Ocean Thermal Energy Conversion

Ocean Thermal Energy Conversion (OTEC) exploits the 20 °C temperature gradient between warm surface seawater and cold deep water to drive a Rankine cycle using ammonia or low-boiling-point working fluids. Closed-cycle systems pump warm surface water through heat exchangers to vaporize the working fluid and cold water to condense it, producing continuous baseload power and fresh water. Modular floating platforms or shore-based plants can supply island nations, naval bases, or coastal industries with 24/7 renewable energy.

Pilot projects from Makai Ocean Engineering, Global OTEC, and Japan’s Saga University are scaling from hundreds of kilowatts to tens of megawatts, integrating with desalination units, hydrogen production, or data centers that benefit from constant cooling. OTEC can also support aquaculture and sea-water air conditioning by bringing nutrient-rich deep water to the surface, creating co-benefits for coastal economies. Because resource potential is vast in tropical regions, OTEC could reduce reliance on imported diesel and stabilize grids vulnerable to storms.

The technology is TRL 4–5: capital costs remain high due to large-diameter cold-water pipes, marine corrosion, and grid interconnection challenges. Advances in composite materials, modular heat exchangers, and public-private finance are needed to reach commercial scale. Policy support through green bonds, blue-economy funds, and carbon credits for avoided diesel can accelerate deployment in island states looking to meet net-zero goals.