Want Energy from Tidal Currents? Go Fly an Underwater Kite.

By: | January 9th, 2014

Nearly everyone has flown a kite in the wind and seen it move about in the constantly changing currents. IndustryTap recently covered how kites are being used in the windy upper atmosphere to possibly provide electricity to the Earth’s electric grid. But what about tidal and ocean currents? Can they be used in a similar way to generate electricity? With 310 million cubic miles of ocean (1.3 billion cubic kilometers) and an average depth of 2.25 miles (3,682 meters), there is a lot of moving water in which to “fly a kite.”

Better Than Wind But Currently More Expensive

Marine device manufacturer Minesto, a subsidiary of Swedish automaker SaaB, is developing an underwater kite called “Deep Green” to produce energy from tidal currents. The kite is tethered to the ocean floor and moves about in the changing currents. According to researchers working on the project, one kite could produce up to 500 kW of electricity. With thousands installed, the amount of electricity would be significant. The company won the International Title Energy Summit’s “Industry Pioneer Award” in London in 2012. According to Minesto: “Deep Green produces electricity by a unique principle illustrated in the figure below. The water current creates a “hydrodynamic lift force” on the wing which pushes the kite forward:

  1. The kite is steered in an 8-shaped trajectory by a rudder and reaches a speed ten times the water current speed
  2. As the kite moves, water flows through the turbine and electricity is produced in the gearless generator.
  3. The electricity is transmitted through a cable in the tether attached to the wing.
  4. The electricity continues in sub-sea cables on the seabed to the shore.

The inventor of “Deep Green,” Magnus Landberg, came up with the idea after working on a study of long carbon fiber blades for large wind turbines at Saab AB. According to Lanberg: “as carbon fiber is compatible with salt water and water is much denser than air (approx. 800 times) I found that the H-rotor machine would be smaller and cost efficient in tidal currents” than in wind currents.

SeaGen Project the Largest of Its Kind on The World

In a “proof of concept” project called “SeaGen,” it has been determined that tidal turbines experience less “flicker”, or intermittent outages from the ebb and flow of water, than wind turbines experience with wind. The UK is currently funding two additional projects with 30 million British pounds for two additional tidal projects.

Financial Support Needed to Fully Develop Technology

It is common for new renewable technologies to receive special tax treatment and government support to get off the ground. The promising technology of deep-sea kites is no different and the speed of adoption will be related to how soon and how much support is provided by governments. Technical information on this technology can be found in a datasheet at Minesto’s website.

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David Russell Schilling

David enjoys writing about high technology and its potential to make life better for all who inhabit planet earth.

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