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Can electric cars produce electricity?

Discussion in 'Technical' started by Efilnikcufecin, Jul 27, 2017.

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  1. Efilnikcufecin

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    New to site so this may have been discussed. Wind turbines and water turbines create electricity from the force of wind and water spinning them correct? Is it possible to have the spinning tires/driveshaft create same? Understood it cannot completely self propel itself, but couldn't this make it more sustainable and generate power between charging?
     
  2. LargeHamCollider

    LargeHamCollider Battery cells != scalable

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    Derp.
     
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  3. HankLloydRight

    HankLloydRight Fluxing

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  4. jelloslug

    jelloslug Active Member

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    Nope. You cannot get more energy out than you put in.
     
  5. Efilnikcufecin

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    Not implying more energy than put in. Simply generating any electricity, such as to power the radio or aux functions rather than drawing that power from battery
     
  6. Efilnikcufecin

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    Appreciate the well thought out response
     
  7. DrivingRockies

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    Using the battery to add mechanical power to create less electricity than you started with?
     
  8. KarenRei

    KarenRei KarenRei KarenRei KarenRei KarenRei KarenRei

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    They're assuming that you're trolling. I'll be nice and assume that you're just a kid.

    No. There is no advantage to taking energy out, turning it to motion, then turning the motion back to electricity, versus simply taking the energy out and using it directly. Every time you convert the form of energy, part of it gets lost to heat.
     
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  9. Efilnikcufecin

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    Thank you. I new there were smart people in this forum.
     
  10. mongo

    mongo Member

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    Any power you pull out of the spinning motor got there either by:
    1 The battery (most cases)
    2 Gravity and a slope (but you got up the slope using the battery)
    3 Someone else's vehicle towing/ pushing you (has been used to recharge certain cars)
    4 A really high wind (seriously, find shelter)

    Regenerative braking does charge the battery by converting the mechanical motion back into electricity.

    Oh and, "nice life" right back at you.
     
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  11. DrivingRockies

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    knew*

    Mostly just smart-*** people on here.:rolleyes:
     
  12. Efilnikcufecin

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    Can I blame autocorrect?
     
  13. KarenRei

    KarenRei KarenRei KarenRei KarenRei KarenRei KarenRei

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    #13 KarenRei, Jul 27, 2017
    Last edited: Jul 27, 2017
    Nothing wrong with asking questions. :) It's just some people will assume you're trolling if they expect anyone who stops by to know the answer to what is being asked.

    One of the great realizations of physics (largely brought together by Newton) was that energy was interchangeable and quantifiable. That you can convert gravitational potential energy, kinetic energy, heat, electricity, and countless other things between forms and end up with a quite predictable amount of energy on the other end. That you could determine energy from force times distance. That you could get force from mass times acceleration. A series of simple equations allowed for an immense wealth of calculations toward understanding our universe.

    One of the unavoidable laws of the universe is entropy, often stated that the universe tends toward disorder (but physics has a very specific definition of "disorder"). All reactions/conversions must increase entropy - and in practice, this generally means "some of the energy turns into heat", which increases entropy. So every time you convert, you lose. And if you want to turn the heat back into electricity, you still have to have a net overall increase in entropy, which in practice limits you to Carnot's law - all heat engines have a maximum possible efficiency based on the difference in temperature between the hot and cold side of the heat engine. This, by the way, is the main reason why electric motors can approach 100% efficiency but internal combustion engines are generally under 50% efficient, and commonly well less.

    So we try to avoid converting energy whenever we can, and just use it directly! :)

    There are, however, times when you may want to convert energy. A good example is hybrid cars. Internal combustion engines vary widely in efficiency. Their maximum efficiency is when run at high torque, low RPM. Outside of that and their efficiency plunges off a cliff. So for a hybrid car, they downsize the engine (meaning that it spends most of its time operating closer to its maximum torque) - but then so that it's not underpowered, they pair it with an electric motor to boost it in hill climbing, acceleration, etc. The battery for this motor is in part charged by regenerative braking, but also by a generator (the motor itself, being spun by the engine). Generating power puts more torque load on the engine, and is particularly done when the engine is otherwise in low torque conditions. In short, a hybrid keeps its engine in high torque, low RPM conditions for much more of the time, and thus operating much more efficiently - and this added efficiency readily overcomes the extra losses incurred by changing the form of energy from motion to electricity and back to motion.

    Whenever you think about the topic of energy generation and use, always think about what you're converting, how much you lose, and what the effects will be. For example, let's say that someone says "I want to put pads on the road such that, as cars drive over them, it pushes them down, turning a generator." Is that a good idea? Well, let's ask ourselves, where is the energy really coming from? Because remember, it never just appears. The answer is, of course, it's actually coming from the cars. How? Because each time the car pushes the pad down a bit, it's now a bit lower than it was before. Height is a form of potential energy. To restore its height (for example, as it moves into the next pad), it is effectively driving uphill, and thus working their engines harder. So you're just taking energy from the cars and making them burn more gas**. Probably not what the person who proposed it wanted!

    *** ... Unless, of course, you're pushing the engines on average into a higher torque regime which, while they will burn more total energy, the increase in efficiency means more energy is being recovered by the pads than the cars are burning extra in gasoline! How is that possible? The efficiency of a combustion engine is the ratio of how much of the energy of the fuel is converted into motion vs. to heat. So if you're boosting the efficiency by making the cars work harder, that just means that just means that you're getting more of the energy as useful work rather than heat, and that's where the extra energy you're capturing is coming from.
     
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  14. jelloslug

    jelloslug Active Member

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    You are talking about regenerative braking. All EVs use regen to slow the car and recapture as much as possible to recharge the battery.
     
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  15. DrivingRockies

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    I assumed. Nice to keep things light-hearted.
     
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  16. animorph

    animorph Member

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    Yes, regenerative braking is generating electricity that charges the battery. It saves some of the energy that would normally be wasted as heat by normal braking.

    But anything that uses the car's motion to charge the battery will cause a similar drag on the car, just like you were using the brakes. You'd have to apply additional power to the motor just to overcome that drag and maintain your speed. And because neither the battery charging nor the motor is 100% efficient, the additional power used for the motor will always be greater than the power being returned to the battery. That means it's never going to be beneficial to harvest energy from the cars motion unless you need to slow the car anyway.
     
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  17. Stirfelt

    Stirfelt Member

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    Every vehicle since the very early days of motor cars ..... have generated electricity. That is the purpose of the generator, then later the alternator. A hybrid has a "motor/generator" and produces electricity when coasting. Prius have 2 .... MG 1 & MG 2.

    Now the answer to the question pertaining to the M3 is .... regenerative brakes generate a little electricity.
    But it is a good question .... I'm not sure if the Tesla power motor is a generator when coasting?
     
  18. Tiger

    Tiger Member

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    As long as there are ICE cars, it would actually be possible to capture energy from all downhills, because the cars do not need this energy for themselves as regenerative energy, but instead capturing the downhill energy would additionally benefit the ICE cars by slowing them down and saving braking material.

    Having said that, however, considering ICE cars hopefully finite era in this world, the energy recovered from these mechanisms would not necessarily recover the energy spent installing these mechanisms ... hmm ... well ... probably would afterall millions or trillions of miles are driven, especially if the locations are optimally chosen. It would be like a hydroelectric plant where the stream of water is a ICE car stream of traffic pushing on the energy generators downhill.
     
  19. SageBrush

    SageBrush Active Member

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    Sure

    Raise the car off the road when parked and attach sails to the tires
     
  20. deonb

    deonb Supporting Member

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    This is like the airplane on a conveyor belt thing. It's intuitively obvious to some people and not at all to others.

    I've stopped immediately assuming people are trolling when they ask this.
     

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