By on December 20, 2010

EVs are, nice wouldn’t there be (putting range and price aside for a moment) one niggling problem: The power has to come from somewhere. And currently, the exhaust that will no longer be produced by the car, will come out of the smokestacks of a mostly coal fired power plant. Wouldn’t it be nice if we could power our cars from sunshine alone? Definitely renewable. And free. Honda is trying to do just that.

Sorry, forget about solar panels on roof and hood of the car. The power produced that way literally won’t get you far. But what about much larger solar panels on the roofs of your house or large parking garages? Now we are getting in the realm of the possible.

Honda said today that they will conduct a joint trial with Japan’s Saitama Prefecture to “examine the potential of low-carbon transportation systems driven by solar power,” as The Nikkei [sub] reports.

The study focuses mainly on train stations, where cars are parked during the day until the salaryman returns from the city. Large solar panels on the roofs of these stations could provide sufficient power to recharge the battery for the short ride home. Which also has the benefit of a clearly defined range.

“Joint use,” i.e. sharing of EVs, will also be studied.

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28 Comments on “Imagine (Again): A Car, Powered By Free Sunshine...”


  • avatar
    Steve65

    “Joint use”? Giving the reality of charging times, this seems the opposite of feasible. The use pattern for EVs needs to be short trips and lots of idle time, until battery swapping or other realistic quick refuling options emerge.

  • avatar
    Contrarian

    At the equator on a clear day, the insolation reaching the ground represents about 1kW per m^2. Ignoring clouds, and accounting for low suun angles and night-time, the average is maybe 250W/m^2.

     High volume solar panels convert about 12-15% of that to electricity. That leaves us with about 30-35 Watts per m^2 available around the clock. And that’s in a sunny low-lattitude environment. Do the math yourself and see how financially impractical solar charging of EVs is.

    • 0 avatar

      Well, I guess if they cover the roofs of the Kagohara Station, with solar panels, along with plenty of roofspace covering the platforms, they should be able to charge at least one car, don’t you agree. Of course, the weather must be cooperative …
       

    • 0 avatar
      nonce

      The annual average for a horizontal flat plane for the 48 states is 3 KWh/m2/day and up.  At around 15% efficiency, each square meter will get you 450Watt-hours, or around 2 miles of range per car per square meter.  4 or 5 square meters will be great.
      That doesn’t use all of the dusk or dawn light, but for most commuters the bulk of the time is when the sun is highest.  But it doesn’t use even the basic trick of angling the panels southward, which bumps every place but Seattle into a minimum of 4 KWh/m2/day.
      The big wrangler is dealing with the averages — some days will be above average, some days will be below average.
      Solar plays especially well with EVs because EVs can handle intermittent charging.

  • avatar
    zbnutcase

    And just wait until the Canada geese get done with those solar panels….

  • avatar
    Conslaw

    The Holy Grail would be all the parking lots and roads covered with thin film solar cells.  Right now we have technology to print solar cells on sheets. They aren’t very efficient but they are cheap and will probably get cheaper.  There are some huge problems with this idea though.   If you think it is hard managing distributed electricity production in every home, imagine a system where every section of pavement is plugged into the grid. Each block of cells would have to have electronics that have redundant connections to keep the system going when any segment gets damaged.  The individual units also need to be self-configuring. It’s basically a huge math and electrical engineering problem.
     

    • 0 avatar
      Educator(of teachers)Dan

      Not to mention what happens when the snow plow runs over those cells or some teenager who got the keys to dads old Roadmaster decides to do a brake assisted burnout.

  • avatar
    1996MEdition

    That first sentence is extremely confusing….is that Yoda speak?

  • avatar
    1996MEdition

    Sorry, I don’t think the sun will be free for very long:

    http://news.yahoo.com/s/afp/20101126/od_afp/spainsunoffbeat

  • avatar
    George B

    I’d start with covered parking and metered conventional 120V outlets to plug in a charger.  Any location with enough sun for photovoltaic panels has enough sun to make your car uncomfortably hot in the summer.  Shade saves energy required for A/C, reduces paint and interior damage, and improves comfort for all cars, not just the electric ones, and electrical outlets are inexpensive mature hardware.  If solar energy becomes cost competitive in the future, the covered parking roof is available for the solar panels.

  • avatar
    djoelt1

    It takes about 400w to drive a small car one mile on electric power.  A 3×5 foot solar panel puts out 200W per hour on a sunny day, for an average of 5 hours per day.  So, roughly, each 15 square feet can move the car 2.5 miles, or approximately 800 feet per square foot of panel.  A 10 mile commute would require 62 square feet of panels.  The footprint of the small car is about 62 square feet (5×12).  Assuming eggress and space for doors to open takes care of the inefficiencies in conversions at all levels, this is easily doable for many people, countries, and situations.

  • avatar
    Steven02

    I looked into solar panels for my house a few years ago.  Very much cost prohibitive for the benefit.  Not only that, my house isn’t situated with much of the roof facing south.  Also, to get maximum benefit of the sun, my roof is at the wrong angle.
     
    Unless all of the stations are going to have a good clear view of the southern sky and the stations are going to have the correct angles of roofs, I think I know what the answer to this study is going to be.
     
    Also, one other point.  Since cars won’t be at these stations all day long, are they going to store the energy in batteries?  I mean, part of the benefit of solar power is that you can catch it all day long.  If you don’t use it, you have to store it.  I can’t see the station filled with cars all day.  It will be interesting to see what happens here.

    • 0 avatar
      djoelt1

      Check the prices now.  I imagine they are down about 40% from several years ago for residential installs, and will probably be less than half your quote by the end of next year.  They install PV in Germany – high cost Germany – for far less than here, due to our permitting process, inexperienced installers, distribution chains, etc.  All those are correctable and will be corrected.

    • 0 avatar
      Steven02

      I am talking about 2 years ago when I was looking.  Very much cost prohibitive then.

    • 0 avatar
      nonce

      The article discussed park-n-ride style commuting.  Drive your car to the train station, leave it under the solar awning, come back to find it (partially?) recharged.
       
       

    • 0 avatar
      Steven02

      That doesn’t change the south facing need, but how many cars do they want to do this for?  I mean, I guess you pay a small bit extra for charging your car, but it seems that setting up a parking lot full of these would be difficult.

    • 0 avatar
      nonce

      Deciding that the new structure you build will have a southern-facing roof is pretty straight-forward, isn’t it?
       
      I mean, I can’t rotate my house.  Maybe you’d need to repaint the lines to get the cars to line up properly.
       
      As for how many, well, like most things you start small.  Find a place where there are several EV owners willing to commit to buying a certain amount of power every day, build it, and see what happens.  Maybe it will work great, maybe it will need refinement, maybe the whole thing will be a boondoggle and we will learn that before trying a widespread rollout.

  • avatar
    MikePDX

    Thanks, Bertel, this is a good topic, with lots of claims and reactions flying around. Let’s run some numbers to get some Truth about solar charging of electric cars.

    Companies are already putting panels up on their roofs and parking areas, notably Google. (Neat construction video here: http://solarpowerauthority.com/solar-car-ports-and-electric-cars/)

    250 Wh/mile is a good figure for a modern small EV. Let’s assume commuting is 40 miles/day, 250 days/year. That’s 10,000 miles/year = 2500 kWh/year.  In Oregon this would require about 2500 watts of solar panels, 250 square feet of solar panels on a roof. (http://solaroregon.org/residential-solar/solarize-communities/what-are-watts-kilowatts-and-kilowatt-hours)

    A typical parking space is 10′ by 20′, about 200 sq. ft. So a parking space in Oregon that’s exposed to the sun all day covered by solar panels would generate 80% of the energy to run a car used for commuting. I’m actually surprised it’s that good. YMMV by location of course.

    As for cost, financed or leased over a period of years, solar panels are making good financial sense. Companies like SolarCity (http://solarcity.com/), whose trucks are often in my Portland neighborhood, are putting up panels on homes and giving the homeowner lease rates that cut their electric bill. My roof needs replacing soon, then I’ll do that myself.

    Of course the gotcha is the car isn’t always parked under that panel, that’s the point after all.  If the parking space is at work, then it is parked under the panel most of the day five days out of seven. If the parking space is at home then most of the solar power comes in when the car’s not there. In any case, the panels feed the grid during the day, offseting some other load like air conditioning, and the car can take charge back from the grid at night.

    Solar is only my third choice for powering electric cars. #1 is nuclear, which is quite safe and ready to scale up today. #2 is wind, which is coming up fast and has the advantage of offering its greatest output at night when most of our cars are charging. Solar pencils out as a fine power source too.

    That’s the real point about electric cars, we can charge them from any source that comes along, starting with coal and and natural gas if necessary now, to break our addiction to foreign oil. Nuclear, wind and solar right away to get unhooked from carbon. When the next energy breakthrough like fusion comes along, our electric cars will be ready to use it.

    • 0 avatar
      charly

      Daytime power is a lot more expensive than nighttime power so the more economical method is to sell the solar power and buy nighttime power to recharge the batteries.
       
      ps. Nuclear isn’t ready to scale. It takes atleast 6 years to build a nuclear powerplant and that is when everything works with you. Other problem is that the West has only the capability to build a few power plants year which is to low to really scacle.

  • avatar
    brandloyalty

    “Plugging in” suggests the hassles of cords and so on, whereas cars could have standardized recharge points so they just “dock” onto the contacts.
     
    I don’t want to make fun of EV’s, but I have to pose the scenario of a particularly dim day when everyone arrives to drive home and their cars are dead.  I guess an installation like this would be connected to the grid to provide power when not needed to charge cars, or to charge the cars on dim days.  Eventually surplus power could be a revenue generator for the lot owner.

    • 0 avatar
      nonce

      There is also inductive charging, where you don’t need any physical contact to get power, just proximity.
       
      If all the cars in the lot were smart enough, they could bid with other on just how much power they want.  The guy who lives only 5 miles away will be fine not getting any power on a dim day, maybe even be willing to sell some of his juice if the price is right.  (Although I’m very skeptical of such battery-to-grid concepts.)
       

  • avatar
    djoelt1

    A weakness of companies that sell old technology like automobiles is they assume that the rate of technological change that they experience in their product is the rate at which other industries change, and the rate at which new industries can impact their industries.

    The comments here have merely scratched the surface of what is possible.  Once cars with batteries exist, the automobile part is done.  The high tech PV, information technology, software, and electronics industry, used to developing products at 10x or 100x the rate of autos, will swing into action.  Parking lots are one of the best places for solar panels, and in many areas you could charge extra to have cover for your car.  The panels are near the point of use and environmental issues are nil.  It’s also easily accessible for cleaning.

    Once the panels are in place, trading of power and other information/game theory driven optimization and trading between cars can take place as an earlier letter writer noted.  The group of cars could even cover a temporary grid spike at less cost and at a small profit to the car owner, vs, a peaking power plant.  When the grid of information can make real time choices in the flow of electrons, new profit opportunities will drive development we can’t imagine now.

  • avatar
    PeteMoran

    Transforming our energy use is going to require imagination. I think it’s exciting, but I also work in the area so….


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