World-first platform generates electricity with sea temperature

A floating prototype has been deployed at the Oceanic Platform of the Canary Islands (PLOCAN), a marine-testing facility off the coast of Spain, under the PLOTEC project. The installation will allow the company to test how its system performs in real offshore conditions, including exposure to waves, currents and extreme weather.

OTEC technology works by harnessing the natural temperature gradient found in the ocean. Warm surface water, typically around 20–25°C in suitable regions, is used to heat and vaporise a working fluid with a low boiling point, such as ammonia. This produces high-pressure vapour that drives a turbine connected to a generator, creating electricity. Cold seawater, drawn from depths of up to 1,000 metres where temperatures can be close to 4°C, is then used to condense the vapour back into a liquid, allowing the cycle to repeat continuously.

Because this temperature difference is present day and night, OTEC offers the potential to provide continuous, baseload renewable power, unlike intermittent sources such as wind and solar. However, scaling the technology offshore has posed engineering challenges, particularly around maintaining stability and efficiency in harsh marine environments.

Global OTEC said its platform, named ‘Don’, has been specifically designed to address these challenges. The structure is engineered to be storm-resistant and capable of supporting systems in open-ocean conditions, where wave loads and structural fatigue can be significant. By validating the design at PLOCAN, the company aims to demonstrate that offshore OTEC platforms can operate reliably over extended periods.

The project is expected to generate valuable operational data, which will be used to refine system design and inform future commercial-scale deployments. Global OTEC is targeting island and coastal markets, particularly in tropical regions where the temperature gradient is strongest and where reliable, locally generated electricity could reduce dependence on imported fossil fuels.

The installation marks a key step toward moving OTEC from concept to commercial reality, with offshore deployment seen as critical to unlocking its full potential.