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On board generator

Discussion in 'Technical' started by longshadows, Apr 14, 2016.

  1. longshadows

    longshadows Member

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    Any thoughts as to why Tesla automobiles don't incorporate any sort of internal generator, which might run when car us in motion, if not charging the main battery itself, might supplement power usage of accessories, like lighting, a/c and heating. Any extension of range has got to be a winner.
     
  2. strider

    strider Active Member

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    Too heavy and too complicated. Tesla will only make pure-electric cars. Plenty of hybrids out there. Having an on-board ICE is a crutch for not doing good EV engineering. Better to sink those development dollars into new tech (battery, supercharger, etc) than old tech (ICE).
     
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  3. JPP

    JPP Active Member

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    ...um, are you maybe thinking like perpetual motion---the generator is driven by the wheels???
     
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  4. McRat

    McRat Active Member

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    Blasphemy. While dual fuel systems are common in engineering, when it comes to Electric Vehicles, it is a religious matter. Even a generator for emergency use only is sinful. :D

    Start with a 2wd Model 70s. Put a 75kW generator in the Frunk. It will be allowed 200 miles of gas and still be considered an EV. It would weigh the same or less than a 90D. It would have no geographic or climate limits at all. The cost would the same as a 90D. For most owners, it would never use gasoline. The generator is there just for emergencies and to pretend you love driving 2500 miles across the US instead of flying or taking a train.
     
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  5. AB4EJ

    AB4EJ Member

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    All you have done is design an extended range Chevy Volt.
     
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  6. longshadows

    longshadows Member

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    Sorry, guys, I didn't express myself more clearly. I had no thought of a hybrid or any sort of ICE device. I was asking about the possibility of the motion of the car running a generator of modest size, which in turn made some energy return to the battery or could run some accessories, thereby extending the miles/charge and keeping everything electric. Not a perpetual motion affair, but headed in that direction.
     
  7. Petra

    Petra Member

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    Sooo... expend energy to drive a generator linked to the wheels in order to provide power to the car? You're describing a perpetual motion machine and/or the regen system EVs already have (being generous). It would be more efficient to just use the power directly.
     
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  8. McRat

    McRat Active Member

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    A faster, larger, better looking, more luxurious, Chevy Volt with SuperCharging.

    Sort of like what the Cadillac ELR should have been but was not.
     
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  9. kort677

    kort677 Active Member

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    do you mean like the one on the fisker? I wonder why you don't see too many of those?
    in all seriousness, the volt has one if carrying around a generator that burns gas is for you then maybe the volt is the car for you.
     
  10. auger

    auger Member

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    This comes up pretty often in various forms. You're describing a perpetual motion machine--getting more out than you put in.

    wile_e__coyote_by_prometheus_plus_fire-d2zanaw.png
     

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  11. deonb

    deonb Active Member

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    Soo...

    1. Battery drives motor (and loses some power due to heat)
    2. Motor drives generator (and loses some power due to heat)
    3. Generator charges battery (and loses some power due to heat)

    It all works...

    But it you want to generate heat, there are cheaper ways to do it.
     
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  12. Johan

    Johan Took a TSLA bear test. Came back negative.

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    I just have one question: how many alternators do you need???
     
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  13. AndreN

    AndreN Member

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    Teslas already have a generator onboard - it's the motor. When you let of the accelerator, instead of the motor being fed electricity to move the car forward, the car's momentum is used to spin the motor and generate some electricity to recharge the battery a bit. It also creates a lot of drag which slows the car down. Look up "regenerative brake" on Wikipedia for more information. The amount of energy returned is always less than the initial amount used to accelerate the car.

    Another way to look at this - if it were possible to spin a generator with no effort to make electricity, why do portable generators people use during power outages require a continuously running gas engine to spin the generator? You're converting one kind of energy to another (chemical energy in gas to kinetic energy in the spinning output shaft to electrical energy). Energy can't come from nowhere.
     
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  14. AB4EJ

    AB4EJ Member

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    Could we please come up with some ideas that don't involve rewriting the first two laws of thermodynamics?
     
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  15. diamond.g

    diamond.g Member

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    Honestly I can't tell if this is a hoax or not.
     
  16. ggr

    ggr Roadster R80 537, SigS P85 29

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    Of course it's a hoax.
     
  17. diamond.g

    diamond.g Member

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    I figure. Lol.
     
  18. roblab

    roblab Active Member

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    That's silly, to me. Just buy a 90D.

    Do you have any idea how big a 75 kW generator is? It would not fit in a frunk. Neither would a 7.5. Maybe a .75 kW. Electricity is virtually (and realistcally) everywhere. Plugging in to even a 110 outlet would get you more miles quicker, but with near no planning, your car will tell you where the next SC is. And hauling around a gas charger plus gas, hoping for some emergency where you need to use it, is folly. In tens of thousands of miles, dozens of superchargings, hundreds of home chargings, I have never needed some gas engine to help me make it through the day.

    Now, if you owned a Volt, and ran out of charge after 30 some miles, well, you might want backup.
     
  19. McRat

    McRat Active Member

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    The State of the Nation in 2016, is you cannot drive an EV anywhere you wish, not even a Tesla.

    It will be true someday, but not today.

    Yes, a 4 cyl engine will fit in the nose of a Model S. They fit V8's in hoods like that.
     
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  20. Saghost

    Saghost Active Member

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    I'm not sure why you'd need a 75kW generator - even 75 mph is only a little over 20 kW in the steady state, and any sane system design/user would bring the ICE on well before the charge is completely drained, which will handle acceleration and hill climbing power demands.

    Of course, that's a lot of weight you'll be carrying around to not use 99% of the time - and a lot of maintenance requirements. Also a lot of manufacturing cost, with catalytic converters and a modern direct injected automotive type engine, too.

    Of course, as other folks have mentioned, Tesla isn't going to do this. It runs contrary to their mission and message, and they'd rather spend their money making it possible to drive an EV anywhere instead. If Tesla made an fossil fuel range extender, lots of folks would take it as an admission their way can't work.

    One of the more intriguing speculations I've seen has centered around a Frunk mounted metal-air "Primary" battery. At the currently demonstrated 1.3 kWh/kg, an Aluminum-Air battery weighing 60 kg/~130 pounds in the Frunk would double the range of a 90D (since it doesn't need anti-bricking protection.)

    The theoretical limits are some 6 times that - a couple thousand miles of range extension from that same 60 kg. Of course, it's a one shot system - you're oxidizing the Aluminum plate into a slurry as you go, and it can't be recharged easily - you'd recycle the slurry and buy new plates and electrolyte instead. Some folks believe the cost of doing that could get down into the range of gas if a good recycling system is instituted (and of course, you'd only use it a bit at a time, to cover places you couldn't charge, stopping to recharge the car where you can.) Tesla apparently has taken some patents related to integrating a metal-air battery into a rechargeable EV...

    If someone did decide to do a fossil fuel range extender, the right way would be with a ~30 kW microturbine. No coolant, no oil, no timing, no maintenance and it'll run on any liquid fuel (or any gaseous fuel - gotta choose one or the other for burner design I believe) - and cleanly enough that it doesn't need a catalyst. Much lighter and potentially somewhat smaller than a comparable ICE. A little expensive at the moment, mostly due to a lack of economies of scale. Propane is likely the ideal fuel for it - it stores at low pressures (mostly as a liquid, even,) won't degrade over time, and is widely available in the correct form, either in self contained bottles or at filling stations.

    But I'm really thinking this approach isn't necessary now, short of a zombie apocalypse - unless you want to drive a Tesla to Alaska or something like that (which I still imagine will become feasible in just a few years if nothing derails Tesla.)

    For the Zombie Apocalypse folks, you want a gasifier to feed the turbine, too - then you can put just about anything into the car (the gasifier takes solid (or possibly liquid) hydrocarbons and breaks them into much shorter chains at high temperatures in an oxygen free environment (generated by burning a small amount of the fuel) yielding a combustible gas mixture to feed the ICE/Turbine. Most folks who use them run them on chipped wood or pellets made from wood/grass/hay I think.)
    Walter
     

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