Development of a floating-type ocean current turbine system and stress measurement of the floater in actual sea area demonstration test

Abstract

　The Kuroshio current flowing near the coastal areas of Japan is one of the strongest ocean currents in the world. In addition, it is expected to be a stable power source of renewable energy from the ocean. Recently various ideas are studied to utilize the Kuroshio current for power generation by researchers worldwide. But there has hardly ever been report on demonstration tests in actual sea areas and stress measurement of the demonstration machine.

　We are developing a floating-type ocean current turbine system to utilize the Kuroshio current for power generation supported by NEDO. In this paper, we report the result of demonstration tests in the actual sea area. Especially the power curve was obtained from the measurement in the demonstration test and we confirmed that the estimated capacity factor using the power curve fulfills our initial expectation.

　As a result of the stress measurement, good agreement was observed in general between the measured stresses and the FEM results. However, it was confirmed that with the turbine rotating, the hull may vibrate significantly with the frequencies corresponding to the multiples of the turbine rotation. This is considered to be a resonance of the hull at those frequencies, and although the absolute amplitude of the vibration is small and does not pose a problem for this demonstration test machine, it may become a design issue for future large-scale commercial machines.