Turbine System Developed to Harvest Energy of Deep Tidal Streams

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Engineers are developing a semisubmersible turbine system designed to harvest the energy of deep tidal currents and hope that within five years they will begin constructing such systems in the Pentland Firth, in northern Scotland. It is estimated that such a system could generate at least as much energy as a 1,200 MW nuclear power plant.

The system would consist of four 20m diameter rotors attached to a large cylindrical tank that in turn would be connected to a long arm. The arm would pivot on a gravity base - a weighted concrete or steel foundation placed on the seabed. The arm would swing with the currents, allowing the system to respond naturally to turbulence in the estuary.

The system has been developed by tidal Stream, a London-based partnership dedicated to exploiting renewable energy sources that is currently seeking industrial partners to help it complete the Pentland Firsth project. The company estimates that £25 million ( US $44 million) would be needed for this endeavor. The buoyant cylindrical tank would make it possible for the entire unit to be floated to its

location and then flooded with seawater so that it would partially sink and swing into a vertical operating position. Each rotor in the system would drive a speed-increasing gearbox, which in trun would drive a 1 MW generator. As in an offshore wind farm, the energy would be conveyed to the mainland through high-voltage submerged cables.

For maintenance, the tank would be floated to the surface, where it would act as a stable platform for access. Units intended for UK waters would most likely be built in the Scottish construction yards that have produced many offshore oil structures for the North Sea, but they could also be built elsewhere by construction facilities with marine experience, Armstrong says. Concerns about interference with shipping are already being addressed by authorities.


Invention Intelligence, July - August 2006