Electricity from Ocean Heat
Engineers at the UK company Global OTEC have introduced DON, a floating platform designed to generate power using Ocean Thermal Energy Conversion (OTEC)—a technology that converts the ocean’s natural heat into electricity. The system is currently undergoing sea trials off Gran Canaria (Canary Islands). The company says more detailed performance and technology data will be shared after testing is completed.
How OTEC works: a “heat engine” powered by seawater
The concept is similar to a conventional thermal power plant, but instead of burning fuel, it uses the temperature gradient between warm surface water and cold deep ocean water.
In a closed-cycle OTEC system (using ammonia), the process is:
-
Warm surface seawater heats a working fluid—often ammonia because it boils at relatively low temperatures.
-
The ammonia evaporates, producing vapor that spins a turbine, generating electricity.
-
Cold deep seawater then cools the vapor so the ammonia condenses back into liquid.
-
The fluid is pumped back through the loop and the cycle repeats.
In simple terms: the ocean provides both the heat source and the cold sink, creating a continuous cycle.
Why this is gaining attention now
OTEC isn’t new, but historically it has been held back by cost, offshore engineering complexity, and maintenance demands. Interest is rising again for several reasons:
-
Steady generation potential. Unlike solar and wind, the ocean’s temperature difference can be relatively stable, enabling near-continuous output in suitable locations.
-
Energy security for islands. Many island communities rely on imported fuels and costly logistics—making predictable local generation valuable.
-
Low operational emissions. No fuel combustion means no direct CO₂ emissions at the point of generation (subject to lifecycle considerations).
-
Possible co-benefits. Depending on the design and permits, cold deep water can also support cooling applications or other industrial uses.
Why test off Gran Canaria?
The Canary Islands offer practical conditions for marine energy trials: access to deep water relatively close to shore, strong maritime infrastructure, and a real-world case where reliable power is valuable for an island grid.
Weather resilience: the real offshore stress test
Global OTEC says the DON system is designed to be resilient in extreme weather—a key hurdle for any offshore power technology. Trials typically validate station-keeping or mooring integrity, structural behavior in waves, operational safety, and maintenance requirements under real sea states.
What the trials will likely focus on
Sea tests usually aim to answer the most important “can it really operate” questions:
-
Real-world efficiency under varying temperatures and sea conditions
-
Heat exchanger performance (biofouling, corrosion, cleaning intervals)
-
Pumps and deep-water intake reliability
-
Working-fluid safety (ammonia containment, monitoring, emergency procedures)
-
Environmental monitoring, depending on discharge configuration and local regulations
If the concept scales, where it could fit
If trials prove successful and economics improve with scale, OTEC could provide stable, low-carbon baseload power for:
-
island nations and remote archipelagos
-
coastal industrial sites
-
hybrid systems paired with wind/solar and storage
-
select port or offshore infrastructure applications (case dependent)
