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Underwater Ocean Kites To Harvest Tidal Energy

Posted by timothy on 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."

2 of 203 comments (clear)

  1. dem dang numbers by Ancient_Hacker · · Score: 0, Offtopic

    The numbers don't look very promising for this kind of device.

    Let's assume you have a 12-meter by 5-meter "kite" and it's moving out with the tide.

    And let's assume the tide is a huge one, like 10 meters.

    Also let's be generous and assume the kite can sequester an average of one meter of depth of water.

    That's 60 cubic meters of water, falling 10 meters, twice a day.

    Jut for fun, switching back to English units, about 60 tons falling 63 feet per day.

    or 120,000 pounds falling 63 feet per day. That's about 87 ft-lbs/sec, or about 110 watts.
    Wholesale electricity is going for about 3 cents a kilowatt-hour, so this kite is at best making .33 cents an hour.

    I don't think you can build deploy, and operate, and pay for a kite that size on that kind of income.
    Just the interest lone has to be more than that.

    1. Re:dem dang numbers by Ancient_Hacker · · Score: 0, Offtopic

      Sorry for my oversimplifying things. I just assumed everybody knew basic physics and knew that it matters not one whit whether the kite is slewing, sliding, swooping or gliding, and it matters even less what speed it's achieving, or whether the water is moving horizontally or vertically, or whether the kite is moving and the water is behind it, or the kite is standing still and the water is moving past it or through it. All those fancy scenarios are just different angular projections of the same basic kinematics. You can't make any more energy than is available by the basic fact that water is dropping in a gravitational field.

      Even if my assumptions are off by a factor of ten, we are still a very long way from even paying the interest on the capital investment, much less paying off the investment, which is in effect saying that we're going to be going to a lot of trouble to lose energy.