Underwater Kite Catches Irish Tides For Power

We’ve seen an underwater sails concept gain a little conceptual traction, so why not underwater kites as a marine energy source? A Swedish company says it’s making it happen, in waters off Northern Ireland, right now.

Minesto, a 2007 startup, said a 1:4 scale “Deep Green” power plant in Strangford Lough, the largest inlet in the British Isles, in County Down, is operating. The company said the deployment of the winged device with a turbine attached out front “proves power production from slow currents using a surface-mounted installation, a concept that is directly transferable to full commercial installations in ocean currents.” Here’s how the concept is supposed to work:

Minesto cites three key elements to the design – the hydrodynamic wing, which moves through the water courtesy the lift forces of water flowing over it; the tether, which can accommodate power cables from the generator and signal cable to the control system; and the swivel at the anchoring point, which allows the device freedom of movement through changing tidal currents.

On its website, Minesto details four versions of the carbon fiber Deep Green kite, ranging from one with a wing span of 8 meters, a turbine diameter of 0.67 meters, and a power rating of 120 kilowatts at tidal flows of 1.3 meters/second [PDF], to a 14 meter model with a 1.15 meter diameter turbine and a power rating of 850 kW at 1.7 m/s [PDF].

Deep Green being deployed (image via Minesto)

Deep Green being deployed (image via Minesto)

“It has been a long fight to get to the point where we are but when you have what we have, it is worth it,” Anders Jansson, CEO of Minesto, said in a statement [PDF]. “This is a breakthrough for the entire renewable energy industry. We will produce renewable electricity with high reliability to a cost that will compete, or even be lower, than conventional energy sources.”

That of course remains to be seen, and meanwhile there is a lot of competition in the in-stream tidal power game, like the crossflow turbine that Ocean Renawable Power Company has been testing off Maine and the Alstom tidal turbine demoing in Scotish waters. The concepts all have some merit, but proving their seaworthiness and economic viability, even with strong policy support, figures to be challenging – as Neptune Renewable Energy found out with the Proteus device that failed up to live up to expectations when tested in the Humber estuary.

Pete Danko is a writer and editor based in Portland, Oregon. His work has appeared in Breaking Energy, National Geographic's Energy Blog, The New York Times, San Francisco Chronicle and elsewhere.

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