National Maritime Research Institute, NMRI, had been studying the analytical method on safety assessments of floating power generation facilities for ten years more. As a part of these studies, an Ocean Thermal Energy Conversion (OTEC) was also studied in our institute.
The OTEC normally has a very long and thick Cold-Water Pipe (CWP) with an unanchored end to pump up a large amount of cold-water continuously. From the viewpoints of the safety assessments of the OTEC operation, it is noteworthy to confirm the effect of the existing long pipe against a floating unit/body and an effect of internal flowing water. It is necessary, moreover, to consider the Vortex Induced Vibration (VIV) effect for floater motions and structural analysis of the pipe itself and a connecting point of the floating structure.
In this paper, the results of model tests and numerical simulations of a spar type floating OTEC with a single CWP in waves and currents are presented. The CWP model was made of material fitting the scaling law for a planned full scale OTEC. The specific and unique phenomena of the floating OTEC were confirmed from the model test results. Based on the results of the tank tests and the numerical simulations, we confirmed the necessary items and arrangements for safety evaluations. In detail, the internal flow increased the bending moment at the connection point.