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Discussion in 'General Electronics Discussion' started by joshwhite, Jun 18, 2010.

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  1. joshwhite

    joshwhite

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    Jun 18, 2010
    Hello, i am really into electronics and learning how they work, but i get puzzled quiet often about things, one of them I'm going to post on here to see if any of you can shed some light on my confusions. If you have a small electric vehicle that doesn't require lights, radio etc..., basically just the motor is running on the battery, i don't understand why you couldn't put a small alternator in the mix and have it constantly return power to the continually draining battery, if this were real, it would be free energy wouldn't it?
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    Thats perpetual motion and cannot be achieved in a system because of losses due to
    things like friction, voltage drop etc etc
    Its a nice thought and one I also queried my science teachers about more years ago than I care to remember

    Basically you cannot generate the same amount than what is being used by the system because of losses within the system

    some of the other guys here may like to elaborate more on my brief comment :)

    cheers
    Dave
     
    Last edited: Jun 18, 2010
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    If you can hear the engine running, or feel vibrations, or it has exhaust hotter than the intake air, etc... then energy is being lost.

    If energy is being lost then you obviously cant capture all the energy put into the system via an alternator (which will have it's own losses).

    Even if there were no losses, all you could ever do is break even. And breaking even isn't going to help anyone.
     
  4. florinanghel

    florinanghel

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    Jun 14, 2010
    It's the same thing that happens with car batteries. They all die at some point. Plus, recharging using an alternator does not actually fully charge the batteries. When you recharge a battery again and again there's more and more unusable current (or voltage, someone who knows better please explain) remaining in the battery. Think about mobile phone batteries, they last less and less while they get older, don't they?

    In order to bring a battery back to life, so to speak, (make it last longer) you need to get rid of that useless current in order to make room for the good one. For this, you need to reset the battery, by fully discharging (maximal battery discharge) and then charging it again.

    And, well, even though you could convert work into current, it's not efficient on such a small scale. You probably loose more energy in the process than you get.
     
  5. joshwhite

    joshwhite

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    Jun 18, 2010
    Thanks for all the coments guys im starting to understand it now, i understand the loss could be less then the gain, but if the electric motor driving the vehicle only needs 12 volt 22 amp 264 watt, and the alternator would provide 12 -14 volt 90 amp, would this idea work if a lithiom ion or deep cycle battery rather than a car battery?
     
  6. florinanghel

    florinanghel

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    Jun 14, 2010
    As I, davenn and (*steve*) previously said, the gain is too low to even consider. Those extra five seconds or so of battery life that you may get are simply not worth the effort. Plus, the alternator would add extra weight to the vehicle which would require the motor to squeeze even more juice from the battery in order to maintain the same efficiency. Been there, tried that... let's just move on. :)
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    There is NO gain. There is only loss.

    (Say that in a Yoda voice)

    Loss leads to sadness, sadness leads to pain, and pain leads to the dark side. Think not, Padewan, of perpetual motion.
     
    Last edited: Jun 18, 2010
  8. Resqueline

    Resqueline

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    Jul 31, 2009
    Like Dave, Steve, & Florin says.
    In your example you have a 264W motor and a 1260W alternator. Obviously the alternator is capable of overloading the motor by 1kW.
    Where is that power going to come from? It's nothing you get for free.
    Even if the alternator only took what the motor could deliver you'd have no power left for propulsion while still losing 50W, considering 90% efficiency for both items.
    The only time you can get someting returning to the battery is when braking (or going downhill). This is called regenerative braking and is often used by electric vehicles.
    Of course you have already spent more on accelleration (or going uphill) than what you get in return, but it beats wasting it as heat with friction brakes.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    considering regenerative braking specifically: You also have to also consider that you need to put approx 150% of the energy back into a lead acid battery that you took out. They are nothing like 100% efficient either. Other battery technologies are better, but nothing is perfect, and even less than nothing is better than perfect.
     
  10. jackorocko

    jackorocko

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    Apr 4, 2010
    If free energy was as simple as putting an alternator on a car that produced more amps then it consumed, we'd already be doing it.
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Admit it, we've all thought of it at some stage.

    I remember thinking about it the first time I learned that turning an electric motor caused power to be generated. If I recall correctly I connected 2 motors up and spun one. When the other failed to spin I pretty quickly realised that the power you generate is not as much as the power required to spin the motor the same amount. (I think I was about 10 years old).

    It was a few years later before I became aware of the formal reasons why.
     
  12. davenn

    davenn Moderator

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    that sounds so familiar, Steve :)
    ohhh those were the days when we were young and innocent ;)

    Dave
     
  13. markus.dnd

    markus.dnd

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    Jun 17, 2010
    all thou i bet that somehow it is possible to use randomly appearing gravitons for making power. I mean else than hydro plants :D
     
  14. ChosunOne

    ChosunOne

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    Jun 20, 2010
    Josh, looking at the specs on devices can be misleading.

    You're apparently looking at a specfic model design and specs (specifications) for your numbers, which I will accept at valid. So "the electric motor driving the vehicle only needs 12 volt 22 amp 264 watts", okay, but that doesn't mean it always needs 264 Watts. I'd guess that's a "cruising" number, the amount the motor needs to produce to cruise at, say, 55mph (just a guess) for long periods. If you go slower, like 10mph between stoplights downtown, it draws considerably less power (= less amps; Voltage remains more-or-less constant). If you're maintaining your 55mph up a steep hill, it draws more power (=more amps).

    So just for the first step, realize that the more mechanical work the motor has to do, the more electrical power it needs to do it. It's not a steady 264 Watts for all situations.

    Moving on to the alternator, the 12 -14 volt 90 amp you see on its specs don't mean that spinning it will necessarily produce 90 Amps of current. What's listed on the specs is the output of the alternator at a certain rpm (rmp = revolutions per minute, i.e., how fast it's made to spin.)

    There is usually a voltage regulator involved that keeps the voltage a constant 12-14 Volts, but the amount of current produced will vary with the speed you spin it. You might spin it slowly with a hand crank and produce as much as (just guessing) 1 or 2 Amps, producing 12 to 24 Watts. It's going to take a lot more mechanical power, like with an electric motor, to get the rated 90 Amps.

    If you ever get a hand-cranked alternator to play with, try this: Crank it with nothing hooked onto it to draw power. You can spin it up pretty fast when it's not producing any current flow (Amps) because it's not doing any work. When you put a load across it, like for instance a 4-Watt flashlight bulb, you discover you have to crank it a lot harder--producing current takes mechanical work. Producing more current takes more mechanical work; so if a 1-Watt bulb made you work hard, a 2-Watt bulb is going to give you hand cramps after a minute or two.

    You've probably figured this out by this time: The electric motor you use in your car, running at 12V/22Amps (=264 Watts) can't supply the mechanical power it takes to spin the alternator fast enough to generate the 90 Amps (which, at 12 Volts, = 1080 Watts).

    Hope that helps to clarify it for you.

    I encourage you to continue to ask questions as ideas occur to you, and keep asking until you get answers that satisfy you. I also encourage you _not_ to accept answers like "If it could be done, somebody would already have done it." That may be true most of the time, but the history of progress is full of examples where it wasn't.

    I'd bet money that most or all of the experienced technical types on this forum have made some innovative improvment, sometime, to something they worked on over the years, because they didn't think, "If it could be done, somebody would already have done it."


    It's probably correct (just guessing) 99.9 % of the time, but if you accept that answer 100% of the time, you're going to miss some very rewarding moments in your life. So keep looking at possibilities and don't let them go until you get answers that satisfy you. Even if it isn't practical, you'll learn something finding out why.

    And don't _ever_ let anybody tell you that all the good ideas have already been thought of.
     
  15. ChosunOne

    ChosunOne

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    Jun 20, 2010
    And speaking of free energy: Kudos to Estonia for developing a strong WECS (Wind Energy Conversion Systems) base in their economy. Not that I'm an expert about Estonia, but they're located right along the Baltic sea and have no mountains and have low hills, so it always seemed to me to be an ideal environment to develop wind energy; and apparently they thought so too.

    Why spend time looking for "free energy" when you have so much right at hand? :D
     
  16. jackorocko

    jackorocko

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    Apr 4, 2010
    when it comes to free energy, breaking the laws of physics isn't gonna be easy. I apologize if it sounded condescending, but it's a hard fact that most people should start accepting. It's not like the concept is new and there is plenty of evidence to show that it will not work already. Which is why it has never been accomplished before. :(
     
  17. garethjones10

    garethjones10

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    Jun 16, 2010
    Hello

    This is Gareth Jones

    Hello, i am really into electronics and learning how they work, but i get puzzled quiet often about things, one of them I'm going to post on here to see if any of you can shed some light on my confusions. If you have a small electric vehicle that doesn't require lights, radio etc..., basically just the motor is running on the battery, i don't understand why you couldn't put a small alternator in the mix and have it constantly return power to the continually draining battery, if this were real, it would be free energy wouldn't it?

    Regards,

    Gareth
     
  18. davenn

    davenn Moderator

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    1,952
    Sep 5, 2009
    Gareth
    read the rest of the topic and you will find that that is what the original person asked
    and you will read ALL the explanations as to why it wont work

    cheers
    Dave
     
  19. WesternSam

    WesternSam

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    Jul 5, 2010
    Bad answers

    Just saying that "there is no way to make free energy" is a bad answer. If you have an equation that implies that you are getting free energy you obviously are misunderstanding something. You still need to understand it.
    ----
     
  20. ChosunOne

    ChosunOne

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    115
    Jun 20, 2010
    At this point I want to make a distinction in the terminology used so far in the thread. This is not directed at you personally, WesternSam--you just happen to be the latest person to use the terminology in the thread title.

    "Free energy" _isn't_ the same thing as "Creating energy out of nothing" (a.k.a. Perpetual Motion), which is the real subject addressed at the outset.

    There's plenty of free energy around us: Water flowing downhill produces kinetic energy that nobody paid a cent for. When that energy is harvested in hydroelectric generating plants, it (the energy, not the plant) is free.

    There is a significant amount of moving air (called wind) above most of the Earth's surface, and that free energy is harvested with Wind Energy Conversion Systems (WECS, often mis-labeled "windmills").

    So please let's be clear that there is plenty of free energy out there. There are just no perpetual motion machines. As was stated earlier, most electronics vets have had the idea originally posted in this thread, way back before they got the mathematical foundation to grasp the Third Law of Thermodynamics.

    On the other hand, folks who don't have that foundation will sometimes pooh-pooh an idea because it _looks_ like a perpetual motion machine.
    I read a proposal years ago of using the capillary action of a large bank of thin tubes to raise water, collect the water at a higher level, and harvest the energy of returning it to its former level; and raising it again to repeat the process.

    The usually response was to cry out, "Aha! It's a Perpetual Motion Machine! Therefore it Won't Work!!"

    In fact, there's no technical reason it wouldn't work. It isn't practical because it requires too much investment for such a small energy return--but technically it's possible to build such a generator--because it isn't a Perpetual Motion Machine anymore than hydroelectric generators are.

    The physics of capillary action are not as widely understood as the evaporation and condensation that produces rivers (and hydroelectric plants), but the energy required to raise water in a thin tube doesn't come from nowhere. Like the energy used to produce rivers, it comes from the environment around it, nearly always (excepting geothermal) powered ultimately by the sun. In other words, it's powered by an outside energy source.

    If you're curious enough to seek a more detailed explanation, this proposed capillary action device is described in "Energy and the Earth Machine" by Joseph Carr, published around 1975.

    I encourge posters like Josh to present ideas like his proposed "Free Energy" idea. There's nothing wrong with asking, and the potential is tremendous for learning new and fascinating stuff, if you're curious enough to explore new (to you) ideas.
     
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