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Theory for a new engine design

  1. Oct 26, 2005 #1
    Hi there,

    I was wondering if you might be able to offer some proof or disproof on a theory for a new engine design that I am working on.

    We all know that steam as it condensates in a closed vessel creates a vacuum, so I am designing an engine which is designed to harness this natural energy as its first priority capturing the power created as a substance seeks to revert to its most natural state of rest.

    The basic design that I am thinking about is as follows.

    Sealed piston chamber with a small amount of liquid which becomes volatile in the presence of light moving from liquid to gas (eg one of the many petrochemical byproducts).

    The transition to gas triggered by a light as a kind of "firing" mechanism forcing the piston from the down position to the up position as the liquid expands to a gas state (is room temperature possible ?)

    With the removal of the light source the gas reverts to a liquid creating a vacuum in the chamber and "pulling" the piston back to the down position (are the up and down forces equal ?)

    My aim is to design an engine which not only converts electromagnetic energy to chemical energy to motive energy but also create a situation where there are no emissions and the only ongoing "fuel" is light itself.

    From my research I have found that there are some volatile light sensitive chemicals which require little "light charge" to enact the transition.

    The primary questions I have are as follows :
    1. Will the vacuum be created at the same rate as the original expansion when the light is off.

    2. Will the chemical breakdown after repeated transitions ? Are there any known ones that dont ?

    3. Is the vacuum force equal to the expansion force as logic suggests or will it retain some degree of electromagnetic charge.

    The engine design is being included as part of a movie to raise money to preserve the worlds oldest rainforest which needs an income stream to be created in order to be shielded from encroaching residential development.

    If you are able to shed some light on whether this design contravenes any of the laws of thermodynamics it will be of great assistance.

    I am not a physicist myself just a guy looking to solve the problem of greenhouse emissions.

    Thanks for any knowledge you are interested in sharing

  2. jcsd
  3. Oct 26, 2005 #2
    In vaccum, a liquid like water or gasoline will vaporize. You won't be able to liquify it.
  4. Oct 26, 2005 #3


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    It won't be a total vacuum, but condensing steam would create an area of low pressure that you could use to drive an engine. That's actually a convoluted description of part of how a conventional steam engine sorta works. Most of the rest seems like gibberish, but lets see if we can figure it out...
  5. Oct 26, 2005 #4


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    It sounds like you want to seal a fluid (liquid/gas) in a cylinder, expose it to light which changes it to gas, then remove the light which converts it back to liquid by condensation. Is that about right?

    The Law of "Conservation of Energy" says that the amount of energy that one might expect out of a process such as this is equal to the amount of energy you put in. The liquid in the sealed cylinder is not producing any more work than is put in by the light in this case. If such a fluid even exists. One could for example suggest that water could be used, and we could simply add energy in the form of heat to the water and remove it again. But the amount of energy would be limited to the amount you put in and whatever efficiency the cycle is limited by.

    That's not to say this idea won't work or won't be more efficient than an engine using gasoline. The concept doesn't have good definition at this point so there's little to evaluate. But understand that the "light" you are proposing must be the source of energy for converting thermal to mechanical energy and there is a major drawback. The energy conversion is slow so the power you might get out of this engine is inherently very low, much lower than would be practical for a car. Heat transfer is always orders of magnitude slower in moving energy than a chemical reaction.

    Another problem is that one must remove the heat to start the cycle over again. You can't expect it to simply condense, the law of conservation of energy forbids that. So you need to remove heat to recondense the fluid which is another source of inefficiency.

    Regarding the amount of force produced on each stroke, the amount of force produced is equal to the difference in pressure across the piston times the area. For a vacuum, the limit is 14.7 psi times the piston area since that is atmospheric pressure. You could put a pressurized chamber on the opposite side of your piston though and increase the force when you pull a vacuum.
  6. Oct 26, 2005 #5


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    So, lets go through this:
    Ok, sealed chamber (so no flow of the working fluid), and a liquid to be vaporized.
    This part is a little unclear. If you use water, for example, there is no "triggering" - the water is vaporized by putting a specific amount of heat into it. It sounds like you are hoping to put a small amount of energy in and get a lot of your working fluid to vaporize. As mentioned, that's a violation of conservation of energy, so no such substance exists.
    Fine, but it would take a long time for the heat to radiate or convect away from the cylinder, to condense your working fluid. The answer to the question there is no, the energy gained from the condensation would be substantially less than the energy gained by the expansion - and would be a much slower proces. That's why most thermodynamic engines don't try to make use of it.
    I think you likely misunderstand how those chemicals work. The energy has to come from somewhere. Can you provide a reference?

    If that's what this is all based on, I don't think there will be much you can accomplish with this.
    No - it is much faster to heat a vessel than cool it. Consider that it takes all of 5 minutes for your car to warm up, but several hours for it too cool.
    I think you misunderstand what these chemicals do. Can you give an example of one you are talking about?
    No - when you vaporize a liquid (such as water) in a thermodynamic engine, you generate hundreds or even thousands of psi of pressure. The maximum you can get by condensing it is -14.7psi (gage pressure of a vacuum).

    And electromagnetic charge has nothing to do with this.
  7. Oct 26, 2005 #6


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    Russ did a great job pointing out the main problems the orig spec, there are some fairly serious flaws to extract any useful energy from this engine and without a energy source this is pointless. Where does the light come from, the sun?

    Clapstyx you have almost described in part the workings of a sterling engine that needs little more than a heat differential to use air as its means of transforming that heat into motion. Do a search online and you'll find examples of its heating-expansion/cooling-contraction principles at work, similar to your description except simpler since they only use air.
  8. Oct 26, 2005 #7
    you have "invented" the first type of steam engine
    unfortuneatly it is very inefficent as it was low pressure
    and ''worked'' on the wrong side of the cycle
    there is far more power to be had on the hot cycle then cooling/vacume


    anyway there is no free lunch and power out is less then the power input
    and you need an external power input
    even if you find a semi-majic working fluid and a lazer it still will be very inefficent
  9. Oct 28, 2005 #8
    Hmm Ok the argument might be a bit pointless by the sounds of it.

    I wasnt thinking of using water vapour because of the obvious energy and cooling requirements but rather one of the chemicals listed in the Merck index which are volayile at near room temperature. Basically I was thinking that a liquid on the that was unstable and on the cusp of moving to a gaseous state (eg some types of chlorine) might move relatively easily between the two states so that the light simply acted as a trigger to defining what state it was in.

    I wasnt aware that there were rules about the strength of a vacuum which would come into play.

    Granted there may be timing issues on the gas to liquid cycle but theoretically if the rest of it worked you could have a long series of piston chambers each "collapsing" in sequence with the liquid to gas transitions put into that timing. ie when a chamber had condensed reactivate it.

    Sounds impractical regardless doesnt it.

    Despite all that though, and I am getting philosophical here, pretty much everything else on the planet has been able to harness solar power sufficiently well to survive over the long term. Conventional solar panels which create electrical energy to my mind seem to not exactly be delivering the kinds of outcomes we are seeking so I was looking at the problem from a new angle ie to see if there was a transitional way of turning solar energy into mechanical energy.

    Thanks for your help though. I just wanted to make sure we werent overlooking the obvious.
  10. Oct 28, 2005 #9


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    Hey Clap, don't be discouraged. The idea there may be a fluid that can absorb light as a liquid and convert to a gas is novel and may possibly even be a fairly efficient process. But understand that this means the light energy provided is going into converting a liquid to a gas and that conversion doesn't create energy, it is only converting it. So if you have 1 joule or Btu of energy coming out of the process, you have to put at least 1 joule or Btu in. Because of losses due to that energy being converted into heat, you won't get all the energy out.

    If such a fluid exists, it might be used for stationary power, say for example by heating using sunlight and cooling in a heat exchanger*, but whatever the process may be, you can only convert energy from one form to another, so whatever energy you are using for your light source is ultimately the source of your energy, not the fluid.

    *Note: one could employ this type of process with a wide variety of fluids though, not just a photosensitive one. Water is commonly used and other fluids can also be used. It is a matter of creating an economical cycle more than finding a way of doing it. It can be done easily, but not economically.
  11. Oct 28, 2005 #10


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    I can envision such a fluid being very useful for actuators in some circumstances as well (eg: solar powered log-splitters).
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