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Do you like dumb questions?

  1. Jan 16, 2005 #1
    Why don't we put a big plate out at space to gain energy from the sun and send it to us?
    Just like telescopes. They send us information. Why can we make something to send us the energy?
     
  2. jcsd
  3. Jan 16, 2005 #2

    dextercioby

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    To answer the question from the title:
    "Yes,far more than dumb answers"... :tongue2:

    For the second question:What would be the point of that??Can't we already use solar energy on Earth??

    Daniel.
     
  4. Jan 16, 2005 #3

    Integral

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    This more of an engineering problem then physics.
     
  5. Jan 16, 2005 #4
    Although it may be true that a solar array in space gathers more energy than on earth, no atmosphere to absorb any rays, but that would only matter if we could make use of 100% or close of the suns energy anyway (Right now we only can make use of 30% max) I think.
     
  6. Jan 16, 2005 #5
    Yes, the problem is not in receiving the energy... its collecting it. Our photoelectric science is still very poor (in my opinion) as we do not have anything that is really efficient enough to start changing over to it as primary sources of energy. Once we get our efficiency of these types of things up to 60+ %, we will be able to really start doing good stuff.
     
  7. Jan 16, 2005 #6
    I agree, right now solar is not cost efficient for most situations due to the low energy gathering efficiency.

    Perhaps, relatively soon, they will make a major advancement in photovoltaic technology that will push it to 60%+ energy efficiency. I think photovoltaic is the way to go... Mirror tech is a bit too cumbersome, but perhpaps if its good enough that won't matter...
     
  8. Jan 16, 2005 #7
    I will rejoice the day that happens! We need solar energy so we can stop killing our only means of life.... unless someone has found a planet we can ferry everyone over to once we have abused this one to irreversible death.
     
  9. Jan 17, 2005 #8
    i disagree, i think nuclear fusion will be the way to go...
     
  10. Jan 17, 2005 #9

    dextercioby

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    I disagree.Sun will shining for about 5 billion years.In a tiny fraction of that time mankind (if it doesn't disappear like the dinosaurs) will have exhausted the Earth's reserves of fossil fuel and Uranium.U can't haave fusion without fission,right??

    Daniel.

    PS.I know nothing about cold fusion... :uhh:
     
  11. Jan 17, 2005 #10
    As of right now Cold Fusion is a myth. Or so I have heard.... :tongue2:

    Don't think I am a major environmentalist or dooms day freak when I say this... but what is safer? Harnessing the sums energy or continuing to develop our nuclear programs?

    Personally, I like nuclear power. It sure as hell beats the old methods we used. But it is still 'creating' something.... which is a waste. Solar power is doing nothing more than converting a resource that will never run out (in relation to the life span of the human race).

    So, not only are we spending all our money buying into energy sources that will run out one day, we are buying into a source of energy that is more dangerous than the alternatives.

    Hmmm... sounds JUST like every other energy source we have bought into in the past. The difference is now we actually have the technology to develop an energy source that is safe and could become the worlds most effcient and safe means of power.... Solar.... but the money isnt there because corrupt greedy pricks would rather kill the earth for their 50 years left of life to be in comfort.

    Whoa... I really do sound like an environmentalist tree hugging hippy. Time to go out and drive my gas hungry truck to the store, smoke a pack of cigarettes, and release aerosol cans into the atmosphere!!
     
  12. Jan 17, 2005 #11

    LURCH

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    Interestingly, most of the proposed techniques for generating fusion power would produce fusion without fission (all the techniques I'm aware of, in fact). The two most popular are "pinched plasma" which heats hydrogen isotopes to a plasma state, then takes advantage of the magnetic properties of this plasma to squeeze nuclie together close enough for the strong nuclear force to grab them, and "mechanical confinement", which puts the isotopes close to one another and then hits them from all sides at once (usually with a laser) to cram them into fussion-range.
     
  13. Jan 17, 2005 #12

    Chronos

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    The big problem with current fusion techniques is it takes an enormous amount of energy to get a trickle in return. It should, in theory, be possible to initiate a self sustaining fusion reaction that can be continuously fueled. Unfortunately, no one appears to have figured out how to sustain and contain the reaction without using more energy than is created. Uncontrolled fusion [e.g., hydrogen bomb] is hard on moral and facilities.
     
  14. Jan 17, 2005 #13
    Thansk for answers

    I thought, we can put it somwhere in space where sun is always (day and night without any dark clouds) shining. (Is there any such a place? :D)
    =============================
    Ok, forget the first question and consider this one:
    How can we transmit energy from out of atmosphere to the Earth?
    (I just want to know a little about the all possible ways)
     
    Last edited: Jan 17, 2005
  15. Jan 17, 2005 #14

    russ_watters

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    Yes, there are, but there are some orbit issues with keeping a mirror there (above the north pole, for exampe). The other posters missed another possibility as well: a parabolic mirror. With a parabolic mirror, you don't need to rely on normal solar cells. There are lots of alteratives, including steam turbines.

    The main problem, to me, is getting a 100 square mile mylar mirror up there. But this is something I've daydreamed about as well. I think its a good idea.
    Electromagnetic radiation. With the mirror, you're shining light. You can also do other frequencies - microwaves, for example.
     
    Last edited: Jan 17, 2005
  16. Jan 17, 2005 #15

    Moonbear

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    Since this seems to be the "dumb questions" thread, I'll add my dumb question. :biggrin: What sort of shadow would a 100 square mile mirror cast on the Earth below?

    My other question is, assuming we're earthbound with solar panels, let's assume technology will improve the efficiency upward toward something like 85% or 90% (nothing's ever perfect), if we were to use solar energy to fully replace other energy sources on the planet, what area of earth would be covered by solar panels? Where would you put them? This question always nags me in the back of my mind when people start suggesting solar energy as the "green" solution to our energy demands. Afterall, massive fields of solar panels are going to pretty severely change the habitat for whatever was living in those fields prior to the arrival of those panels. Anyway, I don't want to debate the "greenness" of the solution here, just wondering the scale, if anyone knows it.
     
  17. Jan 18, 2005 #16

    FredGarvin

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    I've seen current solar panels that are flexible and can be rolled up. I always envisioned that when the time comes, panels will be incorporated into the current buildings and future buildings' structures. I would think that if, in theory, one could simply cover every roof in Manhattan, you'd have a pretty impressive solar panel array. I guess the tough part would be to tie them all together somehow. Details, details.
     
  18. Jan 18, 2005 #17

    Cliff_J

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    Moonbear - using just the US electrical demands for one year and assuming good efficiency and 8 hours of sunlight in the desert, a massive 125 x 125 mile array of regular photovoltaic cells could pretty much generate the equivalent energy. So 16,000 sqaure miles is big, but its a size that would be barely visible from space and would utilize the land in the desert. Now, the trillions of dollars of startup costs and billions of joules in energy needs to create those panels...is another story.

    But the point is that it wouldn't take a meaningful percentage of the inhabitable land to capture enough solar energy to replace the existing means of generating power. Getting there in a cost effective manner is the problem.

    Cliff
     
    Last edited: Jan 18, 2005
  19. Jan 18, 2005 #18

    Moonbear

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    Thanks...though, what makes you think dessert isn't inhabitable land? Don't you think those dessert dwelling critters would be a bit disrupted by suddenly being immersed into shadow? But, it also sounds like the scale is such that the above suggestion of adding the panels to the rooftop of every building in large cities could do the job as well. Thanks. That's the sort of back of the envelope estimate I was curious about.
     
  20. Jan 18, 2005 #19
    Here's something interesting I hadn't considered: Using the infared radition as well as the visible radiation for energy: http://news.nationalgeographic.com/news/2005/01/0114_050114_solarplastic.html

    A questions, when most places say "solar cells gather such-and-such a percentage of energy for the sun", do they take into account the infrared energy there as well? If not then the usefullness of solar is much more...
     
  21. Jan 18, 2005 #20

    Cliff_J

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    Moonbear, that is the point. Its horribly impractical and wasteful given the huge resources of energy needed to make a PV cell. And a big array in the desert bigger than the area of the 5 smallest states is too big to imagine.

    But at like .4% of the available surface area in the country with the highest energy usage per capita shows the viability of using solar energy if it could be captured at even modest efficiencies. Plus the ability to use rooftops that are otherwise not utilized is a big plus too. The desert offers more sunlight and more energy because of the relative angle, but the space requirements are still low enough that we don't need monster sails in space to grab the light or massive floating energy stations in the oceans.

    Like being said in the other thread here, we just need cheap! :smile:

    Cliff
     
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