So I was looking at the roof of the car the other day…

Discussion in 'Gen 2 Prius Main Forum' started by Leopold Porkstacker, Apr 12, 2006.

  1. Leopold Porkstacker

    Leopold Porkstacker New Member

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    The roof is pretty much one nice piece of surface area, sitting there, looking pretty to birds sitting in trees above it. What if, perhaps, Toyota (or some aftermarket venture) decided to make good use of the unused space and have it instead lined with a photovoltaic array? Is this not something that has been thought of before? I would guess that with the high efficiency of today’s photovoltaic technology that some decent power could be generated from having the roof collect energy from the sun, perhaps enough to keep the batteries charged enough that maybe another 50-100 miles of range could be added per tank of gasoline?

    Just a thought. Talk amongst yourselves. ;)
     
  2. aaf709

    aaf709 Ravenpaw of ThunderClan

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    I have seen some pictures of someone who's done that, but I don't know the link. Perhaps someone else can supply that.
     
  3. Kev1000000

    Kev1000000 New Member

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    i thoguht of something like this as well...

    There is just SOO much potential! :p
     
  4. eagle33199

    eagle33199 Platinum Member

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    I know this has been discussed here before... i believe someone posted a link to an article or site wher eyou could get a conversion kit to add soalr panels to the car. Don't remember what it was off the top of my head, though
     
  5. cwerdna

    cwerdna Senior Member

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  6. hycamguy07

    hycamguy07 New Member

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    Its already been done ;)

    Looks neat though but what I dont understand is this:
    conformal rooftop-mounted solar panels that charge the hybrid automobile's auxiliary battery through a proprietary charger/current-limiter system concealed behind interior trim panels.

    So the panels do not charge the hybrid battery but just the 12v aux battery.?

    I would think you would want to replenish the cars hybrid bat pack so then you could ev longer..
     
  7. rdenneyutmb

    rdenneyutmb New Member

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    <div class='quotetop'>QUOTE(efusco @ Apr 12 2006, 05:14 AM) [snapback]238467[/snapback]</div>
    Everyone would like some free power. The first link above (at treehugger.com) provides a sensible discussion of the problem by Steve Lapp. In Ontario summer, the sun can deliver 6 kW/square meter. It concludes that a 270 watt, roof-mounted system could potentially provide 10-20% improvement in fuel efficiency (presumably under optimal conditions). Since volts = watts x amps, the 270 watt system could provide about 270/250 or a bit less than 1.1 amps of current to the Prius traction battery system. For a little perspective, Evan Fusco has noted that according to his CanView, the MFD of the Prius reports no current flow (blank arrows during glide) if less than 6 amps are flowing from the traction battery. In this light, 1.1 amps seems like a rather small amount of current.

    The much lower output, 30 watt , solatec system described in the other two links would provide only 30/250 = 0.12 amps of current to the Prius traction battery. I can't imagine that there could possibly be a 10% improvement in mileage with this system, despite the cost of $2195. I note that the second link above, following its description of the soltec system, has the statement: "Disclaimer: RenewableEnergyAccess.com does not endorse this product, or substantiate the information provided by the manufacturer, and assumes no obligation for this content's accuracy."

    Solar has a great future, but we have to be realistic about what it can do. According to Steve Lapp, the maximum summer sun in Ontario provides about 6 kiloWatts/square meter and current photovoltaic cells capture with about about 10% efficiency (treehugger link, above). A realistic system needs to cover as big an area as possible.

    I would be really happy if someone can prove me wrong...
     
  8. vtie

    vtie New Member

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    Unfortunately, photovoltaic cells are not green. Producing them creates a lot of extremely dirty waste, some of the worst you can find in industry. I don't think it's a good idea to start mass production for a product that has a typical life cycle of around 4 years.
     
  9. grasshopper

    grasshopper Member

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    What? No-one here cares about the birds? Do you know how it feels to be constipated? Plus without target practice how will the little birds learn. This idea is cruel! :eek:
     
  10. daniel

    daniel Cat Lovers Against the Bomb

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    My impression, based on earlier discussions, is that lining the roof of the car is not very practical. You change the aerodynamics of the car, and you really don't get very much power. You could increase the power somewhat by leaving the car in the sun all day long, but it's still not a lot.

    Next issue: recharding the HV traction battery is not a trivial task. It operates at a dangerous voltage, and the car's own computers do not like unexpected charging. It can be done, but not easily. This is why existing systems only charge the 12-v battery. Hardly worth it, and certainly not worth altering your aerodynamics for.

    The place to put photovoltaics is on the roof of your house, not the roof of your car. You get much more surface area, and if your house is well located and aligned, you get sunlight all day long. darelldd (here on PC) charges his EV (not his Prius) from photovoltaics on his roof. That's the way to power a car from the sun.

    One last point: the HV traction battery in the Prius is only good for a mile or two on a full charge. How much are you going to increase your mileage if you add 2 free miles to your daily commute? Not a lot. And again, the loss due to added resistance will probably be greater than the small gain from the extra electricity.
     
  11. hobbit

    hobbit Senior Member

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    If the sun delivered 6 kW/sqm, we'd all be very crispy critters.
    .
    _H*
     
  12. tochatihu

    tochatihu Senior Member

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    Steve Lapp said a sunny day in June or July could provide 6 kwh, which seems reasonable. An unintentional error in reporting here probably occurred. Power and energy units are very often sources of confusion.
     
  13. nerfer

    nerfer A young senior member

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    <div class='quotetop'>QUOTE(vtie @ Apr 12 2006, 07:33 AM) [snapback]238479[/snapback]</div>
    So why do they come with a guarantee of 5 to 10 years (depending on manufacturer), and lifespans of 25 years or more are often reported?

    I agree, manufacturing the PVCs isn't an oil-free or waste-free process, but continuing to burn coal indefinitely is not any better. Windmills probably have a better EROEI.

    As for aerodynamics, the thin-film (CIGS) PVCs could be used - United Solar for instance makes the flat cells that can be glued to the roof, keeping the roof's shape. However, that has a lower efficiency (watts/m^2) than the rigid silicon-based PVCs.

    Getting a couple miles of free energy (after the up-front costs) would be significant for me on my 7.5 mile commute. Park in the sun during the day, at home plug into the grid (PVCs on the roof at home don't do much good for my Prius while I'm always away during useful sun hours). This would require at least a mild PHEV conversion, maybe not the full EDrive solution, since recharging the traction battery is not a simple thing.

    Of course, a more optimal solution is to have covered parking lots, and the cover being a roof of PVCs, that powers the building A/C and PHEVs in the parking lot.

    nerfer
     
  14. khoult

    khoult New Member

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    Unfortunately, the standard "sun" is 1000 W/Sq-meter. A fully covered Prius room might be near one sq-meter. A typical PV panel is 15% efficient. An average number of peak sun-hours per day is around 5 (after accounting for all the tine the sun is not perpendicular to the panel and relecting more and more away).

    All of this gives you at best around 750 W/Hours on good days. If you ran this through a switching converter to charge the traction battery (and it actually needed charging while the sun was shining), you get about one top off of the battery from its 50% to 90% point.

    Since that top off is worth about 1-2 miles of driving, thats what you get per day by adding a $1000+ worth of PV panel and charger (less the aerodynamic loss caused by the panel).

    So overall, best case, you get maybe 30-60 extra miles/month.
     
  15. samoan_ridah

    samoan_ridah New Member

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    I was thinking more along the lines of putting in a sunroof so that I can get my dose of Vitamin D on the way in to work in the morning.
     
  16. TheForce

    TheForce Ron Paul 2012

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  17. andreaswin

    andreaswin New Member

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  18. cooljw

    cooljw Member

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    FYI: there are also solar panels you plug into your cigarette lighter.

    Volkswagen owners routinely get these with their new vehicles (I know I did). Apparently VW uses them to keep the batteries charged before the cars are sold. I sold mine on eBay, people use them to keep batteries in marine boats and RVs charged up too.

    There is a discussion on another website that talked about the practicality of using one of these cigarette lighter plug-in solar panels to recharge the Prius batteries. Unfortunately it sounded like it wouldn't provide much power, and might not even be possible because supposedly the cigarette lighter switch is "closed" when the car is off (not linked to the hybrid battery).
     
  19. Magnus1

    Magnus1 New Member

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    <div class='quotetop'>QUOTE(rdenneyutmb @ Apr 12 2006, 08:21 AM) [snapback]238476[/snapback]</div>
    ahem, watts = volts x amps...sooo volts = watts/amps
     
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