Abstract
Ocean Thermal Energy Conversion (OTEC) provides a continuous, low-carbon electricity source for tropical regions with stable ocean temperature gradients. Floating OTEC systems are particularly attractive for archi pelagic countries, as they enable access to deep cold seawater while avoiding coastal land constraints. This study presents an integrated techno-economic assessment of a floating closed-cycle OTEC plant proposed for North Bali, Indonesia. Three thermodynamic configurations—the Rankine, Kalina, and Uehara cycles—are evaluated using Aspen Plus simulations and validated against published numerical and experimental studies. Site-specific seawater temperatures of 29.28 ◦ C (surface) and 5.29 ◦ C (deep water) are applied. The results show that the Uehara cycle achieves the highest thermal efficiency at 3.3%, followed by the Kalina cycle at 3.0%, and the Rankine cycle at 2.1%. In net power output, the Uehara cycle leads with 11.724 MW, followed by the Rankine cycle at 11.086 MW and the Kalina cycle at 10.081 MW. However, considering simplicity, operational reliability, and offshore suitability, the single Rankine cycle is chosen for the floating OTEC prototype. Despite slightly lower performance, its simpler design and easier control make it the most practical option for initial deployment under the site conditions. Preliminary buoyancy and stability analyses confirm adequate reserve buoyancy and compliance with offshore stability criteria. Economic evaluation over a 30-year lifetime yields a levelised cost of electricity of Rp 2164–2313/kWh and an equity payback period of approximately four years, indicating strong potential for floating OTEC deployment in tropical island regions.