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Can this satisfy the world's energy needs? High-altitude wind power.

  1. Jan 27, 2006 #1

    Ivan Seeking

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    This has come up a couple of times now, and if true then this needs greater exposure and is certainly worthy of discussion. At a glance, this or some variation on the idea seems most promising.

    http://www.skywindpower.com/ww/index.htm

    It seems to me that the energy available in the jet stream is of greater interest than this particular solution; though this may work... There must be at least several ways to approach this problem.
     
    Last edited: Jan 27, 2006
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  3. Jan 27, 2006 #2

    Bystander

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    Little disappointing that the "wind resources" section doesn't include any numbers for "solar power" requirements for driving the wind system. That is, have people looked at "environmental impacts" of extracting wind power vis a vis what fraction of the "available power" can be diverted without affecting weather patterns?
     
  4. Jan 27, 2006 #3

    russ_watters

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    I'm sure you could make the calculation after 5 min of Googling for data, but if it isn't an issue for regular solar power, it won't be an issue for wind power either. IIRC, though, a solar array would need to be on the order of 300 miles square to satisfy the world's energy needs. That's half a percent of the cross sectional area of the earth.

    Besides - one way or another, it all ends up as heat.

    I think this is a good idea that should be pursued. It isn't without flaws (nothing is), but it is worth studying more.
     
  5. Jan 27, 2006 #4

    Cliff_J

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    That is very interesting, especially how easily it could be established in a distributed manner. With the population center density a little higher in NE America it may be a little tougher to find locations, but with a better grid and the prospect of being able to generate and store hydrogen as an energy storage medium this could really be a promising technology for the rest of US. Might get tough again in parts of the EU because of space restrictions, but an offshore variant could maybe be made to work to keep saftey and asthetics in mind. If their charts are correct, most of the population lives at lattitudes that have plenty of power to extract.
     
  6. Jan 27, 2006 #5

    Bystander

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    Certainly. That's the point, no one peddling the idea includes such a calculation.

    "If...." Still a big "if" when the calculation isn't done.

    And, what's the percentage of absorbed sunlight?

    Correct: "one way" it goes through a cycle driving winds, lifting water, dropping it one golf courses, ski runs, and otherwise doing work in global circulation; "the other" is that less "weather" work is done and electrical work is done instead.

    "More study?" Yes. Do the calculation rather than wave hands. Russ, I've done it with my numbers, my assumptions, and my knowledge. I want to see someone else's numbers, assumptions, and knowledge, and I do not want to influence the approaches people might take before orders of magnitude results are compared.

    So, is someone going to do the "five minutes googling?"
     
  7. Jan 27, 2006 #6

    Ivan Seeking

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    I'm not sure about energy lost to space etc, but I come up with something like 1018 KWHrs per year energy influx due to sunlight, and a worldwide yearly energy demand of about 1014 KWHrs, as of 2003.

    ...need to double-check when I get back in my office though. I'm sitting here taking notes on a napkin.
     
    Last edited: Jan 27, 2006
  8. Jan 28, 2006 #7

    Ivan Seeking

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    okay, I was being too generous with the absorption. It is known that 1368 Watts/meter2 enters the upper atmosphere, but we only absorb about a fourth of that:

    http://earthobservatory.nasa.gov/Library/Oven/

    Does this ignore atmospheric abosorption of solar energy before it reaches earth? Still, multiply by the hours in a year and we come out about right - 1.5 X 1018 KWHRS per year. So I guess it was about right

    Here, the world energy demand is cited as being 421 X 1015 BTU per year, or 1.2 X 1014 KWHrs per year, for 2003.
    http://www.eia.doe.gov/pub/international/iealf/tablee1.xls

    Anyway, 0.01% is a promising number.
     
    Last edited: Jan 28, 2006
  9. Jan 28, 2006 #8

    Bystander

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    "0.01%?" Agreed.

    Next question: "How much of the absorbed solar infall is available for conversion to mechanical energy (air circulation)? Numbers get a lot fuzzier here, and if we agree w'in an order of magnitude, I'll be surprised.
     
  10. Jan 28, 2006 #9

    Ivan Seeking

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    It seems that I get to cheat.

    http://www.energy.iastate.edu/renewable/wind/wem/wem-01_print.html

    So we have about 3 X 1016 KWHRS per year in wind energy. We need about 0.4% of this; or say 1-2% in practice, were we to use only wind energy for all the worlds needs.
     
    Last edited: Jan 28, 2006
  11. Jan 28, 2006 #10

    Ivan Seeking

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    ...and this is a bit deceiving since it ignores that all of the converted wind energy will eventually make it back into the atmosphere as heat. I have no idea is this translates into another 2% wind energy or not, but I would tend to assume that more than 2% of this heat energy will be converted back into wind energy again.
     
    Last edited: Jan 28, 2006
  12. Jan 28, 2006 #11

    Bystander

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    Tenths of percent to percent --- again, agreed.

    Check.

    Thermodynamic efficiency is going to be 20-30%. Depends on what you want to use for temperature limits on the "engine."

    Given that tenths of percent in temperature are worrisome, are tenths of percent in atmospheric circulation energy throughput worrisome?
     
  13. Jan 28, 2006 #12

    Ivan Seeking

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    This then has to be weighed against the benefits of the the complete cessation of energy related CO2 emissions, pollution and oil spills etc, river silting and fish habitat loss due to large dams... It seems to me that the positive impacts would be enormous. In fact, this and the ocean tide based generating systems are the first options that I have ever seen that combined, seem to offer a true solution to the energy problem.
     
  14. Jan 28, 2006 #13
    I wonder about practical problems. You need to tether such a kite type of device at some 30,000 feet or so to get into the jetstream area to pick up the real signifiant winds. Probably with a couple of teflon cables or so. That might weight in the order of magnitude of ten metric tons per cable. Then you have to lift a power converter and metal cables weighting some order of
    magnitude more to get the power on the ground

    Interesting engineering problems.

    What with wind direction changes? How large would that make the restricted area for aviation when that giant kite is swarving around?

    But what if CO2 had nothing to do with climate?
     
  15. Jan 29, 2006 #14

    Ivan Seeking

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    How do you come up with ten metric tons? You don't even know how strong the cables would have to be, hence you can't know the size needed or the weight. Also, obviously the conductors would be used as the tether.

    Also, I would tend to expect that a metalized fiber would be used.

    Its funny that most people seem concerned about air traffic. This seems a mere formality to me, esp given the pay-off.
     
    Last edited: Jan 29, 2006
  16. Jan 29, 2006 #15

    Ivan Seeking

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    Six miles doesn't really seem like such a huge challenge. The fiber needed for the space elevator has to be something like 8Kg per Km.
     
  17. Jan 29, 2006 #16

    Bystander

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    Huh? Sure you do, power divided by wind speed is your bare minimum, divided by sin(tether angle from vertical), multiplied by whatever safety factor the neighbors demand. 1.3 MN (60,000 lbs) ( Edit: Thousand pardons, 280,000 --- no excuse.) for his 20MW FEG at 5 km (15,000 feet), ~15 m/s. Safety factor? Depends upon how good a Doppler radar he can get to monitor the "feed stream" for "upset conditions."

    Copper and aluminum won't carry themselves five km in the air, let alone loads. Whatcha got in mind?

    For 20 MW transmission?
     
    Last edited: Jan 29, 2006
  18. Jan 29, 2006 #17

    russ_watters

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    The space elevator is still very hypothetical too. Maybe after someone builds the first carbon nanotube suspension bridge we can start wondering if it is feasible to build a space elevator. Right now, it is a flat - no.

    It makes my crackpot alarm go off when a website says something is possible (the tether technology) and then doesn't explain how.

    Perhaps the energy could be beamed back with microwaves?
     
    Last edited: Jan 29, 2006
  19. Jan 29, 2006 #18

    Ivan Seeking

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    You can't know the total strength needed unless you know the material being used and its linear density. Picking out the blue and citing that as the number to use is ludicrous. Also, I already said that we surely wouldn't use simple steel cables. The tether technology is the key, and I cited the space elevator as an example of a much greater challenge already being pursued. With the many miracles of material science that I see every day, I find it easy to believe that this problem can be managed. And I already suggested a metalized fiber as a possible solution. There are already many incredibly strong and light fiber materials commercially available.

    As for any crackpot alarms, well, that could be, and right away I mentioned that this particular solution may not be the correct one, but the energy is there in concentrated form, and that's the key.

    What doesn't make sense if to assume a combative stance without even knowing what he plans to use. And as for me, I have had all of an hour to solve the problem, so it might take a little more time if you want me to figure it out myself. :biggrin:
     
    Last edited: Jan 29, 2006
  20. Jan 29, 2006 #19

    Ivan Seeking

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    Forget about nuclear power. This is the problem that we need to solve.

    The only reason that nuclear power seemed acceptable is that we didn't see any other immediate options. If this FEG design is feasible, we could be flying these things before the first new nuclear plant could even be commissioned.

    Edit: Okay, I emailed the company requesting more information on the tether. It will be interesting to see how they respond. This could easily be propietary information, for obvious reasons.

    Edit II: As an off-the-shelf grab, maybe something like this can be treated or modified to act as a conductor.
    http://www.unirope.com/fiberropes/fr_db_pobon.shtml

    More edits: Sorry, it seemed better than adding new posts
    Some interesting information on fibers
    http://www.machinedesign.com/BDE/materials/bdemat3/bdemat3_6.html
     
    Last edited: Jan 29, 2006
  21. Jan 29, 2006 #20

    Integral

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    Ivan and I had a pretty good talk about this over dinner and a cup of coffee the other night.

    I now envision the tethers separate from the conductor. It would seem practical to to use the tethers to create a safety zone around your conductor. Perhaps you could further use the tethers to help support the power umbilical.

    We had several interesting possibilities. Use ships at sea as the anchors, this would get away from the not in my back yard problems and allow maneuverability to chase the best winds. The ships would then have Hydrogen production plants using seawater and wind power as the raw materials. The power could then be shipped to anyplace in the world in the form of fuel cells.
     
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