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Earth Moon Power

Underwater Ocean Kites To Harvest Tidal Energy 203

Posted by timothy
from the best-use-for-string dept.
eldavojohn writes "A Swedish startup has acquired funding for beginning scale model trials of underwater kites, which would be secured to a turbine to harness tidal energy for power. The company reports that the kite device allows the attached turbine to harvest energy at 10 times the speed of the actual tidal current. With a 12-meter wingspan on the kite, the company says they could harvest 500 kilowatts while it's operational. This novel new design is one of many in which a startup or university hope to turn the ocean into a renewable energy source."
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Underwater Ocean Kites To Harvest Tidal Energy

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  • Haha (Score:3, Funny)

    by SlothDead (1251206) on Thursday May 06, 2010 @01:41PM (#32115062)

    At first I read "Ocean Kitties" and wanted to see pictures of those...

  • by synaptik (125) * on Thursday May 06, 2010 @01:42PM (#32115074) Homepage

    Because of the tides, the Earth's rotational energy is being stolen by the moon, which is using that energy to slowly escape from orbit. (This is a diminishing effect over time, that will eventually reach equilibrium.) But when we leach this energy for our own purposes, we are changing the delicate balance of that equation. ...Siphon off too much energy from the tides, and we could either increase the rate at which the Earth is slowing, bring the moon crashing down upon us, or both!

    Won't somebody think of the children? We owe future generations a planet fit to live on and capable of sustaining the future.

    • by t33jster (1239616)
      This is an interesting answer to a question I always wanted to ask - how does the first law of Thermodynamics play into harnessing tidal/wave energy? Very interesting, and I'd love to see a citation if available.

      I suppose the next question would be, What's the overall supply, and can/should we focus on not depleting it like we have done with hydrocarbons?
      • This is an interesting answer to a question I always wanted to ask - how does the first law of Thermodynamics play into harnessing tidal/wave energy?

        Exactly as GP described. Well, sort of.

        I suppose the next question would be, What's the overall supply

        Millions of years.

      • I always thought about this in regards to geothermal. What if we cool down the planet enough to stop the core from spinning or solidify it? I've heard numerous "guesses" at the amount of energy available in geothermal, one of which was 9000 years. That is a lot, but in 9000 years we could be out of a magnetic field? Doesn't seem worthwhile to me...

        We got into all this mess with oil because we didn't think ahead at all; It seems we're doing it all over again, just not as an immediate issue as oil is.
      • by Amouth (879122) on Thursday May 06, 2010 @03:28PM (#32116814)

        well based on what i have read - as the moon/tidal effeects work the earth is slowing down and the moon is gaining potential energy related to earths gravity well by moving farther away - assume this is a colosed energy system..

        assume we pull energy out of it.. the moon will come closer to earth (or reduce it's movement away) - so the total energy supply would be the potential energy of the moon in relation to earths gravity well.

        PE = m x g x h

        m = 7.3477 × 10^22 kg
        g = 9.8 m/s2
        h = 363,104,000 m (using it's Periapsis)

        PE = 2.61461968 × 10^32 Joules

        474 × 10^18 = AEC = whole planet annual energy consumption

        PE/AEC = 551,607,527,000 years....

        so the answer is .. keep current rates.. and assume we could get it all from here.. 550 billion years..

        according to this #19
        http://helios.gsfc.nasa.gov/qa_sun.html [nasa.gov]

        "In about 5 billion more years, the useable hydrogen (not all the hydrogen) will have been converted to helium, and the Sun will start burning helium, and become a red giant."

        if i remember right.. if it goes red giant it will grow larger than 1 AU so it will engulf earth..

        basically.. we could increase energy consumption by a factor of 100 and only then would we be toying with maybe crashing the moon into us before the sun burns us away.

    • by Yakasha (42321) on Thursday May 06, 2010 @01:58PM (#32115376) Homepage

      Won't somebody think of the children? We owe future generations a planet fit to live on and capable of sustaining the future.

      Don't worry, it is being developed by a private company. Private industries regulate themselves.

    • Jeez. I was just gonna suggest that this could disrupt marine life... but you... bravo! -gasps-

    • by postermmxvicom (1130737) on Thursday May 06, 2010 @02:03PM (#32115462)
      The solution is obvious. I am selling gravity credits to absolve you of your moon-doom guilt. Each credit you purchase represents energy gathered from sources not directly linked to the moon's potential energy plus some of the profits will be used to fund missions that will increase the moon's potential energy. This gravity offset program will save the earth for our posterity. As the administrator of this program, I will, of course, take a percentage of the sales as compensation. My motives are, however, purely in the interest of the future.
    • Re: (Score:3, Informative)

      by T Murphy (1054674)
      I know you aren't serious, but in case anyone is curious: Last I heard, this process is so slow the sun going red giant on us is a more pressing issue. Somehow changing this moon escapism process shouldn't have any real effect on people even billions of years from now.
      • by e2d2 (115622)

        Obviously a moon energy industry shill. Build a wall of silence around this man!

    • Siphon off too much energy from the tides, and we could either increase the rate at which the Earth is slowing, bring the moon crashing down upon us, or both!

      Joking aside, and I'm sure you already know this, but the Moon's orbit increases as the Earth's rotation slows.
      See: Is the Moon moving away from the Earth? When was this discovered? [cornell.edu]

    • by biryokumaru (822262) <biryokumaru@gmail.com> on Thursday May 06, 2010 @03:07PM (#32116450)
      Heh. Seen my sig, eh?
    • by sammydee (930754)

      Actually this is true, I recently covered this in one of my physics courses. Due to tidal friction the moon is currently receding from the earth at a rate of 4cm a year, about the rate of growth of fingernails or the rate at which continents are drifting apart. Due to conservation of angular momentum, this results in a corresponding decrease in rate of rotation of the earth. Days are actually slowly getting longer and longer. In fact, about 100 million years ago, the dinosaurs experienced a 23 hour day.

      You

  • sweet (Score:5, Insightful)

    by gandhi_2 (1108023) on Thursday May 06, 2010 @01:42PM (#32115094) Homepage

    now whales can enjoy the "renewable revolution" like migratory birds and bats do with windmills.

  • by Anonymous Coward

    Is it possible to exhaust the wind or sea's natural momentum, if there is such a thing? Where does the energy ultimately come from? In other words, is it theoretically possible to have so many wind farms (or, in this case, tide farms) that the atmosphere becomes still?

    (captcha: "universe". heh.)

    • by Nadaka (224565) on Thursday May 06, 2010 @01:48PM (#32115212)

      short answers: No, there is. The sun. No.

    • Re: (Score:3, Insightful)

      by NeutronCowboy (896098)

      Wind farms are unlikely to stop the wind. Wind is a byproduct of temperature differentials, and as such, as long as the earth isn't exactly the same temperature everywhere all the time, there will be wind.
      Tidal farms, on the other hand, I don't know. Tides are due to the difference in gravitational fields at different points on the earth. As such, the tidal energy comes from the Sun's and the moon's gravitational field. Since neither the sun nor the moon are losing mass through the use of tide turbines, wha

    • Re: (Score:3, Informative)

      by Bearhouse (1034238)

      Is it possible to exhaust the wind or sea's natural momentum, if there is such a thing? Where does the energy ultimately come from? In other words, is it theoretically possible to have so many wind farms (or, in this case, tide farms) that the atmosphere becomes still?

      (captcha: "universe". heh.)

      I think we're OK for a while. There's many 'renewable' energy sources that can, and are, being tapped, and we're nowhere near extracting any significant fraction of them so far:
      1. Tides, as in this article, come from the sun & moon interacting with the earth; http://en.wikipedia.org/wiki/Tides [wikipedia.org]
      2. Sunlight; there's plenty to spare: http://en.wikipedia.org/wiki/Solar_energy [wikipedia.org] "Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account fo

    • Yes, while we're at it we should do away with those leafy trees, billions of acres of them, sucking all the energy out of the breeze. Might as well put an end to all the small furry animals too, and I never did trust birds, beady little eyes on them.

      Seriously, the green hysteria machine has a lot to answer for.
    • by gandhi_2 (1108023)

      the tides are not caused by the gravity of the moon, exactly, but by the differential of the moons gravity on the near side of the earth vs. the far side of the earth.

  • Maintenance (Score:3, Interesting)

    by Saishuuheiki (1657565) on Thursday May 06, 2010 @01:46PM (#32115178)

    Seems this would be relatively high maintenance. Anyone who owns a boat knows that stuff can and will grow on it, which will have to be cleaned off eventually, no? Setting aside the initial cost, which isn't mentioned, wouldn't the maintenance be costly?

    • Re: (Score:3, Informative)

      by Bearhouse (1034238)

      Keep 'em deep enough, and nothing will grow. (No sunlight)
      Corrosion will of course be a problem, as will be keeping the electrical generating and transmission bits nice and watertight.

      • by brainboyz (114458)

        As we're finding out, lack of sunlight does not mean lack of life/growth. Animals living on sinking waste, and lifeforms which use chemical-based metabolism (thermal vents), both would remain a problem.

        • by joggle (594025)

          Yes, but a much smaller problem. The very great majority of life in the sea (by biomass) is within a hundred feet or so of the surface.

          You still need an energy source for life--so long as they install this deep enough so that there is no visible light and no thermal vents are nearby maintenance due to life growing on it shouldn't be too bad. However, there are other factors, such as the acidity of the water and sediment accumulation that will have to be dealt with.

      • No no, let's think about this. Mr. Bearhouse is concerned about killing off the biomass of the oceans by BLOCKING OUT THE SUN with KITES.
  • So has anyone considered what will happen when we massively start harvesting global tidal energy?

    Will it affect global oceanic heat redistribution? (( If the ocean currents slow down then northern Europe reverts to looking like northern siberia. ))

    What about the earth/moon relationship that drives the tides? Do we end up sucking more energy out of the moons orbital velocity leading to a decay in the moons orbit?

    Environmentally, what happens to the organisms that live in the tidal zone?

    Someone should have

    • What about the earth/moon relationship that drives the tides? Do we end up sucking more energy out of the moons orbital velocity leading to a decay in the moons orbit?

      No. Slowing of the Earth's rotation, which is due to drag by Moon, increases the Moon's orbit. The Moon orbits slower than the Earth rotates causing a "gravitational/tidal bulge", or warping of the Earth's shape (the ocean tides are caused by this too). This creates drag on the Earth, slows its rotation and the Moon's orbit increases - du

    • Yes. Yes people have.
      synaptik (125) [slashdot.org] (god DAMN that guys old) knew enough to make fun of the concern.
      elashish14 (1302231) [slashdot.org] almost got to the environmental concerns.
      This guy [slashdot.org] brought up a similar question about natural resources.
      gandhi_2 (1108023) [slashdot.org] made a dig against it in reference to bird strikes, even though it's really not a statistical problem.
      Heaven knows we don't have enough environmentalists to think about these sort of things.

      But are you honestly saying we should NOT have tried to switch f
  • by Mikkeles (698461) on Thursday May 06, 2010 @01:48PM (#32115208)

    If they're anything like my kites, they'll just end up nose-first in the silt.

    • If they're anything like my kites, they'll just end up nose-first in the silt.

      Charlie Brown! When did you start posting on Slashdot?

      (Obligatory: "Rats!")

  • by Scareduck (177470) on Thursday May 06, 2010 @01:54PM (#32115324) Homepage Journal
    Like windmills, PV solar (and arguably, thermal solar), this will use a ton of capital (in multiple dimensions -- energetic, costs, and materials) to harvest very diffuse energy. The cries to subsidize installation -- and possibly operational -- costs will start almost immediately.
    • by HeckRuler (1369601) on Thursday May 06, 2010 @02:07PM (#32115520)
      Well ok. Anything wrong with that?
    • The cries to subsidize installation -- and possibly operational -- costs will start almost immediately.

      It's only fair, since we so heavily subsidize the oil industry.

      Or are you one of those people who believe that the cleanup and economic disruption in the Gulf will be eventually paid in full by BP? If so, I have some beachfront property in Prince William Sound I'd like to sell you.

    • Different energy sources make sense for different reasons. Windmills for instance have a very small unit size, but that also means that if one is down for maintainance there is little difference to the total energy generated. Distribution and peaks also drive the use of technologies other than pure base load ideas. Some technologies are actually complementary in ways I doubt you have considered, for instance solar thermal providing preheating at a coal thermal power station (Liddell NSW, Australia). I c
    • Re: (Score:3, Interesting)

      by XNormal (8617)

      Like windmills, PV solar (and arguably, thermal solar), this will use a ton of capital (in multiple dimensions -- energetic, costs, and materials) to harvest very diffuse energy.

      Kites use two orders of magnitude less material than a turbine of equivalent swept area. Water is two orders of magnitude denser than air.

      This is starting to add up to something that doesn't sound so diffuse any more.

  • by T Murphy (1054674) on Thursday May 06, 2010 @01:56PM (#32115356) Journal
    Tidal forces are from the moon, and over time the moon is getting farther away. Clearly, if we harvest tidal energy we will force the moon away faster as it makes up for the difference. If NASA times it just right, we could put people on the moon, launch the moon at Mars and have people walking on Mars just months later. Melt the polar icecaps on Mars, use tidal kites there, and repeat as needed to keep using the moon as our Earth/Mars space shuttle. Add Phobos and Deimos into the mix and space tourism can take off.

    Next, we use the tide from the sun to travel to Alpha Centauri.
    • Actually, most of the tide comes from the Sun, which is why you get six hour variations (Oh noes! Time cube!).
    • by synaptik (125) *

      Tidal forces are from the moon, and over time the moon is getting farther away.

      So far, so good....

      Clearly, if we harvest tidal energy we will force the moon away faster as it makes up for the difference.

      No. The moon is currently getting farther away because it is stealing energy from the Earth's rotational momentum (with the tides being the mechanism of transference.) If we extract energy from the tides to make electricity, then there is less energy remaining in the Earth-Moon system. So the consequence of our tide leeching will be either (1) the Earth slowing down faster than it already is, or (2) the moon moving away slower, possibly even reversing course and coming closer! Or, s

  • by phiz187 (533366) on Thursday May 06, 2010 @02:14PM (#32115618) Homepage Journal
    I was having difficulty visualizing this technology, from the text description. Here is a YouTube video that sheds more light. Spoiler: essentially the tethered kite does figure-8 patterns to continually move the turbine through the water.

    http://www.youtube.com/watch?v=1qCDRj8TE9Y [youtube.com]
    • That's the same system Sky Sails [skysails.info] use (video [youtube.com]). The kite makes, among other manoeuvres, figure 8 loops, and reaches speeds of up to 180 knots (180 nautical miles an hour, 207 mph, 333 kmph) in winds of 3 to 8 Beaufort (10 to 40 knots). It's actually a very similar design, that's also doing its part in reducing fossil fuel consumption.

      I hope they manage to balance construction and maintenance costs with profits. It sounds promising, but then so do a lot of things.

  • The company reports that the kite device allows the attached turbine to harvest energy at 10 times the speed of the actual tidal current.

    What units is that measured in? I'm not making sense of this sentence. Since when did the tidal current harvest energy in the first place?

    • The kite is steered so that the turbine on it gathers energy from the motion of the kite through the water. Sort of like when you see those kites doing figure 8 patterns in the sky. Their saying the kite is moving 10 times faster then just the current, therefore able to gather more energy then the turbine just sitting in the current. I don't know if the power generation is 10 times as much, but I'm pretty sure they are saying that the movement of water through the turbine will be 10 times as fast.
  • This is not gonna work. Those kites would be right in the flight path of the rare spotted owl fish. Their mating habits will change and they might rub a dolphin the wrong way.

  • How long would it take barnacles and other creates or plants to start to grow on this thing thereby increasing drag? I don't recall seeing anything growing on the blades of a windmill...

  • Has anyone thought of the job losses in the oil industry?
  • Well I'm all for tapping into Natures resources providing that it doesn't make too great of an impact on other life on this planet, so lets see if we can tweak this design a little shall we? This could be fun...

    Step one, lets confine these contraptions to a smaller segment so we don't collide with as many other living things, such as blue whales. That's also got to hurt the kite so it make s economic sense too providing you can steer wildlife around them. We will just have them fly closer together, but th

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