Tidal Power’s Surprising Comeback

Below Sea Level: LaRance’s turbine hall

Can a U.K. firm’s novel plant design defuse environmental concerns?
By Peter Fairley

Fifty years ago this July, Électricité de France began sealing off Normandy’s La Rance estuary from the sea. After three years of work, the world’s first large-scale tidal power plant was born. The station operates still, generating up to 240 megawatts of renewable power as the twice-daily tides force water in and out of the estuary through the hydroturbines seated within its 750-meter-long seawall. But the three years of construction were tideless, which devastated La Rance’s ecosystem, killing off nearly all of its marine flora and fauna; it would take another decade for the estuary to bounce back. Due in part to that ecological hangover, La Rance would remain the only tidal station of its scale for nearly five decades …

Excerpted from the July 2013 edition of Spectrum Magazine. Get the full scoop via Spectrum.

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Tidal Power Flowing Stronger

mct-seagen-system-with-yacht1Tidal power developments by British firms show this renewable power technology achieving impressive scale and continued design innovation. Bristol-based Marine Current Turbines (MCT) revealed last month that its SeaGen dual-turbine system achieved full power operation of 1.2 megawatts. MCT’s power peak is four times the global record for a tidal stream system set by the company in 2004, according to U.K.-based renewables journal REFocus, and 30-times more than the output from the tidal turbines pumping electricity in New York’s East River.

Meanwhile the U.K. Guardian reported yesterday that more largescale demonstrations are on the way as Cardiff-based Tidal Energy Ltd prepares to test a 1-MW version of its triple-rotor design by next year off the coast of Wales.

Achieving full power operation clears a major hurdle for MCT. As TechReview reported last July, the company suffered a setback early on when the powerful tidal streams of Northern Ireland’s Strangford Lough damaged one of its blades shortly after installation. In an odd way it’s an affirmation of MCT’s design, which enables the dual rotors to be lifted clear up out of the water for easy maintenance and repair.

While at a considerably earlier phase of development, MCT rival Tidal Energy’s triple-rotor concept provides an equally innovative means of ready repair. Tidal Energy’s rotors sit at the corners of a three-legged platform that can be deposited on the seabed and held in place by the systems 250-ton heft. That should not only ease recovery of the system for maintenance, but also simplify installation by eliminating the need for a fixed foundation in the seabed.

To see these concepts in action see MCT and Tidal Energy’s dueling animations.

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