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Monday, July 14, 2008

Does Car-Mounted Solar Make Sense?

Continued from page 1

By Peter Fairley
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Even that limited improvement comes at considerable cost. Solar Electrical Vehicles sells its panels for $3,500, whereas NREL could have beefed up its lithium battery to draw another kilowatt-hour from the grid for just $1,000.

Markel notes, however, that Solar Electrical is producing at very low volumes--just two to three systems per day, according to company president Greg Johanson. Economies of scale could sharply lower the system's price. Markel says that optimizing the electronic interface between the solar panel and the hybrid batteries could also boost performance. "The electronics are going to be key," he says. "I know their systems are not designed specifically for the application, so they probably are not the most efficient approach."

The other rooftop solar panel on the market, from Solar Electrical competitor Solatec, operates exactly as Nikkei said that Toyota's would: rather than charging the hybrid-system battery, it charges the lead-acid auxiliary battery that drives the Prius's air conditioner, radio, and other peripherals. Solatec's current system provides just 24 watts and costs $1,650 uninstalled--less than half as much as Solar Electrical's. The lower price and output are both a by-product of the less-powerful thin-film solar cells that the system employs.

Unsatisfied with the visual appeal of the flexible amorphous-silicon panels that the company has been using since 2005, Solatec president Howard Fuller says that the company is now testing a prototype for its next-generation product using printed cells from plastic-photovoltaics developer Konarka Technologies. "Konarka puts out a gorgeous panel," gushes Fuller. "It looks like a couple of racing stripes up there on the roof."

Experts such as Frank and Markel say that building large, stationary solar installations to generate the power to charge electric vehicles will be more cost effective than installing solar onboard. "We want to see sunshine drive the entire society, including our transportation," says Frank. That, he says, will require megawatts of energy. "The ultimate would be to have all shopping centers and industrial parking lots with solar arrays on top. It gives you a little shade and at the same time is charging your car."

Frank says that, even if onboard solar is a marketing gimmick, it could advance the electrification of transportation by advertising the possibility of replacing gasoline with renewable energy. "Whether it's perception or real doesn't matter," he says, "because it creates public awareness."
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Comments

  • Flawed Comparisons
    gabrielg01 on 07/14/2008 at 10:07 AM
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    Comparing budding technologies to fully developed ones is unfair, and above all misleading.

    There are many historical examples for this. Watt's first steam locomotive could barely keep up with horse drawn rail carriages. And the first internal combustion cars were more like a joke, than a real transportation technology. So on, and so forth...

    If you don't see the historical perspective, you may be missing the whole point. Solar panels and battery technology will get much better, and electric cars will be ubiquitous.
    Rate this comment: 12345
    • Re: Flawed Comparisons
      robin26 on 07/15/2008 at 2:00 PM
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      Solar panels will continue to improve, but the sun isn't expected to get a lot brighter anytime soon.  Car-mounted solar cells are constrained by the size of the car.  Sunlight, offering us on a good day perhaps 1.4kW per square meter, can provide such automotive solar cells only a small fraction of the power required to satisfy modern drivers' expectations for performance and features. 

      However, if lots of people are willing to purchase cars that won't go above, say, 10 miles per hour, and that are not air conditioned, then an exclusively solar-powered, 'on-demand' automobile could be feasible. 

      What about a 1 square meter solar cell canopy on a motorized bicycle?  This could be a vehicle useful to some commuters and tourists... especially if the canopy can fold away for parking or storage!
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    • Re: Flawed Comparisons
      Kevin Bullis on 07/15/2008 at 4:49 PM      		 Technology Review TR Staff
      Nanotechnology and Materials Science Editor
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      No matter how good solar panels get, putting them on a house or carport rather than on a car may be the best way to go. NREL has another plug-in hybrid / solar project along those lines. See http://denver.bizjournals.com/denver/stories/2007/10/22/story17.html

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      • Come on people...
        msreid on 07/15/2008 at 5:53 PM
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        Let's be honest, no matter how much efficiency we try to put into a vehicle, there is nothing we can do that will compare to simply driving less and consuming less.

        In terms of sheer energy use, planning ahead to only drive to the store once a week rather than twice a week will have far more of an impact than solar or anything else on our vehicles.

        Purchasing fewer consumer goods will have a much greater impact on our overall world energy use than "enviro-pimpin" our vehicles.  Think of just 1 consumer electronics product.  Think of all the raw materials, energy, manpower, transportation, etc. that goes into just one consumer product. 

        Do any of us really think we're going to offset all that energy use by putting a few watts of solar on our cars, or using regenerative suspension systems, or any other car tweaking?  Come on.  The best answer is always the most simple:  Buy and use less stuff, and drive less often to get it.  You won't ever beat that out if you're trying to save energy.
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      • Re: Flawed Comparisons
        johnalphonse on 07/15/2008 at 8:35 PM
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        i think it's a good thing, carports and all, but not the only or best solution.  those who'd like to drive across the country and be independent of needing to "find" a certain location would be free to do so in a self-charging vehicle which is in essence a portable design solution offering unparalleled freedom of movement.  that's a future i want to see, with more freedom than the gas pump or any "station" can provide; that's real progress.
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      • Re: Flawed Comparisons
        drash on 07/16/2008 at 7:11 AM
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        Well anybody who has driven a Prius for a while as I have (4+ years) can tell you anything to cut down on the use of accessories will lead to increased gas mileage.

        A practical use of Solar on a car would not only be useful for driving venting systems but how about utilizing electrochromatic window shades that automatically come on when you lock the doors?  This will keep out a lot of the Sun and prying eyes all at the same time.  Theft detterent systems that could even email you if something happens.  Heck I'd be delighted with electric seat warmers for those particularly cold days or window defrosters so you'd have clear windows when you get in.  It could even help with driving lights and heater fans while the car is running.  Lot's of possibilites, particularly if Toyota left an open plug in the car, so car accessory makers can also come up with ideas.
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    • Re: Flawed Comparisons
      TogetherinParis on 09/29/2008 at 11:57 PM
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      Battery technology will become cheaper with production efficiencies, but the consensus of opinion is that it will not become much better. 
      Charging technology, however, can improve vastly.  Once charging on the go is perfected (via Tesla coils?), batteries may not even be necessary to drive on the road network.  Carrying electricity for fuel in batteries is inefficient anyway.  Electricity is cheaply distributed, and lines follow major roadways already.
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  • grid-less will be the one
    johnalphonse on 07/14/2008 at 10:22 AM
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    of course a plug-in developer is going to downplay an energy source that can bypass the grid.  it may be less efficient today but it's most definitely moving in this direction of energy-sans-grid.  the grid system is flawed and illusory to some extent because the pollution is just being produced at another location, albeit reduced but not nearly eliminated like with solar.

    when the solar arrays cover the ENTIRE car, and are indeed a movable array embedded beneath a clear surface (think "fish scales" or sequins) where perhaps you can actually change the color of the car if you want (at least at night!), this issue of lack of generation will disappear.

    and to get you thinking of the potential(s): wind generation from propellers in the front grill can harness this energy source simultaneously...

    add to this the ability to suck solar energy out of the black, heat-absorbing road surface through your tires and you're talking high-performance solar!  this dream will become real, soon enough.
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    • Re: grid-less will be the one
      mightybob on 07/14/2008 at 3:20 PM
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      "and to get you thinking of the potential(s): wind generation from propellers in the front grill can harness this energy source simultaneously."

      you seem to be ignoring the laws of energy with that one.  the wind you feel coming through the window in the car is mostly from your own forward momentum. probably wouldn't be getting much energy out of that, it would more the likely just add drag and make things worse.

      I really like the fish scale idea though, maybe with nano optics so they don't even have to actively track the sun.
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      • Re: grid-less will be the one
        johnalphonse on 07/15/2008 at 10:09 AM
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        sorry, apparently i wasn't clear that the wind generation would be at speed, when power demands are at their highest.  a steady 60 mph would produce a measurable wind-energy effect, as would even much less speed.  certainly i'm not suggesting they generate power in the inertial state.  the regenerating energy of braking doesn't work when you are standing still, either, but it appears to have created a significant enough advantage at speed to incorporate it into the Toyota design.  if braking energy can be significant enough to manufacture into a design, it's a no-brainer that solar and wind are can-do technologies for electric car battery recharging. This site: <http://hymini.net> is talking about bicycles and even walking being used for small-device charging; six or eight of these in an ultra-high-speed, minimum-drag design in your front grill - or perhaps better still (or additionally) as a rear spoiler - is not against any laws of energy at practically any speed at all: cars are heavy, a front grill is solid and non-areodaynamic as is.  also, think of the engine cooling going on at speed if these air intakes are channeled strategically.  so, solar charges you at rest and on the move; wind assists in the task when you increase your momentum and can maybe help achieve a lower operating temperature.

        true, a multi-directional solar collecting nano-cell may eliminate any need for moving parts there, and it's definitely a more practical approach especially at speed, considering auto body aerodynamics.
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        • Re: grid-less will be the one
          GaryB on 07/20/2008 at 9:52 PM
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          The car spends energy to move and it's movement produces the apparent wind (in still air, lets say going 60mph = 60mph apparent wind).  Any attempt to harness this apparent wind will be at less than 100% efficiency (even before we consider the extra weight of the turbine) at harvesting the wind the car itself spent energy creating.

          So, you're always better off trying to make the car more aerodynamic than to trying to harvest the movement induced wind.

          On the other hand, solar panels make great sense to run cooling systems on the car in hot sunny weather or to charge batteries to run accessories. Especially nice would be an air conditioner run off of solar when you have to leave your car in a hot sunny parking lot. But there's too little area on the car for solar to actually charge or run normal sized consumer cars.
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  • I see it as a luxury item....
    GreenPlease on 07/14/2008 at 10:41 AM
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    There are lots of add ons that don't make sense in cars. I don't see why a solar roof should be subjected to such scrutiny. $3K is steep but if it was ~$1,200 I'd pop for it.

    I live in Florida where it is ALWAYS hot and NO parking lots have shade. Ironic, when I lived in Chicago where it is frequently cold, there was almost always shade.

    Anyways, if I kept the car 4 years and paid $1200 for the solar system, and the solar system kept the car cool 300 days/year, I'd be paying $1/day not to sit in a scorching hot car.

    Totally worth it to me.
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    • Re: I see it as a luxury item....
      gabrielg01 on 07/14/2008 at 11:00 AM
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      So true! Many cars are loaded with junk technology, and few people question it. Do people really need 10 speakers with hundreds of watts of power? Are electric seats necessary?...

      At least a car with solar panels serves a higher purpose. Even non-hybrids could use the extra electricity.
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      • Re: I see it as a luxury item....
        Bruceahz on 07/14/2008 at 11:30 AM
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        the difference between other expensive options and this one is the nominal purpose of this option: to decrease fuel consumption.

        Other options are justified for safety, convenience, or creature comfort reasons. If I choose to spend $2000 on leather seats with heating and cooling, well, that's what it's worth to me.

        But the solar roof needs to be justified based on fuel saved and/or pollution reduced and at first blush it would appear that other approaches provide a better cost/benefit ratio.

        BTW: having a solar panel roof will not solve your hot car problem, but that's a different discussion.
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        • Re: I see it as a luxury item....
          johnalphonse on 07/14/2008 at 11:37 AM
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          why couldn't the energy be used to run your A/C and other gadgets?  the panels heat water quite well, why would they not be able to charge an auxiliary battery?
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        • Re: I see it as a luxury item....
          gabrielg01 on 07/14/2008 at 5:27 PM
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          Different people have different "nominal purposes". If you want to splurge $2k on leather seats, that is your choice. Other people want to splurge $2k on "environmentally pimping" their car, so it should be a commercially available option.
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    • Re: I see it as a luxury item....
      dbdet on 07/31/2008 at 4:35 AM
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      Let's have a reality check here. You point out that there is little shade at parking lots in FL.

      That is not only a problem in FL, but one that would easily be resolved simply by installing high-efficiency solar panels over the parking areas. These are much more efficient than the thin film projected in the article for use on cars, so they would create more energy for the same area.

      Not only would more energy be created in an on the spot local grid, into which you could plug your (elec./hybrid) car for recharging, the panels would also constantly create shade for your car, keeping it cool for your eventual return from shopping. Surplus energy could also be sold into the normal grid.

      But then, you would not be able to find a parking spot, because (elec./hybrid) car owners would want to shop nowhere else (wanting to recharge), while the owners of conventional cars would want the same, simply to steal the shade. The latter problem would create a new job at each solar parking lot, for an attendant to block entry for non-elec. cars.

      That might be an added incentive for conventional car owners to switch to (elec./hybrid) cars. At least in hot areas with lots of solar gain.

      dbd
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  • The Bigger Picture
    kenjstone on 07/14/2008 at 11:45 AM
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    There are a litany fo factors that make solar collectors viable on vehichles-not just to cool interiors.  Pre-heating engine blocks should prolong the life of engines and batteries even in your warmer climates.  Two per cent savings here, one and a half there add up to real change. 
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  • Makes no Sense
    mkogrady on 07/14/2008 at 11:56 AM
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    PV on the roof top? Maybe for charging your cell phone, of trickle charging hte car battery if it's dead.

    Also run it through the car wash 70 or 80 times to see if the device fails, gets scrubbed off etc.

    Roof top PV makes sense in an RV - maybe!
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    • Re: Makes no Sense
      johnalphonse on 07/14/2008 at 5:38 PM
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      if you have wasted that much water driving thru a car wash 80 times, i wonder if this solar benefit is relevant at all to a person such as this.  you don't run delicate graphic work on a mug thru the dishwasher.  i don't think it's too much to wash your car by hand if you aren't satisfied enough with the job mother nature's latest downpour does...  again, marginal sized solar panels can heat water to the point it will scald a person: this is not an insignificant amount of energy being produced here; i believe it's a true, viable option in our very near future and there's no reason to stop at the roof for mounting solar panels...
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  • I still say it's a luxury item...
    GreenPlease on 07/14/2008 at 12:47 PM
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    If my solar roof runs my AC while I'm away from my car, would it not keep it cool? I see that as a luxury item and, IMO, it would be worth more to me than leather/power seats and it would certainly be worth more than a sunroof. Mind you, I'm not a complete green freak. I drive a BMW....

    I've always felt that solar panels on the top of semi trucks would make sense. They could be used to charge the battery, run a heat pump, and run any auxiliary components. This would help reduce drag on the engine and improve fuel economy.
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  • Trains?
    brewvies on 07/14/2008 at 4:51 PM
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    Would solar make sense on the top of train freight cars?  There is a lot more space and I believe that modern trains are run on electricity produced by burning diesel, which is neither cheap nor clean.
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  • Why kilobucks for <100W?
    powdermilk on 07/14/2008 at 6:23 PM
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    With no experience whatsoever and using retail parts, I built a simple 100W peak photoelectric system for less than $1000, including the cost of the solar panel, a sine-wave inverter and a deep-cycle battery, the last two of which wouldn't even be needed in this case.   While I can believe that's what the add-ons mentioned in the article retailed for,  I suspect the vast majority of that price was pure profit.   When I see a ridiculous price for something, my first thought is, "they obviously don't actually want to sell any, just be able to say they offer it."
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  • yes and no
    levialanm on 07/14/2008 at 6:53 PM
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    Solar panels are currently very expensive as a generating source.  If you're going to buy a solar panel, you might as well do grid-tied because you get much better efficiency:
    * better angle relative to the sun (as stated in article)
    * ability to capture the power 100% of the time.  When your solar prius is parked at the mall, you might already have a fully-charged battery so you waste some energy production.
    * the solar panels on the car increase the weight and other physical characteristics of the car and therefore negatively affect overall efficiency.
    * Cost of panels and of installation per watt of production will be much higher on a car than it will be in other simpler applications (e.g. roof-top).

    Another point: it might actually be desirable to have a solar car because you can increase the range of the car, especially if you're willing to wait for it to recharge.  Case in point: drive 2 hours along highway, then stop for a burger.  While you're eating your burger, your car battery is recharging.  This works best with plug-in hybrid configurations because they have deeper battery discharge parameters.
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  • $/KWH
    nekote on 07/15/2008 at 11:35 AM
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    Given the expense of PV cells, it makes most economic sense to use them where the solar energy capture will be greatest.  Capturing absolutely as many solar photons as possible, every minute of every day, maximizes the KWH that can be generated for the $ invested.  Spend more to get less?  That's irrational.

    The best places for (expensive) solar cells are deserts.  The closer to the equator, the better.

    And stationary locations that can tilt, and track, to to further maximize the utilization of the expensive PV asset.  Probably concentrating PV is the most economic, because of PV cells vs. mirror / lense costs.  In the end, $/KWH.

    Car roof tops are a non-economic location.
    Spending billions on such silly status symbols would obviously be a mindlessly wasteful allocation of capital, as compared to locating such cells where they can capture the maximum solar energy.

    An analogy with windmill farms.
    They're placed where there's the most wind energy to capture.  Who, in their right mind, would spend the money to install a wind farm someplace that seldom has much wind energy to capture?
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    • $/mile
      ricke8592 on 07/16/2008 at 3:20 PM
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      The best measure of economic efficiency is $/mile.  If your gas powered car gets 20 mpg and gas is $4.00/gal, then your fuel cost is $0.20/mile.  If your electic car gets 5 miles/kwh and electricity costs you $0.10/kwh, then your fuel cost is $0.02/mile.  This is the easiest way, as well as the most meaningful way, for most people to be able to grasp the difference in fuel efficiency for different fuels.  It even works with plug in hybrids.
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      • $/mile, yes.  But think $/month.
        robin26 on 07/17/2008 at 9:35 AM
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        Another measurement -aside from $/mile- is very important, and helps account for people's driving habits: $/month.  Several writers have commented on wasteful driving habits, and although this does not directly relate to solar power for cars, it does relate directly to personal energy consumption. 

        Ironically, the more efficient one's vehicle is, the more likely one may be to perpetuate personal driving habits that needlessly waste energy: overly aggressive driving, poorly planned errands to individual stores, etc. 

        If gas prices continue to rise, more people may discover they really can reduce their fuel costs simply by planning a little better and modifying their driving habits.
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        • think $/month.
          nekote on 07/17/2008 at 10:47 AM
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          $/month (or $/year? $/life cycle?) is probably the very best metric for those considering alternatives based on economics.  Net cost to consumer.  Such a figure would also then include all the other motor vehicle costs, such as Insurance, garaging, maintenance and repairs, ...

          Unfortunately, lots of those accessory costs are highly variable by location, so not as useful for nationwide comparisons.

          For cars with this PV on their roof silliness - getting those expensive panels damaged and replaced, if on a statistically significant basis, would surely greatly increase the Insurance premiums, for example.

          Or, alternatively, a different scenario - PV topped cars somehow become popular to steal - greatly increasing the theft portion of the Insurance premium.
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  • 100 MPG Truth in advertising?
    Cyruscosmo on 07/15/2008 at 5:06 PM
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