Intelligent Energy

Undersea kites to harness tidal power

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Start-up Minesto receives funding to test its Deep Green system. Will this new tidal stream technology bring tidal energy industry into deeper and calmer seas?

Kites on the beach soar on wind power. Kites beneath the ocean surface? They glide with the tide.

At least that's what Minesto hopes their underwater "kites" will do—and produce 500 kilowatts of electricity while they do it.

The Swedish company (affiliated with Saab) has procured $2.5 million to test their Deep Green tidal power technology off the coast of Northern Ireland in 2011. According to Minesto, the system is lightweight, more portable and easier to install compared to other tidal energy apparatuses, such as barrages.

At 7 tons, the tidal tech entails a kite-like device tethered to the ocean floor by more than 300 feet of "string." As shown in this animated video from Minesto, the kite glides through the water in a figure-8 pattern. A 3-foot turbine rides beneath the kite's 40-foot wing, capturing tidal stream energy and sending it to a generator on the seabed. Underwater cables then transport the electricity to shore.

As the kite travels through the water, the velocity of the water running through the turbine is about 10 times the amount of the speed of the ocean current.

While the tide forces the kite to move, an automatic rudder system controls the device's trajectory. The control system also monitors for depth, turbulence and large objects coming/swimming nearby. For environmental, aesthetic and safety concerns, the company says the kites would also "fly" at least 65 feet below the surface.

Should Deep Green go into the deep blue—and work—these kites could be collecting the energy of deeper waters with lower current velocities, expanding the geographic potential for tidal power.

CNN quotes the Minesto's Chief Technical Officer Ted Rosendahl:

We are in the development stage at the moment so there are many things to look into. Of course there are things in the environment that we don't know about fully yet.

Images: Minesto

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Melissa Mahony

Contributing Editor

Contributing Editor Melissa Mahony has written for Scientific American Mind, Audubon Magazine, Plenty Magazine and LiveScience. Formerly, she was an editor at Wildlife Conservation magazine. She holds degrees from Boston College and New York University's Science, Health, and Environmental Reporting Program. She is based in New York. Follow her on Twitter. Disclosure