thassalia facade

Une façade mystérieuse pour protéger Thassalia.


  • Energy from the deep


Last autumn in Marseille, the French gas utility Engie started harnessing heat energy from the sea. This is a fine example of energy-efficient innovation driving the energy transition.


The Thassalia marine energy conversion plant at Marseille’s commercial port is the first in France to draw heat energy from the sea to supply heating, hot water and air conditioning to a group of buildings (500,000m2 by 2020) – while reducing greenhouse gas emissions by 70%. A 3km network of pipes serves the Calypso, Hermione (Euromedcenter) and Docks buildings and the Golden Tulip hotel. In the long run all the buildings between the CMA-CGM tower and the cathedral will be connected. Engie is keen to develop sustainable alternatives that will meet energy demand while protecting the environment. The project involved several of the group’s subsidiaries: on the design side Cofely (for its expertise in thermal energy) and Climespace (for its expertise in district cooling systems) and, to build the technical part of the plant, Ineo and Cofely (electricity) and Axima and Cofely (all the internal piping). Axima supplied half the system’s refrigeration units. Using the sea as a renewable energy source, Thassalia is an innovative technical solution with a small carbon footprint. The principle is simple enough: the plant pumps seawater from deep down and discharges it after the heat exchangers have recovered the calories to feed the district heating network.


The future with
geothermal energy Marine thermal energy conversion simply takes advantage of the difference in temperature between surface waters and deeper sea layers. In summer, water colder than the air can be used for cooling; in winter, the principle is reversed and the system is used for heating. When temperature differences are not sharp enough, the system is helped out by refrigeration units in summer and gas-fired boilers in winter. The Thassalia project will cost a total of €35 million, €7 million of this being covered by public subsidies. This Marseille pilot project is of more than regional interest: sea energy is a particularly judicious sustainable solution for France, a country with more than 3800km of coastline and where 40% of the population live within 100km of the sea. And there’s more. Two months after the inauguration of Thassalia, Optimal Solutions, a subsidiary of Dalkia (part of the EDF group) presented its Massileo system, which should come online before the summer. The 1.4km system will serve the 58,000m² Smartseille, the futuristic high-tech eco-district in the 15th arrondissement of Marseille, using the same seawater energy conversion principle (with heat exchangers fed by pipes laid at a depth of 5m) and consuming just 1kW/hr to recover 4kW/hr. The pumps will provide offices, homes and the B&B Hotel with heat (between 35° and 45°C for heating and 50-55°C for hot water) and cooling (7-15°C for air conditioning). The overall investment of €28 million will be half financed by the Caisse des Dépôts via its Investissements d’Avenir programme. In the long run, the system should also supply 500,000m² of offices and business premises in the Euroméditerranée 2 development area. With Thassalia and soon Massileo, Marseille is ahead of the field in marine thermal energy conversion.


By Maurice Gouiran
Photo: A. Meyssonnier