Full scale trials for Sabella tide turbine
French company Sabella has now secured funding to establish a full scale prototype of their tide turbine. This follows 10 years of work on tide turbine design and prototype trials which have been focussed on both the efficient design of the turbine blades and structure and also on the problem of preventing marine growth on the underwater units.
The new prototype will be based on the Sabella D10 turbine which will be rated at 0.5 megawatts output but which under ideal conditions will be able to produce 1 megawatt.
It is planned that this larger prototype unit will be installed in the Fromveur Strait which is located in the channels between the island of Ushant and mainland Brittany. Here the tides can run at up to 5 knots in the channels that link the south of the English Channel with the Bay of Biscay. The Sabella design is a fixed unit with the turbine blades designed to be equally efficient with the water flow in either direction. This simplifies the construction of the unit and makes for increased reliability. The supporting structure for the turbine is triangular for stability with the extremities of the base pinned to the sea bed.
In order to transmit the power from this new turbine installation, Sabella has teamed up with the Danish company MacArtney who will provide the essential electrical connections to take the generated power ashore. This will be based on their GreenLink Inline termination system that uses a dynamic subsea export cable starting with custom made flanges with low and medium voltage connectors on the turbine nacelle. The MacArtney link will also convert the generated power into a form suitable for connection to the shore grid.
Trials extending for over a year with a smaller prototype have shown that the finishes applied to the turbine rotor have kept it virtually clear of marine growth which can severely reduce the efficiency of a turbine over time. The Sabella turbines feature a multi-blade rotor and for the Ushant project these will be 10 metres in diameter. The largest design from Sabella to date is a 15 metre rotor generator that can produce 2.5 MW of power in a tidal flow of 4 metres per second.
Sabella has focussed on the development of tidal generating systems and has recently signed a Memorandum of Understanding with the Indonesian authorities to develop tidal and current generation systems in Indonesian waters which can be used to supply power to many of the remote islands in the region where the cost of establishing conventional power systems in prohibitive. The Indonesian archipelago comprises over 17,000 islands.
By Dag Pike
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