Thermal conversion produces electric energy in the sea

UN/DICYT Gaviria is working along with the Universidad Nacional de Colombia (UNal) Faculty of Mining’ Oceanic and Decision Sciences Research Group which is supported by the Deputy Rector's Office of Research.

To obtain energy from the sea researchers use a technique known as ocean thermal energy conversion (OTEC) which uses the surface and deep water temperature difference to run a heat engine and produce useful work, usually in the form of electricity. Electric energy is produced by means of a thermodynamic process in which surface water can reach temperatures of up to 25º C (77º F) evaporating a liquid with a low boiling point such as ammonia. The resulting vapor is used to move a turbine and a generator to produce electricity.

An additional benefit of this technology is that ammonia turned to vapor could return to its original state using water from the depths of the sea which does not exceed 10º C (50º F) by re-condensing.

Then the production cycle is completed by exploiting a resource and recycling it, thus reducing pollution.

The interest from this technological option has been increasing due to the world need for clean energies to mitigate global warming.

This technique has been explored for many years but due to it high costs only a few pilot plants have been installed as in the current conditions it is possible that investment to operate a plant will not be recovered during its useful life.

Therefore Gaviria says the research to determine the potential use of marine water is still in theory research stage which included observing models and project analyses.

“For now there are no commercial power generation plants in the world, only a few developments in Japan and islands such as in Martinique (Caribbean) and Reunion (Indian Ocean),” she said.

Preliminary studies in Colombia indicate that the possible sites for this technology would be in the Island of San Andrés. The most appropriate point would be the southeastern portion of the island which has deep water at only 2.3 kms (1.4 miles) off the coast. The surface temperature in this point can reach up to 22º C (71.6º F) and produce 10 kW.

Furthermore apart from producing power, the water may be used for a desalinization plant and aquaculture.

Precisely in San Andrés on the analyzed location using OTEC technology would help cover the freshwater deficit on the island of between 6,000 and 8,000 cubical meters a day.

There is another possibility of using this technology in building large refrigeration or air conditioning systems for large areas.

This could also reduce the energy expenditure in tourist areas which need to use small and multiple ACs for many spaces.