Going Solar?

Discussion in 'Gen 2 Prius Accessories & Modifications' started by PriusChatJeff, Nov 22, 2006.

  1. PriusChatJeff

    PriusChatJeff New Member

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    Hi Everyone,
    Thanks for the great community -- I'm a newbie... Just bought an 07 touring and LOVE it...
    Something I was curious about even before purchase: Has anyone out there given thought to hooking up flexible solar panels to charge the battery pack? Costco has a couple different models that convert sunlight directly into 12V producing 26 watts max and I was wondering about letting this 85 degree November Phoenix day charge my battery pack to 80% while I park or drive...
    Also 26 watts may not be worth much, but if left to charge in parking lot all day?
    Gotta find some way to make the heat work for us here!
    Peace,
    Jeff[attachmentid=5739]
     

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  2. aaf709

    aaf709 Ravenpaw of ThunderClan

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    I don't think it would work with your main battery pack. It might help the small battery, though.
     
  3. darelldd

    darelldd Prius is our Gas Guzzler

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    All you can do with a product like that is keep the Aux battery topped up. It will only insignificantly effect the traction pack as it may not have to top of the Aux battery when it first comes alive. Honestly though, you'll likely never notice any difference in FE.

    And one point to keep in mind after your comment about "putting this heat to use) - PV panels to not convert heat into electricity. In fact, heat is counterproductive. You need sunlight - the best is sunlight on a cool, clear day. Heat will derate the output substantially.
     
  4. c4

    c4 Active Member

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    Those flexible solar panels are amorphous silicon that are extremely inefficient and they lose as much as 50% of their capacity after as little as 6 months of exposure to the sun... Ie, your 26 Watt panel would be come a 13 Watt panel after a while (luckily, it seems to stabilize at this level).. Now depending on where you want to place the panel (outside or inside, behind the vehicle glass), you may also suffer additional losses.. Putting the panel behind the solar-absorbing glass decreases the output by at least another 30%, so your panel becomes a 9W panel, and that 9W is only available for a few hours a day when the sun is brightest.. The output drops dramatically when there is cloud cover, and obviously there is *no* output at night..

    This means that you might get 30 or so Watt-hours per day, or about 2Ah of charge to a 12V battery, which is barely enough to offset the parasitic drain (about 50-60 mA x 24 hours) of the vehicle electronics.. If you wanted to forego the 12V aux battery top up and wanted to try charging the NiMH hybrid battery instead,, you still need a small 12V battery to accumulate the charge as the direct panel output is too small, then you need a DC-DC boost converter to raise the 12V up to 200+ V, but this circuit generally has about a 65% efficiency, so your 30 Watt-hours becomes 20 Watt hours, or about 10 mAh, which would power your vehicle for about 1/4 second or thereabouts..

    To make a solar electric "top-up" system viable, you have to go with high efficiency crystalline solar panels that are externally mounted.. There is one such Classic Prius around with its entire roof + an extension platform filled with crystalline solar panels, which is used to charge a bank of 12V batteries that runs an inverter to produce the 200+V while the car is running.. Reportedly, the owner gets measureable gains from this arrangement, but it's not a cheap or simple setup, and it does ruin the car's aesthetics due to the large rack of solar panels on the roof..
     
  5. PriusChatJeff

    PriusChatJeff New Member

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    Thanks for the info on the flexi panels and efficiency, esp with heat... Was thinking of forcing EV mode by charging battery passively but guess this will have to wait for better panels... or I could just place a big ol' solar sail on my roof and go for the wind as well! :lol:
     
  6. darelldd

    darelldd Prius is our Gas Guzzler

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    Just put real solar panels on the roof of your home, yank out all that gasoline engine crap in the Prius, and presto, you're ready to roll. :)

    This isn't something we should have to wait for! It is how I'm driving my pure EV today!
     
  7. statultra

    statultra uber-Senior Member

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    i wish they had some 50-100 volt dc panels
     
  8. kaptaink

    kaptaink Junior Member

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    Not too long ago I saw a pic of someone with a solar panel roof . . . I will see if I can find it.
     
  9. Cheap!

    Cheap! New Member

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    Google knows all!

    Image search "Solar" & "Prius"

    Ta Da!
     
  10. Lywyllyn

    Lywyllyn New Member

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    Sweet! Imagine when the come out with the solar paint, you can turn your whole car in an electricity generating machine !! :)
     
  11. bredekamp

    bredekamp Member

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    <div class='quotetop'>QUOTE(kaptaink @ Dec 1 2006, 04:25 AM) [snapback]356050[/snapback]</div>
    Your dogs' expression is precious. :D
     
  12. SomervillePrius

    SomervillePrius New Member

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    KaptaInk!

    Nice shepherd! I have two white ones (one 2.5yrs, the other 6 months).
     
  13. Dan.

    Dan. MPG Centurion

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    OK... So I've always seen a totally different approach to this. I think the best use of anything < 300 Wh of juice is simply to dump it into the block 20 minutes before you start the car. Block heaters do wonders for reducing start-up fuel consumption.

    I use 24 oz on the way to work, > 10oz goes to warm up. Its down near 7oz now that it's warmer, but If I could get my warm up under 5oz, that would be a 10% boost in FE. By warm up, I mean startup to 70C.

    For the mornings when it's in my garage, that isn't a problem, but when I'm around town it is. So I'm thinking of a 20 Ah (12v) batter hooked to solar panels, and some remote control unit (timer or pre-paid cell phone).

    If I know I'm leaving in 20min, activate remote to discharge the Solar charged battery into the Engine Block Heater. Bingo!! 10% fuel savings in first 5 min of driving.

    Hardest part (of course) is the timer and the control unit.

    Another option would be to forgo the solar panels and hook up directly to the stock accessory 12v battery (31 Ah). That gives you (theoretically) >350 Wh to dump into the block. Obviously, using >300 Wh would probably make your battery dead as a post, but there may be an acceptable level you could tap. 150 Wh would probably give you some noticeable improvement at startup.

    11011011
     
  14. c4

    c4 Active Member

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    The engine block heater is just a resistive element that works just as well on DC as on AC, but your calculations are wrong... Because of Ohm's law, to get any appreciable amount of heating, you do need to give it the *same* DC voltage as the AC RMS (ie, 120V nominal).. This is because it's a simple resistor: at 120VRMS AC and 1500W, you can figure out from P=VI and V=IR that R=V^2/P and therefore the heater element has a resistance of somewhere in the ballpark of 9-10 Ohms.. If you dump the 12V battery into this, you get P=V^2/R or approximately 15W input; in 20 minutes you've only used up 5 Wh..

    Your best bet for battery and solar therefore would be to either get a big 300+W solar panel array, a big 12V battery and a 1500W 120V inverted, or, if you want to go DC-only and eliminate the losses in the inverter, set up the array of solar panels in series and ten 12V batteries in series (=120VDC), and under timer control, dump that into the block heater element.. Now, at 120VDC, P=V^2/R = 1500W input; or 500Wh in 20 minutes... The heater will be pulling 12 amps from the batteries in the series configuration, or probably about 150-200 amps from the inverter configuration..
     
  15. daniel

    daniel Cat Lovers Against the Bomb

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    <div class='quotetop'>QUOTE(kaptaink @ Nov 30 2006, 07:25 PM) [snapback]356050[/snapback]</div>
    Darell has some pics of his on his web site (URL in his sig). And once he posted a great pic of his dad's new solar roof. He may have that pic somewhere on his site as well.

    <div class='quotetop'>QUOTE(Cheap! @ Nov 30 2006, 07:46 PM) [snapback]356057[/snapback]</div>
    This is pure BULL!!! Sure, they have solar cells on the roof. But with all the electrons they collect, the car will probably drive an extra 25 feet in a day.

    Put your solar cells on the roof of your house and use them to charge up a ZAP Xebra. The roof-mouted array will get you lots more electrons, and the Xebra drinks no gas at all.

    Some technology is possible, but makes no sense. My friend, many years ago, who used his Radio Shack TRS-80 Color Computer to balance his checkbook, taking at least ten times as long as it took me to balance mine by hand, so he could prove that the computer was useful, and not just a toy, is an example. PV on a car is another example.
     
  16. danatt

    danatt New Member

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    <div class='quotetop'>QUOTE(daniel @ May 13 2007, 10:58 AM) [snapback]441070[/snapback]</div>
    They (SEV) claim "the expected range per day that the PV Prius would have on solar power alone would be between 5 and 8 miles". PV Prius White Paper
    Yes? :unsure: No?
     
  17. metal_chair

    metal_chair Nashville Prii Unite!

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    waiting for plug-in , solar Prius
     
  18. V8Cobrakid

    V8Cobrakid Green Handyman

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    i like that solar engine block heater. I would set up the batteries in series for efficiency and longevity reasons... but i'm no pro.

    I wouldn't use the 12v battery for anything. It's weak.. very weak and dies rather easily. You'll end up with a few of those problems.

    in my opinion, it's best to put a small panel on the 12v... it could use it. if you vacation you'll need it.
     
  19. icarus

    icarus Senior Member

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    RE: Putting a 12vdc engine block heater, solar or otherwise:


    The Prius 12vt battery is pretty undersized to start. I can't remember how may amp/hours it is to start, but run this scenario with the real number.

    Assume the battery has a capacity of say 35 amp hours. That translates to ~400 useable watt/hours of capacity. If you were to plug a 300 watt EBH into the battery for 1 hour you would use 300wh or 75% of it's capacity. You could do this (assuming the original capacity number I guessed at is close) but, and this is a big but, You would spend more replacing your battery every few weeks than you could possibly save on grid power costs, or fuel in the car. Remember that electric heating is a very big draw from any source, battery or grid.

    A lead acid starting battery is designed for a large amperage draw for a very short time, followed by a complete charge. The arrangement and size of the plates allows this with out damage. A long deep cycle draw will QUICKLY lead to the plates dissolving and the battery failing.

    Now, you might say, well I will replace the starting battery with a "deep cycle" type battery. A deep cycle battery by contrast is designed for a lower amperage draw over a longer time, followed by a complete charge. (In the solar world, we design for no more than 50% discharge, and aim for 20% discharge to maximize the life of the batteries.) Once again, you can see that you are drawing the battery down below it's design capacity. (Even though cheap deep cycle batteries are advertised as being able to draw down to 20%, don't believe it. You can draw them down, but the number of cycles that you can use them will decrease exponentially with the depth of discharge.)

    So no matte how much solar you can put into the little battery, since you are going to have to discharge it too far, you are going to kill it anyway. Now if you could put a 300 watt panel on the roof of the car, you could rung the heater directly from the panel. On the other hand, a 300 watt panel would cover the roof of ~ 3 Prius'.

    Or if you use the above mentioned 100 watt panel, coupled to the battery, you could reduce the battery draw somewhat. But here is another catch. You can only get ~75% of rated capacity out of any given panel, into a battery. Add in warm panels, hot batteries etc, and that efficiency goes down considerably.

    So, in my mind, while it may be a nice idea, it doesn't make any sense. Spend your money on a grid tie solar, and then plug in the EBH.

    Icarus

    PS For those that may have some more interest in battery information, read the following: http://www.batteryfaq.org/ or Car and Deep Cycle Battery FAQ or Deep Cycle Battery FAQ
     
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