Abstract
Ocean Thermal Energy Conversion (OTEC) represents the second most promising energy potential among marine renewable sources. Mounting OTEC system on floating platforms could efficiently generate baseload power and freshwater for small island developing states reducing the fossil fuel consumption. A critical component of such systems is the Cold Water Pipe (CWP), whose integration with floating platforms introduces complex hydrodynamic and structural interactions. This study focuses on understanding the response behaviour of a spar-type floating OTEC platform with an attached CWP, combining both experimental and numerical investigations. Regular wave tests are performed for the spar with soft mooring, and the results are validated numerically. For numerical investigation the spar hull is modelled using a boundary element panel method for diffraction analysis, while the CWP is idealized as a rigid body connected to the spar. Time-domain simulations are conducted for operational regular wave conditions with and without the CWP to assess its effect on surge, heave, and pitch responses. The results demonstrate that the presence of the CWP significantly reduces pitch motion due to added damping and inertia effects, has minimum impact on heave, and can either amplify or reduce surge depending on the wave period. These findings emphasize the importance of including the CWP in coupled hydrodynamic analysis to capture realistic platform behaviour. The integration of a CWP with the spar significantly improves hydrodynamic performance, with reductions in mean amplitudes of up to 86% in surge, 37% in heave, and 97% in pitch. These improvements suppress coupling effects and mitigate parametric resonance, thereby enhancing stability and informing preliminary mooring design under diverse sea states. Overall, the study provides a comprehensive preliminary understanding of the hydrodynamic behaviour of spar OTEC platforms and offers guidance for future experimental and numerical investigations.