . . I guess you would need a relatively level driveway – oriented east/west – of about 2.5 times the length of the car for this system to work. So much for maximizing the efficiency of parking space sizes.

    And . . . where would you want to install such a Rube Goldberg contraption? If you work during daylight hours, that Fresnel lens structure does you absolutely no good at home, as it doesn’t produce electricity on its own and also doesn’t directly tie into the grid even when the specified panel-equipped car is parked underneath it. It’s basically burning holes in your driveway.

    Does anyone else here see how absolutely ridiculous this thing is? It’s bordering on lunacy! To call the C-MAX Solar Energi a “solar car” is also completely disingenuous. That automobile is basically a 2.5 ton range extender plug-in hybrid with a somewhat limited electric-only range and, in this particular iteration, with a rather bizarre and expensive solar toy thrown in.

    Here’s how to properly integrate solar PV with an EV, with stuff that’s already in production today and for a whole lot less money . . .

    1) Buy an EV or, alternately, a PHEV (and a “plain old” plug-in C-MAX Energi could be a viable candidate.)

    2) Install solar PV panels on you home’s rooftop – or build a dedicated carport – and tie those panels to the grid . . . maybe 5kW or just a bit more for a typical urban family dwelling. Whenever the sun is shining (while you and your EV are probably at work,) you are not only probably powering most or all of what’s being used in your house (climate control, food refrigerator, etc.) and selling the surplus to your electrical utility via a net metering agreement (and make sure your state’s utility commission isn’t going to take that privilege away from you anytime soon.) You can also be directly recharging your (PH)EV in the process if, in fact, you are employed with nighttime hours and your car is home with you during the day.

    3) Encourage your employer to provide at least enough standard 120V receptacles – or, better yet, dedicated 240V EVSEs with J1772 plugs – in their parking lot for all EV-driving employees and for projected growth in this regard. To put the icing on the cake, have them include grid-tied PV panels to shade these cars and provide some of the “juice” to whatever needs it at any given moment (either car or nearby building infrastructure.)

    4) Go ahead and install a rooftop PV panel onto your car, if you can afford it and want to make a green fashion statement. There’s nothing inherently wrong with doing that. But please also do some rudamentary math to determine – when configured to any street legal EV of conventional weight, aerodynamics and cargo/passenger hauling capability – that a panel with that sort of square footage is only going to give you a few (single digits) extra miles of driving range or provide a little bit of cabin heating/cooling prior to passenger/driver entry. In fact, I wouldn’t be surprised to find out that hauling around a reasonably efficient rooftop monocrystaline panel would add enough extra weight to offset any real gain.

  • Interesting that no one seems to have considered the stuck in traffic, crawling to work scenario.

    In that case, on a nice sunny morning, to or from work, the PV might give a nice amount of free energy to use on your commute. Especially since EVs show their efficiency over gas cars off much better in slow city traffic.

    When youre crawling along at the usual 5mph rush hour speed that PV on the roof is going to be powering quite a bit of that 5mph.

    • I guess a rooftop PV on top of an EV could be used in an “urban crawl” commuting scenario, Stefano. But that just reminds me – for as much as I’m a fan of electric cars – that even EVs minus tailpipe pollution are only a partial solution heading into a future when there are simple too many cars (of any power source) on our streets.

    • To: StefanoR99 and Benjamin:

      Here is a link both of you may enjoy. It deals with the actual amount of energy a typical vehicle needs to travel at different speeds. Be sure to scroll down the page to an article which talks about the 200 mpg car.

      Oh and traffic congestion – Google and others are well on there way to solving that problem with self driving cars. Cars of the future will be under the control of crash avoidance software driving 75 mph 8 feet from each other. No accidents and no traffic jams. At some future date the only time a real person will actually drive a cars is when they put it into the garage.

      Won’t that be fun 🙁

      • Ah, the self-driving car . . . an absolutely lovely idea, until some teenage terrorist hacks into the system one day and has them all drive off a suspension bridge, like lithium-powered lemmings on wheels.

        I hope to be able to buy an EV in the next year or so and will invariably choose one that’s affordable and with the least amount of associated gadgetry (the Mitsubishi i-MiEV is looking very good in this regard.) I’ve got to hurry, though, as I’m sure self-driving technology will be mandatory in new vehicles one day.

      • Yea.. and just what happens when one of these cars that are 8′ from each other have a blowout? You will have MASSIVE pileups.

        The DREAM of having cars 8′ from each other is just that – a dream – at least for the next 50 or so years.

        • My experience with blowouts is that you don’t stop as quickly as you can with four good tires.

          Since the following cars will have better stopping ability and will be informed of the problem instantly there should be no crashes.

          Probably you should read a bit more about autonomous systems and think it through a bit….

      • “Won’t that be fun :-(”

        Most of the fun of driving went away years ago. There just aren’t many places where one gets to do any fun driving. (I don’t count high speed weaving from lane to lane and blasting through yellow lights as ‘fun driving’. Nor do I get a thrill out of speeding through residential areas.)

        Bumper to bumper, stop and go? Not fun.

        Moving from red light to red light, from stop sign to stop sign in cities? Not fun.

        Driving the highways at ‘traffic speed’? Not fun.

        Driving a winding mountain road? Can be fun, but there’s so much traffic on many of them these days that the fun is largely gone. Unless you think crawling along behind a RV fun….

  • When I first read about this vehicle I thought to myself – this sure is a good research project for Ford. And to this day, I believe that this is what this vehicle is. It is a research project.

    The original concept I believe involved some non-movable fresnel light concentrating lenses and the vehicle self driving itself periodically during the day to keep the solar panel in the concentrated sunlight. This of course raised the power output of the panel. But even then with all of the complications this type of solar concentration brings and the technology involved, we are only talking a few miles at best.

    Of course that is with today’s solar panel technology which are on the order of about 15-20% efficient. There are however panels which are 30% efficient but those are not currently affordable for your daily driver. However, 40% panels are technically possible and not all that far off into our future. So again I believe Ford is just doing their homework so to speak.

    And 40% panels are just the beginning. Efficiencies could go even higher someday. In 10 years we might look back and say to ourselves, Ford was pretty darn smart to start studying this stuff. Ford was right, LOL.

    So would I go jump out and buy one. Well it all depends if I have money to play with which I don’t by the way. Where I live in the desert Southwest HEAT is our problem. If I park my car in the sun the steering wheel gets so hot you almost need gloves to drive but we don’t have snow to shovel in the winter, LOL. So to me it would make more sense to build a carport covered with solar panels which would serve two purposes. One it would provide shade for the vehicle and the other would be more plug in power for the vehicle.

    Does that make more sense than beaming concentrated sunlight onto the roof of a car. Well given today’s technology maybe that sounds just a little laughable but in five years Ford might be the one doing all the laughing. But if I had the money, sure, why not. It might give me enough juice to keep a small AC unit operating to keep the interior temperature of the vehicle down to say 90 F. That in itself would be worth an extra 10 grand assuming of course I had the extra 10 grand.

    But in the end, as I stated at the beginning of this posting, this is probably nothing more than a research project for Ford and I compliment them for looking forward to the future. Someday all of our vehicles will be powered by electrical energy.

    Have a great day everyone.

    • OK, fair enough, Tom. For the sake of future research, there could be something practical that comes out of all of this. I still take exception to how its presented in this article, though, were the entire other half of the C-MAX Solar Energi system – namely, that big Fresnel lens carport – isn’t even mentioned.

      I have met far too many people both on the web and in person, when talking about EVs and solar in the same sentance, having them declare that “all we’d have to do is put a solar panel on the roof of the vehicle and all the problems would be solved.” It simply isn’t that simple. I think you are aware of that as well. I wish it were otherwise.

      Automotive journalist Brock Yates coined a phrase a half a century ago in an attempt to explain in layman’s terms why a large displacement gasoline engine running with modest performance parameters was always better than a tiny one screaming to the verge of exploding – even if both measured the same in horsepower . . . “There’s no substitute for cubic inches.”

      I think that applies equally well to describe the performance of solar PV today and, perhaps, for many years to come.

      • Hi Benjamin:

        You are correct. Nothing is ever as simple as it first seems, LOL. Take energy for example. Currently we are using nuclear, coal, natural gas, hydro, hydro kinetic, biomass, waste to energy, geothermal and of course wind and solar and I probably forgot at least a couple more just to meet our current energy needs. While I certainly support the continued development of renewable energy sources; they are not currently capable of meeting all of our needs.

        My guess is that a balanced mix of different energy sources will be our best solution for a long time to come. Have a great day and thank you for the feedback.

      • Car manufacturers are not quite following the ‘no substitute for cubic inches’ philosophy anymore. The vast majority of them use four-cylinder engines, and turbocharging is already in use.

        I mentioned the solar concentrator in my previous C-Max Solar Energi article. The concentrator adds to the 300 watts that the rooftop panels already generate.

  • some how I think this is cool, maybe just because it should be integrated in every car…think about it…..

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