State of the Planet

News from the Columbia Climate School


Sea-kites harvest the energy of the ocean

Here’s another interesting runner in the alternative energy race.  This tech uses the power of oceans themselves to generate electricity – no drilling, no above-the-surface windmills to spoil the view.

One method is to use tidal currents, capturing the energy of the ebb and flow of water moving in relatively shallow areas near the shore.

You can also go farther out, and use the stream of deep ocean currents to turn the turbines and generate electricity.  Deep ocean currents are immune to disruptions from storms or other surface events, and they are entirely constant and predictable.

This second option is about to get off the drafting table and into the real world.  A test site for a process called ‘Deep Green’ will be built off the coast of Northern Ireland in 2011, according to Minesto, a Saab spinoff.  Sea kites will fly deep under water, using ocean currents to lift them, while an attached turbine harvests the the kinetic energy and turns it into electricity.


Minesto, describes how the technology works:

The kite is attached to the seabed at 60-150 metres depth by a tether, and is automatically steered in specific trajectories by a control system.

The principle of the technology can be explained as a two stage process.

The first stage increases the relative flow speed entering a turbine. When the tide hits the wing it creates a lift force, since the kite is mounted to the ocean bed with a tether and is controlled by a rudder, the kite can be taken in the desired trajectory. The method increases the flow velocity into the turbine by 10 times, compared to the actual stream velocity. [you can see an animated example here]

The second stage uses a generator to convert kinetic energy into electrical power.

The net result is increased power from a smaller package. The planned normal full size weighs only 7 tons excluding anchoring which gives an energetic payback time of 3 weeks, compared to 8 months for onshore wind.

The company expects each ‘sea kite’ installation to generate 500 kilowatts of energy, at a cost of €.06 .14 per Kwh.

This scheme has the advantage of being applicable practically wherever there is access to the ocean, but the disadvantage of having to transport the energy longer distances to the consumer.  The theory is that the production cost will be so low that it will still be economical at a distance.

It’s bound to be harder than it sounds (I wonder how the whales, dolphins and other sea life will feel about this), and I wish them luck with the test run.

Here’s a cute Minesta demo video:

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14 years ago

[…] recently posted a blog piece on the ‘Deep Green’ project to generate electricity from deep ocean currents. Here is another […]