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Thassalia, the first marine geothermal plant

Smart buildings
17/11/2015

Located in the heart of Marseille, the Thassalia marine geothermal plant will use the ocean’s geothermal energy to supply heat and cooling to buildings connected to it. In doing so it transforms the Mediterranean into a sustainable source of energy for an area of almost 500,000 m2 of buildings in the Phocaean City.



Thassalia will be the first geothermal power plant in France to operate using salt water, and it will transform the Mediterranean into a sustainable source of energy for an nearly 500,000 m2 of buildings.


The marine geothermal power plant will be situated in the Port of Marseille. A pumping station will draw water from a depth of up to 5 meters, where the water is at a constant temperature. Heat pumps will recover energy from the sea for transfer to the district heating and cooling network. This 3 km-long urban network will cool buildings in summer and warm them in winter. Eventually, the network will service 500,000 m2 of buildings, including the Euromed Center, Les Docks and future Arenc Residential Park.

How does marine geothermal energy production work?

Marine geothermal energy works by making use of the temperature differences between warm surface water and cold water at greater depths, which is pumped through kilometer-long pipelines. Water is pumped into the sea and along the coast, where exchangers and heat pumps regulate production based on heating and cooling needs. The water is then channeled to heat or cool buildings.

With 40% of the population living within 100 km of the coastline, the sea has enormous potential as an energy source in France and around the world. This project highlights the potential of coastal cities in France and around the world to open themselves to the sea as a way to implement the energy transition and benefit both residents and their environment.

Source: ENGIE