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Underwater Ocean Kites To Harvest Tidal Energy
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."
short answers: No, there is. The sun. No.
Well ok. Anything wrong with that?
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
Pretend I said something meaningful or insightful here.
Thats not how it works.
The kite is really a steerable sail that moves back and forth across the current, thereby increasing the velocity through the attached turbine.
An animation is available at http://www.ebase.se/minesto/animation.htm
fava
And as with all numbers, the devil is in the detail.
Tide power is generated by water flowing through a turbine. As a result, what matters is the surface of the turbine times the apparent water speed. That gives you a volume over time, which in turn controls how fast the turbine spins. Considering that apparent water speed depends not only on the size of the tide, but the local ocean floor geometry, and the output of the turbines can vary wildly depending on where they're located.
Finally, you made a key mistake in your calculation: a tide turbine doesn't capture the up and down movement of the tide - it captures the horizontal flow of water as it flows from point A to point B. This means that your entire calculation is completely useless. It isn't captured twice a day, it is captured constantly with an oscillating efficiency. The energy captured is only marginally related to a mass of water falling the height of the tide - the falling is translated into horizontal speed, where g is completely overwhelmed by local geometry. And lets not even get into real and apparent water flow, turbine construction, efficiencies, etc...
Really, you could have saved yourself a lot of time and just said "I don't know how this works".
Those who can, do. Those who can't, sue.