The oceans store vast amounts of thermal energy, with warm surface water absorbing heat while deep ocean water remains cold. Ocean Thermal Energy Conversion (OTEC) harnesses this temperature difference to generate continuous power, making use of a natural and replenishing energy source.

In a closed-cycle OTEC system, warm surface water heats a liquid with a low boiling point, such as ammonia, inside a heat exchanger. As the ammonia turns into steam, it drives a turbine generator to produce electricity. Cold, deep ocean water is then used to condense the steam back into liquid form, allowing the cycle to repeat indefinitely—delivering uninterrupted energy 24/7, 365 days a year.

This process, known as the Rankine Cycle, is commonly used in power generation. The difference with OTEC is its ability to tap into the temperature gradients of the ocean, providing a predictable and scalable power source for remote and strategic locations.

The concept of OTEC dates back to the 1880s, but the first grid-connected, net power-producing facility was developed in Hawaii in the 1990s at the Natural Energy Laboratory of Hawaii Authority (NELHA) with funding from the U.S. Department of Energy.

Today, advances in deep-water piping technology have made large-scale OTEC plants feasible, positioning the technology as a reliable power solution for military bases and coastal communities worldwide.

Click the graphic for a virtual demonstration