More than one hundred buildings of Lyon are cooled by a central production center. A virtuous water recovery system.

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In Lyon, summers are hot, hotter and warmer. How to air conditioning the highly frequented areas, by limiting ecological impact? In the Part-Dieu district, the second tertiary district of France, 150,000 m² of shops and services benefit from the urban cold network.

Water, necessary for the air conditioning of premises and offices, is produced by a refrigeration center and distributed by means of a network of pipes, serving each building concerned.

The Rhône Departmental Archives Building benefits from this air conditioning. The rules of conservation are strict and very precise. “It takes a constant temperature, the humidity rate varies depending on the temperatures, it is scrutinized carefully, to avoid any risk of harvest”, explains Noémie Bréchot, heritage curator. Does she know that cold production is a few steps under her feet?

A press visit was organized to introduce one of the two Metropolitan plants, the Mouton-Duvernet power station. You have to descend underground, under a garden under development in front of the Departmental Archives of the Rhône. A deafening noise reaches visitors. The turbines are installed 13 meters deep, under the water table. The machines produce water at 5 degrees, distributed throughout the metropolitan network. It travels 14 kilometers in a closed circuit. 96 % of ELM’s customers are tertiary buildings: hospitals, shopping center, Orange data center.

The icy water is produced from the pumped waters under the underground car parks of the Part-Dieu shopping center, in the deep water table, to avoid the risk of flooding. 1000 m³ is pumped per hour, the equivalent of an Olympic swimming pool.

“This is called a fatal energy, water not valued. The company ELM which operates the power station, has therefore contracted, with the downstream of the metropolis, an agreement to recover this water”, explains Gérald Campbell-Robertson, Managing Director of ELM, a subsidiary of Dalkia. 1 kilometer of pipe transports water to the power station. The water is transported to cool cold production machines, then it is reinjected in the surface water table. “With this heat, the surface tablecloth can exceed 27 degrees, it is rejected at 19, 20 degrees, so it’s interesting because we cool it”he specifies.

To secure the network operating system, installations have an energy performance optimization system. “When the machines do not need to produce cold, the energy is stored in the form of ice at night and it is destocked, when it is very hot, it allows to double the production capacity”, Add Gérald Campbell-Robertson. “It’s a virtuous system”he says. “This does not pollute, is less energy -consuming, compared to conventional air conditioning. The environmental impact is very favorable”. Half less electricity for the same comfort.

Article written according to the shooting of Marion Picard and Claire Chery-Pellat