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Fusion a suicidal power source?

  1. Apr 27, 2005 #1
    I'm sure most saw the article in today's NY Times on "table top fusion".
    (For those who haven't...)

    http://www.nytimes.com/aponline/science/AP-Tabletop-Fusion.html?hp&ex=1114660800&en=6ac101f390e18d4d&ei=5094&partner=homepage [Broken]

    And the article does mention that this experiment doesn't do much in the way of offering a solution to our energy problems, at least not this week, or even this year, but then again, over enough time, who knows?
    What worries me about fusion is that I don't understand the process very well. I really don't want to start a thread that's going to devolve into a debunking argument, but I've got a question, and I was hoping someone in here would know a bit more about this than I do (not exactly a stretch).

    K; from what I understand you take a pair (actually lots of pairs) of deuterium atoms (which are basically weird hydrogen atoms, hydrogen atoms from "heavy water"), you smack 'em together, or squeeze 'em together almost too tightly to imagine, and you get a helium atom along with one incredible amount of energy.
    What bugs me about this idea is that it seems to turn hydrogen into helium, and you NEED hydrogen. Without hydrogen ya can't have water. Now assuming fusion power actually does become practical, I can see where a few fusion power plants eating up hydrogen wouldn't be a problem, but... If you got to the point where fusion power was the *primary* "power source of the future", where dammed near everything on the planet was dependent on it, wouldn't that start to... well... dehydrate our beautiful little blue world?

    Or is it the case that even having to generate ten times the amount of power we use now would require such miniscule amounts of hydrogen that it wouldn't really have any measurable effect on how much hydrogen is around, let alone start to threaten to "dehydrate" the planet?
     
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Apr 27, 2005 #2

    Integral

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    If we ever are able to generate power by fusing water we will have lots of time to work out the solution to your problem before it becomes a problem.
     
  4. Apr 27, 2005 #3
    "If we ever are able to generate power by fusing water we will have lots of time to work out the solution to your problem before it becomes a problem."
    (snicker fit)
    Better yet if we can learn to fuse manure, or even BETTER than that - Male Bovine Manure! (A.k.a. "massless manure" ;-) There's a LOT of that around)...

    But seriously Integral, where do deuterium and trituim come from? If the ITER were to work tomarrow afternoon, after the party, where would the "fuel" come from for large scale power production? Ya gotta understand that this kind of thing isn't as obvious to me as it is to you.
     
  5. Apr 27, 2005 #4

    Janus

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    By a quick "back of an envelope" calculation, I estimate that if the entire worlds energy for a year was supplied by fusion, it would only use up about 1/150,000 of the world's water supply.
    Besides, with fusion power, we could most likely be able to build spacecraft capable of going out and collecting all that water spread out in the solar system in the form of ice.
     
  6. Apr 27, 2005 #5

    Danger

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    That amount of energy would also allow us to initiate even more powerful fusion reactions, such as helium-lithium and really get us going. :biggrin:
     
  7. Apr 27, 2005 #6

    Pengwuino

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    150,000 years using the water on earth? Still seems like a low-ball. What kind of energy consumption are we using in your calculation and how much water exists on earth?
     
    Last edited: Apr 27, 2005
  8. Apr 27, 2005 #7
    EEEK!
    That sounds friggin HUGE! I realize that's just a b.o.t.e., only in the ball park if ya count the parking lot kinda quicky estimate, but... still.
    Settle me down here a bit.
    That SOUNDS like another way of saying that if all of the world's energy needs were met just by fusion and nuthin else, for just a single year(!), "global warming" would be the very LEAST of our problems. I mean if 1/150,000th of the world's entire water supply went up in helium - in just a year(!), and then kept doing that, year after year after year, holy cr@p! Wouldn't that radically, and I mean RADICALLY change things like the weather?
    In a situation like that it seems to me that we'd better be dammed sure that we have infrasturcture in place to go get all that water spread out in the solar system LONG before we EVER allow ourselves to become anything close to heavily dependant on fusion power.
     
    Last edited: Apr 27, 2005
  9. Apr 27, 2005 #8

    russ_watters

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    That seems high - how did you get that?
     
  10. Apr 27, 2005 #9

    Pengwuino

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    Monster, thats 150,000 years worth of power we're talking about. Thats like saying before we ever decide to cut down a single tree in a forest (and take a year to do it), we better have plans immediately to fix the problems we make. Plus of course, its affect per year would be just like a single tree in a forest lol.
     
  11. Apr 27, 2005 #10

    Integral

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    He would not build up in the atmosphere if that is what you are attempting to say. He is to light to remain in our atmosphere, it would be lost to space. Seems to me like you are being a bit reactionary here. I guess you think it is better to keep burning fossil fuels? :uhh:
     
  12. Apr 27, 2005 #11
    This number is useless without knowing what you mean by "world's water supply". 1/150 000 of all water is a lot, it would reduce the sealevel by almost 20 mm a year and might kill us all fairly rapidly.

    That is pure science fiction. There is nothing to suggest that humans will ever be able to collect anything of size from anywhere in the solar system.

    What would you prefer, live without oil or without water?
     
  13. Apr 27, 2005 #12

    Danger

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    Let's put this into a more everyday perspective. Depending upon the efficiency of the plant, a fusion generator would use between 500 and 1000 gallons of deuterium/tritium to supply the full energy needs of Chicago or Los Angeles for a year. Deuterium composes about 0.02% of all naturally occurring water, and tritium is derived from lithium rather than water.

    Rubbish! It's science fact. There's never been any question that we can do it. The only debate is whether or not we will do it, and which of several practical methods will be utilized.
     
  14. Apr 27, 2005 #13
    It would use 1/150,000 of the worlds deuterium each year, not 1/150,000 of the world's water. Only a small part of the water in the ocean has deuterium in it (heavy water or HDO).
     
  15. Apr 27, 2005 #14

    Janus

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    Your right, it is. I went back over my calculation and realised that I skipped a step (converting km³ to m³ when figuring the volume of the oceans), this drops the fraction down by a factor of 1,000,000,000.
     
  16. Apr 27, 2005 #15

    Janus

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    Oh come on! Remember, we are already assuming that we have practical, controlled fusion power. If we really needed that water, that in itself would give us the means to go out and get it.
     
  17. Apr 27, 2005 #16

    Pengwuino

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    And if we cant, we can at least give ourselves a pat on the back for surviving for such a long time :D

    lol nice conversion error there too. I remember doing E=mc^2 and getting mad at someone who got an answer 3 OOM smaller then mine (hehe... so mass isnt in grams :D)
     
  18. Apr 28, 2005 #17

    Danger

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    Hey, thanks for showing me how to write E=mc^2 without having superscript available! I didn't even know my keyboard had one of these ^^^ keys until I saw your post. So now I can tell him to run E=mc^2*0.04 through his brain and see how much efficiency we're really talking about. :biggrin:
     
    Last edited: Apr 28, 2005
  19. Apr 28, 2005 #18

    Integral

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    Running out of oil is just a matter time. So the choice is not oil or water, it is use water or revert to the preindustrial age.
     
  20. Apr 28, 2005 #19

    Pengwuino

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    Man, what if someone found a way to synthesize petroleum... All hell would break loose.
     
  21. Apr 28, 2005 #20

    Danger

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    What's the big deal? All you need is a dinosaur and some really big pliers...
     
  22. Apr 28, 2005 #21

    Pengwuino

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    Pliers, check.
     
  23. Apr 28, 2005 #22

    ZapperZ

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    Probos76, meet the Sun. Sun, meet Probos76.

    Just don't look at the Sun too long....

    Zz.
     
  24. Apr 28, 2005 #23
    So given then choice you would live without both, a brilliant choice if I may say so.

    That is a much more sensible number, it might even keep us going until the end without resorting to science facts from the makers of Star Trek.
     
  25. Apr 28, 2005 #24
    Actually, you seem to be reading exactly the opposite of what I am from that statement. It appears to me he's saying we had *better* use the water unless we're willing to go back to the 18th century technology-wise.

    The thing about Star Trek is that the numbers just don't add up. It's essentially hand-waving on the part of the writers. No physics known today allows us to do what they do on the show.

    On the other hand, activities like mining water from a comet or 3He from the lunar surface seem to be possible using currently known physics. We can run the numbers and it seems likely that we *can* do it someday. I think a good analogy would be a person in the 40's trying to figure out how to put men on the moon. You had a long way to go technologically from the V-2 rocket to the Saturn V and a lot of bugs to work out along the way, but the numbers would indicate it was at least feasible.
     
  26. Apr 28, 2005 #25
    If look what was said before then he was saying that it is better to use up the worlds oceans at a rate of 20 mm a year and increase power consumption by a factor of 1 000 000 000 and kill us all in no time rather than to reduce power consumption in half and live on just like before.

    That was imagined quite successfully a century before. Now that we know how difficult it is, it does not seem likely that we will ever be able to bring in sizable portions of the Oort cloud to feed a fusion reactor that is large enough keep the planet above boiling.
     
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