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Although some aftermarket operations have tried installing rooftop solar panels on the Toyota Prius, none of the pioneering hybrids have ever come so equipped from the factory. This will reportedly change next year when the third-generation model hits the streets. Top trim levels of the new Prius and likely the Lexus-badged version will be equipped with photovoltaic cells on the roof. The solar cells won't generate enough power to do any significant charging of the battery pack but will be able to power accessory drives like the air conditioning. That should reduce the parasitic loads on the power-train, helping to improve the mileage slightly. The solar panels could also be used to keep the ventilation system running on hot days while the car is parked. That would reduce interior temperatures, cutting the load on the air conditioning when the driver gets in. The new Prius and the Lexus hybrid will debut in January 2009 at the Detroit Auto Show. Thanks to Mike, Max and Kevin for the tips!

[Sources: CNet, the Gaurdian]


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    • 1 Second Ago
  • 25 Comments
      • 6 Years Ago
      I hate this idea. Such a gimmick.

      If you want solar cells to do any good at all for an electric car, sell them as an accessory panel that can be installed permanently, properly, and at the optimum tilt angle for the latitude. You'll get twice as much power, and you'll get it all the time (what about if you want to park your Prius in a garage? In an underground parking lot?).

      This "green image" nonsense is such painful BS.
        • 3 Months Ago
        I assume you mean panels to be installed on the roof of your house and not on the car,otherwise your comment makes no sense. There's nothing stopping you from doing that on your own and hooking it to the car's battery. The ROI is measured in decades however. Every car should have a solar panel in the roof these days if for nothing else than keeping the starter battery charged and running the fan. You've been able to buy these at auto parts stores for years, but they require you to set them up on the dash when you leave the car.
      • 6 Years Ago
      Going to work...working 8-10 hours...the Prius parked in the sun..dont tell me the sun will not give me during that sunny day energy only for the ventilation? No, it will i´m sure give med enough energy in the batterys to also take me home if im living in the same city as im working.
      • 3 Months Ago
      Nice gag - I have my own gag at http://www.youtube.com/watch?v=6h_XPz-GKS4 The solar cruiser! may be with lighter vehicles the panels may really contribute in a few years with higher efficiencies of the cells.
      no gags at: greentfleet.info - recodrive.eu
      • 3 Months Ago
      Let us do some math.

      It takes a large area of solar cells to get a significant amount of power, solar cells are not very efficient, 10-20% and there just is not that much energy there to begin with.

      1000 watts per square meter, at 10% efficiency becomes 100 watts, and that is only when the angle is right full sun no clouds etc.

      http://store.sundancesolar.com/gopo50wasorv.html

      Here is a 50 watt rated panel for $500.
      They say with 5 hr of sun a day it will deliver 100 amp hrs per week.

      It is rated at 17 volts if it were operating at this voltage, 17 X 100 is 1.7 kwh per week.

      The prius has a 6.5 ah rated pack at 375 volts.
      If we take the self discharge rate of the battery pack as 1/64 of capacity per day http://www.hardingenergy.com/faq.htm
      we have 6.5 ah * 375 * 7 * 1/64 = 0.266 kwh per week

      So how far could one go per week on "solar power"
      1.7 -266 / the number of watt hrs required to go a mile

      we'll use 290, this is what the rav4 ev is rated at city.

      That works out to 4.94 miles per week, less than 1 mile a day.

      Ok say gas is $4, that $500 will buy 125 gallons of gas, if the prius gets 43 mpg that is 5375 miles. It would take almost 21 years to break even.

      Ok well then lets run the fan.

      The blower motor on my car is on a 30 amp fuse, lets say it draws only 20 amps when it is running.
      How long can we run the fan each day?
      20 amps * 12V = 240 watts

      We have 1700 watt hrs per week. So we could run the fan for 1 hr each day.

      Would this help?
      Try this, park your car in the hot sun all day.
      measure the temp

      Park the car in the sun, run the fan for an hr, measure the temperature.

      Park your car in the hot sun with a solar panel on the roof
      measure the temp

      One would expect the car with the fan running to be the coolest, and the car with the black square on the roof absorbing heat to be the warmest.

      Can the solar panel generate enough electricity and run the fan often enough to offset the added heat load it adds to the car?

      I don't know, I am not willing to spend $500 to find out, especially not when I could use the same $ to have my car painted white which I know would help reduce interior temps, or for $5 I can get a window shade.

      This is a gimmick, that is not to say that it will not help some.
      Would you pay $20 for a mcdonalds hamburger? Maybe if you had no other choice, would you still if you could buy steak for $2?

      And so it is with solar, it only makes sense if you have no other option, but we do have other options.




        • 3 Months Ago
        - You've proved that the solar panels can be used to stop the self discharge of the batteries And keep the car cool.
        - We don't know the efficiency of this thin-film solar panel.
        - Since the solar panel is converting sunlight to energy it is reducing the roof's heat load, better then White paint? We don't know.

      • 6 Years Ago
      Audi has had that exact feature for more than a decade now. Granted it is not the entire roof they have been using but they used the sunroof, anyway. Effect is great: a nice and cool car by the time you get in. Makes driving so much safer through being more focused. I agree it should be standard on all cars. Let common sense rule!
      • 6 Years Ago
      This looks very sleek. I like it!
      • 6 Years Ago
      While TurboFrog is right that this is not an efficient use of solar panels, I also agree with bluegreen.

      After all, if you are parked in the sun, keeping those vent fans on is 10x more important than if you are parked in the shade. If they can do it without adding too much to the price I say go for it. Every little bit helps drive up volumes, and drive down costs, for PV.
      • 6 Years Ago
      Didn't Ford/Mazda do this in the 90's? I wonder why it didn't take off then.
        • 3 Months Ago
        Mazda did offer this on the 929.
        • 3 Months Ago
        Mazda had it in the 929...
      • 3 Months Ago
      Assuming that you have 1 square meter to work with, and you use thin-film PV (pasted onto the roof's contour), which have an efficiency of maybe 8%, you get 80 watts or so at high noon, and an average of maybe 50 watts.

      Certainly enough to run a vent fan to keep the interior at ambient temperatures without draining the battery. A fine idea, and usable for all cars, not just hybrids.

      Only question is whether a square meter of thin-film PV installed and integrated is cheap enough. Many people might go for this at $100, but few will be interested at $1000.
      • 6 Years Ago
      This is SOOO stupid. This would completely turn the Prius into just a gadget or fashion accessory. Solar panels mounted on cars have almost no benefit. It might save half an mpg or something like that, which means it is not cost effective at all.
        • 3 Months Ago
        The Prius IS a gadget. That doesn't make this a bad idea. A/C sucks a ton of power out of an engine, especially a dinky one (i.e., a Prius'), and frankly I hate getting into a sweltering car. Bring on the solar, if for no other reason than that!

        Besides, this is a good way to generate a demand for PV, and if that technology is improved upon at the same rate as, say, the internal combustion engine was, we'll all be better off soon.

        ...Now, if only they manufactured Priuses (sp?!) in an eco-friendly way, it would actually be getting us somewhere. Still, its a first step.
      • 6 Years Ago
      Joseph if you leave in the snow, and there is no sun ever, Then it doesnt make sense. HOWEVER, my car is parked in the sun for 8 to 10 hours a day. Every day. And when I get to my car, its freggin' hot.

      So for people that leave in california, Arizona, new mexico, nevada. Texas, Florida. Makes sense.

      I sooo owant solar panels in my car. Good choice toyota.

      • 6 Years Ago
      I suppose I'm just taking issue with it because it's an inefficient allocation of materials. The fact of the matter is, mounting them on a car is a compromise - integration is more expensive, in-use performance is degraded (as opposed to a roof-mounted tracking array, or even just a simple flat array tilted to compensate for your latitude), and you end up with additional weight and complexity.

      If Toyota offered an investment stake in a co-op solar plant, it would be an infinitely better proposition for the planet and the owners alike, but because it's not tangible and visible, I doubt it would be a popular option. It wouldn't let me stroke their egos and flaunt to society at large nearly as much.

      I'm not one of the people who bash Prius-owners for smugness, because I think it's a quality, efficient, and practical vehicle with numerous virtues as a car. But it just seems like the realistic value you get out of mounting solar panels on a car is far outweighed by the image benefits that it would confer.

      Very smart marketing by Toyota, but take the long view and realize that that's what's driving the decision, not pragmatic environmentalism.
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