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Liquid solar generator

  1. Sep 8, 2012 #1
    If I had a black liquid that was thin, and I had a transparent liquid that was just lighter than the black liquid but didn't mix with the black liquid, and I put them in a dish out in the sun would the black liquid absorb the photons causing it to heat up and rise during the day, and cool down, and sink during the night?
     
  2. jcsd
  3. Sep 9, 2012 #2

    Bobbywhy

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    anaximenes, I am of the opinion that yes, the black liquid, as it absorbs infared energy from the sun, would rise to the top because it would become less dense as its temperature increased.

    After nightfall, it would dissipate that stored heat energy. Therefore it's density would increase and sink to the bottom, just as you have described.

    But to call that a "solar generator" seems to be an exaggeration: It does not generate anything.
     
  4. Sep 11, 2012 #3
    It would still be a cool experiment
     
  5. Sep 11, 2012 #4

    Bobbywhy

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    Yes, I agree, it would be a cool experiment! Why not perform it and come back here and tell everyone the results? Prove my speculative hypothesis wrong.

    Cheers,
    Bobbywhy
     
  6. Sep 11, 2012 #5
    Unless you put a little turbine in there to be spun by the transition. Not that it would generate much power, but still.
     
  7. Sep 13, 2012 #6
    ill do an experiment this weekend and post the results maybe if the turbine sometimes provided shade and sometimes didn't it would work but right now i just want to see if the change in pressure will have an effect
     
  8. Sep 14, 2012 #7
    While i was researching liquids i learned that this is really just how a lava lamp works but instead of using a lightbulb i would use the sun
     
  9. Sep 16, 2012 #8

    Low-Q

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    A better setup would be a hose containing the black liquid. Black color absorbs not only IR, but also the rest of the visible spectrum, and heats up the liquid. Make a closed loop and place the loop upright. Shield one side from the sun, so only the other side is heated. The fluid will start to circulate inside the hose. A small generator inside could for sure generate something useful - if the scale of the experiment is large enough.

    In your initial experiment, the transparent liquid will absorb heat from the black liquid, making it less efficient as a powersource. A lava lamp works about in the same way as your experiment.

    Vidar
     
  10. Sep 17, 2012 #9
    So far my experiment hasn't been working at all i think the problem is that i need a very precise density. If the black liquid is too dense it wont rise when it heats up but if its too thin it will mix in with the transparent liquid
     
  11. Sep 17, 2012 #10
    Vidar/ low q
    Im not sure where i would find a transparent hose thats long enough so that this experiment would generate energy and it would be very difficult to get a turbine in the hose. Also it would need to be a perfect ratio of density that might not even exist so that the black liquid would move horizontally
     
  12. Sep 18, 2012 #11

    Bobbywhy

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    anaximenes, May I suggest you study the following paragraph? This should explain for you exactly how this process works. I repeat, you should not expect to generate any significant power from this action. The operation of a Lava Lamp:

    “A classic lamp contains a standard incandescent bulb or halogen lamp which heats a tall (often tapered) glass bottle containing water and a transparent, translucent or opaque mix of mineral oil, paraffin wax and carbon tetrachloride.[1] The water and/or mineral oil can be colored with dyes. The density of common wax is much lower than that of water and would float on top under any temperature. However, the carbon tetrachloride is heavier than water (also nonflammable and miscible with wax), and is added to the wax to make its density at room temperature slightly higher than that of the water. When heated, the wax mixture becomes less dense than the water because wax expands more than water when both are heated.[2] It also becomes fluid, and blobs of wax ascend to the top of the device where they cool (which increases their density relative to that of the water) and then descend.[3] A metallic wire coil in the base of the bottle acts as a surface tension breaker to recombine the cooled blobs of wax after they descend.
    The underlying mechanism is a form of Rayleigh–Taylor instability.”
    http://en.wikipedia.org/wiki/Lava_lamp

    Cheers,
    Bobbywhy
     
  13. Sep 20, 2012 #12
    The problem I'm having is that the wax isn't at a big enough change in temperature ill try using ice water so that by the time the wax is hot enough the water is still cold enough to remain dense. After this I'm going to try a magnifying lens to get direct heat
     
  14. Sep 20, 2012 #13
    Does melted wax have any affect that immediately breaks microwave proof glass, i wanted to have my wax be hotter than the water early on so that it would be closer to the density swap initially so i put some cold wax with some water into a microwave hoping the water would heat up the wax but i immediately saw a layer of wax condensation on the cup and i assumed the wax was heated enough. When i took out the cup the bottom half fell off.
     
  15. Sep 21, 2012 #14

    Low-Q

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    Wax have (Most probably) a higher boiling point than water. The temperature could likely exceed 100 degrees C - maybe 200 degrees C or more. Maybe the reason why the cup "exploded".
     
  16. Sep 22, 2012 #15
    I don't think it was that the wax was boiling i think the wax somehow got inside the glass and expanded
     
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