The sea a powerful source of energy

How does marine geothermal work?

Marine geothermal exploits the difference in temperature between warmer surface water and the cold water found at greater depths. Water is pumped from the sea through pipelines as long as 1 km to coastal facilities where heat exchangers and heat pumps are used to meet heating or cooling needs. The heated or cooled water is then piped to individual buildings.

Although this geothermal power plant system is already a reality in Paris using water from the River Seine, the Group is now developing two entirely new and unique projects using seawater in Marseille and La Réunion.

Thassalia: The first marine geothermal power plant in Marseille

The Thassalia Marine geothermal project has been designed specifically to meet the needs of Marseille's Euroméditerranée eco-city business center - the largest urban regeneration program in Southern Europe - and is the first project of its kind to generate space heating, water heating and air conditioning services on such a scale. In practical terms, the Thassalia plant will transform the Mediterranean Sea into a sustainable energy source for around 500,000 m2 of buildings in the city of Marseille.

As a partnership between the public-sector Euroméditerranée development agency, local authorities, regional authorities and private enterprises, this project is an excellent example of how innovation is driving the energy transition and energy efficiency, and one to which Cofely Services has contributed its expertise in heating technology, whilst Climespace, the ENGIE Group specialist in urban cooling networks, has contributed its refrigeration expertise.

Using water from deep beneath the sea to provide air conditioning for La Réunion

Using water from deep beneath the sea to provide air conditioning for La RéunionOn the island of La Réunion, the communities of St-Denis and Ste-Marie will be air-conditioned using water piped from 1,100 meters below the sea 6 km offshore. By using this inexhaustible source of local energy to meet the air-conditioning needs of around 50 large-scale public- and private-sector buildings, including the airport, hospital and university, this project directly addresses the challenges involved in achieving energy independence for the island.

 It should deliver electricity savings of 75% and reduce CO2 production by 620,000 metric tons over 24 years. Lastly, this €150 million project is expected to create 100 full-time jobs during the four-year construction period, rising to 400 at peak times.