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Model 3 may have Solar Roof that can charge the vehicle

Discussion in 'Model 3' started by X-Auto, Nov 25, 2016.

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  1. brucet999

    brucet999 Active Member

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    Does that green smiley mean you are joking? I hope so, because for solar cells to generate power from the sun, they must absorb solar radiation and convert it to electricity. Obviously, anything that absorbs light cannot also be transparent because the very meaning of the word is allowing light to pass through.
     
  2. Dan Detweiler

    Dan Detweiler Active Member

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    I don't necessarily disagree with your speculations but I think the important question is your last question. Would I be willing to do what is necessary? No, I wouldn't...not based on your requirements. Nor do I think the VAST majority of people would either. But...that's just me.

    Dan
     
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  3. dsvick

    dsvick Active Member

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    Unless they are directly involved in the Model planning and production, it is more likely that Tesla employees know as much as the people on this forum about the current state of the production ramp.
     
  4. dhanson865

    dhanson865 Active Member

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    1. The leaf panel was too small and to old/low effeciency to make a huge difference. Tesla has the advantage of time to use better cells and space to use more of them.

    2. Tesla needs it more than the Leaf since the vampire drain is higher on the Model S/X and presumably 3 than it is on the Leaf.

    3. The leaf used traditional lead acid 12v instead of AGM or anything more reliable. Had they started with an AGM the 12v failure rate would have been lower. You can't blame the panel for the underlying technology issues that caused the failure, namely:

    A. Lowest cost/quality 12v battery they could spec
    B. Poor charging algorithm
    C. The inherent Hybrid/EV reliance on the 12v to disconnect and reconnect the HV pack making the 12v a point of weakness/failure.

    Really I get the whole "It's better to put panels on the roof of your house than the roof of your car" argument and in general I agree. I'd rather put more panels on houses if it is an either/or choice.

    I'm just saying there is a need for the car and it can solve a technical problem. The reliability increase might make it worth it for just enough solar to improve reliability/extend the life of the 12v battery. I'm not looking for it to give me kWh and get me down the road on self charged solar to the HV battery.
     
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  5. dhanson865

    dhanson865 Active Member

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    Have you never seen transparent solar PV? It does exist.

    Photovoltaic Transparent Glass For BIPV - Onyx Solar
    BIPV Transparent Photovoltaic Solar Glass: PolySolar
    Transparent solar cells

    It might be worth mentioning that there is a lot of energy in sunlight that isn't in the visible spectrum and people like tint (as in you don't have to let all the light through). You can harvest power and still have a piece of glass that looks clear or shaded but appears to have nothing in it technology wise.
     
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  6. ecarfan

    ecarfan Well-Known Member

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    Agreed, and thanks for your post. Upthread I have been dismissive of the idea of charging "the vehicle" (as stated in the thread title) using solar cells on the surface of the car, if by "charging" one means "charging the main battery" which I believe is what the OP meant.

    I am not nearly as dismissive of the idea of using solar cells to maintain the 12V battery. Clearly (pun intended) that is possible. But the fact remains that during extended periods of disuse many cars are parked indoors or in covered parking structures and therefore would not receive enough light of adequate intensity for the car solar cells to be useful. It would work for cars parked outdoors. But is that a sufficiently common use case -- car parked outdoors, not plugged in, for more than a couple of weeks -- to justify Tesla investing resources into developing and producing an option for solar cells on the surface of the car simply to maintain the 12V battery? I think not.
     
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  7. brucet999

    brucet999 Active Member

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    #67 brucet999, Nov 30, 2016
    Last edited: Nov 30, 2016
    In the future, maybe. According to the article, MIT researchers have achieved 2% PV efficiency with 70% visible light transmitted. They hope someday to achieve as much as 12% PV efficiency with unstated visible light transmission. Present day opaque solar panels run about 20% efficiency.

    That having been said, isn't it exciting to think of every south-facing window in every office building (above the shadow line of adjacent buildings) generating power while screening out undesirable IR and UV rays? Combination of power generated and power saved in reduced AC load would result in huge reductions of fossil fuel consumption.
     
  8. N5329K

    N5329K Active Member

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    #68 N5329K, Nov 30, 2016
    Last edited: Nov 30, 2016
    One way around this is to introduce dyes into the glass that are photoreactive, then direct the resulting "glow" to the periphery through careful optical design, where PV's can be located out of direct view. The entire glass surface becomes a kind of prismatic all-angle "focusing" collector, with a fewer number of PV cells in the glass surround (cheaper than plastering the entire surface) operating at much higher efficiencies. This has been shown to work well in ordinary (well, sort of ordinary) window glass installations.
    Still won't collect enough to run a car. Maybe run a few of its systems, or offset "vampire" loss when parked.
    Robin
     
  9. Topher

    Topher Energy Curmudgeon

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    If it would save the lives of your great granddaughters, would you?

    Thank you kindly.
     
  10. Topher

    Topher Energy Curmudgeon

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    Yes, I can make the financial case for that, just on personal experience.

    Thank you kindly.
     
  11. Dan Detweiler

    Dan Detweiler Active Member

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    No, because I don't share your long term prognosis...neither do the majority of the general public, I believe. Certainly respect your views though.

    Dan
     
  12. BluestarE3

    BluestarE3 Active Member

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    Rather than putting resources into designing and developing a kludgey solar roof panel to maintain the 12V battery, why not redirect resources to developing a better 12V battery option that isn't as susceptible to self-destruction from repeated discharge/recharge due to vampire drain?
     
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  13. Topher

    Topher Energy Curmudgeon

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    Do you have any evidence to back up your prognosis? Is your prognosis based on a sound foundation of the details of the science involved? If not, would you be receptive to evidence to the contrary?

    Thank you kindly.
     
  14. Topher

    Topher Energy Curmudgeon

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    Because I can buy a PV that plugs into an accessory socket. Developing new battery technology takes a PhD and years of work.

    Thank you kindly.
     
  15. BluestarE3

    BluestarE3 Active Member

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    It doesn't have to be a brand new battery technology. Just use an existing technology but, more importantly, engineer the battery to better withstand repeated discharge/recharge cycles than off-the-self lead-acid batteries.
     
  16. JeffK

    JeffK Well-Known Member

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    I think evidence in this case would be the current state of our observable world.

    If the vast majority of people would be willing to change to solar self powered cars with today's technology then why is it we do not see that change reflected in today's environment. Why has the sale of super low Cd cars stagnated (hint: they're often ugly unlike the future Model 3). The current limitations of the rail system also would prove a challenge to implement your proposed changes.

    Long narrow cars would handle worse than normal cars and many ideas of the future do not involve longer parking spaces, but instead doing away with parking lots altogether in order to increase living and business space. autonomous cars can pick you up and drop you off wherever you want to go in the future.

    There's also the human fun factor...

    The future will definitely be interesting no matter which path we take.
     
  17. Frank Schwab

    Frank Schwab Member

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    >>more importantly, engineer the battery to better withstand repeated discharge/recharge cycles
    I think it would be far simpler to engineer the vehicle electronics to effectively eliminate vampire drain. I hope Tesla has done that for the Model 3, as well as the Model S/X with the introduction of AP2 which would have required a significant redesign of many systems.

    I have a computer in my pocket with a quad-core 2 GHz CPU and 3 GB of RAM that will listen for LTE calls and monitor it's environment for 3 days with a 10 W-hr battery. A standard 12V Lead-Acid battery is about 720 w-hrs, and the main battery pack is 75,000 w-hr. When the car is parked and idle, it doesn't need to do anything more than my phone does; thus there's no reason that the vampire drain can't be reduced to the same as my phone - draining the 12V battery in roughly (3* 720/10) = 216 days. Let the main pack charge the 12V battery once a week, and the main pack will be reduced to 50% charge in roughly 30 years.

    If you insist, a 1 sq. foot solar panel on the dashboard will keep the 12V battery fully charged and then all we need to worry about is self-discharge of the main pack...
     
  18. JeffK

    JeffK Well-Known Member

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    How long does your phone take to turn on and connect to the network... would you be willing to wait that long every time you get into the car?

    Personally I'd find a small loss perfectly fine if it gives me instant on and I don't plan on parking it for an extended period of time. For everything else there's energy saving mode and unchecking always connected.
     
  19. Garlan Garner

    Garlan Garner Supporting Member

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    Again...We are only talking about reclaiming 0.1% of the battery in an 12 hour period of time - IF the roof is pointing at 33.3 degrees directly toward the sun as it rotates across the sky.

    You are willing to pay ....? for this tiny amount of juice?

    Or are you simply enamored with the concept? ...efficient or not?



    I mean....Elon is a genius. He had to be joking - in his dry humor - when he said that a solar roof is a possibility.
     
  20. Topher

    Topher Energy Curmudgeon

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    My question was directed at the assertion that my question, about whether he was willing to kill his great granddaughter, was unwarranted.

    Thank you kindly.
     

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