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New Scientist - "Wind and Wave farms could affect Earth's energy balance."

Discussion in 'Energy, Environment, and Policy' started by JimmWilks, Apr 11, 2011.

  1. JimmWilks

    JimmWilks Member

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    http://www.newscientist.com/article/mg21028063.300-wind-and-wave-farms-could-affect-earths-energy-balance.html?full=true

    Very interesting article. The basic premise being that if wind and wave power are produced on the Terawatt scale, the rate of energy removal from the sea and atmosphere could potentially have unforeseen implications for weather and subsequently climate. Certainly merits discussion and further research. Imagine the irony if in the effort to negate climate change, we irreversibly altered the, errr...Climate.

    Edit: Scientific brains, don't be put off by the use of the term "free energy". No perpetual motion problems here.
     
  2. Doug_G

    Doug_G Lead Moderator

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    There are some basic flaws in the article. All thermodynamic machines increase entropy, and that includes photosynthetic plants. Plants might not build up a sweat the way, say, humans do, but they most certainly do generate waste heat. Is photosynthesis actually any better or worse than solar cells?

    All sunlight absorbed on the Earth ultimately ends up as heat, whether it becomes electricity in-between or not. The real question is "would we have enough NET effect on the Earth's overall albedo (reflectivity) to significantly affect the energy balance?"

    Wind energy losses are huge in the real world, or else we'd have 24/7 gales. The wind experiences "friction" with the ground and topography. Would wind farms really make any appreciable net difference on a global basis?

    I think the real question is can we practically extract the needed terrawatts of energy from renewable power sources?
     
  3. TEG

    TEG TMC Moderator

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    I guess we have already blocked a lot of wind by building tall buildings, dams, bridges and such. To me it seems like a bunch of wind turbines would barely make a dent in the flow.

    But to me, solar is the lowest maintenance way to get clean energy so I haven't spent a lot of time thinking about wind power.
    (I suppose if I lived somewhere with more wind and less sun, I would have a different perspective.)
     
  4. JimmWilks

    JimmWilks Member

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    This is a horrible reminder that I should be revising Physics rather than on the Tesla forums. I was dismayed by the plant factoid as well, my take on it was that it will behave basically the same way as the solar panel, but would re-radiate the unused energy at wavelengths more likely to be radiated away from the Earth, as the solar panel will likely radiate more in the infra-red, i.e. that absorbed by greenhouse gases, amongst everything else.

    You are right about the albedo change, but I think anthropogenic change of that fairly unlikely. The majority of the radiating surface will remain unchanged, i.e. the oceans. The main change in albedo I imagine will be caused by the melting of glaciers and ice caps, which reflect a considerable amount of the radiation incident on the Earth.

    I think the article was considering the internal energy distribution of the Earth, more than it's net gain/loss of energy. How large-scale energy conveyor belts via currents and air flow may be altered. Again it sounds far fetched that wind and wave power production could affect them but how can we really know? I can't really conceive of much that humans have done that is comparable, except maybe the mass deforestation over the millennia?

    As for your final point, I think that is particularly important. It seems unlikely to me that wind/wave power could ever be economically justifiable or even possible on that scale. It is huge, they're talking replacing the fossil fuel output with renewable, which is 17 TW! It will have to be part of a mix, of renewable, fission, CCS coal and gas, and hopefully and eventually, fusion power.
     
  5. SByer

    SByer '08 #383

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    The article just doesn't pass the physics sniff test.

    As for wind power, air is heavy, dense stuff, and the earth has a lot of it (think volume, not area), and it's moving quite fast. See http://en.wikipedia.org/wiki/Wind_power:

    Also note that added entropy to near-ground airflow aids in nearby farm production - a nice, even distribution of temperature and airflow is better. (If you've ever been to Napa, you'd see the 'opposite' of wind farms in effect, where they power big fans to do the same stirring up of the air).

    It's not like we're beaming the energy from wind farms into space. We're just taking advantage of swirls and ripples in the entropy field to take advantage of local gradients - they would even out anyway, with the energy ending up in the same forms. Just like a hydroelectric dam - the water ends up at the same place, we just take advantage of (in the case of dams, artificially created) local maxima in potential.

    Let's do the thought experiment - say we construct a checkerboard of wind blocks that go all the way past the jet streams (52,000 feet). Would the wind stop? I think you'd just change it's flow - a lot more vertical component, a lot more turbulent, but the same energy.

    Now maybe, just maybe, there's some 'trick' we're all not seeing, but I really doubt it. The faster-than-wind car makes sense when you actually think through the thought experiments, this doesn't.
     
  6. JimmWilks

    JimmWilks Member

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    #6 JimmWilks, Apr 12, 2011
    Last edited: Apr 12, 2011
    Hmm. Surely, ultimately, you are "beaming" the energy from wind farms into space? Or rather a portion of it. You extract some energy from the wind by using a turbine to make the wind do useful work, i.e. generate electricity. Whatever that energy is used to do, it will ultimately just be a tiny amount of the Earth's total internal energy, which over time is just radiated away, according to Stefan's law. Anyway, that is not particularly important in this context. The important thing is that yes, the irregularities in the distribution of energy in the atmosphere would even out anyway, BUT the energy is not in the same form still if you have used some of it to do work. The hydoelectric dam is a good example, the water does end up in the same place, but if you consider all the water that flowed out of the upper reservoir and into the lower in a given period of time, you have reduced it's total internal energy, by converting it's loss of gravitational potential energy into kinetic, into electrical. The total energy of the water has been reduced, much the same as the total energy of a given amount of air flowing past a wind farm will be reduced by using it to turn turbines. If the turbines weren't in the dam, the total energy will be same (consider no friction), the water speeds up between reservoirs, the lower dam has more turbulent and slightly warmer water.

    This is where I have the biggest issue with what you are saying, in the thought experiment part. If you built that checker-board of wind towers, no the wind wouldn't stop, but if on a massive scale, it would slow down. Yes more turbulent, but definitely not the same energy, that is what you've removed from the air system, which you consider to be the same large mass of air. It had potential energy, between the area of high pressure and low pressure, that potential is converted to kinetic as the air mass moves, and without turbines would just be converted to heat. With turbines that all happens, but a portion of it is converted to electrical, and extracted from the air mass as a whole. So the total energy of the air system is reduced.

    Edit: I will be suitably embarrassed if I'm wrong.:redface:
     
  7. Eberhard

    Eberhard #421 Model S #S32

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    But thats only one side of the coin. The other side - all electricity will by the very end converted to heat again. And the cycle is closed. Anyway in the whole balance of our earth - its only one drop of water in a huge ocean.
     
  8. JimmWilks

    JimmWilks Member

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    I agree that all the electrical energy will eventually be converted back to heat. But that heat will not be distributed amongst the atmosphere as it was, i.e. not amongst the same mass of air I considered earlier. The energy may be radiated in a different place at a very different time to when it was converted to electricity, thus heating a different part of the atmosphere, and implying that the cycle when considering the same block of air is not closed. I should have made the block of air thing clearer earlier. The basic implication of that is the you change the local weather and subsequently climate if wind generation is used on such a massive scale. I know that is extremely unlikely, but I think the article is at least theoretically sound, subject to a few corrections and clarifications, e.g. the plant thing. Overall I think maybe New Scientist should stay away from such headlines as "Sustainable energy isn't sustainable after all" after one study.
     
  9. zack

    zack Member

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    I guess New Scientist's advertising revenue has been flagging of late, huh?
     
  10. JimmWilks

    JimmWilks Member

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    #10 JimmWilks, Apr 12, 2011
    Last edited: Apr 12, 2011
    I've been trying to avoid that conclusion. In the edition that this article was in, there were two straight adverts by Statoil, and a 2 page spread article in collaboration with New Scientist about how lovely their new unmanned subsurface gas rig is in the Barents Sea North of Norway. 8 pages were also devoted to "A complete guide to the technology that could save the planet" - CCS. The article that this thread is about was also headed by a caption: "The fantasy of renewable energy". Apart from the slightly sensational captions I thought it was quite interesting though, and this shouldn't be material to judge NS by. They often have very speculative articles about future discoveries, it is part of what they do to look at where research may be heading in the long-term future.
     
  11. vfx

    vfx Well-Known Member

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    Sounds familiar.
     
  12. doug

    doug Administrator / Head Moderator

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    Yes it sounds familiar. That's why it's worth while to do the calculation. Perception is often very different from reality. Putting measurements in proper (and honest) context helps tell if a concern is legitimate or irrational (cf. radiation levels in California due to the Fukushima disaster).

    My science educated gut feeling is that in this case, it really is a drop in the bucket. However, I always appreciate seeing actual numbers (with error bars).
     

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