TIDAL CURRENT POWER GENERATION MAKING USE OF A BRIDGE PIER

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In 2007, attaching the Savonius rotor to the Darrieus turbine was attempted to enhance the starting torque of the turbine. A Savonius rotor composed by buckets of the semi-circular section is classified as a resistant type turbine by making use of the difference of resistance of bucket in the flow directions. It generates large starting torque so that the Darrieus and Savonius combined turbine is anticipated that it would be a good performance turbine in wide rotational range. At first, the hydrodynamic characteristics of the lift, resistance and moment of the semi-circular section were obtained in the wind tunnel. Then, the torque of Savonius rotors of several combinations of the buckets was measured in the circulating water channel. A combined Darrieus-Savonius turbine was also tested, too. The starting torque was enhanced by the Savonius rotor in the experiments but the combined turbine was inferior to the mono Darrieus turbine in the higher rotational range where the maximum efficient was attained. It is explained that the performance of the combined turbine became worse by the change of flow field due to the attachment of Savonius rotor. However, we should select the starting torque rather than the performance at the high rotation range since the starting rotation comes first. We conducted the power generation experiments in the towing tank, where a 48 pole coreless electric generator of 1KW was used. The maximum efficiency of the power was attained about 0.2 as the final power. If we consider the efficiency of the electric generator around 0.7, the estimated efficiency of the turbine around 0.3 is in good performance. Finally, we have made a revised tidal power generator of the Darrieus-Savonius turbine and it was installed at the insitu near the pier of Ikitsuki Bridge.